ABSTRACT
Traditionally, neurons have been viewed as specialized for single functions or a few highly related functions. However, at the higher levels of processing, neural specialization is less obvious, rather a mix of disparate, seemingly unrelated, sensory, cognitive and behavioural quantities drive neural activity. Task relevant variables can be decoded by reading out populations of neurons as the neural code is highly distributed. Here we show that this seems to be the case also in the dentate gyrus subregion of the hippocampus. Using calcium imaging we simultaneously recorded the activity of hundreds of cells from the dentate gyrus of mice while they freely explored an arena. Their instantaneous position, direction of motion and speed could be accurately decoded from the neural activity. Ranking neurons by their contribution to the decoding accuracy revealed that the response properties of individual neurons were often not predictive of their importance for encoding position. Furthermore, we could decode position from neurons that were important for encoding the direction of motion and vice versa, showing that these quantities are encoded by largely overlapping populations. Our analysis indicates that classical methods of analysis based on single cell response properties might be insufficient to characterize the neural code and that the lack of observation of easily interpretable place cells in one brain area is not necessarily the indication that position is not efficiently encoded in that area.
