Abstracts

Visual confrontation naming requires patients to generate the name of visually presented objects. Auditory responsive naming requires the generation of an object name in response to an auditorally presented short definition of the target word. The later type of naming task may more closely approximate everyday language. Research suggests responsive naming is more sensitive to post-surgical naming deficits than confrontation naming. Intra-operative mapping studies show responsive naming to be more widely distributed than confrontation naming, in particular involving anterior temporal regions which are the target of resection in a standard temporal lobectomy. Functional MRI (fMRI) examining language lateralization has shown confrontation naming to be less lateralizing than many other language paradigms. No study has compared fMRI activation associated with responsive naming versus confrontation naming. Participants included 20 healthy right-handers: 10 completed the fMRI confrontation naming paradigm and 10 completed the responsive naming paradigm. Imaging was acquired using a 1.5 tesla scanner. All tasks were block design paradigms. During the active condition of the confrontation naming paradigm subjects viewed line drawings and were instructed to covertly name the drawing. The baseline task consisted of sets of lines that were viewed passively. During the active condition of the responsive naming task subjects heard short definitions and covertly generated the word associated with the definition; the baseline consisted of short sentences read backwards. Specific regions of interest (ROIs) were defined within the frontal and temporal lobes, and hippocampus. A laterality index (LI) was calculated for each ROI and volume of activation was also measured. The LIs associated with auditory responsive naming were significantly higher than for visual confrontation naming in all frontal and temporal ROIs except for the fusiform gyrus. Responsive naming produced significantly more activation (as measured by extent of activation) within the left middle and superior temporal gyri as compared to confrontation naming. The activation within the dominant temporal lobe also extended more anteriorly during responsive naming, as was suggested by previous brain mapping studies. Both confrontation naming and responsive naming produced hippocampal activation. Findings suggest that auditory responsive naming may be a more useful fMRI paradigm in assessing language lateralization than confrontation naming. Responsive naming also activates large portions of the temporal lobe, which may enable it to be useful as a predictor of post-surgical language changes. Both naming tasks activated the hippocampus, findings that are consistent with several other studies that also implicate this structure as part of the neural network involved in naming.