Visual cortex neurons phase-lock selectively to subsets of LFP oscillations

It is generally thought that apart from receptive field differences, such as preferred orientation and spatial frequency selectivity, primary visual cortex neurons are functionally similar to each other. However the genetic diversity of cortical neurons plus the existence of inputs additional to those required to explain known receptive field properties, might suggest otherwise. Here we report the existence of desynchronised states in anesthetised cat area 17 lasting up to 45 minutes, characterised by variable narrow-band local field potential (LFP) oscillations in the range 2 - 100 Hz and the absence of a synchronised 1/f frequency spectrum. During these periods, spontaneously active neurons phase-locked to variable subsets of LFP oscillations. Individual neurons often ignored frequencies that others phase-locked to. We suggest that these desynchronised periods may correspond to REM sleep-like episodes occurring under anesthesia. Frequency selective codes may be used for signalling during these periods. Hence frequency-selective combination and frequency labelled pathways may represent a previously unsuspected dimension of cortical organisation.