Bilateral hemispheric activation in language processing remains a challenging problem for both the hemispheric language dominance theory and the lesion-based models of linguistic function. One possible explanation postulates that right-hemisphere activation represents the spread of left-hemisphere activity through the commissural system (Vigneau et al., 2011), with right-sided regions engaged by but not critical to the processing of a given language task (Price, 2000). To investigate the role of callosal connectivity on right hemispheric activations in receptive language tasks, we compared the haemodynamic response of an adult callosotomized patient (ME) with those of 24 healthy participants. ME’s epilepsy started in 1981, three years after head trauma and, the subsequent, partial removal of the right prefrontal cortex. A complete callosotomy was performed over a six-month interval, with preservation of the anterior commissure. The patient, who is right-handed, has left-lateralized language and typical signs of interhemispheric disconnection in vision, somaesthesis and praxis. The fMRI data showed the middle temporal gyrus to be jointly and bilaterally active in both word listening and sentence plausibility judgement tasks, in both the patient and the controls. Moreover, both the patient and controls showed a left-lateralised activation patterns. The results obtained do not support the interpretation that right hemispheric activity is a mere by-product of callosal connectivity, at least in a mature brain system in which the callosal connectivity has been lost after a normal maturation. We conclude that a left-hemisphere dominance for language persists also after a late callosotomy, at least in simple receptive tasks such as word listening and sentence comprehension. References Price C. (2000) The anatomy of language: contributions from functional neuroimaging. J. Anat. 197(3): 335-59. Vigneau M., Beaucousin V., Hervé P.Y., Jobard G., Petit L., Crivello F., Mellet E., Zago L., Mazoyer B., Tzourio-Mazoyer N. (2011) What is right-hemisphere contribution to phonological, lexico-semantic, and sentence processing? Insights from a meta-analysis. Neuroimage. 54:577-93.
Danelli, L., Paulesu, E., Bottini, G., Colombo, N., Sberna, M., Tassinari, G. (2013). The role of the corpus callosum in the lateralization of language cortical networks: fMRI observations in a callosotomized patient during auditory language comprehension tasks. In Thirty-first European Workshop on Cognitive Neuropsychology.
The role of the corpus callosum in the lateralization of language cortical networks: fMRI observations in a callosotomized patient during auditory language comprehension tasks
DANELLI, LAURA;PAULESU, ERALDO;
2013
Abstract
Bilateral hemispheric activation in language processing remains a challenging problem for both the hemispheric language dominance theory and the lesion-based models of linguistic function. One possible explanation postulates that right-hemisphere activation represents the spread of left-hemisphere activity through the commissural system (Vigneau et al., 2011), with right-sided regions engaged by but not critical to the processing of a given language task (Price, 2000). To investigate the role of callosal connectivity on right hemispheric activations in receptive language tasks, we compared the haemodynamic response of an adult callosotomized patient (ME) with those of 24 healthy participants. ME’s epilepsy started in 1981, three years after head trauma and, the subsequent, partial removal of the right prefrontal cortex. A complete callosotomy was performed over a six-month interval, with preservation of the anterior commissure. The patient, who is right-handed, has left-lateralized language and typical signs of interhemispheric disconnection in vision, somaesthesis and praxis. The fMRI data showed the middle temporal gyrus to be jointly and bilaterally active in both word listening and sentence plausibility judgement tasks, in both the patient and the controls. Moreover, both the patient and controls showed a left-lateralised activation patterns. The results obtained do not support the interpretation that right hemispheric activity is a mere by-product of callosal connectivity, at least in a mature brain system in which the callosal connectivity has been lost after a normal maturation. We conclude that a left-hemisphere dominance for language persists also after a late callosotomy, at least in simple receptive tasks such as word listening and sentence comprehension. References Price C. (2000) The anatomy of language: contributions from functional neuroimaging. J. Anat. 197(3): 335-59. Vigneau M., Beaucousin V., Hervé P.Y., Jobard G., Petit L., Crivello F., Mellet E., Zago L., Mazoyer B., Tzourio-Mazoyer N. (2011) What is right-hemisphere contribution to phonological, lexico-semantic, and sentence processing? Insights from a meta-analysis. Neuroimage. 54:577-93.
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