Statistical learning in the hippocampus and neocortical regions: Evidence from intracranial neural entrainment

Poster Session D - Monday, April 15, 2024, 8:00 – 10:00 am EDT, Sheraton Hall ABC

Daniela Herrera Chaves¹, Greydon Gilmore^2,3, Lyle Muller^4,5, Ana Suller Marti^6,7, Seyed Mirsattari⁷, Stefan Köhler*⁸, Laura Batterink*⁸; ¹Graduate Program in Neuroscience, Western University, London, ON, Canada, ²Centre for Functional and Metabolic Mapping, Robarts Research Institute, Western University, London, ON, Canada, ³Department of Clinical Neurological Sciences, Division of Neurosurgery, Schulich School of Medicine & Dentistry, Western University, London, ON, Canada, ⁴Department of Mathematics, Western University, London, ON, Canada, ⁵Western Academy for Advanced Research, Western University, London, ON, Canada, ⁶Department of Paediatrics, Schulich School of Medicine and Dentistry, Western University, 339 Windermere Rd. London, Ontario N6A 5A5, Canada, ⁷Epilepsy Program, Department of Clinical Neurological Sciences, Schulich School of Medicine and Dentistry, Western University, 339 Windermere Rd. London, Ontario N6A 5A5, Canada, ⁸Department of Psychology, Western University, London, ON, Canada

Statistical learning (SL) is a powerful mechanism that supports the ability to extract regularities from environmental input. Yet, its neural underpinnings are not well understood. There is strong evidence pointing to the involvement of sensory cortices in SL, but a recent computational model proposes that the hippocampus may support this learning mechanism as well. However, direct neural evidence for the role of the hippocampus in extracting patterns in speech through SL is scarce. In addition, the degree to which engagement of the hippocampus and non-hippocampal cortical regions relates to subsequent behavioral learning effects has not yet been explored. In the current study, six patients with drug-resistant epilepsy who received stereoelectroencephalography listened to a continuous speech stream containing repeating “hidden” trisyllabic words. Neural entrainment at the frequency of syllables provided an index of sensory processing, while entrainment at the frequency of the embedded words provided an index of statistical learning. After listening, SL was further assessed through explicit and implicit behavioral measures. At the behavioral level, we found evidence of statistical learning on our implicit task, with nearly all patients showing facilitated performance for predictable syllables. Moreover, preliminary analyses at the neural level revealed different temporal tuning responses across electrodes. Critically, a subset of electrodes showed entrainment uniquely at the word rate, indicating specific sensitivity to the word structures. These electrodes were mainly located within the hippocampus, frontal cortex, and middle temporal cortex. Further analyses will aim to elucidate how neural entrainment across regions relates to performance on our behavioral tasks.

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