A Disinhibitory Circuit for Contextual Modulation in Primary Visual Cortex

How Cortical Circuits Implement Cortical Computations: Mouse Visual Cortex as a Model

“…These two neurons have complementary responses to iso-and cross-oriented surrounds. On one hand, iso-oriented stimuli elicit strong responses in SOM cells (as mentioned above) but only weak ones in VIP cells (Keller et al 2020a) (Figure 6c). On the other hand, cross-oriented stimuli trigger strong responses in VIP cells but poorly stimulate SOM cells (Keller et al 2020a).…”

“…On one hand, iso-oriented stimuli elicit strong responses in SOM cells (as mentioned above) but only weak ones in VIP cells (Keller et al 2020a) (Figure 6c). On the other hand, cross-oriented stimuli trigger strong responses in VIP cells but poorly stimulate SOM cells (Keller et al 2020a). Importantly, VIP cells are integrated in the cortical circuit in a very particular manner: They preferentially inhibit inhibitory neurons rather than excitatory neurons (Pfeffer et al 2013) (Figure 1c; see also the section on cell types and circuit organization in the Supplemental Appendix).…”

“…Surround suppression is not only observed in excitatory neurons but also in two types of inhibitory neurons: the PV and vasoactive intestinal peptide (VIP) cells (Adesnik et al 2012, Keller et al 2020a). Remarkably, the other main type of inhibitory neuron, the somatostatin (SOM) cell, shows much less surround suppression, and the responses of these neurons instead often continue to increase with increasing stimulus size (Adesnik et al 2012, Keller et al 2020a) (Figure 6a). This property of SOM cells, and the fact that SOM cells inhibit all other cell types (Figure 1c), suggests that SOM cells may actually be a key contributor to surround suppression.…”

“…This phenomenon may represent the physiological basis for the fact that the perception of a stimulus with a cross-oriented surround is more salient than the same stimulus with an isooriented surround, as demonstrated by many visual illusions (Figure 6c). Work in L2/3 of mouse V1 suggests that this contextual modulation relies, at least in part, on the reciprocal interaction between two types of inhibitory neurons, namely VIP and SOM cells (Keller et al 2020a). These two neurons have complementary responses to iso-and cross-oriented surrounds.…”

“…Their activity thus has a disinhibitory impact on excitatory neurons in V1. Recent experimental and modeling approaches suggest that the activation of VIP cells by a cross-oriented surround suppresses SOM cells, thereby leading to the relief of excitatory neurons from suppression (Keller et al 2020a). This same disinhibitory circuit has been shown to regulate the degree of surround suppression based on the contrast of the stimulus (Millman et al 2019) as well as to enhance visual responses based on attentional inputs from cingulate cortex (Zhang et al 2014).…”