Merging information in the entorhinal cortex: what can we learn from robotics experiments and modeling?

Abstract

Place recognition is a complex process involving idiothetic and allothetic information. In mammals, evidence suggests that visual information stemming from the temporal and parietal cortical areas ('what' and 'where' information) is merged at the level of the entorhinal cortex (EC) to build a compact code of a place. Local views extracted from specific feature points can provide information important for view cells (in primates) and place cells (in rodents) even when the environment changes dramatically. Robotics experiments using conjunctive cells merging 'what' and 'where' information related to different local views show their important role for obtaining place cells with strong generalization capabilities. This convergence of information may also explain the formation of grid cells in the medial EC if we suppose that: (1) path integration information is computed outside the EC, (2) this information is compressed at the level of the EC owing to projection (which follows a modulo principle) of cortical activities associated with discretized vector fields representing angles and/or path integration, and (3) conjunctive cells merge the projections of different modalities to build grid cell activities. Applying modulo projection to visual information allows an interesting compression of information and could explain more recent results on grid cells related to visual exploration. In conclusion, the EC could be dedicated to the build-up of a robust yet compact code of cortical activity whereas the hippocampus proper recognizes these complex codes and learns to predict the transition from one state to another.

Microcircuits for spatial coding in the medial entorhinal cortex

“…A full discussion of grid cell models is beyond the scope of this review [see e.g. (14,(46)(47)(48)(49)], in which we will focus on local excitatory and inhibitory microcircuits in the mature animal, and the extent to which they exhibit connectivity consistent with CAN dynamics. Although there is a large body of work on spatial coding and microcircuits in the MEC or its functional analogues in species ranging from the fly [e.g.…”

Identifying Core Regions for Path Integration on Medial Entorhinal Cortex of Hippocampal Formation

“…These 11 papers include a review article on a robotics experiment and modeling [42], and articles on self-organizing maps [43][44][45]. These four articles are not in the field of neuroscience and were excluded in this paper.…”

Time as the fourth dimension in the hippocampus

“…HS architecture comprises a cascading network suited to rapidly encoding sequences and coincidences between complex cortical signals, under the modulation of motivational signals (Banquet et al, 1997(Banquet et al, , 2005Gaussier et al, 2002Gaussier et al, , 2019Hirel et al, 2013). The HS, through its capacity to bridge temporal intervals separating events (Wallenstein et al, 1998), could thus form the building blocks of memories of sequences.…”

“…Indeed, speed signals could be path integrated over time to give rise to position signals, perhaps via mechanisms involving summation of plateau potentials, or a theta rhythm based clock (Navrátilová and McNaughton, 2014). The elaboration of grid cell activity in MEC would benefit from such a mechanism (Gaussier et al, 2007(Gaussier et al, , 2019Gil et al, 2018). However, the engagement of a time signal for carrying out such integration has not yet been shown, although LEC ramping signals could participate (Section 2.3).…”