Brock M Carlson¹, Joseph Emerson^1,2, Vera Lindh¹, Ryan Holland², Yifan Hu², Audrey Sederberg³, Cheryl Olman^1,2, Gordon Smith²; ¹Department of Psychology, University of Minnesota College of Liberal Arts, ²Department of Neuroscience, University of Minnesota School of Medicine, ³School of Psychology, Georgia Institute of Technology

Cross‐orientation suppression (COS) is a robust form of neuronal response suppression in the early visual cortex, typically attributed to divisive normalization and recurrent excitatory–inhibitory interactions. Theoretical work on inhibition-stabilized networks predicts a “paradoxical” response in which increases in intracortical drive lead to decreases in inhibitory activity (Tsodyks et al., 1997; Rubin & Miller, 2015). Indirect physiological support comes from membrane conductance estimations of intracellular recordings, which show reduced inhibitory conductance during surround suppression in cat area 17 (Ozeki et al., 2009). A direct demonstration of paradoxical suppression in inhibitory neurons in vivo has been lacking. Using two-photon calcium imaging and post-hoc histology in ferret V1, we examined COS responses in functionally characterized excitatory and inhibitory neurons. We observe strong COS in both excitatory and inhibitory neurons, with most inhibitory neurons exhibiting response reductions approaching the theoretical limit (COS index ≈ –1). These results provide preliminary in vivo evidence that inhibitory neurons in ferret V1 exhibit paradoxical suppression during COS, consistent with predictions of inhibition-stabilized networks.

Acknowledgements: This work was supported by NIH R01 NS123482