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Parietal and hippocampal activity in the rhesus monkey during a virtual navigation task| old_uid | 12437 |
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| title | Parietal and hippocampal activity in the rhesus monkey during a virtual navigation task |
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| start_date | 2013/05/14 |
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| schedule | 16h |
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| online | no |
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| location_info | 1er étage, salle D52 |
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| summary | Many goal-directed behaviours of everyday life require individuals to find their way towards specific locations. Spatial orientation and navigation require an internal model whereby important environmental landmarks are encoded relative to the subject or to each other. The contribution of the hippocampus (HPC) and the posterior parietal cortex (PPC) to the representation of space is well documented via imaging and lesion studies in human. Yet, neuronal activity underlying spatial representation has been so far only largely studied in the rodent. Here, we aimed at understanding how neurones in the PPC and the HPC support navigation in the closest experimental model to human, the macaque monkey. To this end, we trained two rhesus macaques to manoeuvre in a virtual reality environment with a joystick. Animals moved on the paths of a radial star maze, learning by trial and error, the location of a reward in one of the arms. Only distal landmarks outside the paths allowed locating the goal. We recorded 184 cells in the HPC and 130 in the PPC in two monkeys. More than half of the cells showed activity modulated by the task. These activities were more frequent at the starting points and at decisional points. In the HPC, only less than 10% of the cells exhibited pure encoding of the animal's position inside the virtual maze. These cells resembled typical place cells in rodents. However, the majority of selective cells showed activity in multiple positions that were explained by a brief visual saccade to a meaningful landmark regardless of the position of the animal. The relevance of the landmark to navigation appeared more important then its physical properties. Indeed, when the goal position was changed after learning, cells exhibited new selectivities related to the newly learned goal position. In the PPC, cells coded egocentric positions relative to specific landmarks or to the rewarded area. As in the HPC, the meaning of landmarks appeared more important than its visual appearance. In summary, HPC contains allocentric representations (by signalling external landmark irrespective of self-position) and PPC a mixture of egocentric and allocentric representation (signalling self-position, but relative to external landmark). Both activities would appear critical to navigation. |
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| responsibles | Pascalis |
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