Is there a difference in activation or in inhibition of cortical auditory centers depending on the ear that is stimulated?

CONCLUSIONS: 1.With auditory stimuli cortical activation of Brodmann's areas 39 and 40 and inhibition of area 38 is bilateral. Inhibitory and excitatory relays play a role in the auditory pathways. 2. A statistically significant increased activation on the left side in areas 39 and 40, regardless of the stimulated ear, is suggestive that pure tones are preferably processed in the left hemisphere. 3. The significant difference in central inhibition depending on which ear is stimulated is supportive of the idea of a leading ear.

OBJECTIVES: The objectives were to determine cortical activation/inhibition, ipsi/contralateral in response to monaural stimulation with pure tones, and if the response differs for right/left ear stimulation.

SUBJECTS AND METHODS: Tc99m-HMPAO brain perfusion SPECT was done during monaural stimulation with pure tones in 10 volunteers. Ears were tested independently.

RESULTS: During auditory stimulation perfusion increased in both hemispheres in Brodmann's areas 39-40 and decreased in area 38,>2 SD above and below the normal mean respectively, in both hemispheres, regardless of which side was stimulated. A significantly more intense response was seen in left versus right in areas 39 and 40. In area 38 there was bilateral inhibition, significantly more intense in response to left than right ear stimulation.