Experience-Dependent Plasticity in S1 Caused by Noncoincident Inputs

• Published in: Journal of neurophysiology 2005-09, Vol.94 (3), p.2239-2250
• Main Authors: Blake, David T, Strata, Fabrizio, Kempter, Richard, Merzenich, Michael M
• Format: Article
• Language: English
• Subjects: Action Potentials - physiology; Animals; Aotidae; Behavior, Animal; Brain Mapping; Hand - physiology; Learning - physiology; Neuronal Plasticity - physiology; Primates; Psychomotor Performance - physiology; Reaction Time - physiology; Sensory Thresholds; Somatosensory Cortex - anatomy & histology; Somatosensory Cortex - physiology
• ISSN: 0022-3077; 1522-1598
• DOI: 10.1152/jn.00172.2005

Coleman Laboratory and Keck Center for Integrative Neuroscience, University of California, San Francisco, California Submitted 17 February 2005; accepted in final form 4 June 2005 Prior work has shown that coincident inputs became corepresented in somatic sensory cortex. In this study, the hypothesis that the corepresentation of digits required synchronous inputs was tested, and the daily development of two-digit receptive fields was observed with cortical implants. Two adult primates detected temporal differences in tap pairs delivered to two adjacent digits. With stimulus onset asynchronies of 100 ms, representations changed to include two-digit receptive fields across the first 4 wk of training. In addition, receptive fields at sites responsive to the taps enlarged more than twofold, and receptive fields at sites not responsive to the taps had no significant areal change. Further training did not increase the expression of two-digit receptive fields. Cortical responses to the taps were not dependent on the interval length. Stimuli preceding a hit, miss, false positives, and true negatives differed in the ongoing cortical rate from 50 to 100 ms after the stimulus but did not differ in the initial, principal, response to the taps. Response latencies to the emergent responses averaged 4.3 ms longer than old responses, which occurs if plasticity is cortical in origin. New response correlations developed in parallel with the new receptive fields. These data show corepresentation can be caused by presentation of stimuli across a longer time window than predicted by spike-timing–dependent plasticity and suggest that increased cortical excitability accompanies new task learning. Address for reprint requests and other correspondence: D. T. Blake, 513 Parnassus Ave., S-877, San Francisco, CA 94143-0732 (E-mail: dblake{at}phy.ucsf.edu )