The Journal of Neuroscience, February 15, 1998, 18(4):1559-1570
Practice-Related Improvements in Somatosensory Interval
Discrimination Are Temporally Specific But Generalize across Skin
Location, Hemisphere, and Modality
Srikantan S.
Nagarajan,
David T.
Blake,
Beverly A.
Wright,
Nancy
Byl and
Michael M.
Merzenich
Coleman Laboratory, Keck Center for Integrative Neuroscience,
University of California, San Francisco, California 94143-0732
This paper concerns the characterization of performance and
perceptual learning of somatosensory interval discrimination. The
purposes of this study were to define (1) the performance characteristics for interval discrimination in the somatosensory system
by naive adult humans, (2) the normal capacities for improvement in
somatosensory interval discrimination, and (3) the extent of generalization of interval discrimination learning. In a
two-alternative forced choice procedure, subjects were presented with
two pairs of vibratory pulses. One pair was separated in time by a
fixed base interval; a second pair was separated by a target interval that was always longer than the base interval. Subjects indicated which
pair was separated by the target interval. The length of the target
interval was varied adaptively to determine discrimination thresholds.
After initial determination of naive abilities, subjects were trained
for 900 trials per day at base intervals of either 75 or 125 msec for
10-15 d. Significant improvements in thresholds resulted from
training. Learning at the trained base interval generalized completely
across untrained skin locations on the trained hand and to the
corresponding untrained skin location in the contralateral hand. The
learning partially generalized to untrained base intervals similar to
the trained one, but not to more distant base intervals. Learning with
somatosensory stimuli generalized to auditory stimuli presented at
comparable base intervals. These results demonstrate temporal
specificity in somatosensory interval discrimination learning that
generalizes across skin location, hemisphere, and modality.
Key words:
somatosensory; vibrotactile; temporal processing; perceptual learning; psychophysics; tactile; touch; human; auditory; hearing; interval; time
Copyright © 1998 Society for Neuroscience 0270-6474/98/1841559-12$05.00/0
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