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Poster Session B: Wednesday, August 13, 1:00 – 4:00 pm, de Brug & E‑Hall

Why is GABA related to neural distinctiveness? A computational account of age-related neural dedifferentiation

Quan Zhou¹, Thad Polk¹; ¹University of Michigan - Ann Arbor

Presenter: Quan Zhou

Neural activation patterns in response to different stimuli (e.g., houses vs. faces) are less distinctive in older than younger adults—a phenomenon known as age-related neural dedifferentiation. A growing body of evidence suggests that GABA, the brain’s primary inhibitory neurotransmitter, may play a role: GABA levels decline with age and are associated with individual differences in neural distinctiveness. To explore why, we used an independently developed model of koniocortex to simulate the relationship between GABA (measured using MR spectroscopy) and neural distinctiveness (measured using fMRI) in a large sample of older adults. We manipulated the amount of divisive normalization in the model to simulate individual differences in GABA levels and assessed the impact on the distinctiveness of the model’s output activation patterns (measured by computing the average cosine similarity among the patterns). Cosine similarity significantly predicted empirical neural distinctiveness values measured by fMRI and mediated the relationship between GABA and neural distinctiveness. These findings provide a computational account of how age-related declines in GABA reduce the brain’s ability to maintain distinct neural representations.

Topic Area: Reward, Value & Social Decision Making

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