Otolaryngologists
4 years of experience

500 University Dr
Hershey, PA 17033
800-243-1455
Locations and availability (2)

Education ?

Medical School Score Rankings
Virginia Commonwealth University (2006)
  • Currently 3 of 4 apples
Top 50%

Affiliations ?

Dr. May is affiliated with 1 hospitals.

Hospital Affilations

Score

Rankings

  • Milton S. Hershey Medical Center
    Otolaryngology
    500 University Dr, Hershey, PA 17033
    • Currently 2 of 4 crosses
  • Publications & Research

    Dr. May has contributed to 80 publications.
    Title Systematic Review of Endoscopic Airway Findings in Children with Gastroesophageal Reflux Disease.
    Date March 2011
    Journal The Annals of Otology, Rhinology, and Laryngology
    Excerpt

    We performed a systematic review of published literature correlating findings on endoscopic evaluation of the larynx and trachea in the pediatric population with the incidence of gastroesophageal reflux disease.

    Title Checkerboards and Color Aftereffects.
    Date July 2010
    Journal Science (new York, N.y.)
    Title Minimal Brain Dysfunction: Dopamine Depletion?
    Date July 2010
    Journal Science (new York, N.y.)
    Title Sex Differences in Tolerance to Visually-induced Motion Sickness.
    Date November 2005
    Journal Aviation, Space, and Environmental Medicine
    Excerpt

    BACKGROUND: Women report a history of motion sickness (MS) about twice as frequently as men, but the results of experimental studies are equivocal. In the present investigation, we sought to replicate previous findings that women report a greater history of MS than men when interrogated with MS history questionnaires. We examined the hypothesis that those reporting that they are prone to MS are less likely to volunteer for MS provocative experiments than those who are MS resistant. Finally, using a subset of these participants, we exposed men and women, during two separate sessions, to visually elicited apparent motion, with and without voluntary head motion (pseudo-Coriolis stimulation), to examine any differences in MS elicited between these two groups on exposure to such motion stimulation. METHOD: Experiment 1 used a MS History Questionnaire, which included an opportunity for male and female participants to volunteer for "psychology experiments" in the coming semester. This instrument was used to determine effects of sex and volunteer status on motion sickness susceptibility (MSS). Experiment 2 involved exposing a subset of these participants to rotation of a vertically striped rotating drum under static and head movement conditions. Measures of vection and MS were recorded. RESULTS: We found higher MSS scores in women vs. men, particularly when looking at participants who elected to volunteer. Women in the second experiment reported significantly more MS, but they exhibited less tolerance with head movement. No significant differences in vection were observed. CONCLUSIONS: The results indicate that laboratory manipulations that are more provocative of MS reveal reliable sex differences.

    Title The Role of Vection, Eye Movements and Postural Instability in the Etiology of Motion Sickness.
    Date February 2005
    Journal Journal of Vestibular Research : Equilibrium & Orientation
    Excerpt

    Motion sickness is a term that is commonly used to describe the ill effects of many provocative motion (e.g. seagoing or air travel) and apparent motion (e.g. IMAX movies and virtual reality) environments on human well-being and performance. It can be extremely debilitating and yet we do not have a precise understanding of its cause. This study evaluates the importance of three factors that are purported to be involved in the etiology of motion sickness (MS). Most provocative motion environments cause three distinct, but possibly related, responses: reflexive eye movements (EM), sensory conflict (SC), and postural instability (PS). Three current theories, concerning the etiology of motion sickness, emphasize one of these responses, but deny the importance of the others. Such theoretical approaches preclude the possibility of a synergistic interaction of these factors. This experiment employed a three-factor experimental design wherein each factor was manipulated alone or in combination with the others. The independent variables involved two levels of: PS (induced by having the subject stand on a stationary platform or on a posturally challenging platform mounted atop a partially inflated rubber inner tube); SC (with or without illusory self movement elicited visually by whole field stimulation); and EM (unrestricted or controlled by a stable fixation point). Analysis of measures of PS, SC and EM confirmed the effectiveness of these manipulations. Analysis of MS measures (questionnaires, magnitude ratings, tolerance times) revealed a main effect of SC (p < 0.01), increased MS found with illusory self motion conditions. In addition, measures of MS symptomatology revealed a significant three-way interaction between SC, PS and EM (p < 0.05), greater amounts of MS found with conditions of illusory self motion, postural challenge, and unrestricted EM. This suggests support for a multi-factorial approach to the study of MS etiology. These findings suggest a major role of SC in the elicitation of MS, but also suggest important contributions from the EM and PS mechanisms.

    Title The Influence of Visual Reference on Stance and Walking on a Moving Surface.
    Date November 2003
    Journal Aviation, Space, and Environmental Medicine
    Excerpt

    BACKGROUND: It is apparent that visual information is used in maintaining stable posture and ambulating throughout the stationary world. Considerable previous research has indicated that significant perturbations of posture can be induced with a shift in the entire visual scene. In motion environments, it is assumed that posture and ambulatory ability are controlled more by vestibulo-spinal reflexes, but the role of visual reference has not been extensively studied. METHOD: In the present study, the frequency of motion-induced interruptions (MIIs) under conditions which did and did not provide a stable visual reference were compared. Subjects were tested on a motion platform driven by a simulated ship-motion profile. Two independent observers recorded MIIs for standing and walking under two conditions. In one, the subjects were allowed to see the walls and ceiling of the stationary test cubicle that housed the motion platform. In the other, curtains attached to the motion platform prevented this view. Force plate recordings were also obtained during the standing tasks. RESULT: Observers reported significantly more MIIs, and force plate recordings indicated more postural instability under the condition involving curtains. CONCLUSIONS: These results suggest that manipulations, such as artificial horizons, that provide stable visual representations of the static environment within which the motion occurs may provide important health and safety measures for individuals working in modern vehicular conveyances.

    Title Disappearance Elicited by Contrast Decrements.
    Date October 2003
    Journal Perception & Psychophysics
    Excerpt

    The observation that physically present visual stimuli can sometimes disappear from consciousness has intrigued vision scientists for centuries. Two situations are known to cause such disappearance: stationary peripheral images and images (centrally or peripherally viewed) masked by abrupt contrast increments of stimuli in adjacent retinal areas. Both of these situations require near-image stabilization on the retina. Here, we describe a third way to remove stimuli from conscious awareness. It involves contrast decrements (CDs) of nearly stabilized images in the periphery. Unlike the Troxler effect, with sufficient CD, complete disappearance can be achieved almost instantaneously without significant adaptation periods. Unlike traditional masking effects, CD disappearance does not result in an after-image at or near the locus of stimulation. We report the results of four experiments in which some of the characteristics of this newly discovered phenomenon were examined. The results indicate that CDs produced by changes in the luminance of the target (see Experiment 2) or by changes in background luminance (see Experiment 3) result in an immediate loss of sensitivity to stimuli that would take much longer to fade with Troxler-like adaptation (see Experiment 1). However, the duration of such loss of sensitivity (approximately 2 sec) is comparable for the two paradigms. The frequency of disappearance increased with greater contour eccentricity, but disappearance duration remained fairly constant.

    Title Optokinetic Nystagmus, Vection, and Motion Sickness.
    Date February 2003
    Journal Aviation, Space, and Environmental Medicine
    Excerpt

    BACKGROUND: Two current theories concerning the etiology of motion sickness (MS)-the eye movement hypothesis and sensory conflict theory-were evaluated under conditions that manipulated the degree of optokinetic nystagmus (OKN) and/or vection. METHOD: Eye movement and perceptual responses were elicited with whole field stimulation in a vertically striped rotating drum and modulated with fixation and/or a restriction of the field of view (FOV). Measures of OKN, vection, and MS were recorded under the various conditions. RESULTS: Both visual field restriction and/or fixation diminished circular vection, OKN, and MS. Conditions involving both fixation and restricted FOV resulted in greater reductions in MS than did either restriction alone. CONCLUSIONS: These findings lend support to a multi-factor explanation of MS, involving both sensory conflict and eye movement.

    Title Saccadic Latency During Perceptual Processing and Sequence Learning.
    Date December 2000
    Journal Documenta Ophthalmologica. Advances in Ophthalmology
    Excerpt

    The difference between simple and choice manual reaction time (RT) has been taken to be a measure of the time necessary for various cognitive operations. In contrast, simple and choice saccadic latencies (SL - time elapsing from stimulus onset to saccade initiation) are quite similar, suggesting that such responses may be more automated. In the present investigation, SL and saccadic reaction times (SR - time elapsing from stimulus onset to saccade completion) were measured for targets appearing in the same and different locations, and to different ends of compound stimuli (big arrows) composed of small elements (little arrows) using either the global figure or the local elements as indicators of required saccade direction. In addition, measures of sequence learning were obtained behaviorally over iterative trials (decreases in response time) and with post-test interrogation. The results indicated that local response times were significantly slower than choice or global response times. Both global precedence and consistency effects were observed. Robust sequence learning was observed under the local condition, but only in the choice condition were all subjects able to recall the sequence correctly. These results are discussed in terms of proposed models of visual perception and saccade generation based on parallel processing.

    Title Afterimages, Grating Induction and Illusory Phantoms.
    Date February 2000
    Journal Vision Research
    Excerpt

    Under some conditions (dark or light inspection areas) illusory gratings often appear to be in-phase with the inducing gratings and under others (gray inspection area) illusory gratings often appear to be out-of-phase with the inducing gratings. McCourt reported that point-by-point brightness matches reveal only out-of-phase illusory gratings, no matter what the luminance of the inspection area (McCourt, M. E. (1994). Vision Research, 34, 1609-1617). Since the technique used might have led to afterimages which mimic out-of-phase illusory gratings, the present series of experiments was undertaken to determine how such afterimages might bias illusory grating judgments. Afterimages were induced during fixation with brief flashes of inducing gratings within the inspection area (Experiment 1), or by vertical shifts in the entire stimulus which exposed the retina to real gratings prior to judgments within the inspection area (Experiment 2). Experiment 2 was replicated with drifting inducing gratings (Experiment 3). The subjects were asked to indicate whether illusory gratings appeared in- or out-of-phase. The results of all three experiments reveal that out-of-phase illusory gratings predominate, and that afterimages can only bias judgments with stationary displays. It is suggested that grating induction is perceived when subjects attend to local contrast differences, while phantom visibility is facilitated when attention is captured by the more global aspects of the stimulus.

    Title Change in the Mode of Inhibition of Acetylcholinesterase by (4-nitrophenyl)sulfonoxyl Derivatives of Conformationally Constrained Choline Analogues.
    Date April 1998
    Journal Chemical Research in Toxicology
    Excerpt

    A chiral, five-step synthesis of 2-(hydroxymethyl)-2,4-dimethylmorpholine (12) from (R)- and (S)-2-methylglycidols gives an overall yield of 63%. Morpholines (R)- and (S)-12 are converted into 2-(azidomethyl)-2,4-dimethylmorpholine (15) via 2,4-dimethyl-2-[[(4-nitrophenyl)sulfonoxy]methyl]morpholine (14). The tertiary morpholines 12, 14, and 15 are quaternarized to afford 2-(hydroxymethyl)-2,4,4-trimethylmorpholinum iodide (2), 2,4,4-trimethyl-2-[[(4-nitrophenyl)sulfonoxy]methyl]morpholinium iodide (3), and 2-(azidomethyl)-2,4,4-trimethylmorpholinium iodide (4), respectively, which all inhibit acetylcholinesterase (AChE). These morpholinium inhibitors are compared with conformationally constrained aryl hemicholinium AChE inhibitors. Enantiomers of 2 and 4 are reversible competitive inhibitors of AChE, with values of Ki = 360 +/- 30 microM for (S)-2, 650 +/- 90 microM for (R)-2, 450 +/- 70 microM for (S)-4, and 560 +/- 30 microM for (R)-4, respectively. Enantiomers of 3 are noncompetitive inhibitors of AChE with values of Ki = 19.0 +/- 0.9 microM for (S)-3 and 50 +/- 2 microM for (R)-3, respectively. AChE shows a 2-fold chiral discrimination in the case of inhibition by 2 and 3. Inhibition also changes from competitive to noncompetitive when (3-hydroxyphenyl)-N,N,N-trimethylammonium iodide (18) [Ki = 0.21 +/- 0.06 microM; Lee, B. H., Stelly, T. C., Colucci, W. J., Garcia, J. G., Gandour, R. D., and Quinn, D. M. (1992) Chem. Res. Toxicol. 5, 411-418] is converted into [3-[(4-nitrophenyl)sulfonoxy]phenyl]-N,N,N-trimethylammonium iodide (5), Ki = 6.0 +/- 0.5 microM. These results indicate that the 4-nitrobenzenesulfonyl group controls the mode of inhibition.

    Title On a Failure to Replicate: Methodologically Close, but Not Close Enough. A Response to Hogben Et Al.
    Date October 1996
    Journal Vision Research
    Excerpt

    Williams, Brannan and Lartigue (1987) (Clinical Vision Science, 1, 367-371) reported that poor readers took significantly longer to search letter arrays for a target than did good readers. In addition, they reported that blurring the letter arrays leads to faster search times for poor readers and a loss of the significant differences between the groups seen with unblurred displays. In a recent attempt to replicate these findings, Hogben et al. (1996) (Vision Research, 36, 1503-1507) found no differences in search rates between good and poor readers using unblurred arrays, and no differences in search rate between the groups when blurred arrays were used. In the present article, we have compared these two research efforts, and a third paper on the same topic, with regard to methodological factors in an attempt to understand how these two different results could occur. It is our belief that the letter spacing employed in the two studies may account for the difference and should be the focus of future studies of the original effect.

    Title The Effectiveness of a Motion Sickness Counselling Programme.
    Date September 1995
    Journal The British Journal of Clinical Psychology / the British Psychological Society
    Excerpt

    Unselected volunteers were offered a course of instruction in using the cognitive-behavioural approach to helping individuals tolerate the deleterious effects of different motion environments. In order to evaluate that programme, 11 of the participants volunteered to counsel independently individuals who were prone to motion sickness, using cognitive-behavioural training which included reinforcement by visually induced apparent motion. The subjects were pre- and post-tested by an independent observer using tolerance and motion response as the dependent variables. These test scores were compared to previous data obtained with subjects who had received counselling from an experienced counsellor, or had received no such counselling. The results indicated that the newly trained counsellors' subjects showed significant pre- to post-test tolerance to the motion stimulus, although they did not benefit as much as subjects trained by the experienced counsellor. However, in terms of post-test symptomatology and magnitude estimates of motion sickness, the trainees' subjects exhibited as much benefit as did those of the experienced counsellor. These data are taken as strong support for the feasibility of training counsellors to employ this method of alleviating motion sickness.

    Title The Time-course of Global Precedence and Consistency Effects.
    Date July 1995
    Journal The International Journal of Neuroscience
    Excerpt

    The global precedence effect refers to the finding that global aspects of a scene are processed more rapidly than local detail in the scene. In experiments with large Hs and Ss (global stimuli) made up of small Hs and Ss (local stimuli), choice reaction time (RT) to the global letters is shorter than RT to the local letters (global precedence effect). In addition, RT for local letters is shorter when the local letters are the same as the global letter (consistency effect). We sought to determine the time course of the global precedence and consistency effects by delaying the global information relative to the local information. In Experiment I, the middle cross-bar of the global letter (S or H) was presented followed by the rest of the global letter at delays of 0, 48, 80, 160, 320 and 640 ms. The results indicated that the global precedence effect was obtained at delays < 48 ms and local precedence effects are obtained at delays > 80 ms. Consistency effects were found in the absence of global precedence effects, but only at delays of 48 and 80 ms. Experiment II was a replication with delays of 16, 32, 48, 64, 80, and 96 ms. The results of this experiment were in agreement with those of Experiment I. These findings offer support for the notion that the consistency effect is mediated by a higher level process than is the global precedence effect.

    Title Stimulus Manipulations That Reduce the Square-wave Illusion.
    Date March 1995
    Journal Spatial Vision
    Excerpt

    When observers view a triangle-wave luminance profile, they often report a square-wave illusion with a depth component. Alternate bars appear to be in different depth planes and the surface appears corrugated; illuminated from either the right or the left. These perspectives alternate with continuous viewing. One explanation for this illusion stems from a local energy model of feature detection proposed by Morrone and Burr (Proc. Roy. Soc. Lond. B235, 221-245, 1988). This model assumes two phase-sensitive mechanisms that process lines and edges in the visual image. It is suggested that the square-wave illusion derives from rivalry between these two mechanisms. In experiment 1, the aim was to determine whether phase alternation of the triangle wave would lead to differences in the duration and number of perceptual reversals of the illusion. The results indicate a decline in illusion duration and frequency of reversal rate with increased alternation rate. With the addition of some assumptions about the temporal resolution of the line and edge detectors, the results support the proposed explanation. In Experiment 2, the effects of high spatial-frequency contrast increments and decrements were explored. Increments did not lead to significant increases in the duration of the square-wave illusion or reversal rate, but decrements resulted in a substantial reduction in the illusion duration and reversal rate. The results indicate that manipulations which alter the phase relationships of the triangle wave decrease the illusion, but manipulations which maintain them do not.

    Title The Effects of Spatial Filtering and Contrast Reduction on Visual Search Times in Good and Poor Readers.
    Date February 1995
    Journal Vision Research
    Excerpt

    Recent experiments with reading disabled children have shown that image blurring (produced with frosted acetate overlays) results in an immediate benefit in search performance, eye movement pattern and reading comprehension. This suggests that the contrast and spatial frequency content of visual stimuli are important factors for these children. In the present experiment, spatial frequency filtering and contrast reduction were employed to determine whether either of these factors contributes to the beneficial effects observed. Letter arrays were spatially filtered to produce low pass (< 3.5 c/deg) and high pass (> 7.0 c/deg) images. In addition, a low contrast control image was generated to match the low contrast of the high pass image. Children classified as good reader controls (CON), specific reading disabled (SRD), attention deficit disordered (ADD) or comorbid SRD/ADD (COM) were asked to perform a visual search task with each type of image. With high contrast, unfiltered arrays, the search times for the CON and ADD groups were much shorter than those of the SRD and COM groups. While both high pass and low pass filter conditions improved the search speed for the COM group, improvement for the SRD group was only obtained with low contrast stimuli. These results support the notion that the beneficial results of image blurring with SRDs derives from the contrast reduction produced by such manipulations.

    Title Phase Shifts and the Square-wave Illusion.
    Date December 1992
    Journal Spatial Vision
    Excerpt

    When observers view a vertical triangle-wave luminance profile, they often report a square-wave illusion with a depth component, resembling a corrugated surface. Alternate bars seem to be in front of or behind adjacent bars and the surface appears to be illuminated from the right or left. These perspectives alternate with continuous viewing. One explanation for this illusion stems from the notion of instability among phase-selective mechanisms. Two experiments (1 and 3) were designed to determine whether systematic phase shifts introduced between the fundamental and the odd harmonics of the waveform would lead to a systematic bias of the illusion. The results indicated that a significant bias occurred when a phase shift as small as 9 deg was introduced, and that the bias from the phase shifts was more powerful than previous reports of drift-induced bias. There was a highly significant effect of direction of phase shift and the corresponding perceived direction of illumination. Another experiment (2) was designed to determine if illusional cues within the phase-shifted profiles aided phase discrimination. The results indicated that experienced subjects, presumably using cues within the profiles, discriminated between the stimuli significantly better than did naive subjects. These data support the role of phase in the square-wave illusion, but they also raise questions about the role of contrast changes in local regions of the stimulus.

    Title A Posteriori Digital Filtering to Reduce Signal-averaging of Steady-state Evoked Potentials.
    Date June 1992
    Journal Optometry and Vision Science : Official Publication of the American Academy of Optometry
    Excerpt

    This paper describes a signal extraction technique that involves taking the time series representation of signals, transforming them into the frequency domain, determining the chance occurrence of power at each frequency, and filtering accordingly. An inverse Fourier transform is then used to recreate the new time domain representation, which has been appropriately filtered for extraneous noise. Thus, this technique involves a posteriori digital filtering based on a statistical criterion for component inclusion. Computer simulation indicated that, at poor signal-to-noise ratios and with fewer samples, this technique is 5 to 10 times better at signal extraction than conventional signal averaging. Examples of pattern-elicited electroretinograms (PERG's) are used to illustrate the efficacy of this method.

    Title Emotional Processing and Fear Measurement Synchrony As Indicators of Treatment Outcome in Fear of Flying.
    Date May 1991
    Journal Journal of Behavior Therapy and Experimental Psychiatry
    Excerpt

    Minimal-therapist-involvement stress inoculation training was used to treat flying phobics. Relative to no-treatment controls, treatment subjects reported more fear reduction, were more likely to participate in an exposure session, and flew more during a two-month follow-up period. Subjects who exhibited synchronous changes in heart rate and report of anxiety during exposure had greater fear reduction than subjects showing less synchrony. Subjects who voluntarily took plane flights in the two months following treatment showed greater indications of emotional processing during in vivo exposure. Relative to flight avoiders, fliers had higher mean heart rate in the plane, a greater reduction in heart rate from the beginning to the end of the flight, and greater reported fear reduction from pre- to post-flight.

    Title The Transfer of Adaptation Between Actual and Simulated Rotary Stimulation.
    Date March 1991
    Journal Aviation, Space, and Environmental Medicine
    Excerpt

    It is well known that continued exposure to motion environments leads to adaptation, but it is not clear whether such changes are specific to the particular type of motion experienced. The present investigation sought to evaluate the extent of transfer between real motion and visually-induced apparent motion. In addition, the direction of motion was varied and these two factors, mode of exposure and direction of rotation, were examined in a cross-adaptational design. Thirty-two subjects were pre- and posttested on measures of disorientation after active bodily rotation and visually-induced self-vection. Two groups received ten consecutive trials of active bodily rotation (clockwise or counter-clockwise) for 4 consecutive days. Two other groups received ten consecutive trials of visually-induced self-vection (clockwise or counter-clockwise) in a rotating drum for 4 consecutive days. During the exposure phase, dizziness and self-vection increased over trials for the groups exposed to the drum, while dizziness remained unchanged over trials for the groups exposed to bodily rotation. Repeated exposure to bodily rotation resulted in improved walking performance over trials and days. Subjects exposed to bodily rotation exhibited increased tolerance to visually-induced self-vection; however, exposure to visually-induced self-vection did not result in greater tolerance to bodily rotation. No support for directional specificity was evident.

    Title Relaxation Pretraining, Pulse Wave Velocity and Thermal Biofeedback in the Treatment of Essential Hypertension.
    Date February 1991
    Journal International Journal of Psychophysiology : Official Journal of the International Organization of Psychophysiology
    Excerpt

    Twelve white male subjects with a physician's diagnosis of essential hypertension participated in the study over a 3- to 4-month period (23-38 sessions). Subjects were assigned to one of four sequences of training in which the order of presentation of pulse wave velocity (PWV) or thermal feedback, and presence or absence of relaxation pretraining were varied. The overall effectiveness of the treatment program was demonstrated by average blood pressure decreases of 8.8 mm Hg/4.1 mm Hg from initial session measures to follow-up one month after completion of the program. Systolic pressures were significantly lower at follow-up but not diastolic. In addition, 3 subjects had ceased taking any blood pressure medication by follow-up, and maintained normal pressure. The effectiveness of relaxation pretraining was demonstrated by the fact that relaxation pretrained subjects attained significantly greater blood pressure decreases from baseline to the last 3 sessions of training, and by the fact that relaxation pretraining appeared critical in the acquisition of PWV feedback training.

    Title Response Persistence of Cat Retinal Ganglion Cells to the Temporally Discrete Presentation of Sinewave Gratings.
    Date February 1991
    Journal The International Journal of Neuroscience
    Excerpt

    The neural basis of visible persistence is not well understood. In the present study the initial onset responses of cat retinal ganglion cells to the abrupt onset and offset of sinewave gratings were examined to determine if ganglion cells display a degree of response persistence that might account for the phenomenon of visible persistence. The responses of X and Y ganglion cell axons were tested using single-unit extracellular recording techniques. Both cell types displayed some degree of response persistence and over a limited range of short stimulus durations response persistence was inversely related to stimulus duration. These data suggest that neural persistence at the ganglion cell level may be the initial physiological basis for some types of visible persistence.

    Title Eye Movement Indices of Mental Workload.
    Date January 1991
    Journal Acta Psychologica
    Excerpt

    Four investigations were carried out to assess the feasibility of using eye movement measures as indices of mental workload. In the first experiment, saccadic extent was measured during free viewing while subjects performed low, moderate and high complexity, auditory tone counting as the workload tasks. The range of saccadic extent decreased significantly as tone counting complexity (workload) was increased. In the second experiment the range of spontaneous saccades was measured under three levels of counting complexity with a visual task that did not require fixation or tracking. The results indicated that the extent of saccadic eye movements was significantly restricted as counting complexity increased. In the third experiment, the effects of practice were examined and decreased saccadic range under high tone counting complexity was observed even when significant increases in performance occurred with practice. Finally, in experiment 4, the first experiment was repeated with additional optokinetic stimulation and the saccadic range was again observed to decrease with tone counting complexity. The results indicated that the extent of spontaneous and elicited eye movements was significantly restricted as counting complexity increased. We conclude that this measure may provide a valuable index of mental workload.

    Title Generalization of Tolerance to Motion Environments.
    Date October 1990
    Journal Aviation, Space, and Environmental Medicine
    Excerpt

    The aim of the present investigation was to determine to what extent training tolerance to one motion stimulus would generalize other motion experiences. Twenty subjects prone to motion sickness were selected and assigned to one of four groups after pretesting in a Dichgans and Brandt drum to determine their susceptibility to visually-induced apparent motion. They were also pretested with a VDT display of an expanding surface, and on a revolving/tilting chair. Subjects were assigned to one of the four groups by matching their mean tolerance to visually-induced motion. Subjects in the first group served as controls and received only cognitive counseling regarding their ability to tolerate motion environments. Subjects in the other groups received the same counseling coupled with incremental exposures to the drum, chair, or VDT, respectively. Posttests on each apparatus revealed that the treatments involving the chair and the drum provided specific increases in tolerance to the device used during treatment, and that the treatment involving the chair provided a generalized tolerance to visually-induced motion. These results support the notion that there are both specific and general components in learning to tolerate motion environments.

    Title The Acuity Card Procedure: Longitudinal Assessments.
    Date September 1990
    Journal Journal of Pediatric Ophthalmology and Strabismus
    Excerpt

    Traditional methods of visual assessment in preverbal pediatric patients rely on refined but subjective measurement techniques. A standard ophthalmologic examination includes evaluation of a child's fixation patterns, with performance ranked on the basis of ability to fix and follow an object (F & F) or maintain central, steady fixation (CSM). In the hands of a skilled clinician, these evaluations are important for diagnosis and treatment. Documentation of quantitative changes in visual abilities of preverbal patients, however, has only recently become feasible. We began using the acuity card procedure in our pediatric clinical practice more than 3 years ago. This assessment, a modified version of the standard Forced-Choice Preferential Looking paradigm (FPL), provides quantitative evaluation of visual functioning in preverbal patients. The total number of patients assessed on one or more occasions exceeds 900. Of this group, we followed 83 patients with at least four acuity card evaluations on separate visits. Thirty of these patients, all with different diseases, have been evaluated with acuity cards on six or more visits. We found the information provided by the acuity card assessments extremely helpful in quantifying the developmental and therapeutic changes in vision, previously monitored only qualitatively.

    Title Changes in Erg Amplitude Following Laser Induced Damage to the Primate Retina.
    Date September 1990
    Journal Current Eye Research
    Excerpt

    The flash evoked ERG is used extensively as a measure of retinal function. To understand better the relationship between extent of retinal damage and the ERG we created multistage laser lesions in one eye each of three Macaca fascicularis monkeys. An argon-dye laser was used to deliver 630 nm energy to cumulative quarter sectors of the temporal hemiretina and the foveal region at two week intervals. Latencies of the a- and b-waves and amplitude from the trough of the a-wave to peak of the b-wave were measured preoperatively and one week after each new lesion. Following the last recording session the eyes were removed and prepared for histological examination. In general, but depending on stimulus condition, the maximum decrease in ERG amplitude (50-70% of normal) occurred following the third or fourth sector lesions. These lesions accounted for a loss of the outer nuclear layer in 18-25% of the entire retinal surface area extending from the edge of the fovea into the anterior equatorial region. Surprisingly, subsequent lesions of the remaining sector and fovea did not result in further reduction of ERG amplitudes. Significant increases in amplitudes were even observed for some stimulus conditions following these final lesions. Latencies of the a- and b-waves were not affected. The fact that in the present study ERG amplitudes recovered, suggest that such values may be tenuous evidence of amount of functional retina in laser-lesioned eyes.

    Title The Effects of Spatial Phase on Reaction Time to Spatially Filtered Images.
    Date September 1990
    Journal Psychological Research
    Excerpt

    Many studies of visual perception have used periodic stimuli such as sine-wave gratings and checkerboard patterns. It is well known that reaction time (RT) to such stimuli increases with increasing spatial frequency and decreasing contrast. While this is the case with periodic stimuli it is not clear that these relationships obtain for aperiodic stimuli such as natural scenes. A digitized image of an object (a vase) was submitted to two-dimensional Fourier analysis. Four pairs of spatial frequency band-limited images were created for each image. Each pair consisted of a normal-phase (NP) and a scrambled-phase (SP) version, with the magnitude spectrum and space-averaged luminance the same within each pair. Filter band-widths were 1 octave wide. Manual RT was measured for onset and offset of each spatially filtered image. Mean RT for SP images increased significantly with increasing spatial frequency, while no other significant differences were found with the NP images. This suggests that the temporal processing of complex, aperiodic images is influenced by the spatial frequency and contrast of local regions within the image, rather than by the space-averaged contrast of the entire image, and cannot be predicted by global estimates of contrast and spatial frequency.

    Title Spatial Localization Discrepancies: a Visual Deficiency in Poor Readers.
    Date July 1990
    Journal The American Journal of Psychology
    Excerpt

    In two studies, we compared the size of the spatial discrepancies made by young, good and poor readers when locating patterns in space. In the first study, each child was asked to point to the location of a briefly displayed pattern in a 7 x 7 matrix, and the discrepancy between the target's location and the child's response was recorded. The pattern was either a shape or a letter, and the target appeared at nine distances from the middle of the display. The discrepancies made by both groups of children increased with eccentricity, but the rate of increase was significantly greater for the poor readers. The second study required that two temporally and spatially separated target patterns be located on each trial. The discrepancies between their positions and the positions specified by the children were recorded for each target as a function of its eccentricity, and the results for both targets were similar to those obtained in the first study. That is, the discrepancies made by both groups of children increased with eccentricity, but the rate of increase was significantly greater for the poor readers. It was argued that the results of both studies are consistent with the hypothesis that poor readers are handicapped by a low-level processing or perceptual deficiency in the visual encoding system.

    Title Visual Motion Response Properties of Neurons in Dorsolateral Pontine Nucleus of Alert Monkey.
    Date March 1990
    Journal Journal of Neurophysiology
    Excerpt

    1. In this study we sought to characterize the visual motion processing that exists in the dorsolateral pontine nucleus (DLPN) and make a comparison with the reported visual responses of the middle temporal (MT) and medial superior temporal (MST) areas of the monkey cerebral cortex. The DLPN is implicated as a component of the visuomotor interface involved with the regulation of smooth-pursuit eye movements, because it is a major terminus for afferents from MT and MST and also the source of efferents to cerebellar regions involved with eye-movement control. 2. Some DLPN cells were preferentially responsive to discrete (spot and bar) visual stimuli, or to large-field, random-dot pattern motion, or to both discrete and large-field visual motion. The results suggest differential input from localized regions of MT and MST. 3. The visual-motion responses of DLPN neurons were direction selective for 86% of the discrete visual responses and 95% of the large-field responses. Direction tuning bandwidths (full-width at 50% maximum response amplitude) averaged 107 degrees and 120 degrees for discrete and large-field visual motion responses, respectively. For the two visual response types, the direction index averaged 0.95 and 1.02, indicating that responses to stimuli moving in preferred directions were, on average, 20 and 50 times greater than responses to discrete or large-field stimulus movement in the opposite directions, respectively. 4. Most of the DLPN visual responses to movements of discrete visual stimuli exhibited increases in amplitude up to preferred retinal image speeds between 20 and 80 degrees/s, with an average preferred speed of 39 degrees/s. At higher speeds, the response amplitude of most units decreased, although a few units exhibited a broad saturation in response amplitude that was maintained up to at least 150 degrees/s before the response decreased. Over the range of speeds up to the preferred speeds, the sensitivity of DLPN neurons to discrete stimulus-related, retinal-image speed averaged 3.0 spikes/s per deg/s. The responses to large-field visual motion were less sensitive to retinal image speed and exhibited an average sensitivity of 1.4 spikes/s per deg/s before the visual response saturated. 5. DLPN and MT were quantitatively comparable with respect to degree of direction selectivity, retinal image speed tuning, and distribution of preferred speeds. Many DLPN receptive fields contained the fovea and were larger than those of MT and more like MST receptive fields in size.(ABSTRACT TRUNCATED AT 400 WORDS)

    Title Reduction of Visually-induced Motion Sickness Elicited by Changes in Illumination Wavelength.
    Date September 1989
    Journal Aviation, Space, and Environmental Medicine
    Excerpt

    This experiment was undertaken to assess the degree of stimulus generalization in visually-induced motion sickness. Sixteen subjects participated in six sessions in which they were exposed to a rotating field of vertical stripes for five 4-min trials. This stimulus elicited the perception of self-vection. In the first three sessions, the stripes were illuminated by one monochromatic light (red or green) and in the last three sessions, the stripes were illuminated by the other monochromatic light. Magnitude estimates of motion sickness increased significantly within sessions, but the rate at which this measure increased was significantly diminished across trials in the last three-session block. Magnitude estimates of vection increased within sessions and decreased across sessions, but did not increase with color change. These results can be explained in terms of a model of stimulus generalization and have implications for the reduction of motion sickness in applied settings.

    Title Stress and Rheumatoid Arthritis: Can a Cognitive Coping Model Help Explain a Link?
    Date June 1989
    Journal Seminars in Arthritis and Rheumatism
    Title An Evaluation of Cognitive-behavioral Therapy for Training Resistance to Visually-induced Motion Sickness.
    Date May 1989
    Journal Aviation, Space, and Environmental Medicine
    Excerpt

    This investigation examined the techniques for reducing visually-induced motion sickness. On the basis of their responses to a motion sickness history questionnaire, 32 subjects were selected and assigned to 1 of 4 groups such that the groups were matched on the basis of their ability to tolerate visually-induced apparent motion (VM). One group received 10 sessions of desensitization training only (DT); a second group received 10 sessions of cognitive therapy only (CT); a third group received 10 sessions of combined desensitization and cognitive therapy treatment (CG); and a fourth group received no treatment (C). (There are many speculations about why and how an individual's response changes with repeated stimulation. We have arbitrarily selected the term desensitization to connote the decrease in sensitivity over time with repeated exposures). The results indicated that only the groups which received cognitive therapy (i.e., CT and CG) exhibited significant increases in tolerance to VM when pretreatment measures were compared to posttreatment measures. No significant differences in pre- vs. posttreatment measures were observed in the desensitization only or control groups (i.e., DT and C). A similar pattern of results was obtained with the symptomatology data.

    Title Clinical and Serum Lipid Findings in a Large Family with Autosomal Dominant Retinitis Pigmentosa.
    Date April 1989
    Journal Ophthalmology
    Excerpt

    Retinitis pigmentosa, of unknown cause, has recently been associated with decreased amounts of the polyunsaturated fatty acid, docosahexaenoic acid, in the plasma of affected as compared with unaffected relatives. It has been suggested that this finding may serve as a marker for the disease and might indicate alterations in photoreceptor cell metabolism. The authors studied 54 members of a family with dominantly inherited retinitis pigmentosa in five generations. In addition to the typical clinical findings of retinitis pigmentosa, eight persons also had a bull's eye maculopathy, and four persons had uni- or bilateral optic nerve drusen. When the authors determined the plasma fatty acid and lipid contents, they saw the expected age-related effect on cholesterol and triglycerides, but an unexpected, significant reduction in fatty acids in the unaffected controls as compared with persons with retinitis pigmentosa. The authors' results emphasize the heterogeneity of phenotypic expression of retinitis pigmentosa within a single family.

    Title Teller Acuity Cards Versus Clinical Judgment in the Diagnosis of Amblyopia with Strabismus.
    Date February 1989
    Journal Ophthalmology
    Excerpt

    Teller acuity card testing, which is a form of the preferential-looking procedure, is a popular way of assessing visual acuity in preverbal patients. The authors suspected that the clinical judgment of a pediatric ophthalmologist is superior to the Teller acuity cards in diagnosing amblyopia when strabismus is present. Acuity card and fixation preference measurements on each eye were compared at the same clinical visit in a group of 108 strabismic patients. The authors found that the acuity cards could be used to detect amblyopia. However, the pediatric ophthalmologist was more sensitive in diagnosing amblyopia than the Teller acuity cards in the presence of strabismus.

    Title Temporal Order Judgements in Good and Poor Readers.
    Date January 1989
    Journal Neuropsychologia
    Excerpt

    The amount of time required to make accurate (75% correct) temporal order judgements was measured in groups of 3rd and 4th grade children who were selected on the basis of reading ability. The stimuli, two words (Box and Fox), were tachistoscopically presented to the left and right or above and below a fixation point. Subjects were asked to say which word came first under one condition, or which position contained the stimulus that occurred first under another condition. The stimulus onset asynchrony (SOA) was varied in half octave steps until threshold was determined. The results indicate that good readers required significantly longer SOAs to achieve 75% correct than adults, but significantly shorter SOAs than poor readers. There was not a significant difference in thresholds for the word and position conditions for adults or good readers, but poor readers required significantly more time to achieve criterion for the word condition. The word thresholds were highly correlated (-0.77) with reading level, but the correlation between position threshold and reading level was not significant. The implications of a temporal order deficit are discussed.

    Title Ganglioside Administration in Retinitis Pigmentosa.
    Date December 1988
    Journal Journal of Ocular Pharmacology
    Excerpt

    The retinitis pigmentosa process typically causes variably progressive visual loss due to retinal photoreceptor and pigment epithelial cell deterioration. No effective agent either to retard or stop the deterioration has been known. Because gangliosides have been shown to have a variety of trophic effects on peripheral nervous tissue, we administered a daily 40 mg intramuscular dose in a prospective, double-blind, randomized, placebo-controlled trial in 30 persons with retinitis pigmentosa with or without congenital deafness. When we compared baseline performance on the two principal study outcomes, visual field area and electroretinographic response amplitudes, there was a marginally statistically significant increase in visual field area in the ganglioside-treated group. The subgroup of subjects who had recordable electroretinograms at baseline and who received the drug showed in three of five cases an increase in amplitude to all stimuli. These results appear encouraging; however, the data must be interpreted cautiously because the numbers of individuals are very small. Further study of the possible benefits of ganglioside administration to retinitis pigmentosa patients appears warranted.

    Title Eeg Biofeedback and Relaxation Training in the Control of Epileptic Seizures.
    Date September 1988
    Journal International Journal of Psychophysiology : Official Journal of the International Organization of Psychophysiology
    Excerpt

    Research utilizing sensorimotor rhythm (SMR) biofeedback with epileptics suggests that it is useful in decreasing seizures. Subjects were 6 young adults with a diagnosis of epilepsy of at least two years who had been unable to control their seizures with different regimens of anticonvulsant medications. Subjects ranged from severely mentally handicapped to above average functioning. Seizure type, frequency, and duration were recorded by subjects and caretakers. Measures of operant learning were percent time in SMR. The experiment utilized a single subject multiple baseline design which consisted of 6 phases: baseline one, relaxation training; baseline two, biofeedback training one; baseline three, biofeedback treatment two and follow-up. The results of this study are in agreement with other studies using SMR biofeedback. All subjects were able to significantly increase percent time in SMR. Five out of the 6 subjects demonstrated decreases in seizure frequency during the treatment phase. Two of the 6 subjects benefited from relaxation training. Four subjects demonstrated significant negative correlations between percent SMR and seizure rats. Consistent with other studies utilizing multiple baseline designs, a majority of the subjects did not follow the design of the study.

    Title The Effects of Spatial Frequency and Temporal Waveform on Three Measures of Temporal Processing.
    Date September 1988
    Journal The Journal of General Psychology
    Excerpt

    The effects of spatial frequency and temporal transition of sine-wave grating onset and offset were assessed using measures of reaction time, visual persistence, and temporal order judgements. The stimuli were lateralized fields, separated by 1 degree of visual angle. Slow temporal transition resulted in significantly poorer performance than did abrupt onset and offset, but spatial frequency had a minimal effect. Thus, the latency, temporal resolution, and temporal ordering of events are mediated by a mechanism that is sensitive to abrupt temporal transients. The stimulus conditions employed did not result in a shift in the point of subjective simultaneity.

    Title Spatial Requirements for Visual Simulation of Aircraft at Real-world Distances.
    Date August 1988
    Journal Human Factors
    Title Reaction Time Measures of Backward Masking.
    Date July 1988
    Journal The Journal of General Psychology
    Excerpt

    We employed both simple and choice reaction time (RT) paradigms in which the subjects were required to respond to 3.0 cycles per degree (c/d) square-wave gratings presented to one eye, while checkerboard masks were presented at various stimulus-onset asynchronies to the other eye. No masking was evident using the simple RT paradigm, but with the choice RT task, checkerboard masks presented to the contralateral eye of three subjects resulted in substantial decreases in response speed when the test preceded the mask by stimulus-onset asynchronies of 25 to 75 ms. Masks that contained lower fundamental spatial frequencies (1.0 c/d) than the target were more effective than masks containing fundamental spatial frequencies (6.0 c/d) higher than the target, while masks that contained fundamental components identical to those in the target (3.0 c/d) produced maximum masking. The results offer support for the sustained-transient theory of visual processing and validate RT as a technique for examining spatio-temporal factors in masking.

    Title Smooth-pursuit Eye Movement Deficits with Chemical Lesions in the Dorsolateral Pontine Nucleus of the Monkey.
    Date June 1988
    Journal Journal of Neurophysiology
    Excerpt

    1. Anatomical and single-unit recording studies suggest that the dorsolateral pontine nucleus (DLPN) in monkey is a major link in the projection of descending visual motion information to the cerebellum. Such studies coupled with cortical and cerebellar lesion results suggest a major role for this basilar pontine region in the mediation of smooth-pursuit eye movements. 2. To provide more direct evidence that this pontine region is involved in the control of smooth-pursuit eye movements, focal chemical lesions were made in DLPN in the vicinity of previously recorded visual motion and pursuit-related neurons. Eye movement responses were subsequently recorded in these lesioned animals under several behavioral paradigms. 3. A major deficit in smooth-pursuit performance was produced after unilateral DLPN lesions generated either reversibly with lidocaine or more permanently with ibotenic acid. Pursuit impairments were observed during steady-state tracking of sinusoidal target motion as well as during the initiation of pursuit tracking to sudden ramp target motion. Through the use of the latter technique, initial eye acceleration was reduced to less than one-half of normal for animals with large lesions of the dorsolateral and lateral pontine nuclei. 4. The pursuit deficit in all animals was directional in nature and was not dependent on the visual hemifield in which the motion stimulus occurred. The largest effect for horizontal tracking occurred in all animals for pursuit directed ipsilateral to the lesion. Animals also showed major deficits in one or both directions of vertical pursuit, although the primary direction of the vertical impairment was variable from animal to animal. 5. Chemical lesions in the DLPN also produced comparable deficits in the initiation of optokinetic-induced smooth eye movements in the ipsilateral direction. In contrast to this effect on the initial optokinetic response, in the one lesioned animal studied during prolonged constant velocity optokinetic drum rotation, smooth eye speed increased slowly over a 10- to 15-s period to reach a level that closely matched drum speed. These results suggest that pathways outside the DLPN can generate the steady-state optokinetic response. 6. Saccades to stationary targets were normal after DLPN lesions, but corrective saccades made to targets moving in the direction ipsilateral to the lesion were much more hypometric than similar prelesion control saccades. 7. The pursuit deficits produced by lidocaine injections recovered within 30 min. The ibotenic acid deficits were maximal approximately 1 day after the injection and recovered rapidly thereafter over a time period of 3-7 days.(ABSTRACT TRUNCATED AT 400 WORDS)

    Title Measures of Auditory Evoked Potentials During Optokinetic Stimulation.
    Date November 1987
    Journal Aviation, Space, and Environmental Medicine
    Excerpt

    In this investigation auditory brainstem responses (ABR) elicited by click stimuli were recorded before, during, and after optokinetic stimulation in subjects that were (N = 10) or were not (N = 10) prone to visually induced motion sickness. The latency of Wave I, and the I-III and I-V interwave intervals were measured. A significant increase in the I-III interwave interval occurred only during optokinetic stimulation. Neither the Wave I latency nor the interwave interval differed with respect to subject groups and this factor did not interact with any other variables. These results suggest that optokinetic stimulation may alter neural activity in the region of the superior olivary complex, a structure known to be important in sound-source localization.

    Title The Effects of Grating Complexity on Transient Evoked Potentials.
    Date July 1987
    Journal Electroencephalography and Clinical Neurophysiology
    Excerpt

    In the present investigation, the effects of spatial frequency (1.0, 3.0 and 9.0 c/deg), grating complexity (1 + 3 or 3 + 9), and relative phase relationships (peaks-add or peaks-subtract) on the amplitude and latency of VEP components were examined with a pattern appearance (50 msec, 1.9 Hz) technique. The effects of temporally modulating one spatial component of a complex grating while the other component was continuously viewed were also investigated. Two components of the response obtained with pattern appearance were differentially affected by these stimulus manipulations. In general, most conditions that involved spatial complexity resulted in a loss of information that could be obtained when simple sine-waves were used.

    Title Spatial Frequency Tuning in the Visual Evoked Potential Elicited by Sine-wave Gratings.
    Date January 1985
    Journal Vision Research
    Excerpt

    This investigation examined the onset response of the transient visually evoked potential elicited by the appearance-disappearance of sine-wave gratings at various levels of spatial frequency, suprathreshold contrast, and stimulus duration. The response was most easily characterized by two negative-positive complexes that were differentially tuned to spatial frequency. The earlier complex peaked at high spatial frequencies while the later complex peaked at low spatial frequencies. For both complexes, amplitude showed only slight variations across three-octave ranges of contrast and duration. Latency was curvilinearly related to spatial frequency, decreased with increasing contrast, and showed no apparent change as a function of duration.

    Title Evaluation of the X-chrom Lens and Color Deficiency.
    Date May 1984
    Journal The Clao Journal : Official Publication of the Contact Lens Association of Ophthalmologists, Inc
    Title Spatio-temporal Processing in Multiple Sclerosis.
    Date May 1984
    Journal Documenta Ophthalmologica. Advances in Ophthalmology
    Excerpt

    The processing of spatial and temporal detail was investigated in patients with multiple sclerosis. Normal observers and 13 patients with optic neuritis secondary to multiple sclerosis performed a battery of visual tests that included contrast sensitivity, temporal integration, evoked potentials, and visual masking. The multiple sclerosis patients exhibited losses of pattern processing, and these deficits became more noticeable when the patterns were presented briefly. Moreover, these patients exhibited diverse response patterns for the different visual tests. For some, temporal integration functions appeared severely attenuated, while evoked potential latency was within normal limits. Others displayed poor performance in the visual masking test, yet contrast sensitivity functions were comparable to those of the control group. We suggest that a battery of tests that incorporates spatial as well as temporal stimuli is necessary for the detection of visual dysfunction in multiple sclerosis.

    Title Learned Helplessness and the Facilitation of Biofeedback Performance.
    Date May 1984
    Journal Biofeedback and Self-regulation
    Excerpt

    The present article reports the results of two studies, which, taken together, support the hypothesis that learned helplessness resulting in effort cessation, while detrimental to performance on cognitive tasks, is actually facilitative to performance in a biofeedback relaxation task. Data are presented indicating that false failure feedback leads to the typically reported decrement in performance on a cognitive arithmetic task, while such feedback leads to enhanced performance in biofeedback relaxation. Self-report data suggest that this occurs because when subjects encounter failure, they revise their expectancies of future success downward and consequently plan to exert less effort. Reduction of effort is proposed as the common mechanism underlying the contrast in results between the arithmetic and biofeedback tasks. Results are discussed in terms of their implications for the way in which theories of self-efficacy and learned helplessness are commonly interpreted.

    Title The Relationship Between Temporal Integration and Persistence.
    Date January 1984
    Journal Vision Research
    Excerpt

    We measured the persistence for gratings of three different spatial frequencies after they had been equated for visibility by manipulating: (1) the contrast of the stimulus, (2) the duration of the stimulus, or (3) both contrast and duration. When we presented gratings of equal apparent contrast and equal duration, persistence increased with increasing spatial frequency. This effect occurred when apparent contrast was equated in terms of extended-duration or brief duration contrast sensitivity. However, when we examined persistence using gratings equated for temporal integration (i.e. equal apparent contrast but unequal durations), no differences in persistence as a function of spatial frequency were observed. Thus, the increase in persistence which is typically found with higher spatial frequencies can be accounted for by knowledge of the spatio-temporal characteristics of the visual system. Our findings are discussed in terms of the notion of different filter time-constants for different spatial channels.

    Title Surgical and Visual Results of Pediatric Epikeratophakia.
    Date November 1983
    Journal Metabolic, Pediatric, and Systemic Ophthalmology
    Excerpt

    We performed epikeratophakia for the correction of aphakia in 31 children, ages 2 months to 7 years, who had unilateral congenital or traumatic cataracts. In 27 patients with more than 4 months of follow-up, 23 of 30 (77%) grafts were successful. In the 15 patients with 6 months or more followup, the average increase in corneal curvature was 12.39 diopters. The average overrefraction needed to achieve emmetropia was + 2.14 diopters spherical equivalent. Two patients operated on within the first year of life have achieved 6/15 (20/50) visual acuities, as measured by visual evoked potentials. One patient operated on in the second year of life achieved 5/30 visual acuity, as measured by Allen cards. Two patients operated on for traumatic cataracts at ages 2 and 4 years achieved 6/9 (20/30) and 8/30 (Allen cards) visual acuities, respectively. Five older patients who had congenital cataracts or persistent hyperplastic vitreous showed some improvement in visual function. Advantages of epikeratophakia include the placement of most of the correction directly on the eye in a permanent attachment and the elimination of contact lens manipulation in uncooperative patients, so that more time and energy can be devoted to the occlusion therapy.

    Title Preliminary Visual Results of Pediatric Epikeratophakia.
    Date November 1983
    Journal Archives of Ophthalmology
    Excerpt

    Although cataract surgery is feasible in children with unilateral cataracts, visual rehabilitation depends on optical correction and conscientiously maintained amblyopia therapy. Epikeratophakia for the correction of aphakia was performed in 47 children (50 grafts). Postoperative keratometry readings showed an average increase of 12.68 diopters in early patients. With new tissue-handling techniques, the last eight patients showed an average increase of +16.80 D, with -0.64-D overrefraction for emmetropia. Visual results indicate that epikeratophakia is an effective primary procedure for patients with unilateral traumatic cataracts and that it is superior to leaving vision uncorrected in children who have had unilateral congenital cataracts removed and are contact-lens intolerant. Further studies with younger patients will be necessary to define its role in neonates; however, individual results demonstrate that good vision is obtainable with epikeratophakia.

    Title Developmental Aspects of Dichoptic Viewing.
    Date October 1983
    Journal Brain and Language
    Excerpt

    Age-related performance changes on a dichoptic viewing task were examined with twenty-five (25) individuals in a cross-sectional design. Using a double-report procedure, subjects were asked to identify two different consonant-vowel graphemes presented separately to the same foveal area of each eye (i.e., dichoptic stimulation). Stimuli were presented at stimulus-onset asynchronies (SOAs) ranging from 0 to 300 msec in 50-msec steps. Results indicated that the number of both-correct trials (i.e., correct reports of both stimuli in a dichoptic pair) significantly increased with age, while single-correct trials (a correct report of only one stimulus in the pair) significantly decreased with age. In addition, the shape of the masking functions indicated lagging stimuli were reported more accurately than leading stimuli at SOAs of 50-300 msec for all subjects. Younger subjects exhibited peak masking effects for synchronous presentations (0-msec SOA) while older individuals showed peak masking at SOAs of 50 msec. Results suggest developmental performance changes noted in processing visual information parallel, to a remarkable degree, those observed in processing auditory information.

    Title Pitch Shifts Contingent on the Modulation Frequency of an Adaptation Tone.
    Date June 1983
    Journal The Journal of the Acoustical Society of America
    Excerpt

    Following adaptation to a frequency-modulated tone, the perceived pitch of a similarly modulated tone of slightly higher frequency is shifted upwards, while that of a tone of lower frequency is shifted downwards. These shifts are greatly reduced or absent when the adaptation and test tones are frequency modulated at different rates.

    Title Meridional Differences in Temporal Resolution.
    Date December 1982
    Journal Perception
    Excerpt

    Previous investigations of temporal resolution have shown that performance is influenced by a number of stimulus parameters. The interstimulus interval needed for accurate two-pulse discrimination has been shown to (i) decrease monotonically with flash duration, luminance, and contrast; and (ii) increase monotonically with the spatial frequency of the target. A signal-detectability two-alternative forced-choice procedure was employed to reexamine the effects of spatial frequency on temporal resolution. Also assessed was the effect of grating orientation on such performance. The results confirm that temporal resolution declines with increases in spatial frequency. Furthermore, temporal resolution was significantly lower when oblique, as opposed to vertical, grating targets were used. The 'oblique effect' in temporal resolution was observed only with the highest-spatial-frequency target (15 cycles deg-1), and not with stimuli of lower spatial frequency (0.9 and 3.8 cycles deg-1). These findings suggest that stimulus parameters which elicit greater transient channel activity, as opposed to sustained channel activity, enhance temporal resolution. When transient activity is at a minimum, meridional differences in temporal resolution are likely to be attributable to sustained channel activity.

    Title Loss in Pattern-elicited Electroretinograms in Optic Nerve Dysfunction.
    Date June 1982
    Journal American Journal of Ophthalmology
    Excerpt

    Both flash- and pattern-elicited electroretinograms and visual-evoked potentials were recorded from a patient with well-documented unilateral optic nerve dysfunction. Although the flash-elicited electroretinograms from the left and right eyes did not differ in amplitude or latency, the flash-elicited visual-evoked potentials were greatly attenuated. Prominent pattern-elicited electroretinograms and visual-evoked potentials, were recorded from the better eye, but neither could be obtained from the affected eye. These results supported the contention that pattern-elicited electroretinograms are derived from optic nerve activity and that the absence of such responses may be diagnostic of loss of optic nerve function. This suggests that testing protocols aimed at assessing optic nerve function might benefit from the inclusion of pattern-elicited electroretinographic recordings. We also obtained contrast sensitivity functions from both eyes. Although considerably suppressed, the contrast sensitivity of the affected eye exhibited a 3-octave range, indicating some pattern-processing capability.

    Title Effects of Emg and Thermal Feedback Training on Tinnitus: a Case Study.
    Date April 1982
    Journal Biofeedback and Self-regulation
    Excerpt

    This case report describes a patient who exhibited the usual complaints of frustration, annoyance, and lack of sleep associated with severe tinnitus. After 2 months of weekly biofeedback sessions along with home training with a portable thermal biofeedback unit, the patient was relieved of the psychological symptoms associated with the tinnitus. A 1-year follow-up demonstrated that the patient remained complaint-free of psychological symptoms although the subjective loudness of the ringing was judged to be the same as at the onset of the tinnitus. The results indicate that biofeedback is a useful procedure in the treatment of severe tinnitus.

    Title Effects of Age on Color Preference for Black and White by Infants and Young Children.
    Date July 1981
    Journal Perceptual and Motor Skills
    Excerpt

    The purpose of this study was to determine whether age influenced preference for the colors black and white by infants and young children. The investigator administered a color-preference test to 160 subjects who attended day-care centers and who ranged in age from 6 mo. to 4.5 yr. There were equal numbers of males and females and equal numbers of Afro- and Euro-American subjects. Ages of the subjects were controlled so there were 20 subjects in each 6-mo. age interval. Data were obtained from a 12-term test in which pairs of toys were presented to each subject. The toys were identical except that one was black and the other was white. The toy the subject selected was considered the subject's preference and the color of that toy was recorded. Results of a chi-squared test and of an analysis of variance indicated that, as a group, age affected color preference. A pro-black bias was found for the younger children. The findings suggest that color preference of infants and young children is not the same as for older children and adults.

    Title Electrophysiological and Psychophysical Measures of Interocular Suppression.
    Date April 1981
    Journal Psychophysiology
    Title The "lag Effect" in Dichoptic Viewing.
    Date January 1981
    Journal Brain and Language
    Title Effects of Meridional Variation on Steady-state Visual Evoked Potentials.
    Date April 1980
    Journal Vision Research
    Title Color Preference for Black and White by Infants and Young Children.
    Date January 1980
    Journal Perceptual and Motor Skills
    Excerpt

    The purpose of this study was to determine whether a preference for the color white was present in infants and young children. A color preference test was administered to 160 subjects who ranged in age from 6 mo. to 4.5 yr. Data were obtained from a 120-item test in which 12 different pairs of toys were presented to each subject. The toys in each pair were identical except that one was black and the other was white. The toy the subject selected was considered the subject's preference and the color of that toy was recorded. Statistical analysis did not support existing literature, refuting the published idea that white preference is a general quality in all human beings.

    Title Absence of Ocular Pathology After Repeated Exposure of Unanesthetized Monkeys to 9.3-ghz Microwaves.
    Date October 1979
    Journal The Journal of Microwave Power
    Excerpt

    Unfettered monkeys (Macaca mulatta) have been trained to expose the face and eyes to pulsed microwave radiation at a frequency of 9.31 GHz and an average power density of 150 mW/cm2. Performance of an operant response required the monkeys to maintain the head within the field of the radiation source. Twelve monkeys were individually irradiated during 30 to 40 sessions and then were observed for a period of one year. No deleterious effects such as cataracts have been observed.

    Title The Range of Spatial Frequency Contingent Color Aftereffects.
    Date December 1978
    Journal Vision Research
    Title Manic-depressive Illness in Adolescence. A Case Report.
    Date November 1978
    Journal Journal of the American Academy of Child Psychiatry
    Title Recording Monocular Veps Under Binocular Conditions.
    Date September 1978
    Journal American Journal of Optometry and Physiological Optics
    Excerpt

    This report describes a technique for recording the visual evoked potential (VEP) arising from 1 eye under conditions of binocular pattern stimulation. The subject views a sinusoidally modulated vectographic checkerboard with orthogonally oriented polarizing filters before the eyes. This technique results in waveforms that contain monocular VEPs distributed in time. The technique is sensitive to interocular suppression and controls for the influence of various extraneous sources of variability. It is useful in clinical VEP testing.

    Title Visual Evoked Potentials and Reaction Time in Normal and Dyslexic Children.
    Date March 1977
    Journal Psychophysiology
    Title Behavioral and Biochemical Effects of Neonatal Treatment of Rats with 6-hydroxydopa.
    Date October 1976
    Journal Pharmacology, Biochemistry, and Behavior
    Excerpt

    Rats receiving injection of either 6-hydroxydopa (60 mug/g) or saline on Days 1, 3, and 5 of life were studied in adulthood on a number of behavioral tasks before being sacrificed at 8 or 12 months for NE assay. The treated rats exhibited impaired passive avoidance, less shock-induced aggression, and more locomotor open-field activity than the control rats. There were no differences between the groups in male copulatory behavior, food and water intake, or thermoregulation. In comparison to the saline rats, 6-hydroxydopa rats showed elevated levels of endogenous NE in lower brainstem regions, e.g., midbrain and pons-medulla, as well as cerebellum. Hypothalamic NE level was not affected. Significant depletions of NE were obtained in the hippocampus and neocortex.

    Title Spatial Frequency-contingent Color Aftereffects.
    Date May 1976
    Journal Science (new York, N.y.)
    Excerpt

    Two-dimensional Fourier analysis of checkerboards reveals that major components are at a 45 degree angle to the check edges. After adapting to chromatic checkerboards, subjects who viewed achromatic grating stimuli reported that complementary color aftereffects are aligned with spatial frequency components rather than with the edges in the pattern.

    Title Effects of Conditioned Aversive Stimuli Presented During Tonic Immobility in Guinea Pigs.
    Date December 1974
    Journal Journal of Comparative and Physiological Psychology
    Title Letter: Evoked Potential Correlates of Adaptation to Wavelength and Orientation.
    Date April 1974
    Journal Vision Research
    Title Effects of Magnesium Pemoline on the Habituation of an Innate Fear Response in Carassius Auratus.
    Date February 1974
    Journal Behavioral Biology
    Title Emotional Responses in a Pediatric Icu.
    Date December 1973
    Journal Rn
    Title Habituation and Sensitization of an Innate Fear Response in Carassius Auratus.
    Date July 1973
    Journal Psychological Reports
    Title The Effects of Electrical Stimulation of the Eye Upon Increment Threshold for Square-wave Gratings.
    Date May 1973
    Journal Vision Research
    Title Chromatic Adaptation of Orientation- and Size-specific Visual Processes in Man.
    Date November 1972
    Journal Vision Research
    Title A Psychiatric Study of a Pediatric Intensive Therapy Unit. A Child Psychiatrist Looks at the Emotional Responses of Children and Staff in This Treatment Setting.
    Date June 1972
    Journal Clinical Pediatrics
    Title The Visual Evoked Response Obtained with an Alternating Barred Pattern: Rate, Spatial Frequency and Wave Length.
    Date July 1971
    Journal Electroencephalography and Clinical Neurophysiology
    Title Spectral Sensitivity of the Human Ver Obtained with an Alternating Barred Pattern.
    Date July 1971
    Journal Vision Research
    Title The Presence of a Temporal Discrimination in the Conditioned Emotional Response with Humans.
    Date February 1970
    Journal Journal of the Experimental Analysis of Behavior
    Excerpt

    Six college students participated in matching-to-sample tasks. Conditioned emotional response (CER) training consisted of pairing a tone with a "painful" level of shock. Three of the subjects demonstrated response suppression, one subject showed facilitation, and two showed no change. Analysis of response rate during the tone interval indicated that, for those subjects who showed response suppression, the decrease in response rate was greatest immediately before onset of the unconditioned stimulus. This temporal discrimination was similar to that obtained with infrahumans.

    Title "we Just Want to Help You"--a Note on Anger in Adolescent Group Therapy.
    Date December 1969
    Journal Mental Hygiene
    Title Establishment and Control of a Bar-pressing Habit by Means of Fixed Interval Icss Reinforcement.
    Date December 1965
    Journal Psychological Reports

    Similar doctors nearby

    Dr. Rantonio Portela

    Otolaryngology
    Hershey, PA

    Dr. Soha Ghossaini

    Otolaryngology
    16 years experience
    Hershey, PA

    Dr. Stuart Ort

    Otolaryngology
    7 years experience
    Hershey, PA

    Dr. Sohrab Sohrabi

    Otolaryngology
    3 years experience
    Hershey, PA

    Dr. Irina Chaikhoutdinov

    Otolaryngology
    Hershey, PA

    Dr. Genevieve Andrews

    Otolaryngology
    7 years experience
    Hershey, PA
    Search All Similar Doctors