  Most cortical inhibitory cell types exclusively express one of three genes,
parvalbumin, somatostatin and 5HT3a. The visual responses of cortical neurons
are affected not only by local cues, but also by visual context. As the
inhibitory neuron types have distinctive synaptic sources and targets over
different spatial extents and from different areas, we conjecture that they
possess distinct roles in contextual processing. We use modeling to relate
structural information to function in primary visual cortex (V1) of the mouse,
and investigate their role in contextual visual processing. Our findings are
threefold. First, the inhibition mediated by parvalbumin positive (PV) cells
mediates local processing and could underlie their role in boundary detection.
Second, the inhibition mediated by somatostatin-positive (SST) cells
facilitates longer range spatial competition among receptive fields. Third,
non-specific top-down modulation to interneurons expressing vasoactive
intestinal polypeptide (VIP), a subclass of 5HT3a neurons, can selectively
enhance V1 responses.
