A POSITRON EMISSION TOMOGRAPHY STUDY OF BINAURALLY AND DICHOTICALLY PRESENTED STIMULI - EFFECTS OF LEVEL OF LANGUAGE AND DIRECTED ATTENTION

Regional cerebral blood flow (rCBF) was measured using positron emissi on tomography with oxygen-15 labeled water as 10 normal subjects liste ned to three types of auditory stimuli (environmental sounds, meaningl ess speech, and words) presented binaurally or dichotically. Binaurall y presented environmental sounds and words caused similar bilateral rC BF increases in left and right superior temporal gyri. Dichotically pr esented stimuli (subjects attended to left or right ears) caused asymm etric activation in the temporal lobes, resulting from increased rCBF in temporal lobe regions contralateral to the attended ear and decreas ed rCBF in the opposite hemisphere. The results indicate that auditori ly presented language and non-language stimuli activate similar tempor al regions, that dichotic stimulation dramatically changes rCBF in tem poral lobes, and that the change is due both to attentional mechanisms and to hemispheric specialization. (C) 1996 Academic Press, Inc.