Thalamic mechanisms in language and rhythm (temporal perception and expression)--comparison of cortical and thalamic damaged patients from the neurobehavioral aspect.

We investigated the relationship between language disturbances and the impairment of rhythmic capabilities (temporal perception & expression) in the patients with thalamic hemorrhage and compared them to patients with cortical lesions to probe the relationship of the thalamus to the mechanism of aphasic symptoms. 101 right-handed individuals, including 12 with thalamic hemorrhage, were studied to analyze language (verbal) and rhythmic (non-verbal) functions. Comparison of left- and right-hemisphere damaged patients revealed significant hypofunction of language and rhythmic capabilities in the group with lesions of left hemisphere. Some correlation could be seen between the rhythm disturbance and the language impairments in terms of severity and types. In contrast, the patients with thalamic hemorrhage showed a dissociation between the severely abnormal rhythm (non-verbal) and milder language (verbal) impairments. The language function values were constantly higher in the cases with thalamic hemorrhage than with cortical damages, while rhythmic capabilities were reduced, a tendency unlike that of the group with cortical damages. These findings suggest that language is primarily a function of the cerebral cortex of the dominant hemisphere, and that the thalamic area, necessary for the timing mechanism (rhythmic function), plays a part in the overall mechanism of aphasic symptomatology.