Hippocampus Function Related with Space Map in Humans

Abstract

Objective: Perception of spatial orientation and self-motion can benefit from integration of multiple sensory cues, including vestibular signals. Place cells were found in hippocampus areas, and correlates of head orientation collectively map spatial locations. To elucidate hippocampus function related with spatial orientation in humans, we examined subjects who had undergone hippocampectom. Method: Data were obtained from 16 patients with hippocampus sclerosis and temporal lobe epilepsy. Eleven patients were also investigated after amygdalohippocampectomy. To determine the path integration, they were investigated by modified step test. We also investigated sound lateralization test (the interaural time difference and interaural level difference). Results: A modified step test may provide a sense of direction and path integration. In this test, initially the subjects walk for 1m on a straight road and turn 90° to the right or left, and then walk straight for 1m with their eyes opened. Subsequently they return with their eyes closed. The results of the modified step test got worth after amygdalohippocampectomy. Sound is an important factor of a sense of direction. The insufficiency of the sound lateralization test was detected in patients, and this was also detected after amygdalohippocampectomy. Conclusion: The hippocampus should play a role in path integration and sound lateralization in humans.