Walk of life: How brain state, spatial, and social context affect neural processing in rat perirhinal cortex, hippocampus, and sensory cortices

In this thesis I report the results of two in vivo electrophysiology experiments I have conducted during my PhD. During the first experiment, called Touch and See, we developed a new, expanded, micro recording device which allowed us to record from four areas of the rat brain simultaneously; primary visual cortex, barrel cortex, perirhinal cortex, and the CA1 subfield of the hippocampus. In this experiment we investigated how neurons communicate with each other, both within and between areas, and during different brain states; active, quiet, sleeping. We have found that: 1) Gamma oscillations are important for inter-areal communication, but intra-areal communication is mediated by slower brain rhythms. 2) Different types of excitatory and inhibitory neurons are activated during different parts of the gamma cycle. 3) Excitatory and inhibitory neurons are differentially involved in short- and long-range communication. 4) Neurons that were functionally coupled during execution of the task remain coupled even during post-task rest. 5) Finally, we report a new function of the perirhinal cortex in coding spatial segments of the environment. The second experiment was named the Rat Robot project. In this project we investigated whether place fields of rat hippocampal neurons can be used to not only track the position of the animal itself, but also to keep track of the position of other moving agents. We found that even though there was no overlap in firing fields of place cells for the rat and robot, movements of the robot did modulate the activity of rat place cells.