Place cells in the hippocampus: Eleven maps for eleven rooms

Abstract

Significance The hippocampus is thought to store a large number of experiences that, despite their similarity, can be individually retrieved with minimal interference. Studies have shown that place cells in hippocampal area CA3 form statistically independent representations of pairs of environments. It has remained unclear, however, whether CA3 place cells maintain this independence when the number of environments is increased. We recorded activity from CA3 in 11 environments with nearly identical geometric features. Spatial firing patterns remained uncorrelated across all 55 pairs of environments, with minimal overlap in the populations of active cells. The data suggest that the capacity of the CA3 network is large and speak against extensive recurrence of spatial motifs across experiences.

Spatial representation in the hippocampal formation: a history

“…Not only do they have periodic firing fields but the relationship between the firing fields of different cells also follows a different rule. Whereas place cells often remap completely between environments and multiple fields can appear in large environments, with no more overlap in the subset of active cells than expected by chance 106,153,[160][161][162] , the ensemble activity of grid cells is normally maintained coherently from one environment to the next, without changing phase or orientation relationships between cells 145,163 , much like in early recordings from MEC cells before grid cells were discovered 22 . The coherence of the grid map is particularly strong within ensembles, or modules, of similarly scaled grid cells 154 .…”

Topography of Place Maps along the CA3-to-CA2 Axis of the Hippocampus

“…In contrast, in the proximal and middle part of CA3, pairs of representations overlapped minimally. Previous work has shown that the lack of overlap in the proximal and middle region is maintained when the number of test rooms is increased from 2 to 11, suggesting that this part of the network has considerable storage capacity (Alme et al, 2014). In the next experiment, we asked whether overlap between representations increases at more distal levels when test rooms are added.…”

“…Two forms of remapping have been described. During global remapping, a new subset of the place-cell population is activated (Muller and Kubie, 1987;Wilson and McNaughton, 1993;Leutgeb et al, 2004Leutgeb et al, , 2005bColgin et al, 2008;Alme et al, 2014). Subsets of place cells may overlap between two environments, but those cells that fire in both environments generally fire at unrelated locations.…”

Hippocampal Mechanisms for the Segmentation of Space by Goals and Boundaries

“…Many studies have emphasized the random nature in which place fields remap Leutgeb et al 2004;Vazdarjanova and Guzowski 2004;Rolls 2013;Alme et al 2014;Rich et al 2014). However, the remapping of place fields to goal locations can be predicted.…”