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Biomedical subjects

M Hollins

Publications and source records attributed to M Hollins.

5 recordsLinked to original sources
PubMed1991

Vibrotactile adaptation on the face.

Threshold amplitude for vibration is elevated if testing is preceded by extended exposure to a vibratory adapting stimulus of appropriate amplitude and frequency. This phenomenon, previously studied almost exclusively on the hand, is here shown for the first time to occur on the face as well. Adaptation is then used analytically to determine that the two-branched threshold-versus-frequency function obtained on the face by Verrillo and Ecker (1977) represents the activity of two distinct mechanisms. Action spectra of vibrotactile adaptation reveal the presence of both mechanisms even in subjects whose unadapted threshold function (like that reported by Barlow, 1987) shows no sign of duplexity. Finally, the data suggest that on the face (unlike the hand), cross-channel adaptation may occur at high adapting amplitudes.

Adult↗
PubMed1978

Factors influencing cutaneous directional sensitivity.

The influence of stimulus velocity and traverse length on the ability of human subjects to indicate in which of two opposite directions a brush moved along the skin was determined using a forced choice procedure. Stimulus velocities ranged from 0.75 to 250 cm/sec, and traverse lengths ranged from 0.5 to 6 cm; measurements were made on both the thenar eminence and the preaxial upper arm. Performance was expressed in terms of "critical traverse length" i.e., that traverse length at which, for a given velocity, the subject would correctly identify the direction of brush motion on 75% of the trials. The data indicate that the capacity to identify direction of tactile stimulus motion increases with traverse length and is optimal for velocities between 3 and 25 cm/sec. The overall level of performance was better on the thenar than on the upper arm.

Adult↗
PubMed1978

Representation of moving stimuli by somatosensory neurons.

The findings obtained in neurophysiological and psychophysical investigations using tactile stimuli that move at constant velocity across the skin are reviewed. For certain neurons in the postcentral gyrus of the cerebral cortex (S-I) of macaque monkeys, direction of stimulus motion is a "trigger feature"" i.e., moving tactile stimuli evoke vigorous discharge activity in these neurons only if the stimuli are moved in a particular direction across the receptive field. This directional selectivity is maximal when stimulus velocity is between 5 and 50 cm/sec, and falls off rapidly at lower or higher velocities. The capacity for human subjects to correctly identify the direction of stimulus motion on the skin exhibits a similar dependence on stimulus velocity. The similar effects of velocity on neural and psychophysical measures of directional sensitivity support the idea that direction of stimulus motion on the skin can only be recognized if the moving stimulus optimally activates the group of S-I neurons for which that directions of simulus motion is the trigger feature.

Action Potentials↗
PubMed1976

Does accommodative micropsia exist?

Subjects matched the size of a test target seen under various conditions of accommodation and convergence to the size of a reference target seen under constant conditions. Convergence, as expected, had a substantial effect on perceived size, while accommodation by itself had little or none.

Accommodation, Ocular↗