Retrosplenial and hippocampal synchrony during retrieval of old memories in macaques

Abstract

To understand the neural activity behind recollections of the distant past, we recorded from the hippocampus and retrosplenial cortex of macaques as they retrieved year-old and newly-acquired object-scene associations. Year-old memoranda preferentially evoked retrosplenial sigma oscillations (10-15 Hz), and phase-locking between RSC and eye movements during retrieval. In contrast, gamma-band retrosplenial-hippocampal synchrony was stronger during retrieval of new items. Primate retrosplenial oscillations may therefore guide retrieval of visuospatial events long past.

Circuit dynamics of superficial and deep CA1 pyramidal cells and inhibitory cells in freely-moving macaques

“…Although many aspects of hippocampal physiology are conserved between rodents and primates, differences in oscillatory dynamics [36][37][38][39][40][41] and behavior-specific modula�on [42][43][44][45][46][47][48][49][50][51] suggest there may be phylogene�c specializa�ons that may be uncovered by an understanding of the underlying func�onal cell composi�on. A first-pass bisec�on of hippocampal (and medial temporal lobe) cells in primates into puta�ve inhibitory and excitatory classes (or four groups 52 ) reveals characteris�c responses at both the circuit-level 38,[52][53][54] and cogni�ve/behavioral levels 55,56 .…”