Lateralization of affective prosody in brain and the callosal integration of hemispheric language functions

Although affective prosody appears to be a dominant function of the right hemisphere, its degre of lateralization has not yet been established since various publications have reported affective-prosodic deficits following left brain damage in association with aphasia. This paper explores the mechanisms underlying affective-prosodic deficits following left and right brain damage by testing the ability of subjects to repeat and comprehend affective prosody under progressively reduced verbal-articulatory conditions. The results demonstrate that reducing verbal-articulatory conditions robustly improves the performance of left but not right brain damaged patients, a finding that supports the supposition that affective prosody is strongly lateralized to the right hemisphere. However, the performance of left brain damaged patients was not correlated to the presence, severity, or type of aphasic deficit(s). Based on functional-anatomic correlations for spontaneous affective prosody and affective-prosodic repetition, deep white matter lesions located below the supplementary motor area that disrupt interhemispheric connections coursing through the mid-rostral corpus callosum may contribute to affective-prosodic deficits that are both additive and independent of any aphasic deficits. In light of these and other findings, various anatomical, functional, and maturational hierarchic relationships between the affective-prosodic and verbal-linguistic aspects of language are posited in order to help further explain discrepancies that exist in the literature regarding the neurology of affective prosody.