POSTER: LANGUAGE Auditory Perception, Silent Repetition and Naming of Single Words W. Huber', K. Specht':', I. Radermacher', S. Posse\ L. Jancke" I RWTH Aachen. 1 Research Center Jlilich. J Otto-von Guericke-University Magdeburg, Germany Introduction Since 1988, functional brain imaging studies have unanimously demonstrated len prefrontal activation in addition 10 perisylvian involvement when the task required controlled processing of word meanings. However, the tasks used - verb generation (I). semantic word fluency (2) and semantic judgment (3. 4) - do notonly require access to word meanings, but also engage working memory, executive control and metalinguistic awareness. which might explain the prefrontal activation (5). In the present fMRI study. we applied a simple semantic access task in contrast with tasks aiming at word form activationand auditory-phonetic perception (cf. 6). Methods Six right-handed male subjects. 23-31 years old. were scanned while carrying out three tasks: A. Passive listening to 1-2 syllable words of German. OAT recorded and played back in reverse, B. Silent repetition of the same words played back naturally. C. Silent naming to short definitions consistingof two content wordseach, e.g. furniture to sit on => chair. animal us ride on => horse. container for flowers => vasco The same set of 45 words was used in each condition. The tasks were given in runs of three alternating OFF/ON periods lasting 90s each. The rate of presentation was I word per 2 s. - The data were acquired at 1.5 Tesla on a Siemens Magnetom VISION system equipped with a standard head coil and echo-planar imaging (TE=66ms, TR=5s. FOV=200x200mm, 64x64 matrix, voxel size=3.lx3.lx4.4mm, 16 contiguous axial slices parallel to AC-PC line starting at the boltom of temporal and frontal lobe, 108 sequential images per slice). The data were analysed using SPM96 software (Wellcome Dept. of Cognitive Neurology, London UK). Condition-specific effects were assessed by comparing the ON·periods of each task to their control conditions (OFF periods)and by assessing the specific interaction effects between naming (ON- OFF) and listening (ON-OFF) as well as repetition(ON-OFF). 4 minus LISTENING 5 3 .. ,.:.--\-;.1.. i"' "'J [' .- 'J i\- , ;,. ( ! ....... .. REVERSED WORDS REAL WORDS LISTENING REPETITION NAMING I I 3 I5 3 {f ,-:rJi, (:._ ; , ..J f:·;: ·J :', '.) .Y., :aL: '.Y. ,\.., .... /, -':"'. '_', .» . ,l..... ...... '. 2 2 4 2 6 4 NAMING minus REPETITION 3 ::' . ';;.! . [.. I ) (' 1 'J \ .., ., , .. , ... .. J: .... '(, 2. Frith. C.D., et al, Neuropsychologia, 1991.29: 137-148. 4. Binder. IF. et al, Ach Neural, 1995.52: 593-601. 6. Price. C.J.. et al. Brain. 1996.119: 919-931. Fig. I. Statistical parametric maps(SPM.height threshold Z=3.tl9 (p=.OOI). corrected p=.(5) Results and Conclusion The three task conditions - listening.repetition. naming - activated bilateral perisylvian areas of increasing size (cf. fig. I). Listening to reversed words was restricted to the middle superior gyrus (BA 41/21) with activation peaks in the superior temporal sulcus of both hemispheres (I and 2 in fig. I). Silent repetition of real words led to additional activation of left and right inferior frontal gyrus (BA 45/47. 3 and 4 in fig. I). Silent naming to two-word definitions further extended the activation into basal ganglia with peaks in the left and right putamen (5 and 6 in fig. 1). So far all activation peaks were found in symmetrical left and right perisylvian sites. The expected left hemisphere dominance showed up when naming (ON-OFF) was compared to both listening and repetition (ON,OFF respectively). The left inferior frontal gyrus (BA 47. 3 in figure I) was crucially involved. No significant interactions were found between repetition and listening. These result are in agreement with cognitive models that assume hierarchically nested subcomponentsof word processing. Access to word meanings is necessarily preceded by auditory-phonetic analysis and word form activation. It remains. however. to be seen in what sense the left inferior frontal gyrus (BA 47) contributes to the naming task. References I. Petersen. S.E.. et al, Nature. 1988. 331:585-589. 3. Demonet, J.F.• et al. Brain. 1992. 115: 1753-68. 5. Warburton. E.• el al. Brain. 1996. 119: 159-179. 8169