Structural Synaptic Remodeling in the Perirhinal Cortex of Adult and Old Rats Following Object-Recognition Visual Training

Abstract

The ultrastructural features of layer II synapses in the perirhinal cortex of adult (4- to 6-monthold) and old (25- to 27-month-old) rats exposed to a six-session object recognition visual training were investigated by morphometric methods. The comparative analysis showed a higher synaptic numeric density, a lower synaptic average area, and a lower percentage of megasynapses (S > 0.5 µm²) in old trained rats versus controls, and a higher percentage of small (S < 0.15 µm²) junctions in adult trained rats versus controls. The more marked synaptic remodeling underlying memory consolidation in the perirhinal cortex of old rats might reflect a pre-existing lower dynamic status.