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Biomedical subjects

F L Royer

Publications and source records attributed to F L Royer.

At least 19 recordsLinked to original sources
PubMed1991

Comparison of two methods of contrast sensitivity assessment with young and elderly adults.

The sensitivity of the neural channels which process spatial frequency information may be assessed by determining the threshold contrast for a range of spatial frequencies. The stability and reliability of two methods of assessment, von Bekesy tracking and increasing contrast, were examined over 4 sessions with a sample of 12 young and 12 elderly adults. The stimuli were presented as either a static display or in counterphase at a rate of 7.5 Hz. The method of increasing contrast proved to be the more stable and reliable of the two methods. Given the superior psychometric properties of this method and its ease of administration, the method of increasing contrast is recommended as a rapid and reliable screening tool. It should be of particular use for spatial contrast sensitivity assessment of patients who have a limited attention span.

Adolescent↗
PubMed1989

Age-related changes in auditory temporal processing.

Two tone bursts separated by a silent interval and imbedded in a background white noise were presented to elderly subjects (M age = 71.3 years) and young subjects (M age = 22.2 years). Subjects were required to judge when the two tone bursts fused perceptually by adjusting the duration of tone-one. The bursts were separated by six discrete interstimulus intervals of 4, 8, 16, 24, 32, or 40 ms. The tone-two burst was held constant at 100 ms. Fusion point was defined as that critical tone-one duration at which the two tones fused (were perceived as one). Elderly subjects reached fusion point at longer critical tone-one durations than young subjects at each interval tested. The function relating tone-one duration and interval conformed to an exponential curve and is discussed with respect to an exponential decay model of the inhibitory interactions of neural systems responding to onsets and offsets of sensory events.

Adolescent↗
PubMed1987

Auditory temporal processing: two-tone flutter fusion and a model of temporal integration.

Auditory temporal processing was examined using a flutter-fusion paradigm in which two tones were separated by a silent interval. The listener's task was to judge when the two tones, presented in a background noise, fused perceptually. The fusion point was studied in a series of six experiments. In the first five experiments, the duration of the first stimulus (T1) was the dependent variable. In the last experiment, the duration of the second stimulus (T2) was the dependent variable. An inverse relationship was found between T1 duration and the interstimulus interval (ISI) such that, when ISI was decreased, T1 duration had to be increased to maintain fusion. When ISI was plotted as a function of T1 duration, the data were represented by a negative exponential equation. Increasing the level of the tones, increasing the bandwidth of the background noise, or presenting the stimuli dichotically lowered the duration of T1 necessary for fusion. Changing the frequency of the tones had no effect on fusion. Decreasing the duration of T2 and holding T1 constant also resulted in fusion. A neurophysiological model implicating ON and OFF neural response interactions is postulated to account for the data.

Adult↗
PubMed1986

Iconic memory and aging.

Previous attempts to measure the capacity of iconic memory in elderly adults have been unsuccessful, demonstrating in one case that 80% of the elderly adults tested could not perform above chance level. The present experiments illustrated that the partial report paradigm designed by Sperling (1960) could be used with elderly adults to obtain such a measure. Both the young and older adults exhibited a strong partial report superiority that declined with delays in the cue interval. The effect of the perceived organization of an array on readout from iconic memory also was examined. Contrary to Merikle (1980), the differences due to the display layout were attributed to better acuity for one type of display and not to perceptual organization factors.

Acoustic Stimulation↗
PubMed1985

Aging and similarity grouping in visual search.

It has been argued that principles of perceptual organization play an important role in the representation of a visual stimulus and that elderly adults may be deficient in perceptual unit formation. The present study examined the extent to which the Gestalt principles of grouping by proximity and similarity predicted the formation of large perceptual units that could affect performance in a visual search task. The verbal reaction time to determine the presence or absence of a target letter in arrays of 1, 5, or 9 elements was determined for young (20 years) and elderly (69 years) adults. Both age groups could take advantage of the organization implied by Gestalt principles in finding a target in the context of a small implied group. The elderly adults, however, were not able to organize a single perceptual unit composed of eight elements. Thus, although the visual search performance of the age groups was similar, the elderly adults did yield evidence of a perceptual organization deficit.

Adolescent↗
PubMed1984

Stimulus parameters that produce age differences in block design performance.

Administered block designs that varied according to two parameters, Task Uncertainty and Perceptual Cohensiveness, to 83 persons 49 years of age or older. Performance was adjusted to remove motor speed differences. Performance changed significantly over the age span as a function of Task Uncertainty. From 49 years up, performance did not change as a function of Perceptual Cohesiveness. An analysis that included a group of 20 persons 30 years of age or younger yielded an interaction of Age and Perceptual Cohesiveness. From 49 years on, analytic or image segmentation processes do not seem to change, but other information processing becomes slower.

Adult↗
PubMed1983

Age differences in symbol-digit substitution task performance.

A decline in performance on the Digit Symbol Substitution test related to aging is well documented. There is no agreement on the reason for the decline, however. In part, the lack of consensus with regard to changes on the test may be attributed to the limitations imposed by comparing groups on a single performance measure. In the present study, three forms of a Symbol-Digit Substitution task that varied in difficulty level were administered to 125 persons between the ages of 30 and 92. On all forms there was a clear performance decline associated with age. The differences observed among the age groups were interpreted as evidence for a change in a sensorimotor component and in two information-processing operations: Symbol encoding and visual search.

Adult↗
PubMed1981

Normative data for the Symbol Digit Substitution Task.

Administered three forms of a Symbol-Digit Substitution task to normals, 16 to over 80 years of age, to schizophrenic and other hospitalized groups. Their data are presented for normative purposes. The three forms vary in difficulty and provide a measure of visual information processing ability, Clinical and research implications of the data are discussed.

Adolescent↗
PubMed1981

Detection of symmetry.

The time to detect symmetries in square field patterns was measured. The same relationships among mean detection times for different symmetries was found in both well-practiced and naive subjects. When the task was to detect any symmetry, detection times were faster for multiply symmetry was faster than diagonal, singly symmetric ones. Horizontal-vertical symmetry was faster than diagonal, which was faster than centric. When the task was to detect specific symmetry, that is, vertical, horizontal,diagonal, or centric only, detection times were faster again for multiply symmetric patterns, suggesting that "irrelevant" symmetry facilitates performance. Errors and response times indicate that certain symmetries are more difficult to reject than others, depending on the type of symmetry to be detected. Thus, the results suggest interference effects arising from certain symmetries. The data are best accounted for by a model in which symmetry is encoded integrally. When decoding is required by the task, as in detection tasks, the observer performs a serial hierarchical decomposition of the code.U

Discrimination Learning↗