Quiescent dependent consolidation of spatial and motor-skill memory: investigation of the neural mechanisms with animal models and computational modelling

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Memory is a crucial brain function for humans and other animals. It has been broadly categorized into declarative memory (a type of memory that you can verbally describe, for example, the breakfast you had this morning) and non-declarative memory (a type of memory that you cannot verbally describe, for example, the motor skill required to ride a bike). Memory also provides the basis of other higher-order cognitive functions such as decision making. Thus, understanding how the brain learns and remembers is crucial to understanding many brain functions. The goal of my research program is to clarify how different forms of memory are stored and integrated to allow efficient access. In order to explain the mechanisms involved in the acquisition of memory, I propose a theory of Quiescent Dependent Memory Consolidation: Memory is consolidated during sleep when both motor output and sensory input are shut down. The quiescence of sleep, when the brain’s network is free from external interference, provides a permissive environment for memory consolidation. Sleep in mammals is categorized into Rapid Eye Movement sleep (REM sleep) and non-Rapid Eye Movement sleep (non-REM sleep). Our investigation and studies from other laboratories suggest that neural activity in the hippocampus and prefrontal cortex during non-REM sleep is important for consolidation of declarative memory, whereas neural activity in the motor cortex (and possibly dorsal striatum) during REM sleep is important for consolidation of non-declarative memory. However, it is not known how the brain areas that are involved in declarative memory influence the activity of the brain areas that are involved in non-declarative memory, and vice versa, particularly when the memory task involves both declarative and non-declarative components. The evolution of multi-electrode recording, which my lab is at the forefront of, now permits large-scale, multi-site recordings that are necessary to address these questions. Using this technology, I will investigate the interaction of these brain areas when animals learn a declarative type memory task, a non-declarative type memory task and a combined memory task. To elucidate the underlying mathematical principles, I will also construct an artificial neural network model of the brain areas of interest. Mathematical analysis and computer simulation will be performed and the results will be compared with electrophysiological data. My research will improve our understanding of neural plasticity during waking and sleeping, biological mechanisms of memory consolidation and the underlying mathematical principles of memory formation. Because memory is the basis of other higher-order brain functions, my research program will deepen our knowledge of the executive functions such as decision making.