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Functional magnetic resonance imaging study of word production: the role of the supplementary motor area and of the dorso-lateral prefrontal cortex
ABSTRACTS
Functional Magnetic Resonance Imaging study of word production: the role of the Supplementary Motor Area and of the Dorso-Lateral Prefrontal Cortex F. Di Salle 2, A. Iavarone ~, A. Di Costanzo ~, R. M o r r o n e 2, L. Brunese 2 , F. S m a l t i n o 2 and H. Hacker 3
Institute of Neurologwal and Radiological-" Scwnces Faculty of Medicine First2 and Second University of Naples - Italy Klinikum der Johann Wolfgang Goethe-iIUh~?~5k_r~'tmr,Frankfitrt am Main 3 - Germany 9
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Summary Functional Magnetic Resonance Imaging (fMPd) is a new, powerful tool for studying the functional anatomy of the brain. Its high spatial and temporal resolution overcome PET potentialities in defining brain areas involved in mental activity. Some studies have shown tMRI to be a potential tool for langnage localization in speech production (Cuenod, 1995), even using conventional equipment and taking into account only a single brain slice. The fMRI potentialities have been fl~rther increased by the ultra-fast echo-planar (EPI) techniques with the multislice facility, which provides evidence of activation even in brain regions whose involvement is not a priori expected. Furthermore, a larger number of data is acquired, enhancing the perspectives for a favourable statistical significance. In this study, we ilwestigated neuroanatomical correlations of single word production using EPI: the possibility for a complete brain examination permitted to analyze not only the behaviour of the basal frontal lobe, but also of supplementary motor area (SMA) and of the dorso-lateral prefrontal cortex (DLPFC).
Methods Twenty normal healthy volunteers, 15 men and 5 women, all but one (male) right handed, with age ranging from 27 to 55 years (mean 35) were enrolled in the study, with a previous informed consence. The subjects were requested to silently generate as many words as possible beginning with a given letter or belonging to a semantic category. A control condition was applied, consisting in the covert production of the nonsense syllable "blah". hnages were acquired by a 1.5 T MR unit (Vision, Siemens, Erlangen) with high amplitude gradients (25 roT/m) and a single shot EPI device. The EPI protocol consisted in 20-slices gradient-recalled echo acquisitions with a high T2* sensitivity (TE 66 ms) and a short scan time (126 ms per slice, and about 2.5 sec for the entire 20-slices acquisition). The images were parallel to the bicommissural plane, 4 mm thick with 2.5 mm of interslice gap, a 64x64 nmtrix (interpolated to 128x 128) on a field of view (FOV) of 18-20 cm. The EPI images entered a statistical image analysis protocol with multiple evaluation (z-score, t of Student, correlation) using both a Siemens software and Stinmlate (by J.P. Strupp, University of Minnesota). The identification of the activated cortical areas was done by comparison with the standard Talairach reference atlas.
Results All the experiments showed well defined activation areas, where signal intensity varied up to 15%9 Broca's activation was observed in lg subjects; 12 had left unilateral (LU), 4 bilateral (B) and 2 right unilateral (RU) activation; RU activation was found only in two women. SMA was active in 17 subjects, 13 LU, 4 B (3 women)9 A clear activation of left DLPFC was observed in 19 subjects, with 1 13 and no RU DLPFC activation.
Discussion and Conclusion The present study gives new ilfformation on the lateralization of linguistic fimctions: the linkage with the left hemisphere has been recently analyzed by Sha3~vitz et al. (1995) who report clear sex differences in phonological language tasks, the females showing activation in the Brodman's areas 44-45 of the right hemisphere. Our results comqrm this indication and conversely show that the RU pattern is at least not common for SMA and DLPFC and the B pattern appears less frequent than for Broca, even in woman and left-handed volunteers. These results suggest a stronger limkage of SMA and DLPFC function with the left hemisphere and outline their role in the establishment of language dominance.
References 1. Cuenod C.A. et al. Neurology 1995, 45:1821-1827. 2. Shaywitz B.A. et al. Nature 1995, 373:607-609. $435
Functional Magnetic Resonance Imaging study of word production: the role of the Supplementary Motor Area and of the Dorso-Lateral Prefrontal Cortex F. Di Salle 2, A. Iavarone ~, A. Di Costanzo ~, R. M o r r o n e 2, L. Brunese 2 , F. S m a l t i n o 2 and H. Hacker 3
Institute of Neurologwal and Radiological-" Scwnces Faculty of Medicine First2 and Second University of Naples - Italy Klinikum der Johann Wolfgang Goethe-iIUh~?~5k_r~'tmr,Frankfitrt am Main 3 - Germany 9
1
.
.
")
-
Summary Functional Magnetic Resonance Imaging (fMPd) is a new, powerful tool for studying the functional anatomy of the brain. Its high spatial and temporal resolution overcome PET potentialities in defining brain areas involved in mental activity. Some studies have shown tMRI to be a potential tool for langnage localization in speech production (Cuenod, 1995), even using conventional equipment and taking into account only a single brain slice. The fMRI potentialities have been fl~rther increased by the ultra-fast echo-planar (EPI) techniques with the multislice facility, which provides evidence of activation even in brain regions whose involvement is not a priori expected. Furthermore, a larger number of data is acquired, enhancing the perspectives for a favourable statistical significance. In this study, we ilwestigated neuroanatomical correlations of single word production using EPI: the possibility for a complete brain examination permitted to analyze not only the behaviour of the basal frontal lobe, but also of supplementary motor area (SMA) and of the dorso-lateral prefrontal cortex (DLPFC).
Methods Twenty normal healthy volunteers, 15 men and 5 women, all but one (male) right handed, with age ranging from 27 to 55 years (mean 35) were enrolled in the study, with a previous informed consence. The subjects were requested to silently generate as many words as possible beginning with a given letter or belonging to a semantic category. A control condition was applied, consisting in the covert production of the nonsense syllable "blah". hnages were acquired by a 1.5 T MR unit (Vision, Siemens, Erlangen) with high amplitude gradients (25 roT/m) and a single shot EPI device. The EPI protocol consisted in 20-slices gradient-recalled echo acquisitions with a high T2* sensitivity (TE 66 ms) and a short scan time (126 ms per slice, and about 2.5 sec for the entire 20-slices acquisition). The images were parallel to the bicommissural plane, 4 mm thick with 2.5 mm of interslice gap, a 64x64 nmtrix (interpolated to 128x 128) on a field of view (FOV) of 18-20 cm. The EPI images entered a statistical image analysis protocol with multiple evaluation (z-score, t of Student, correlation) using both a Siemens software and Stinmlate (by J.P. Strupp, University of Minnesota). The identification of the activated cortical areas was done by comparison with the standard Talairach reference atlas.
Results All the experiments showed well defined activation areas, where signal intensity varied up to 15%9 Broca's activation was observed in lg subjects; 12 had left unilateral (LU), 4 bilateral (B) and 2 right unilateral (RU) activation; RU activation was found only in two women. SMA was active in 17 subjects, 13 LU, 4 B (3 women)9 A clear activation of left DLPFC was observed in 19 subjects, with 1 13 and no RU DLPFC activation.
Discussion and Conclusion The present study gives new ilfformation on the lateralization of linguistic fimctions: the linkage with the left hemisphere has been recently analyzed by Sha3~vitz et al. (1995) who report clear sex differences in phonological language tasks, the females showing activation in the Brodman's areas 44-45 of the right hemisphere. Our results comqrm this indication and conversely show that the RU pattern is at least not common for SMA and DLPFC and the B pattern appears less frequent than for Broca, even in woman and left-handed volunteers. These results suggest a stronger limkage of SMA and DLPFC function with the left hemisphere and outline their role in the establishment of language dominance.
References 1. Cuenod C.A. et al. Neurology 1995, 45:1821-1827. 2. Shaywitz B.A. et al. Nature 1995, 373:607-609. $435