Rhythmic revelations Neural representations and oscillatory dynamics in the cortico-hippocampal system

The brain continuously integrates sensory, motor, and cognitive information to support adaptive behavior. Using electrophysiological recordings in freely behaving rats, this thesis investigates interactions between sensory cortices, the perirhinal cortex (PER), and the hippocampus (HPC) during a multisensory object discrimination task. Chapter 2 reviews the functional role of the PER in object and spatial processing. While traditionally associated with object perception, converging evidence from primate and rodent studies suggests a broader role for the PER in integrating spatial and contextual information. Chapter 3 examines how sensory and reward-related information is represented across sensory cortex, PER, and HPC. We show that although sensory cortices and the hippocampus encode object identity, PER neurons predominantly signal trial outcomes, particularly reward omission, indicating a role in motivational rather than perceptual processing. Chapter 4 investigates the role of theta oscillations in coordinating neural activity across sensory cortices and the hippocampus, demonstrating that theta phase entrainment supports interregional communication during object discrimination. Chapter 5 further explores how hippocampal theta rhythms shape object recognition driven by whisker stimulation, revealing that theta oscillations regulate sensory processing within specific temporal windows. Together, these findings advance our understanding of dynamic coordination within the cortico-hippocampal network, highlighting how sensory, cognitive, and reward-related signals are integrated to enable flexible perception and decision-making.