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Are levels of language processing reflected in neural activation? — an fMRI study
Neurolmage
13, Number
6, 2001, Part 2 of 2 Parts
1 D E blw
LANGUAGE
Are levels of language processing reflected in neural activation? - an fMRI study Mary Rudner*, Jonny Cedefamn*, Ola Frimant, Hans Knutssont, Peter Lundberg& Birgitta SSderfeldt* *Department of Neurology and Locomotion, University of Linkiiping, Linkiiping, Sweden TDepartment of Biomedical Engineering, University of Linkiiping, Linkiiping, Sweden SDepartment of Radiation Physics, University of Linkiiping, LinkCiping, Sweden Summary Linguistic theory describes language as a symbolic system organised at three levels: phonological, semantic and syntactic. This study investigates whether these components are reflected in neural activation. Tests were used to activate A) the phonological level alone, B) the phonological and semantic levels together without the syntactic layer and C) all three levels at once. Tests A and B were production tasks using visual stimuli, Test C was an understanding task using aural stimuli. Neural activation patterns produced by tests A and B were similar while those produced by test C differed. Thus results reflected task type and stimulus channel rather than level of processing. Method Phonological processing was activated using a rhyming task (test A), semantic and phonological processing using a naming task (test B) and phonological, semantic and syntactic processing using a listening task (test C). Test A: the subjects covertly produced rhymes for pseudowords presented visually. Test B: the subjects covertly generated names of objects to be found in a particular room, the name of which was presented visually. Test C: the subjects listened to a text. The experiment was performed on a GE Signa Horizon Echospeed 1.5 T scanner (v 5.8) using the EPIBOLD sequence. Bite fixation was used. Data analysis was performed using an implementation of Canonical Correlation Analysis [l]. Results Activation patterns were similar for tests A and B covering frontal areas, mainly showed activation in left and right temporal lobes. There was little overlap between B and on the other hand for test C.
in the left hemisphere. The pattern for test C areas activated on the one hand for tests A and
Discussion Tests A and B generated similar patterns of activation. This may indicate that test A does not rigorously separate phonological from semantic processing. Another interpretation is that phonological and semantic aspects of language have a common representation. This agrees with some findings [2] and conflicts with others [3]. Contrary to expectations, there was little overlap between the areas activated for test C and the areas activated for tests A and B. Instead of reflecting levels of processing, results reflect difference in task type (production/understanding) and stimulus channel (visual/aural). This indicates that it may be one or both of these factors (task type and stimulus channel), rather than levels of processing that are reflected in patterns of neural activation. References 1. Friman, 0.. Cedefamn, J., Lundberg, P., Borga, M., Knutsson, H. (in press). Magnetic Resonance in Medicine. 2. Klein, D., Milner, B., Zatorre, R., Meyer, E., & Evans, A. (1995). Proceedings of the National Academy of Sciences, 2899-2903. 3. Shaywitz, B., Shaywitz, S., Pugh, K., Constable, R., Skudlarski, P., Fulbright, R., Bronen, R., Fletcher, J., Shankweller, L., & Gore, J. (1995). Nature, 373, 607-609.
s594
USA,
92,
D., Katz,
13, Number
6, 2001, Part 2 of 2 Parts
1 D E blw
LANGUAGE
Are levels of language processing reflected in neural activation? - an fMRI study Mary Rudner*, Jonny Cedefamn*, Ola Frimant, Hans Knutssont, Peter Lundberg& Birgitta SSderfeldt* *Department of Neurology and Locomotion, University of Linkiiping, Linkiiping, Sweden TDepartment of Biomedical Engineering, University of Linkiiping, Linkiiping, Sweden SDepartment of Radiation Physics, University of Linkiiping, LinkCiping, Sweden Summary Linguistic theory describes language as a symbolic system organised at three levels: phonological, semantic and syntactic. This study investigates whether these components are reflected in neural activation. Tests were used to activate A) the phonological level alone, B) the phonological and semantic levels together without the syntactic layer and C) all three levels at once. Tests A and B were production tasks using visual stimuli, Test C was an understanding task using aural stimuli. Neural activation patterns produced by tests A and B were similar while those produced by test C differed. Thus results reflected task type and stimulus channel rather than level of processing. Method Phonological processing was activated using a rhyming task (test A), semantic and phonological processing using a naming task (test B) and phonological, semantic and syntactic processing using a listening task (test C). Test A: the subjects covertly produced rhymes for pseudowords presented visually. Test B: the subjects covertly generated names of objects to be found in a particular room, the name of which was presented visually. Test C: the subjects listened to a text. The experiment was performed on a GE Signa Horizon Echospeed 1.5 T scanner (v 5.8) using the EPIBOLD sequence. Bite fixation was used. Data analysis was performed using an implementation of Canonical Correlation Analysis [l]. Results Activation patterns were similar for tests A and B covering frontal areas, mainly showed activation in left and right temporal lobes. There was little overlap between B and on the other hand for test C.
in the left hemisphere. The pattern for test C areas activated on the one hand for tests A and
Discussion Tests A and B generated similar patterns of activation. This may indicate that test A does not rigorously separate phonological from semantic processing. Another interpretation is that phonological and semantic aspects of language have a common representation. This agrees with some findings [2] and conflicts with others [3]. Contrary to expectations, there was little overlap between the areas activated for test C and the areas activated for tests A and B. Instead of reflecting levels of processing, results reflect difference in task type (production/understanding) and stimulus channel (visual/aural). This indicates that it may be one or both of these factors (task type and stimulus channel), rather than levels of processing that are reflected in patterns of neural activation. References 1. Friman, 0.. Cedefamn, J., Lundberg, P., Borga, M., Knutsson, H. (in press). Magnetic Resonance in Medicine. 2. Klein, D., Milner, B., Zatorre, R., Meyer, E., & Evans, A. (1995). Proceedings of the National Academy of Sciences, 2899-2903. 3. Shaywitz, B., Shaywitz, S., Pugh, K., Constable, R., Skudlarski, P., Fulbright, R., Bronen, R., Fletcher, J., Shankweller, L., & Gore, J. (1995). Nature, 373, 607-609.
s594
USA,
92,
D., Katz,