Insensitivity of place cells to the value of spatial goals in a two-choice flexible navigation task
Résumé
Hippocampal place cells show position-specific activity thought to reflect a self-localization signal. Several reports also point to some form of goal encoding by place cells. We investigated this by asking whether they also encode the value of spatial goals, which is crucial information for
optimizing goal-directed navigation. We used a continuous place navigation task in which male rats navigate to one of two (freely chosen)
unmarked locations and wait, triggering the release of reward, which is then located and consumed elsewhere. This allows sampling of place
fields and dissociates spatial goal from reward consumption. The two goals varied in the amount of reward provided, allowing assessment of
whether the rats factored goal value into their navigational choice and of possible neural correlates of this value. Rats successfully learned the
task, indicating goal localization, and they preferred higher-value goals, indicating processing of goal value. Replicating previous findings, there
was goal-related activity in the out-of-field firing of CA1 place cells, with a ramping-up of firing rate during the waiting period, but no general
overrepresentation of goals by place fields, an observation that we extended to CA3 place cells. Importantly, place cells were not modulated by
goal value. This suggests that dorsal hippocampal place cells encode space independently of its associated value despite the effect of that value on spatial behavior. Our findings are consistent with a model of place cells in which they provide a spontaneously constructed value-free spatial representation rather than encoding other navigationally relevant but nonspatial information.
Origine | Fichiers éditeurs autorisés sur une archive ouverte |
---|
Loading...