Tomographic mapping of human cerebral metabolism: subcortical responses to auditory and visual stimulation

We measured cerebral glucose metabolism with positron computed tomography during audio-visual stimulation in 42 studies of 21 subjects. Metabolic activations and stimulus-induced asymmetries were examined in subcortical structures (thalamus, caudate, lenticular nuclei). Bilateral activations of the thalamus occurred with verbal stimuli. The head of the left caudate was activated when subjects used visual imagery as a strategy to identify sequences of tones. These two types of stimuli produced dominant (left) hemisphere cortical activations in this same group of subjects. Clinical evidence has implicated the participation of subcortical (thalamus and basal ganglia) structures in the processing of language and auditory information. The present results demonstrate this functional role directly in normal subjects.