Basic and Clinical Neuroscienceswith Robert Hawkins, PhD, current research interests are the aggregation of presynaptic proteins during LTP and the roles of nitridergic neurons in the neuronal circuit for siphon withdrawal in Aplysia conditioning. He received his PhD in psychology from the University of California, San Diego, and is currently professor at the Center for Neurobiology and Behavior, College of Physicians and Surgeons, Columbia University.
Synopsis
How do we learn? And how do we retain that information? The field of synaptic plasticity, which addresses these questions, has exploded in recent years. In this timely lecture, Dr Robert Hawkins discusses the role of the hippocampus and temporal lobes in handling memory and compares them in their respective roles and capacities of transmitting and storing memory. Focusing on the important neuronal phenomenon known as long-term potentation, Dr Hawkins illustrates the synaptic plasticity that occurs when neurons process and store memory information.
The hippocampus and the neocortex play a symbiotic relationship in how memory is processed (or discarded). The hippocampus has a "time-limited role" in storing memories: It learns things in a single trial yet has a small capacity for storing this information. In contrast, it is thought that the neocortex requires more than a single trial to learn information, yet its capacity is limitless, its storage of memory is permanent; whereas in the hippocampus, the memory is vulnerable to "accidents" (i.e., brain injuries).
Interestingly enough, memory goes through a series of stages: encoding, consolidation, an accident-prone stage where the memory can be "forgotten," and the final stage where the hippocampus helps the neocortex "rehearse" the memory so that it is securely stored in it. After the amalgamation of the memory is complete, the hippocampus can forget the memory and quickly learn new ones.
But how do we get good at what we do after that memory is stored? The brain clearly shows that practice makes perfect indeed. By discussing different types of learning, such as priming, classical conditioning, habituation, and sensitization, Dr Hawkins shows the phenomenon of long-term potentiation (LTP), wherein if you give a series of high frequency electric stimulations to a neuron synapse, the synapse potentiates or strengthens. Therefore, it becomes more sensitive to transmitting information. This gave rise to the idea of the Hebbian potentiation: If you have presynaptic action potentials at approximately the same time as postsynaptic action potentials, then the synapse between those cells would get strengthened. The biological mechanisms behind LTP involve AMPA-type receptors for glutamate and calcium flux channels, which stimulate a number of kinases.
LTP has tremendous implications not only for learning but also for strengthening memory (and hence learning) and in those whose memories are failing. If we practice a task, are we voluntarily potentiating specific synapses? Those are the types of questions for future investigation.
