The Journal of Neuroscience, January 1, 1999, 19(1):401-419
Velocity Invariance of Receptive Field Structure in Somatosensory
Cortical Area 3b of the Alert Monkey
James J.
DiCarlo and
Kenneth O.
Johnson
Krieger Mind/Brain Institute, Departments of Neuroscience and
Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland
21218
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).
Key words:
receptive field; somatosensory; cortex; area 3b; SI; tactile; velocity; monkey; reverse correlation
Copyright © 1999 Society for Neuroscience 0270-6474/99/191401-19$05.00/0
Previous Article | Next Article
