Our lab studies the neural mechanisms of memory in the everyday sense of the word: the ability to learn new facts and remember recent events.

Although for many years scientists believed that only one form of learning existed in the brain, we now know that multiple memory systems exist. Each of these different systems is specialized for encoding different aspects of experience. In people, structures in the medial temporal lobes, including the hippocampus, are crucial for learning new facts and remembering recent events. Other brain structures are crucial for other forms of learning. For example, the amygdala is crucial for learning emotional associations, and the neostriatum is required for certain forms of skill learning.

My research focuses on how the hippocampus, prefrontal cortex, and other brain areas contribute to memory in experimental animals, mostly rats, and how mechanisms of neuronal plasticity within these structures may underlie memory functions. Experiments in my lab are guided by cognitive, computational, physiological, and pharmacological hypotheses. The basic idea is that the properties of the NMDA receptor allows cells in the hippocampus to conjoin temporally overlapping cortical inputs into representations of events, and that recurrent connections within the hippocampus allow these events to be linked into the sequences that comprise episodic memories. Experiments investigating the links between these different levels of analysis are aimed toward providing an integrated perspective of memory. Doses of NMDA receptor antagonists that block the induction, but not expression, of long-term potentiation (LTP) in the hippocampus also impair learning, but not performance, in several tasks that require the hippocampus. We have found that persistent encoding of environmental information by hippocampal neurons also requires NMDA receptor dependent mechanisms. Thus, learning that requires the hippocampus, stable neural encoding within the hippocampus, and synaptic plasticity within the structure each depends upon NMDA receptor activation. We are now investigating the real-time firing patterns in groups of hippocampal neurons to test new hypotheses concerning how populations of these cells encode learned information.

Visit Dr. Matthew Shapiro's Cognitive and Behavioral Neuroscience of Memory Laboratory for more information.