Functional heterogeneity of inferior frontal gyrus is shaped by linguisticexperience

A crosslinguistic, positron emission tomography (PET) study was conducted t o determine the influence of linguistic experience on the perception of seg mental (consonants and vowels) and suprasegmental (tones) information. Chin ese and English subjects (10 per group) were presented binaurally with list s consisting of five Chinese monosyllabic morphemes (speech) or low-pass-fi ltered versions of the same stimuli (nonspeech). The first and last items w ere targeted for comparison: the time interval between target tones was fil led with irrelevant dis tractor tones. A speeded-response, selective attent ion paradigm required subjects to make discrimination judgments of the targ et items while ignoring intervening distractor tones. PET scans were acquir ed for five tasks presented twice: one passive listening to pitch (nonspeec h) and four active (speech = consonant. von el, and tone; nonspeech = pitch ). Significant regional changes in blood Row were identified from compariso ns of group-averaged images of active tasks relative to passive listening. Chinese subjects show increased activity in left premotor cortex, pars oper cularis, and pars triangularis across the four tasks. English subjects, on the other hand, show increased activity in left inferior frontal gyrus regi ons only in the vowel task and in right inferior frontal gyrus regions in t he pitch task. Findings suggest that functional circuits engaged in speech perception depend on Linguistic experience. All linguistic information sign aled by prosodic cues engages left-hemisphere mechanisms. Storage and execu tive processes of workings memory that are implicated in phonological proce ssing are mediated in discrete regions of the left frontal lobe. (C) 2001 A cademic Press.