Visually Induced Γ Band Rhythm in Spatial Summation Beyond the Receptive Field in Mouse Primary Visual Cortex

Recent studies in many kinds of mammals have established the existence of multiple gamma rhythms in the cerebral cortex subserving different functions. In the primary visual cortex (V1), visually induced gamma rhythms are dependent on stimulus features. However, experimental findings of gamma power induced by varying the size of the drifting grating are inconsistent. Here, we reinvestigated the spatial summation properties of visually induced spike and gamma rhythm activities in mouse V1. Our results show that drifting sinusoidal grating stimuli mainly induce 2 gamma band rhythms, including a low-frequency band (25-45 Hz) and a high-frequency band (55-75 Hz). Unlike previous findings, we discovered that visually induced gamma power could also exhibit extrareceptive field (ERF) modulatory properties. The modulation by ERF stimulation could be either suppressive, countersuppressive, or nonsuppressive, mostly similar to the local spike activity. Moreover, further analysis of the neuron group exhibiting surround suppression in both spike and gamma activity revealed that the strength of the surround suppression and the receptive field size showed moderate correlations between measurements by spike and gamma rhythm activity. Our findings improve the understanding of the characteristics and neural mechanisms of induced gamma rhythms in visual spatial summation.