@article {107, title = {Velocity Invariance of Receptive Field Structure in Somatosensory Cortical Area 3b of the Alert Monkey}, journal = {The Journal of Neuroscience}, volume = {19}, year = {1999}, month = {01/1999}, pages = {401 - 419}, abstract = {

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;\ DiCarlo et al., 1998). 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).

}, keywords = {Adaptation, Animals, Brain Mapping, Cortical Synchronization, Evoked Potentials, Female, Macaca mulatta, Male, Neural Inhibition, Physiological, Somatosensory Cortex, Visual Fields}, issn = {0270-6474}, doi = {10.1523/JNEUROSCI.19-01-00401.1999}, url = {http://www.jneurosci.org/lookup/doi/10.1523/JNEUROSCI.19-01-00401.1999}, author = {DiCarlo, James J. and Johnson, Kenneth O.} } @article {110, title = {Structure of Receptive Fields in Area 3b of Primary Somatosensory Cortex in the Alert Monkey}, journal = {The Journal of Neuroscience}, volume = {18}, year = {1998}, month = {04/1998}, pages = {2626 - 2645}, abstract = {

We investigated the two-dimensional structure of area 3b neuronal receptive fields (RFs) in three alert monkeys. Three hundred thirty neurons with RFs on the distal fingerpads were studied with scanned, random dot stimuli. Each neuron was stimulated continuously for 14 min, yielding 20,000 response data points. Excitatory and inhibitory components of each RF were determined with a modified linear regression algorithm. Analyses assessing goodness-of-fit, repeatability, and generality of the RFs were developed. Two hundred forty-seven neurons yielded highly repeatable RF estimates, and most RFs accounted for a large fraction of the explainable response of each neuron. Although the area 3b RF structures appeared to be continuously distributed, certain structural generalities were apparent. Most RFs (94\%) contained a single, central region of excitation and one or more regions of inhibition located on one, two, three, or all four sides of the excitatory center. The shape, area, and strength of excitatory and inhibitory RF regions ranged widely. Half the RFs contained almost evenly balanced excitation and inhibition. The findings indicate that area 3b neurons act as local spatiotemporal filters that are maximally excited by the presence of particular stimulus features. We believe that form and texture perception are based on high-level representations and that area 3b is an intermediate stage in the processes leading to these representations. Two possibilities are considered: (1) that these high-level representations are basically somatotopic and that area 3b neurons amplify some features and suppress others, or (2) that these representations are highly transformed and that area 3b effects a step in the transformation.

}, keywords = {Afferent, Animals, Data Interpretation, Electrophysiology, Female, Macaca mulatta, Male, Neural Inhibition, Neurons, Reproducibility of Results, Somatosensory Cortex, Statistical, Touch}, issn = {0270-6474}, doi = {10.1523/JNEUROSCI.18-07-02626.1998}, url = {http://www.jneurosci.org/lookup/doi/10.1523/JNEUROSCI.18-07-02626.1998}, author = {DiCarlo, James J. and Johnson, Kenneth O. and Hsiao, Steven S.} }