Prof. Masato Taira

Prof. Taira

ISP2012 Symposium Talk Abstract:

Neural mechanisms for navigation: Comparison between the medial parietal region and the parahippocampal gyrus

When we drive to our office, we can take the correct route subconsciously, making a turn or going straight at each intersection. This phenomenon suggests that we may have an internal list of what we have to do at a given location (route knowledge) in our brain. Lesion and neuroimaging studies of humans suggest that the medial parietal region (MPR), including the retrosplenial and posterior cingulate cortices, is critically involved in navigation based on route knowledge. On the other hand, it has been well known that the place cell which codes the location of animal is in the hippocampus and the hippocampus is also suggested to be involved in navigation. In this study, we recorded a single unit activity from the monkey MPR and the parahippocampal gyrus (PG) while the monkey navigated in the virtual environment.

We found that many neurons in MPR showed significant responses to the monkeys' movements in the virtual environment. Many of their responses associated with a specific movement at a specific location (navigation neurons). We also found some navigation neurons whose responses to the same movement at the same location were modulated depending on the route. We further investigated the visual responses of those neurons when the monkeys were shown animations of the navigation route. We observed that the responses of some neurons reduced when the monkeys viewed the preferred field in the segmented animation or in the still image. In PG, we also found that many neurons became active during the navigation task. In those, there were neurons responded to the instruction slides which indicated the destination. We further found the neurons responding to the scene at the middle point of route, which looks like the place cell in the hippocampus.

Thus, these results suggest that neurons both in MPR and PG play a critical role in navigation. MPR neurons may be involved in route-based navigation by integrating location information and self-movement information, however, PG neurons may encode the location information along the route.

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ISP2012 Abstracts