Spatial view cells in the primate hippocampus: effects of removal of view details.

Hippocampal function was analyzed by making recordings from hippocampal formation neurons in macaques actively walking in the laboratory. "Spatial view" cells, which respond when the monkey looks at a part of the environment were analyzed. It is shown that many of these cells retain their spatial characteristics when the view details are obscured totally by curtains and by darkness. It is shown that many of these cells respond more when the monkey is gazing toward one location in the room than toward other locations, even though none of the view details can be seen. Such cells were found in the CA1 region, the parahippocampal gyrus, and the presubiculum. Other cells stopped responding when the monkey looked toward the normally effective location in the environment if the view details were obscured. These cells were in the CA3 region of the hippocampus. The results indicate that for CA3 cells, the visual input is necessary for the normal spatial response of the neurons, and for other cells in the primate hippocampal formation, the response still depends on the monkey gazing toward that location in space when the view details are obscured. These latter cells therefore could reflect the operation of a memory system, in which the neuronal activity can be triggered by factors that probably include not only eye position command/feedback signals, but also probably vestibular and/or proprioceptive inputs. This representation of space "out there" would be an appropriate part of a primate memory system involved in memories of where in an environment an object was seen and more generally in the memory of particular events or episodes for which a spatial component normally provides part of the context.