Cellular and network dynamics of temporal lobe memory structures

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My laboratory investigates the neural processes that underlie memory permanence (consolidation). We are most interested in the episodic subtype of memory which can be described as recollections of the "who, what, where, and when" aspects of unique experiences. These memories are dependent on the medial temporal lobe memory system which includes the broad inter-connections between the neocortex and the hippocampus in the brain. The patterns of neural activity in this extended circuit are not only important for encoding memories as they occur (that is, ONLINE memory encoding) but also for strengthening existing memories after the fact (that is, OFFLINE memory consolidation). Our laboratory is especially interested in how different patterns of offline spontaneous activity in the period just after active learning (especially during slow-wave activity like that occurring during sleep) may play a role in memory consolidation. The period just after learning has been demonstrated to be essential to the maintenance of memory itself. For example, following a particular novel episodic experience, hippocampal neuronal activity is known to "replay" the actual sequenced patterns that replicate those occurring during the actual experience itself. This replay may be a form of "neural rehearsal" since the more it occurs, the better future memory performance for that specific information actually is (and vice versa - interfering with replay worsens subsequent memory performance). This can be summarized by the saying: "practice makes permanent". The ability of the brain to engage in this rehearsal also appears to be state dependent, occurring only when the brain is actually "offline", for example during sleep. Thus, studying how this activity can take place is important to understand its role in consolidation. Our continuing program will focus on 3 main objectives: 1) To identify and characterise the circuit dynamics in the medial temporal lobe that shape slow-wave offline states using high-density multi-site neurophysiological methods and both chemo- and opto-genetic techniques. 2) To use this information to assess how manipulations of circuit dynamics during slow-wave and other offline states might directly affect memory consolidation. 3) To contrast and compare our activity-dependent model of memory permanence to the more classic molecular synaptic model. Understanding the brain mechanisms of memory is likely one of the most intriguing and potentially important questions in neuroscience today. Our research will help shape how we might optimally deliver information in order to ameliorate memory. Another important and direct contribution of our research program will be to evaluate very simple manipulations that might have profound influences on modulating memory strength and longevity.