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Impaired Perceptual Discrimination Despite Intact Mismatch Negativity Following Selective Lesions to the Dentate Gyrus

Poster Session F - Tuesday, March 10, 2026, 8:00 – 10:00 am PDT, Fairview/Kitsilano Ballroom

Ricky Chow^1,2 (), Stevenson Baker^1,2, Shimin Mo^1,3, Claude Alain^1,3, R. Shayna Rosenbaum^1,2; ¹Rotman Research Institute, Baycrest Academy for Research & Education, ²York University, ³University of Toronto

The hippocampal dentate gyrus (DG) is implicated in pattern separation of overlapping representations at encoding, with emerging evidence suggesting its role in perceptual discrimination. BL, an individual with selective bilateral DG lesions, has shown impairments in complex perceptual discrimination of highly similar objects. The current research investigates the extent to which BL shows a neural signature of perceptual discrimination of complex auditory stimuli and its relationship to perceptual discrimination and subsequent memory discrimination. The mismatch negativity (MMN), an event-related potential of auditory sensory memory, was measured in BL and 25 controls (51–68 years, 14 females) using a passive oddball paradigm of tone sequences differing in pitch contour. Participants then completed a subsequent memory test for targets against similar lure sequences (differing in contour) and dissimilar foil sequences (differing in frequency and contour). Finally, participants completed a back-to-back perceptual discrimination task for identical, similar, and dissimilar tone sequence pairs. Single-case analyses were conducted using Bayesian tests of deficit. On the perceptual discrimination task, BL showed a selective deficit in discriminating between similar pairs (3rd percentile) despite showing comparable MMN amplitudes to controls. On the subsequent memory test, BL showed greater response thresholds (i.e., more likely to endorse lures as old) than controls (4th percentile). Results suggest that DG damage impairs the transformation of sensory traces into accessible representations for explicit behavioural discrimination, despite neural evidence for incidental discrimination of similar stimuli. Findings reinforce the role of the DG extending beyond mnemonic discrimination to perceptual discrimination, and from vision to audition.

Topic Area: PERCEPTION & ACTION: Audition