of a memory task in the absence of changing sensory or feedback cues (Fig. 4A). Importantly, several measures of the place cell metric, including the duration of activity episodes of the neurons and the temporal relationship of their spikes relative to the reference theta oscillation cycle during translational behavior (O’Keefe and Recce, 1993) were similar in the internally organized sequences during the delay period, when the rats were required to run steadily in a wheel and remember a previously made choice (Pastalkova et al., 2008). The implication of these observations is that the physiological mechanisms which govern the progression of cell assembly sequences in the hippocampus during navigation and cognitive behaviors are quite similar. The behavioral relevance of self-organized sequential activity is emphasized by the observation that identical initial conditions (e.g., a left choice was rewarded) induced a similar assembly sequence each time, whereas different conditions (i.e., different memories) gave rise to uniquely different trajectories, which accurately predicted upcoming choices in the maze, including erroneous turns (Figure 4A). In situations when keeping track of two concurrent information streams (local and distant cues) were required for correct behavioral performance, two distinct assemblies toggled between representations of the two spatial frames (Johnson
