title: Functional differences among stimulation-identified cortical naming sites in the temporal region.
abstract: To preserve postoperative language, electrical stimulation mapping is often conducted prior to surgery involving the language-dominant hemisphere. Object naming is the task most widely used to identify language cortex, and sites where stimulation elicits naming difficulty are typically spared from resection. In clinical practice, sites classified as positive undergo no further testing regarding the underlying cause of naming failure. Word production is a complex function involving multiple mechanisms that culminate in the identification of the target word. Two main mechanisms, i.e., semantic and phonological, underlie the retrieval of stored information regarding word meaning and word sounds, and naming can be hampered by disrupting either of these. These two mechanisms are likely mediated by different brain areas, and therefore, stimulation-identified naming sites might not be functionally equivalent. We investigated whether further testing at stimulation-identified naming sites would reveal an anatomical dissociation between these two mechanisms. In 16 patients with refractory temporal lobe epilepsy (TLE) with implanted subdural electrodes, we tested whether, despite inability to produce an item name, patients could reliably access semantic or phonological information regarding objects during cortical stimulation. We found that stimulation at naming sites in superior temporal cortex tended to impair phonological processing yet spared access to semantic information. By contrast, stimulation of inferior temporal naming sites revealed a greater proportion of sites where semantic access was impaired and a dissociation between sites where stimulation spared or disrupted semantic or phonological processing. These functional-anatomical dissociations reveal the more specific contribution to naming provided by these cortical areas and shed light on the often profound, interictal word-finding deficit observed in temporal lobe epilepsy. Additionally, these techniques potentially lay the groundwork for future studies to determine whether particular naming sites that fall within the margins of the desired clinical resection might be resected without significant risk of decline.
authors.affiliation: Department of Neurology, Columbia University Medical Center, New York, NY, United States. Electronic address: mh61@columbia.edu.
authors.forename: Marla J
authors.initials: MJ
authors.lastname: Hamberger
authors.affiliation: Department of Neurology, Columbia University Medical Center, New York, NY, United States.
authors.forename: Michele
authors.initials: M
authors.lastname: Miozzo
authors.affiliation: Department of Neurology, Columbia University Medical Center, New York, NY, United States.
authors.forename: Catherine A
authors.initials: CA
authors.lastname: Schevon
authors.affiliation: Department of Neurology, New York University Medical Center, New York, NY, United States.
authors.forename: Chris
authors.initials: C
authors.lastname: Morrison
authors.affiliation: Department of Neurology, New York University Medical Center, New York, NY, United States.
authors.forename: Chad
authors.initials: C
authors.lastname: Carlson
authors.affiliation: Department of Neurological Surgery, North Shore LIJ Medical Center, New Hyde Park, NY, United States.
authors.forename: Ashesh D
authors.initials: AD
authors.lastname: Mehta
authors.affiliation: Department of Neurological Surgery, North Shore LIJ Medical Center, New Hyde Park, NY, United States.
authors.forename: Gad E
authors.initials: GE
authors.lastname: Klein
authors.affiliation: Department of Neurological Surgery, Columbia University Medical Center, New York, NY, United States.
authors.forename: Guy M
authors.initials: GM
authors.lastname: McKhann
authors.affiliation: Department of Neurology, Columbia University Medical Center, New York, NY, United States.
authors.forename: Alicia C
authors.initials: AC
authors.lastname: Williams
mesh_terms: D000293:Adolescent; D000328:Adult; D001931:Brain Mapping; D004558:Electric Stimulation; D004567:Electrodes, Implanted; D004833:Epilepsy, Temporal Lobe / Q000503:physiopathology* / Q000523:psychology*; D005260:Female; D006801:Humans; D007802:Language; D008297:Male; D008875:Middle Aged; D009275:Names; D011578:Psycholinguistics; D011597:Psychomotor Performance; D012660:Semantics; D013702:Temporal Lobe / Q000503:physiopathology*; D055815:Young Adult
keywords: Cortical stimulation; Language mapping; Lexical access; Naming