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Conférences du GDR

Prochaine conférence du GDR-Le 26 Novembre 2021 à 13h

par le Professeur Colin Lever (Durham University, UK)

Vector trace cells in the subiculum of the hippocampal formation

Successfully navigating in physical or semantic space requires a neural representation of allocentric (map-based) vectors to boundaries, objects and goals. Cognitive processes such as path-planning and imagination entail the recall of vector representations, but evidence of neuron-level memory for allocentric vectors has been lacking. Showing such evidence is the main focus of the talk, centred on (Poulter et al, 2021, Nature Neuroscience) and unpublished work in 2-D Virtual Reality. I will first introduce the subiculum, and argue that we should end the neglect of this hippocampal region, e.g.: a) its expansion from the great apes to Pan/Homo clade may be the biggest ‘jump’ in primate hippocampal evolution; b) the subiculum may be the key hippocampal node in the default mode network.

I will describe a novel neuron type, the vector trace cell (VTC), whose firing generates a new vector field when a cue is encountered and a ‘trace’ version of that field for hours after cue removal. (Memory duration is likely much longer in other circumstances.) VTCs are concentrated in the distal (not proximal) region of subiculum (i.e. distal to CA1), consistent with anatomical evidence linking the distal subiculum to the “Where? Memory” pathway. Compared to non-trace cells, VTCs fire at further distances from cues and exhibit earlier-going shifts in preferred theta phase in response to newly introduced cues. This latter finding demonstrates a novel theta-linked neural substrate for memory encoding.

VTCs suggest a vector-based model of computing spatial relationships between an agent and multiple spatial objects, or between different objects, freed from the constraints of direct perception of those objects. Vector representations may be used to organize conceptual or semantic memories in quasi-physical and non-physical spaces.

Pour ceux d’entre vous qui n’ont pas pu assister à la conférence précédente:

La conférence de Leila Reddy est accessible

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