When rats negotiate a previously learned T maze for a reward, hippocampal place cells are activated during periods of large-amplitude irregular activity (containing ripples) punctuated by theta activity (Johnson and Redish 2007) when an animal moves (Vanderwolf 1969). The ripple activity is robust when the rats pause prior to deciding which of two arms to choose at a T junction. The place cells signal the arm containing the reward by projecting an efference-copy signal forward and down the arm to be chosen. Communications between the neocortex and hippocampus during periods of ripple activity may be instrumental in choosing the future (Dickey et al. 2022). This idea is reinforced by the finding that a seasoned London taxi driver becomes severely impaired at locating sites in the city following bilateral hippocampal lesions (Maguire et al. 2006), which eliminates the connection between the memories stored in the neocortex and the motor system.
And when narrating a story, memory retrieval via neocortical-hippocampal channels (Hassabis et al. 2007ab) links one’s memories with Broca’s area and M1 to drive the vocal apparatus (Tehovnik, Hasanbegović, Chen 2024). The global reach of the hippocampal formation (see Fig. 1) allows for information to be transmitted globally, and when relating a story, declarative/conscious units need to be concatenated to recreate a historical record of events (see Fig. 2). Historians require an extraordinary system of record-keeping and memory consolidation and retrieval, so that the next generation does not repeat the errors of the past. All stories, however, are contaminated by personal bias, therefore harsh (but fair) peer-review can provide a more balanced record of past events. When studying for the US citizenship exam, ten or so lines of text were devoted to the Vietnam war (1955-1975) in the study booklet, a war that was disastrous for the United States. Such ‘minimization’ of significant history guarantees that a society will continue to repeat the errors of the past: e.g., the Afghanistan war (2001-2021), the Iraq war (2003- 2011), and now the Gaza war (2023-?).
Figure 1: Hippocampal network that transmits information between the outside world and neocortex for long-term storage (i.e., learning) and that transmits information between the neocortex and the outside world for story telling (i.e., retrieval).
Figure 2: Pools of declarative conscious units concatenated to produce the phrase ‘I want to be as scientist’. Here both the neocortex and cerebellum are engaged. The neocortex triggers the automated response, and the cerebellum preserves an efference-copy of the response, which can be altered at the level of the Purkinje neurons via sensory feedback.
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