Neuroscience Seminar: Fear and Memory

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Dr. Fred Helmstetter. Photo courtesy of uwm.edu

Even the briefest of experiences can change the biological makeup of an organism’s brain for the rest of its existence. Well, how exactly does this changing process work?

Fred Helmstetter, Distinguished Professor at the University of Wisconsin—Milwaukee, visited St. Mary’s on October 17 to answer this question from the perspective of fear conditioning. First, he went over classical conditioning—an automatic type of learning that we associate with Pavlov’s dog experiments. This conditioning is essentially the process through which a subject learns to respond a certain way to a previously neutral stimulus. Fear conditioning, then, describes how subjects learn to fear things.

Rats are often the choice animal for psychology and neuroscience experiments, because their brains fundamentally work the same, but fear conditioning is also something we can test on humans. Dr. Helmstetter described a simple model: people are shown images on a computer screen. Certain images are accompanied by electric shocks. The subjects quickly learn to associate those images with the shocks.

This is a straightforward experiment, but by imaging the subject’s brain under an MRI while he or she completes it, scientists can learn about how the brain processes the stimuli.

As may be expected, memory plays a critical role in this natural learning process. Experience—from little shocks associated with a shape to the narrative of a complex event—is encoded in the brain. There is a period when this encoded experience, this memory, can be disrupted, but through what scientists call consolidation, it becomes “solid” over time, able to be retrieved as long term memory later in life. The speaker stressed, however, that memory retrieval is actually an active process: decoding and pulling out a well-formed memory makes it susceptible to disruption again.

This implies that using memory can change it. From the perspective of fear conditioning, this makes perfect sense. In Dr. Helmstetter’s words, “Say you meet Ivan when you’re 25, and never again for ten years. You have to update your representation of him.” Ivan may have been a scary man ten years ago, but perhaps now he is different, and the brain accepts this possibility. From imaging, scientists have found that using memory triggers similar processes to those that occurred in its original formation.

The professor then went into more scientific depth regarding his recent work on fear conditioning. He has been using optogenetics, an incredibly precise method of controlling cells, to zoom in on cells in the amygdala through the course of fear experiments. Through this relatively new technological process, he managed to affect the level of control rats had of their own memory as they worked through standard fear learning experiments.

Dr. Helmstetter ended the seminar mentioning that he is always interested in bright and motivated students to work in his graduate program, and suggested that any of those interested in the audience contact him.

The third and final neuroscience seminar is scheduled for Monday, October 24. Dr. Margaret McCarthy from UMD’s School of Medicine will speak on sex differences in the brain.

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