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Biomedical subjects

J G May

Publications and source records attributed to J G May.

At least 73 records · Page 4Linked to original sources
PubMed1983

Developmental aspects of dichoptic viewing.

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.

Adolescent↗
PubMed1983

Pitch shifts contingent on the modulation frequency of an adaptation tone.

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.

Adaptation, Physiological↗
PubMed1983

Surgical and visual results of pediatric epikeratophakia.

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.

Age Factors↗
PubMed1982

Loss in pattern-elicited electroretinograms in optic nerve dysfunction.

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.

Adult↗
PubMed1982

Meridional differences in temporal resolution.

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.

Form Perception↗
PubMed1981

Effects of EMG and thermal feedback training on tinnitus: a case study.

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.

Adolescent↗
PubMed1981

Effects of age on color preference for black and white by infants and young children.

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.

Child Development↗
PubMed1980

Effects of neonatal 6-hydroxydopa on behavior in female rats.

Litters of female rats were treated at birth and 48 hr later with either saline or 6-hydroxydopa (60 microgram/g, IP), were ovariectomized in adulthood and tested on a number of behavioral tasks including age of vaginal opening, sexual receptivity, open-field activity, equilibrium, and habituation to acoustic startle. Results of the open-field test indicated that the treated animals were more active overall, were more likely to enter inner segments, reared more often, and defecated less than the control animals. On a rod-balancing task, the treated animals exhibited impaired equilibrium. Treated animals were more reactive than controls in response to acoustic startle, but there were no differences between the groups in rate of habituation or sensitization to the startle stimulus. Norepinephrine content of treated animals was significantly lower than controls in the cortex, amygdala, hippocampus, and spinal cord, but higher in the cerebellum and brainstem. There was no difference between the groups in cardiac norepinephrine nor in striatal dopamine.

Animals↗
PubMed1979

Effects of pentobaribtal and ketamine on brain stem auditory potentials. Latency and amplitude intensity functions after intraperitoneal administration.

Latency and amplitude intensity functions of two short latency (less than 5 ms) components (I and IV) of the brain stem auditory potentials were recorded from scalp electrodes in 18 paralyzed, hooded rats breathing with the assistance of artificial respirators. Averaged responses were obtained in three groups of rats before and 30 minutes after intraperitoneal injections of saline, ketamine hydrochloride (Ketalar), and pentobarbital sodium. Although both ketamine and pentobarbital significantly decreased heart rate and altered the gross EEG, they did not significantly change the latency or amplitude intensity functions of the two evoked-potential components.

Acoustic Stimulation↗
PubMed1979

Absence of ocular pathology after repeated exposure of unanesthetized monkeys to 9.3-GHz microwaves.

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.

Animals↗
PubMed1979

Color preference for black and white by infants and young children.

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.

Child Development↗