Abstract

Cerebral metabolic responses to verbal and nonverbal auditory stimuli were examined, using 18F-fluorodeoxyglucose and positron CT. Twenty right-handed subjects were studied in both control and stimulated states. Monaural verbal stimuli produced diffuse metabolic changes in the left hemisphere and bilateral activation of the transverse and posterior temporal lobes. Monaural nonverbal stimulation with chords demonstrated bilateral parietotemporal activations and diffuse right greater than left frontotemporal asymmetries. Tone sequence pairs presented monaurally produced asymmetries that differed by the subject's analysis strategy. Nonanalytical, musically naive subjects had right greater than left frontotemporal asymmetries, whereas analytic or musically sophisticated subjects had an absence of right greater than left relative hypermetabolism and demonstrated left greater than right temporal asymmetries. Binaural presentation of a factual story and music produced diffuse bilateral activations of the temporal and frontal cortex. Known anatomic asymmetries of the perisylvian cortex were revealed by high-resolution tomography. These results demonstrate that metabolic responses to auditory stimuli are determined by the content of the stimulus and the analysis strategy of the subject rather than the side of stimulation. The results also demonstrate the capacity of functional imaging techniques to study the physiologic cerebral mechanisms underlying auditory processing.