CCN Colloquium: "Cognition in the noise: remembering, remapping, and reframing cognition dynamics"

How do we learn and know? For much of my career it was assumed that neurons respond to external stimuli as if to represent them, but an equally plausible model asserts that neuronal activity is fundamentally internally-organized and instead fit to external features of the world. I will report on our investigations of acquired cognition through studies of spatially-tuned cells in the medial entorhinal cortex and hippocampus. We started with the "noise," uncertainty of spatially-tuned action potential discharge, a clue that cognitive variables might be driving that noise. Our studies of knowledge embrace the interplay across the molecular, synaptic, network, and behavioral levels of biological organization. I'll discuss the discharge of hippocampus place cells and molecular signaling during phencyclidine intoxication and I will discuss head-direction cells in the medial entorhinal cortex as different examples of internally-organized neural representations during purposeful navigation of the environment. We will then consider how cognitive control training causes learning-to-learn, persistently enhanced information processing, altered synaptic function and molecular expression across synaptic populations of the entorhinal-hippocampal system. Finally, I will discuss recent studies of the hippocampal remapping phenomenon, in which place fields rearrange according to cell-specific rules when the environment is changed. I suggest a "reregistration" reinterpretation, that hippocampal neural activity is fundamentally internally-organized such that cofiring relationships amongst the cells are largely invariant across distinct environments, despite the cell-specific rearrangement of place fields. Collectively these studies promote a view that rather than represent external information, subjective, internally-organized activity in the entorhinal-hippocampal circuit is actively fit to the environment for processing information that enables navigation and serves cognition. André Fenton is a Professor of Neural Science. He studies how brains store experiences as memories, and how the expression of knowledge activates information that is relevant without activating what is irrelevant. His laboratory uses molecular, electrophysiological, behavioral, engineering, and theoretical methods to investigate these fundamental and interrelated issues in neuroscience.