Details

Autor(en) / Beteiligte

• Wills, Thomas Joseph

Titel

Attractor dynamics in the hippocampal representation of the local environment

Ort / Verlag

ProQuest Dissertations & Theses

Erscheinungsjahr

2005

Quelle

ProQuest Dissertations & Theses A&I

Beschreibungen/Notizen

• Pyramidal cells of the CA1 field of the hippocampus fire at relatively high rates only when the animal is in a restricted region of the environment (Place cells). A collection of these cells may form the neural substrate of a map-like representation of the animal's environment. Previous work has shown that place cells have different firing patterns, or 'remap', in different environments. In this thesis, it was found that exposing rats to environments differing in the shape (square vs circle), colour (brown vs white) and texture of their walls resulted in rapid remapping between the environments. The environments were then substituted, so that both were constructed from the same deformable box, and only differed in their shape (square vs circle). The place cells remained remapped in this condition. In order to investigate the nature of the remapped place cell representations, rats were then exposed to a series of octagonal environments which varied incrementally from square-like to circle-like. Despite environmental shape changing continuously, all recorded place cells switched abruptly between square and circle representations: no intermediate firing patterns were observed. Furthermore, all simultaneously recorded cells switched between representations at the same point in the octagon series. In 2 animals, remapped place cells were tested in a series of hybrid shapes which were octagonal at one end and square at the other. Place cells always responded to these shapes as either an octagon or a square but different cells responded differently to each hybrid. These results can be interpreted as evidence for the existence of attractor networks in the hippocampal representation of space. Under some circumstances, representations of familiar environments form stable attractors, and environmental inputs sufficiently similar to these cause the place cell representation to converge onto them. The results also suggest that place cells can form a coherent, map-like representation of the environment.