“…we investigated neural responses to a silent, 15 iso-luminant, black and white movie in head-fixed mice without any task or locomotion demands, or rewards. The activity of most neurons (97%, 6554/6785) in the thalamo-cortical visual areas [LGN, V1, AM/PM] was significantly modulated by the 30s long movie clip. Surprisingly, a third (33%, 3379/10263) of hippocampal–dentate gyrus, CA1 and subiculum–neurons showed movie selectivity, with elevated firing in specific movie sub-segments, termed movie-fields. On average, a cell had more than 5 movie-fields in [the] visual areas, but only 2 in [the] hippocampal areas.” (Purandare and Mehta 2022, abstract).

The hippocampal formation is activated during the learning of new associations when two stimuli are temporally overlapped, even if the activated cells are not necessary for the learning as verified using a hippocampectomy (Berger and Thompson 1976; Swain, Thompson et al. 2011). This suggests that all new information [even if it does not need to be consolidated in neocortex--but see Pavlov 1927] is transmitted through the hippocampal formation. The experiments of Purandare and Mehta (2022) support this viewpoint for the serial presentation of movie images presented to stationary animals (also see Footnote 1).

What this means is that every time you attend a lecture, the hippocampus is activated according to the serial order of the lecture, as we have argued (Tehovnik, Hasanbegović, Chen 2024). Now, whether the details of the lecture are sufficiently consolidated to obtain an ‘A’ in the course depends as much on the lecture as it does on the way one memorizes the lecture material prior to an examination. During an examination, if the lecture material is well consolidated in the neocortex, then the details will be retrieved via the hippocampus to achieve an A grade. Of course, the order of the retrieval does not need to match the order of the lecture or the order of pre-exam memorization, albeit matching either should facilitate the speed at which the exam questions are answered. Significantly, AI models can learn by the repetition of sequences of ‘neural discharges’, thereby facilitating the retrieval of familiar sequences (citation: Google AI, Aug. 14, 2024) to suggest that AI, like the human brain, has a hippocampal analogue.

Footnote 1: That the number of movie fields is reduced from up to10 per cell in the visual system (i.e., LGN, V1, and AM/PM) to up to 2 per cell in the hippocampus (Fig. 2a of Purandare and Mehta 2022), indicates that the information is being partitioned by the neurons in the hippocampus for storage in specific locations of the neocortex. Unlike the topographic maps of the visual system that are interconnected for the immediate transfer of information across the sensory field, the hippocampus is non-topographic and ordered into independent channels (Bartlet, Doty et al. 2005; Doty 1965, 1969; Knight 1964), such that elements of sensation (faces, places, etc.) can be stored separately (Brecht and Freiwald 2012; Bruce et al. 1981; Schwarzlose et al. 2005; Schwiedrzik, Freiwald et al. 2015; Freiwald and Tsao 2010).