A Conserved Mammalian Hippocampal Navigation Motif Reconfigured for Primate Vision.

Area of Science:

• Neuroscience
• Comparative Psychology
• Behavioral Biology

Background:

• Spatial navigation relies on integrating external sensory information with internal spatial representations.
• In rodents, hippocampal sharp-wave ripples (SWRs) during pauses are crucial for memory recall during navigation.
• The role of SWRs in primate spatial navigation remains largely unexplored.

Purpose of the Study:

• To investigate hippocampal activity, specifically SWR dynamics, during spatial navigation in freely moving primates (marmosets).
• To compare navigation strategies and SWR patterns between marmosets and rodents.
• To understand how primate visual specializations influence the conserved hippocampal navigation motif.

Main Methods:

• Recorded hippocampal local field potentials in marmosets navigating a 3D maze.
• Analyzed the relationship between behavioral states (locomotion, pauses) and SWR rates.
• Correlated SWR activity with head orientation, visual exploration, and memory-guided navigation.

Main Results:

• Marmosets exhibit alternating periods of locomotion and pauses during navigation, similar to rodents.
• Pauses in marmosets are longer and associated with increased SWR rates compared to locomotion.
• SWRs were more prominent during stable head orientations toward goals and reduced during rapid head movements, increasing with memory use.

Conclusions:

• A phylogenetically conserved hippocampal navigation motif, involving SWRs during pauses for memory-guided computation, exists across mammals.
• Primate evolution has adapted this motif by integrating it with active visual sampling and gaze control for vision-guided navigation.
• The core hippocampal navigation algorithm is preserved, but its sensory inputs and behavioral context are modified for diurnal, vision-guided species.