Q&A with Morgan Barense
In high school biology, students often learn about different parts of the brain, accompanied by a description like “the area of the brain responsible for memory” or “…for attention.” But in recent years, cognitive neuroscientists have found that such sharp boundaries in cognitive functions are really a myth. The brain is not as modular as once thought, but rather an intertwined and dynamic system of networks. Nowhere is this truer than in the study of memory, where researchers like Morgan Barense are overturning the idea of exclusive areas in the brain dedicated to remembering.
Co-recipient of the CNS Young Investigator Award, Barense studies the complex interplay between memory and perception at her lab at the University of Toronto. Working with amnesics, she and colleagues have developed a new theoretical framework for understanding common neural architecture for memory and perceptual systems, and is now applying that work to understanding and diagnosing Alzheimer’s disease. “I am driven to continue this work not only because these questions pertain to fundamental organizing principles of the mind, but also because they have important implications for a devastating disease that is on the brink of reaching epidemic proportions,” she says.
CNS spoke with Barense about how her work and upcoming award talk at the CNS annual meeting in Boston, including her thoughts on the next 25 years in cognitive neuroscience.
Nothing lays bare the vulnerability of human cognition quite like severe Alzheimer’s disease.
CNS: How did you become interested in memory and perception?
Barense: As an undergraduate, I was interested in many topics relating to the mind and brain, but I was always particularly drawn to aspects of cognition that had a salient clinical manifestation. I think nothing lays bare the vulnerability of human cognition quite like severe Alzheimer’s disease. I had the great fortune of pursuing my undergraduate honors thesis project in the lab of Mark Baxter, whose work was focused on creating animal models of cognitive decline in aging and Alzheimer’s disease. After running my first study, I knew that a career in research was for me.
As part of this experience, I was introduced to some new ideas regarding the organization of memory in the brain. In particular, some scientists in Cambridge and Oxford were challenging the long-standing notion that there is a memory system in the medial temporal lobes (MTL) that is dedicated exclusively to memory. Instead, these researchers were suggesting that the neural underpinnings of memory might not be separable from the neural underpinnings of other cognitive functions like perception. I was drawn to the idea that memory is dynamically integrated into other aspects of cognition, but until that point, all the evidence in support of this view had come from animal research. So, I went to Cambridge to do my Ph.D. and under the supervision of Kim Graham, we began to pursue the idea with studies in human amnesics.
CNS: What has been the traditional view of memory and perception until now, and how is that changing?
Barense: Following the early descriptions of patient HM in the 1950s, scientists have known that damage to the MTL causes amnesia. And for nearly 60 years, the dominant view of memory organization has held that MTL structures form a dedicated long-term memory system, with no role in other cognitive processes such as perception, attention, or language. This view is consistent with a popular paradigm in cognitive neuroscience, in which the brain is understood in terms of a modular organization of cognitive function. Within this framework, it is argued that separate brain systems account for distinct cognitive processes, like “memory,” “attention,” or “perception.”
However, this modular view is coming under question. We have shown that human amnesics with MTL damage, like HM, do, in fact, show deficits in perceiving complex objects and scenes. This finding is fundamentally incompatible with the notion of a dedicated MTL memory system specifically, or cognitive modules more generally. A new theoretical framework – the representational-hierarchical model – offers a mechanistic account of these findings by proposing that apparently distinct mnemonic and perceptual functions may arise from a unified neural architecture and common mechanisms. That is, the representations for memory and perception may be one and the same and the function of so-called “memory systems” may not be best characterized as memory.
CNS: What is the role of computational modeling in this new work?
Barense: Since the very beginning our research has always been guided by a connectionist model that was initially developed by my colleagues Lisa Saksida, Rosie Cowell, and Tim Bussey. Simulations from this neural network have generated novel predictions which we have then tested with neuroimaging and neuropsychology. The convergence of evidence of from these different methodologies has created a clear mechanistic framework to understand the relationship between memory and perception.
CNS: How is this new work changing our understanding of Alzheimer’s disease?
Barense: I think our work offers some important implications for understanding the genesis of memory impairments in individuals with MTL damage, such as those afflicted with Alzheimer’s disease. The memory impairments observed in the disorder may, in part, reflect a more fundamental problem with perception at the time of initial encoding: If a stimulus is not processed accurately at the time of initial perception, how can it be accurately remembered?
Although most textbooks still respect sharp boundaries between perceptual and mnemonic functions, I think that the field will benefit as we move away from mapping these broad psychological constructs onto neatly segregated modules in the brain.
CNS: And how is that new information informing diagnosis of dementia and Alzheimer’s disease?
Barense: In the search for a potential neuroimaging predictor of dementia, we found that selective volume loss in a specific MTL structure, the anterolateral entorhinal cortex, occurs years prior to diagnosis – even before individuals notice memory problems. Moreover, this volume loss was accompanied by fundamental perceptual deficits in directing eye movements to complex conjunctive objects.
That means that long before receiving any diagnosis, patients at risk for Alzheimer’s were showing disruptions in how they visually sampled their environment, indicating early problems with one of the most foundational steps necessary for accurate perception. This core perceptual deficit was directly associated with volume reductions in a brain area known to be one of the first affected by Alzheimer’s disease.
My hope is that this work will not only add to basic understanding of the mechanisms of Alzheimer’s disease, but will also help to inform advances in diagnosing and monitoring those at risk for dementia.
CNS: How do you want to see the field move in the next 25 years in terms of its pursuit of cognitive neuroscience discoveries?
Barense: Although most textbooks still respect sharp boundaries between perceptual and mnemonic functions, I think that the field will benefit as we move away from mapping these broad psychological constructs onto neatly segregated modules in the brain. The attempt to carve up cognition in this way is certainly understandable, and, in large part, matches introspection and phenomenological experience. However, I think that the focus on functional modularity has sometimes obscured the vast and dynamic interplay between different aspects of cognition. I believe we will have better luck with recent methodological advances that allow us to consider the nature of information represented and the computations performed by the brain.
CNS: What do you most want people to take away from your work and your award talk?
Barense: In short, we’re beginning to understand that the MTL is not just for memory and that memory is not just for the MTL. More broadly, I hope that the talk gets people thinking about the best way to understand the relationship between the mind and brain. Should we be thinking in terms of anatomically segregated systems that are each devoted to a cognitive process, or should we be thinking of different aspects of cognition as closely intertwined and dynamically distributed across the brain?
CNS: What are the next steps for your work?
Barense: We’ve recently expanded in some new translational directions that I find very exciting. Despite advances in understanding the neuroscience of memory, the field is no closer to rehabilitating persons with memory impairments. To remedy this, we have created a novel digital memory aid – we call it the “Hippocamera” – to boost everyday memory in individuals at risk for Alzheimer’s disease.
The Hippocamera device captures videos of real-life events during a user’s day, and replays them later in a way that externally mimics the internal function of “hippocampal replay” – the reactivation of hippocampal activity associated with memory for an event. The device organizes and replays events based on keystone principles of cognitive psychology and hippocampal neuroscience: The user is presented with events that are spaced throughout each day, self-generated, distinctive and personally relevant, and organized in accelerated replay sessions that maximize contextual reinstatement. I hope that this work will represent the successful translation of cognitive neuroscience theory to the practical rehabilitation of memory impairments that profoundly affect millions of people.
CNS: And finally, what are you most looking forward to about the CNS meeting in Boston?
Barense: It’s an incredible line-up of speakers. I love that everyone brings their best work to CNS, and I can’t wait to see what’s new in the field. I imagine that the 25th Anniversary Gala will be quite a bit of fun, too!
-Lisa M.P. Munoz