Effect of attention on central auditory processing: an fMRI study.

Functional magnetic resonance imaging was used to investigate preattentive and attentional processing of auditory stimuli in 18 right-handed normal volunteers. Responses to trains of 1000-Hz pure tones and infrequent (15%) deviant 1300-Hz tones were characterized while subjects ignored all tones; listened for deviants in the left ear; or listened for deviants in the right ear. Preattentive detection of deviants, associated with the mismatch negativity in electrophysiology, was associated with bilateral temporal lobe activation, with a rightward predominance. Processing of deviant stimuli while attending to either ear produced a more robust and widespread activation of these temporal regions, again with a rightward predominance. Thus, preattentive tone processing appears to be linked to asymmetric activation of a core set of temporal regions in which activity is significantly amplified by selective attention. Extratemporal regions activated by attending to targets in either ear included the anterior cingulate cortex, supramarginal gyrus, and dorsolateral prefrontal cortex.