CAREER: Testing a unified theory of perception and memory in the medial temporal lobe

University Of Massachusetts Amherst, Amherst MA

Investigators

Abstract

Memory is critical to our everyday existence, enabling us to recognize an acquaintance's face, remember where we have parked our car, or recall an event from last week in vivid detail. And yet, it is fragile: memory performance can decline noticeably with age and deteriorates even more dramatically in individuals with damage to the medial temporal lobes of the brain. Until recently, theories of memory assumed that the medial temporal lobes are dedicated solely to memory function. However, recent evidence suggests that these brain regions are important for other cognitive tasks, including imagining the future and visually discriminating between two highly similar objects. Therefore, a critical gap in current knowledge is a theory of how memory interacts with high-level visual perception and why both of these cognitive functions depend upon the medial temporal lobes. With the support of this NSF CAREER award, Dr. Rosie Cowell will develop such a theory and test it with empirical studies. By applying the theory to both amnesia caused by brain damage and the more moderate memory loss caused by normal aging, this project will investigate whether these two forms of memory loss can be explained by the same mechanisms. In addition, the project will benefit society more broadly by (1) providing a uniquely integrated research training regime in which graduate students receive direct experience with both theory-building and hypothesis-testing, and (2) broadening participation in STEM fields via hands-on science workshops for female students from high-schools that serve under-represented groups, and via public outreach in the local Massachusetts community. To develop a unifying theory of memory and high-level perception, the proposed research will employ behavioral studies, functional magnetic resonance imaging (fMRI) and computational modeling. The studies will examine the effect of perceptual interference on memory in two cognitively-impaired populations: individuals with medial temporal lobe (MTL) damage and heathy, older adults. The central hypothesis of this proposal is that the MTL houses conjunctive representations of objects and events that are critical for both memory and perception. The conjunctions are critical for perception because they allow differentiation between two similar objects or events, and critical for memory because they shield against a constant stream of perceptual interference that would otherwise cause dramatic forgetting of an object or event. It is assumed that both MTL damage and normal aging compromise the conjunctive representations, forcing a person to rely upon the fragmental, feature-based representations that remain in sensory cortex. Feature-based representations are inadequate for differentiating similar items (leading to perceptual impairments) and highly susceptible to perceptual interference (leading to memory problems). The planned studies are expected to reveal that MTL structures contribute to any cognitive task, mnemonic or perceptual, whenever the task solution requires complex, conjunctive representations of stimuli. This representational approach to understanding cognition will be fully exploited by developing a formal, neuro-computationally plausible model that links neural representations to cognitive performance with an explicit mechanism.