Electrophysiology of proper naming in the human left anterior temporal lobe

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DESCRIPTION (provided by applicant): The left anterior temporal lobe (ATL) is crucial for retrieving names for proper nouns. Evidence for this comes from lesions studies that demonstrate a specific deficit in proper noun naming, with preservation of recognition, in patients with left ATL damage. The ATL is commonly encountered in temporal lobe epilepsy (TLE), traumatic brain injury (TBI), and frontotemporal dementia (FTD), where it significantly impacts quality of life. Studying the physiology of the ATL is extremely difficult because of technical limitations imposed by functional neuroimaging techniques (e.g. functional MRI susceptibility artifact). Thus, studies of the ATL have relied on lesion data and positron emission tomography (PET), which lack the spatial resolution to study eloquent left ATL subregions. Intracranial electrocortiography (ECoG), typically used for seizure localization, is an emerging technique for functional mapping that circumvents these limitations, but has not been previously used to study the ATL since traditional ECoG grids do not conform to the ATL convexity. The proposed work will characterize the physiology and connectivity of the ATL using ECoG in human subjects undergoing left ECoG implantation for seizure localization. A novel ECoG array has been developed and implemented that provides dense coverage of the ATL for seizure localization and functional mapping. Using this array, we will describe ATL responses to visual and auditory proper noun naming, and then characterize connectivity of the ATL to sensory cortices that support naming. Using classifier analysis techniques, the neural activity associated with specific categories (actors, politicians, landmarks, tools) and specific entities (Bill Clinto, Barak Obama) will be decoded to define the organization and functional subregions of the left ATL. Using electrical stimulation tract tracing (ESTT), the anatomical and functional connections between fusiform gyrus and superior temporal gyrus will be defined. Phase synchrony analysis of ECoG data obtained during proper noun naming will be used to map functional connections between the fusiform gyrus or superior temporal gyrus, and the ATL. The results of these experiments will provide new and timely knowledge of the physiology and connectivity of the left ATL to perform proper noun naming. The proposed work will generate important knowledge of the mechanisms mediating cognitive dysfunction in patients with ATL damage and has the potential to influence neurosurgery of the language dominant temporal lobe to spare previously undefined functional subregions of the left ATL.