Fig. 3.

Thalamic theta units express a smaller degree of bursting during spindle periods. A: log-scale ISI histograms for a representative fast-spiking theta unit during theta (left) and spindle (right) periods. B: log-scale ISI histograms for representative slow-spiking theta unit during theta (left) and spindle (right) periods. The red horizontal line denotes the units within bursting mode. C: estimation of burst length for fast-spiking theta cells. The majority of burst segments are composed of 3 spikes. Right inset: the higher number of bursts (defined as 3 consecutive spikes with an interspike duration of 4 ms) per second during theta periods (red) compared with spindle periods (blue; P < 0.05). D: theta (red) and spindle (blue) periods share similar bursts duration (P > 0.05). The highest number of burst counts occurs for the length of 4–7 ms for both periods. E: representative 700 ms autocorrelogram of a fast-spiking theta unit during theta periods (left) compared with spindle periods (right). F: representative 700 ms autocorrelogram of a slow-spiking theta unit during theta periods (left) compared with spindle periods (right). G: burst frequency histogram reveals a predominantly low frequency of the burst counts for spindle periods (blue), compared with theta periods (red). H: state-dependent firing pattern of thalamic theta units. Two second duration plots of spike times for 3 fast-spiking units recorded from AV during theta periods (top) and spindle periods (bottom).