Abstract Body

A recent study from our group has described the effect of pulvinar inactivation on the contrast response function (CRF) of neurons in areas 17 and 21a of the cat visual cortex (de Souza et al., 2019). It revealed that pulvinar signals modulate the activity of area 17 neurons, while modulatory and driver influences are observed in area 21a. These findings were based on the linear change of the CRF position (driver effect) and nonlinear variation in the CRF dynamic range (Rmax; modulatory effect). To study whether oscillatory cortical signals depend on the activity of the pulvinar, we investigated the contrast response of the gamma band in areas 17 and 21a during thalamic inactivation. Extracellular responses to full-field gratings of varying contrast were recorded in both cortical areas in anesthetized cats using linear probes before, during, and after the GABA inactivation of the pulvinar. Local field potentials (LFPs), from low-pass filtering of raw recordings, were analyzed with Wavelet to assess oscillatory gamma waves. The gamma-band contrast response was different across areas and cortical layers during inactivation. In area 17, the inactivation showed no significant changes across cortical layers. In area 21a, the inactivation yielded an increase in Rmax in most layers but mainly in layer IV. On average, for layer IV in area 21a, the coefficient of variation for Rmax increased by ~25%. These findings indicate that pulvinar signals modulate gamma rhythms in area 21a but not in the primary visual cortex.

Funding : CIHR to CC