Retrieving names of unique entities engages the left temporal pole

NeuroImage

11, Number

5, 2000, Part 2 of 2 Parts 10

E b[@

LANGUAGE

Retrieving names of unique entities engages the left temporal pole T.J. Grabowski, H. Damasio, D. Tranel Department of Neurology, University of Iowa Introduction We have previously reported mat a sector of the left temporal polar cortex is associated with retrieving names for persons, but not names for nonunique entities, such as animals or manipulable objects. We hypothesize that this anatomical effect relates to the requirement to retrieve words at unique level, rather than to the existence of a neural system dedicated to faces. In this study, we predicted that the left temporal pole would also be engaged by retrieving names for famous geographic landmarks (another category of unique entities). Methods Ten normal subjects (5M 5F, aged 2828 years) who were right-handed (>+90) native English speakers were studied with [ ‘50]Hz0 positron emission tomography on a GE 4096B tomograph. Subjects performed two word retrieval tasks (naming persons [PN] and naming landmarks [LN]) and two baseline tasks (judging the orientation of upright and inverted faces [FO] and houses [HO]). Each task was performed twice. Data were prepared for statistical analysis by coregistration to 3D structural MRI, transformation to Talairach space, and 16mm FWHM gaussian smoothing. Data were analyzed with a pixelwise linear model. The contrasts of interest were the effects of task ([PN+LN]-[FO+HOJ) and category ([PN+FO]-[LN+HO]), and the task by category interaction effect ([PN-FO)-(LN-HO)]. Results were corrected for multiple comparisons using gaussian random field theory, over a search volume comprising the left and right temporal poles. We also performed, post hoc, a whole brain search with an appropriately conservative threshold. Results Retrieving names for unique entities was associated with significant increases in activity in the L temporal pole (t = +7.30, -36 + 12 -25). There was not a significant task by category interaction effect (I = -2.83) nor was there a significant main effect of category (t = +2.43). The R temporal pole was also weakly activated (t = +3.62, +32 + 16 -28). Across tasks, the use of faces as stimuli, as opposed to places, was associated with more activity in the lateral temporal cortices, and in the R (not L) temporal pole, consistent with previous reports. There was a trend for greater engagement of the L temporal pole in the face orientation baseline task, as opposed to the house orientation baseline task, accounting for a trend for the difference in activity in the L temporal pole to be larger for naming landmarks (relative to house orientation) than for naming persons (relative to face orientation). Conclusions The results support the hypothesis that naming entities at the unique level (retrieving proper nouns) engages the L temporal pole, regardless of conceptual category, consistent with the interpretation that its engagement is determined by the level of specificity required. (Supported by NIH DC03189.) References Damasio H, et al (1996) Nature 380:499-505 Kanwisher N, et al (1997) .I Neurosci 17:4302-4311 Gauthier I, et al (1997) Current Biol 7645-651 Kuskowski MA and Pardo JV (1999) NeuroImage

9:599-610

S262