Abstracts

RATIONALE: In addition to traditional visual naming sites in language dominant temporal cortex, we and others have identified auditory naming sites in this region as well. Among auditory sites, we have observed two distinct types of stimulation-induced errors: 1) Non-responses followed by accurate word retrieval immediately following stimulation cessation, and 2) Responses suggesting impaired verbal comprehension. We hypothesized that an anatomical distinction might underlie these different response types. Specifically, stimulation in primary auditory cortex would impair comprehension, whereas stimulation in adjacent areas would impede word retrieval.
METHODS: Subjects were 21 Left TLE patients (7 MTS, 4 tumor, 7 negative, 1 cavernous malformation, 2 mild cortical atrophy) who underwent cortical language mapping (8 intraoperative, 13 extraoperative) before surgical resection and exhibited impaired auditory naming with stimulation at one or more sites. Naming was tested at 13-39 sites per patient, depending on time constraints (intraoperative) or extent of implantation (extraoperative). Responses were recorded verbatim. Fisher[ssquote]s exact test was used to test distribution of naming sites as a function of error type.
RESULTS: Across patients, 59 auditory naming sites were identified (1-8 positive sites per patient). Stimulation elicited comprehension errors at 14 sites (in 9 patients), whereas stimulation elicited retrieval errors at all other sites (18 patients). Of the 14 comprehension sites identified, 11 were located between 2.5 and 6 cm from the temporal pole on the superior temporal gyrus, which corresponds with Heschl[ssquote]s area (i.e., auditory projection cortex, Brodman[ssquote]s areas 41 and 42). Fisher[ssquote]s exact test for error type [dsquote]within[dsquote] versus [dsquote]outside[dsquote] this region was significant (p[lt] .001).
CONCLUSIONS: These findings suggest an anatomical distinction between cortical areas supporting two sub-processes of auditory naming (i.e., verbal comprehension and word retrieval). The results also raise questions regarding the potential clinical implications of this functional distinction. Among these is the possibility that surgical encroachment on comprehension sites might be more detrimental to post operative language functioning.
Support: The National Institute of Neurological Disorders and Stroke, Grant Number: NS35140-01A1.