Subcortical source and modulation of the narrowband gamma oscillation in mouse visual cortex

Abstract

SummaryPrimary visual cortex (V1) exhibits two types of gamma rhythm: broadband activity in the 30-90 Hz range, and a narrowband oscillation seen in mice at frequencies close to 60 Hz. We investigated the sources of the narrowband gamma oscillation, the factors modulating its strength, and its relationship to broadband gamma activity. Narrowband and broadband gamma power were uncorrelated. Increasing visual contrast had opposite effects on the two rhythms: it increased broadband activity, but suppressed the narrowband oscillation. The narrowband oscillation was strongest in layer 4, and was mediated primarily by excitatory currents entrained by the synchronous, rhythmic firing of neurons in the lateral geniculate nucleus (LGN). The power and peak frequency of the narrowband gamma oscillation increased with light intensity. Silencing the cortex optogenetically did not affect narrowband oscillation in either LGN firing or cortical excitatory currents, suggesting that this oscillation reflects unidirectional flow of signals from thalamus to cortex.

Cortical states control visual spatial perception

“…First, narrowband gamma in mouse V1 has origins and mechanisms distinct from broadband gamma (Saleem et al, 2017). Second, our effects on gamma and correlations were not directly elicited by visual attentional cues, as in primate studies.…”

“…The power spectral density (FFT of the autocorrelation of the LFP) was calculated during the pre-stimulus and stimulus presentation epochs. Narrowband gamma (50-70 Hz) residual power was estimated by fitting the spectral density between 30-90 Hz, excluding 50-70 (Saleem et al, 2017). Residual low frequency power was estimated in the same manner, by fitting between 2-20 Hz excluding 4-12 Hz.…”

Snapshots of the Brain in Action: Local Circuit Operations through the Lens of γ Oscillations

“…␥ oscillations in the 20 -80 Hz range in cortex are thus largely cortical in origin and may result from the activity of multiple laminarly distinct generators, but ␥ sources may vary across species. ␥ power in the LFP can also be inherited from long-range corticocortical synaptic connections and can entrain local neurons (Engel et al, 1991;Roelfsema et al, 1997;Tallon-Baudry et al, 2001;Gregoriou et al, 2009). ␥ activity recorded in the LFP at any particular cortical site may thus emerge from a mix of local and long-range circuit operations, presenting experimental and analytical challenges to assigning underlying sources and mechanisms.…”

“…Repeated visual stimulation results in increased ␥-band synchronization among putative cortical pyramidal neurons and interneurons, even when overall firing rates decrease (Brunet et al, 2014). ␥ power likewise varies with a number of other stimulus features, as reviewed extensively by Ray and Maunsell (2015). ␥ frequency rises with increasing stimulus contrast and varies over cortical distance in response to stimuli with spatially variable contrast values (Ray and Maunsell, 2010).…”

“…Activity in the ␥ range can represent the outcome of more than one neural mechanism, either independently or in coordination. Although the observed frequency bands are approximately similar, ␥ activity varies across an array of species from insects to humans (Ribary et al, 1991;Eckhorn et al, 1993;Laurent et al, 1996;Nase et al, 2003) and across brain regions, including the olfactory bulb, thalamus, hippocampus, and cortex (Ghose and Freeman, 1992;Pinault and Deschênes, 1992;Steriade et al, 1993Steriade et al, , 1996Chrobak et al, 2000;Kay, 2015). ␥ oscillations are also significantly modulated in peak frequency and power across behavioral and developmental states.…”