Spatial modulation of hippocampal activity in freely moving macaques

Area of Science:

• Neuroscience
• Cognitive Science
• Primate Behavior

Background:

• The hippocampal formation's role in spatial navigation is established, but direct evidence from freely moving primates is limited.
• Concurrent monitoring of head and gaze is crucial for understanding spatial representation in naturalistic behaviors.

Purpose of the Study:

• To investigate how the hippocampal formation represents three-dimensional (3D) space in rhesus macaques during free foraging.
• To determine the influence of head and gaze stances on neural activity within the hippocampal formation.

Main Methods:

• Recorded neural activity in hippocampal regions of rhesus macaques during unconstrained movement in an open environment.
• Tracked head and eye movements concurrently with neural recordings.
• Analyzed neural data for theta activity, phase-locking, phase precession, and spatial variable encoding.

Main Results:

• Theta activity was observed at movement onset and modulated by saccades.
• Most hippocampal neurons encoded a mix of spatial variables, with facing location and allocentric direction being dominant.
• Spatial representations were primarily in head coordinates, not gaze coordinates.
• Eye movements significantly modulated neural activity across all recorded hippocampal regions.

Conclusions:

• The macaque hippocampal formation employs a multiplexed code for representing 3D space.
• Head orientation and eye movement dynamics are key components of spatial representation during active exploration.
• These findings advance our understanding of the neural basis of navigation in primates.