Neural dynamics and coding in the cortico-hippocampal hierarchy during multisensory and mnemonic processing

The cortico-hippocampal hierarchy consists of lower order sensory areas and higher-order associative areas. The cortico-hippocampal hierarchy processes and integrates peripheral sensory information and integrates it with episodic memory systems. In this thesis, we advance our understanding of how sensory stimuli are represented along different stages of the cortico-hippocampal hierarchy.
This thesis represents a collection of studies that investigate the cortico-hippocampal hierarchy during free behavior in rodents. Animals were trained to recognize sensory cues associated with reward. During these experiments, cortico-hippocampal electrophysiological activity was recorded using intracortical tetrode recordings from areas at different stages of the cortico-hippocampal hierarchy: sensory areas, multimodal association area perirhinal cortex and the hippocampus. These experiments allowed us to investigate neural representations and dynamics along the cortico-hippocampal hierarchy during multisensory and mnemonic processing.
Four aspects of multisensory and mnemonic processing are investigated. In Chapter 2, we report the neural representations in the perirhinal cortex during multisensory discrimination, while comparing those to neural representations in sensory cortices and the hippocampus. In Chapter 3 we investigate neural synchronization by analyzing the local field potentials in these areas, and single cell phase entrainment thereon. Chapter 4 investigates non-sensory signals in sensory areas visual and auditory cortices. Chapter 5 investigates a computational model which could explain how active inference underlies decision making during tactile perception using whiskers in rodents.
This thesis provides an account of our efforts to further understand neural representations and mechanisms underlying perception, object recognition and decision-making. These works demonstrate the versatile processing of the neocortex and its harmonious orchestration, which underly multisensory and mnemonic processing.