Figure 4.

Internally generated assembly sequences during cognitive activity. A. Sequential firing patterns of hippocampal neurons in a memory task. Center, color-coded spikes (dots) of simultaneously recorded hippocampal CA1 pyramidal neurons. The rat was required to run in the wheel facing to the left during the delay between the runs in the maze. Left, normalized firing rate profiles of neurons during wheel running, ordered by the latency of their peak firing rates during left trials (each line is a single cell). Right, normalized firing rates of the same neurons during right trials. B. Sequential firing patterns of prefrontal pyramidal cells in a working memory task. Middle, cheese odor or chocolate odor in the start area signals the availability of cheese or chocolate reward in the left or right goal area (position 1), respectively. Travel trajectories were linearized (0 to 1). Left, neurons were ordered by the location of their peak firing rates relative to the rat’s position in the maze during left trials. Each row represents the position-dependent normalized firing rate of a single neuron. Right, normalized firing rates of the same neurons during right trials. A, reprinted from Pastalkova et al. (2008). B, reprinted from Fujisawa et al. (2008).