Understanding how the Brain Turns Experience into Memory

Brian Gonsalves’ academic interest in the human brain and mind originated with a philosophical approach to those topics, but has evolved into research that is very much based in the down-to-earth realms of neuroscience and imaging techniques.

Brian Gonsalves’ academic interest in the human brain and mind originated with a philosophical approach to those topics, but has evolved into research that is very much based in the down-to-earth realms of neuroscience and imaging techniques.

“When I was a freshman in college they had these freshman seminars, small discussion groups, and one offered by the Philosophy Department was called Mind and Brain,” Gonsalves said. “It talked about the philosophy of the mind and how that’s connected to the human brain, and I was just fascinated by that. I started out as a bio-chemistry major and that shifted me toward biology, neuroscience, and some psychology courses.”

Gonsalves was a freshman from the Boston area attending Maine’s Bowdoin College at the time, and after getting his undergraduate degree there, he went on to earn a Ph.D. in Psychology at Northwestern University. It was there that he was introduced to the work of neuroscience researcher and professor Kenneth Paller, and it was there that his research interest crystalized around the topic of memory.

“In Ken Paller’s lab we were using psychophysiological techniques (EEG) to investigate memory,” Gonsalves said. “Once I started grad school it was all memory.”

Gonsalves joined the University of Illinois as a faculty member in the Department of Psychology and as a member of Beckman’s Cognitive Neuroscience group in 2005. He directs the Cognitive Neuroscience of Memory Laboratory at the Institute, and regularly employs the Headscanner and Trio magnets from Beckman’s Biomedical Imaging Center in his work.

“What we are looking at is to understand the neural bases of two different kinds of memory that contribute to our ability to recognize something that we haven’t encountered before.
– Brian Gonsalves

Gonsalves’ lab has a broad focus on the organization of human memory and seeks, as he writes, to answer “the general question of how memory is implemented in the brain” by delineating “the component processes of memory and how different brain regions subserve these component processes.”

It is research that emphasizes a multimodal neuroimaging approach and is currently centered on two lines: the neural basis of recognition memory, and false memories. Memory, from Gonsalves’ perspective, is a constructive process that is prone to systematic errors, and one method for understanding this most vital cognitive function is to study the brain mechanisms of those errors.

“What we are looking at is to understand the neural bases of two different kinds of memory that contribute to our ability to recognize something that we haven’t encountered before,” Gonsalves said. “Those are typically called recollection and familiarity and refer to the subjective states that are associated with these kinds of memory.”

Gonsalves said familiarity means having a strong sense of knowing someone or something but without any of the associated detail for accurate recall, while recollection involves remembering the associated detail.

“So the idea is that those two different kinds of memories depend on different parts of the medial temporal lobes,” he said. “What we are looking at is that familiarity depends on structures outside the hippocampus, adjacent to the hippocampus, in particular the periehinal cortex; whereas recollection depends on the hippocampus, which is based on work by (Beckman faculty member) Neal Cohen and others that is fairly well-established. The controversial point is whether these structures outside the hippocampus will support – without the hippocampus – the kind of memory that is based on familiarity.”

A recent study related to this topic by Gonsalves and Beckman Fellow Joel Voss found distinct neural substrates that were revealed by priming and recognition, which are behavioral expressions tied to memory. Priming, a response used to measure implicit memory, and recognition, considered an explicit expression of memory, have been thought to result from the operation of two distinct memory systems and indeed their experimental results showed that. They found that the duration of time that test subjects studied an object in the experiment had opposite effects on their priming and recognition performance, suggesting different neural substrates for the different kinds of memory.

Gonsalves said some recent models for explaining how this type of memory works have challenged that distinction but their experiment, in which they changed the duration a subject was exposed to an image of an object, affected priming and recognition differently.

“You get less priming if you get to see it longer, which is weird, and we’re not sure why, whereas duration affects recognition in a pretty linear way.” he said. “The longer you get to look at it, the higher your recognition. So you have this nice disassociation, one goes up and then down and then the other one goes right up. What that allowed us to do both behaviorally and with ERPs, was disassociate recognition from priming. What you see is the behavior is exactly what we expected, and we find different ERP signatures associated with those two different kinds of memory.”

Providing subjects with misinformation in experiments is one way Gonsalves tests theories about false memories. Gonsalves and graduate student Carol Baym from his lab focused on misinformation and the neural mechanisms underlying memory failure. In the experiment, they had participants look at photos of a common activity and, later, descriptions of the activity that conflicted with the photo.

The results showed reliable creation of false memories, with participants reporting information that had been presented in the misinformation but not in the photographs. These results suggested, they wrote, “that strong encoding of the general contextual frame of an event, combined with weaker encoding of the particular details that turn out later to be important – such as the identity or specific features of objects present during the event – are optimal conditions for the formation of false memories.”

The experiment used functional Magnetic Resonance Imaging (fMRI) to study how the brain encoded these memories.

“The most interesting thing that came out of that study was looking at brain activity as you are first encoding an event,” Gonsalves said. “We looked at the brain activity during the original event and as they are encoding it again to see when they encode it really well and remember the exact thing that appeared in the original event, versus when they choose the misinformation, or if they completely forget and choose the third alternative.

“What we found is that in some brain regions, particularly in the medial temporal lobes, it was very similar to brain activity that led to an accurate memory. So they are encoding quite a bit of what’s going on, particularly the overall context. The idea would be, and this is partially supported by other data and needs to be followed up on and clarified, is that people encode the general scene but fail to encode the central detail. The outcome seems to be that it was this intermediate level of encoding that leads to susceptibility to misinformation.”

Gonsalves said the magnets at BIC were crucial to this study, as well as much of his work.

“It’s important to me to have a research dedicated scanner where I can get time on the magnet,” he said. “Some of the other places I’ve been access to the scanner wasn’t so easy. Here we have a student who is probably running about a dozen subjects a week. So we can collect a lot of data in a short period of time. And we have full-time techs.”

In addition to the support facilities, the interdisciplinary environment at Beckman played a role in Gonsalves coming to Illinois.

“Beckman was part of the deal,” he said. “It’s the collaborative atmosphere that I really like. One of the things that I liked about Northwestern was that it was a collegial environment, where there was often collaboration between labs. That wasn’t the case at every place, so that was really appealing to me that Beckman had that too.”

 While he ended up in a career that focuses on neuroscience, Gonsalves didn’t ignore the philosophy aspect of the class that got him pointed toward his current path.

“I did a philosophy minor,” he said. “But that class is what really got me started in (neuroscience research). It was more looking at the overall question than the philosophy itself.”