Short Communication: Functional ear (a)symmetry in brainstem neural activity relevant to encoding of voice pitch: A precursor for hemispheric specialization?  

Oleh:

Krishnan, Ananthanarayan ; Gandour, Jackson T. ; Ananthakrishnan, Saradha ; Bidelman, Gavin M. ; Smalt, Christopher J.

Jenis: Article from Journal - ilmiah internasional
Dalam koleksi: Brain and Language (Full Text) vol. 119 no. 3 (2011), page 226-231.
Topik: Auditory; Human; Brainstem; Pitch; Language; Mandarin Chinese; Fundamental frequency-following response; (FFR); Functional ear asymmetry; Experience-dependent plasticity; Subcortical
Fulltext: 119_03_Krishnan.pdf (333.63KB)

Isi artikel

Pitch processing is lateralized to the right hemisphere; linguistic pitch is further mediated by left cortical areas. This experiment investigates whether ear asymmetries vary in brainstem representation of pitch depending on linguistic status. Brainstem frequency-following responses (FFRs) were elicited by monaural stimulation of the left and right ear of 15 native speakers of Mandarin Chinese using two synthetic speech stimuli that differ in linguistic status of tone. One represented a native lexical tone (Tone 2: T2); the other, T20 , a nonnative variant in which the pitch contour was a mirror image of T2 with the same starting and ending frequencies. Two 40-ms portions of f0 contours were selected in order to compare two regions (R1, early; R2 late) differing in pitch acceleration rate and perceptual saliency. In R2, linguistic status effects revealed that T2 exhibited a larger degree of FFR rightward ear asymmetry as reflected in f0 amplitude relative to T20 . Relative to midline (ear asymmetry = 0), the only ear asymmetry reaching significance was that favoring left ear stimulation elicited by T20 . By left- and right-ear stimulation separately, FFRs elicited by T2 were larger than T20 in the right ear only. Within T20 , FFRs elicited by the earlier region were larger than the later in both ears. Within T2, no significant differences in FFRS were observed between regions in either ear. Collectively, these findings support the idea that origins of cortical processing preferences for perceptually-salient portions of pitch are rooted in early, preattentive stages of processing in the brainstem.

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