Freyja Olafsdottir:

Institute of Behavioural Neuroscience. UCL.

haufrey@gmail.com

Predicting Future Trajectories: The Role of Sleep

In 1948, Edward C. Tolman put forward the hypothesis that animals contain a ‘cognitive map’ of the world which allows them to navigate along well-worn routes, as well as support their ability to take novel routes.  The neurobiological mechanism underlying the former function has been attributed to the so called ‘place cells’ (O’Keefe & Nadel, 1978) - cells that have a spatial firing correlate, while attempts to elucidate the latter function have been met with challenges (references). The challenge lies in the consistent finding that the formation of place fields – spatial firing fields, is dependent upon the animal traversing an environment.  However, recently Gupta and colleagues (2010) found that during non-REM sleep sharp-wave ripples (SWR) in the hippocampus - traditionally associated with replay of wakeful neural activity (e.g.Wilson & McNaughton, 1995), pre-played a novel route in a familiar environment.  Furthermore, Hassabis and colleagues (2007) found that the hippocampus supports the ability to reconstruct novel images Thus, perhaps the hippocampus may underlie an animal’s ability to take novel routes, and that this ability is dependent on SWR during sleep.  To assess this hypothesis, a study has been designed to specifically ‘encourage’ rats to construct a novel route in a familiar environment.  Specifically, rats will be allowed to explore two linear tracks that are separated from each other by a middle track.  During exploration of the disconnected tracks, single neuron activity of cells in CA1 of the hippocampus will be recorded.  After a period of sleep, where SWR will be recorded, the three tracks will be connected and activity recorded while the rats explore the connected track.  The sequence of neural activity observed during exploration of the connected track will then be used to decode activity during SWR in order to investigate whether the hippocampus had pre-played the novel route along the connected track.