Velocity invariance of receptive field structure in somatosensory cortical area 3b of the alert monkey

TitleVelocity invariance of receptive field structure in somatosensory cortical area 3b of the alert monkey
Publication TypeJournal Article
Year of Publication1999
AuthorsDiCarlo JJ, Johnson KO
JournalThe Journal of Neuroscience: The Official Journal of the Society for Neuroscience
Date Publishedjan
KeywordsAdaptation, Animals, Brain Mapping, Cortical Synchronization, Evoked Potentials, Female, Macaca mulatta, Male, Neural Inhibition, Physiological, Somatosensory Cortex, Visual Fields

This is the second in a series of studies of the neural representation of tactile spatial form in cortical area 3b of the alert monkey. We previously studied the spatial structure of 330 area 3b neuronal receptive fields {(RFs)} on the fingerpad with random dot patterns scanned at one velocity (40 mm/sec; ). Here, we analyze the temporal structure of 84 neuronal {RFs} by studying their spatial structure at three scanning velocities (20, 40, and 80 mm/sec). As in the previous study, most {RFs} contained a single, central, excitatory region and one or more surrounding or flanking inhibitory regions. The mean time delay between skin stimulation and its excitatory effect was 15.5 msec. Except for differences in mean rate, each neuron's response and the spatial structure of its {RF} were essentially unaffected by scanning velocity. This is the expected outcome when excitatory and inhibitory effects are brief and synchronous. However, that interpretation is consistent neither with the reported timing of excitation and inhibition in somatosensory cortex nor with the third study in this series, which investigates the effect of scanning direction and shows that one component of inhibition lags behind excitation. We reconcile these observations by showing that overlapping (in-field) inhibition delayed relative to excitation can produce {RF} spatial structure that is unaffected by changes in scanning velocity. Regardless of the mechanisms, the velocity invariance of area 3b {RF} structure is consistent with the velocity invariance of tactile spatial perception (e.g., roughness estimation and form recognition).

Refereed DesignationRefereed

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