Nonlinear Center-Surround Interactions in the Barrel Cortex
Alireza S. Boloori and Garrett B. Stanley
Division of Engineering and Applied Sciences
Harvard University
A common feature among sensory modalities is the spatiotemporal integration of stimuli
from both center and surround portions of a cell's receptive field (RF). As rats actively
explore their environment using their vibrissa, naturalistic textural stimuli
engage multiple whiskers in correlated movements which in turn elicit spatiotemporal response
interactions. The simplest instance of response integration across a cell's spatiotemporal RF
consists of a 100-200ms suppression of ensuing activity to a single deflection, referred to
as a second-order interaction. In this study we demonstrate how second-order
interactions nonlinearly combine to yield responses to more complex deflection sequences, such
as periodic multi-whisker stimuli arising from whisking on a periodic grating. Dependence of the
timescale and magnitude of second-order suppression on stimulus properties were studied. We
observed that stimuli with larger PSTH responses (a) cause longer-lasting suppressive effects and
that (b) their responses display quicker recovery from an existing suppression. Response predictions
for more complex single and multi-whisker contact sequences were developed on the basis of the observed
characteristics of second-order response attenuations. Based on the above studies, a cortical response
model accounting for spatiotemporal integration was used to determine the influence of response
interactions on the cortical representation of periodic textures. Using both single and multiple
cells, an ideal-observer analysis showed that discrimination performance (a) suffers as a result
of stimulus-induced response suppression, but (b) is improved due to response nonlinearities. Altogether,
these results demonstrate the significance of spatiotemporal interactions in the coding
of naturalistic stimuli, and can be used to develop methods for efficient estimation of barrel cortical
response dynamics. This work was supported by grants from the Whitaker and Whitehall foundations.