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Neuropsicologia Latinoamericana

On-line version ISSN 2075-9479


MENDONCA, Lucia Iracema Zanotto de. Considerations about the cortico-subcortical circuits in speech and language. Neuropsicologia Latinoamericana [online]. 2010, vol.2, n.2, pp. 1-10. ISSN 2075-9479.

The cerebral cortex is considered to be the neural substrate of language by most of the scholars. However, subcortical lesions lead to aphasic symptoms that result from cortical dysfunction, through disconnection, diaschisis or hypoperfusion. Other authors sustain the putative role of subcortical structures in speech and language related to phonological segmentation, automatic speech aspects, cortical activation, syntactic-semantic integration and semantic monitoring. Since subcortical damage impairs the executive aspects of language, the importance of the frontosubcortical circuit and its interconnection with attention and working memory is stressed. Notwithstanding the recent recognition that the basal ganglia and thalamus participate in language processing, the true role of subcortical structures in cognitive processes is still not clear. It is known that subcortical aphasias are less severe than cortical ones and many times reversible. They are manifested by hypophonia, impairment of motor speech production with preserved repetition, and auditory comprehension is generally better than verbal expression. Also, there are some differences between the cases with thalamic and extra-thalamic lesions. It seems that phonological impairment is more evident in extra-thalamic cases. Conversely, semantic impairment is predominant in thalamic lesions. The motor and motivational cortico-subcortical loops and the pyramidal tract are involved in voice and speech disorders in subcortical damage, together with speech apraxia. This lesion site probably affects multiple aspects of verbal communication processing. To better understand the role of subcortical structures in speech and language processing the hierarchical organization of the nervous system during its evolution must be taken into consideration.

Keywords : Aphasia; Apraxia; Basal ganglia; Thalamus.

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