T104. Neural correlates of sign language and spoken language revealed by electrocorticography

Abstract

Introduction Electrocorticography (ECoG) is a powerful tool to monitor cortical neurophysiology and can be employed to elucidate high order cognitive functions such as language. Clinically, electrical stimulation mapping (ESM) is the gold standard used to identify eloquent cortex which should be spared resection during surgery for patients. We developed a battery of tasks that mirror the ESM paradigm but can functionally track neural activity from stimulus presentation through speech output under multiple cognitive demands. Here we describe the neural propagation maps during both speech and sign language output in a case of a 28 year old male, hearing intact and bilingual in English and American sign language, with pharmaco-resistant epilepsy who was surgically implanted with electrodes for the clinical purpose of identifying his seizure onset zones. Methods The patient was implanted, for the purposes of his clinical care, with an electrode grid over the left temporal parietal occipital cortex, strips over the left frontal, temporal, and occipital regions, and depths within the left parietal lobe. During lulls in clinical treatment, we administered five language tasks involving visual naming, word reading, auditory repetition, auditory naming, and auditory comprehension. We focused our analyses on changes in high gamma activity (70–150 Hz) during the tasks, as high gamma activation has been previously shown to robustly track single trial cortical activity and correlates with neural population firing rates and fMRI BOLD responses. The patient also underwent electrical stimulation mapping using similar language tasks of visual naming, auditory naming, and auditory comprehension, as part of his clinical work up to identify eloquent cortex. Results We identified brain regions with high gamma activation during our language tasks in both spoken English and sign language. In addition we identified discrete regions in the frontal, temporal, parietal, and occipital cortices with sign language specific responses compared to spoken English and provide evidence for temporal propagation of neural activity from post-central to occipital cortices during sign language production. Conclusion We used ECoG high gamma activity to track neural dynamics of language processing in both spoken English and American sign language and to help map language cortex to assist in identifying eloquent regions during electrical brain stimulation.