Figure 4.

Network oscillations as an intrinsic reference frame for partitioning spike sequences in auditory cortex. (a) Sound wave of the 52 s sequence comprising natural and environmental sounds presented during the experiment. Dashed lines illustrate the random selection of 10 stimulus epochs used for the decoding analysis (stimulus epoch duration not to scale). (b) Spike raster from one example neuron with spikes colour-coded according to the phase of the concurrently recorded 2–6 Hz LFP during multiple repetitions of each stimulus epoch. (c) Schematic of the different partitioning schemes within a stimulus epoch of width T. The timing of spikes can be measured by temporal binning relative to stimulus onset. This ‘time-partitioned code’ is defined as the vector consisting of the number of spikes per time bin. Alternatively, the timing can be measured relative to an intrinsic slow oscillatory signal. Here, the phase of such an oscillation was divided into four phase quadrants and spikes are colour-coded by their respective phase angle. This ‘phase-partitioned’ code is defined as the vector consisting of the number of spikes per phase range. For comparison, a ‘spike count’ code was defined as the total number of spikes within the window T. (d) Stimulus information provided by each code across neurons sampled in auditory cortex (mean ± s.e.m.; n = 40). Figure is redrawn from [50].