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Cellular and Circuit Mechanisms of Right-hemispheric Language Functions in Aphasia

Poster C114 in Poster Session C, Wednesday, October 25, 10:15 am - 12:00 pm CEST, Espace Vieux-Port
This poster is part of the Sandbox Series.

Laura Schiffl¹, Lisa M. Held¹, Bernhard Meyer², Jens Gempt³, Simon N. Jacob^1,2; ¹Translational Neurotechnology Laboratory, Technical University of Munich, Germany, ²Department of Neurosurgery, Technical University of Munich, Germany, ³University Medical Center Hamburg-Eppendorf, Germany

Disease or injury to the brain's left-lateralized cortical language network can lead to severe behavioral impairment of language functions. While the majority of these patients are chronically impaired, sub-functions can reorganize in healthy brain areas and compensate for loss of brain tissue. The mechanisms allowing for such functional reorganization in aphasia, involving in particular right-hemispheric language-homotopic areas, are not well understood. Similar to the general lack of understanding regarding the role of individual neurons and cell assemblies in the language system, this knowledge gap is due to the limited temporal and spatial resolution of non-invasive recording methods that currently dominate language research. We hypothesize that following left-hemispheric damage, single neurons as well as local and long-range networks in right-hemispheric language-homotopic areas play a significant role in regaining language functions. In order to investigate this hypothesis and promote our understanding of the circuitry and plasticity of the language system, we chronically implanted a patient with aphasia with intracortical microelectrode arrays into the right-hemispheric supramarginal gyrus, angular gyrus, inferior and middle frontal gyri. Our recordings allow us to collect neuronal data with sub-millimeter and sub-millisecond precision previously unattainable in aphasia research. Recordings are performed several times a week, while the patient engages in high-intensity language training of words with varying linguistic complexity (e.g. word frequency, word length, phonological complexity, phonological neighborhood size) and semantic and syntactic categories. We study heavily impaired as well as better preserved language functions in production and comprehension of single words. With recordings spanning many months, we will be able to describe changes in the functional recruitment and response profiles of individual neurons and their networks as potential correlates of behavioral improvements (e.g. naming accuracies and reaction times). We present preliminary findings of single units showing task-related responses, specifically variations of spiking activity with respect to stimulus features (e.g. visual vs. auditory modality, syntactic properties, semantic category, and phonological similarity), task phase (e.g. delay vs. production), and brain region.

Topic Areas: Methods, Disorders: Acquired