Lateralization in the dichotic listening of tones is influenced by the content of speech
Ikusi/ Ireki
Data
2020Egilea
Mei, Ning
Flinker, Adeen
Zhu, Miaomiao
Cai, Qing
Tian, Xing
Ning Mei, Adeen Flinker, Miaomiao Zhu, Qing Cai, Xing Tian, Lateralization in the dichotic listening of tones is influenced by the content of speech, Neuropsychologia, Volume 140, 2020, 107389, ISSN 0028-3932, https://doi.org/10.1016/j.neuropsychologia.2020.107389.
Laburpena
Cognitive functions, for example speech processing, are distributed asymmetrically in the two hemispheres that mostly have homologous anatomical structures.
Dichotic listening is a well-established paradigm to investigate hemispherical lateralization of speech. However, the mixed results of dichotic listening, especially
when using tonal languages as stimuli, complicates the investigation of functional lateralization. We hypothesized that the inconsistent results in dichotic listening
are due to an interaction in processing a mixture of acoustic and linguistic attributes that are differentially processed over the two hemispheres. In this study, a
within-subject dichotic listening paradigm was designed, in which different levels of speech and linguistic information was incrementally included in different
conditions that required the same tone identification task. A left ear advantage (LEA), in contrast with the commonly found right ear advantage (REA) in dichotic
listening, was observed in the hummed tones condition, where only the slow frequency modulation of tones was included. However, when phonemic and lexical
information was added in simple vowel tone conditions, the LEA became unstable. Furthermore, ear preference became balanced when phonological and lexicalsemantic
attributes were included in the consonant-vowel (CV), pseudo-word, and word conditions. Compared with the existing REA results that use complex
vowel word tones, a complete pattern emerged gradually shifting from LEA to REA. These results support the hypothesis that an acoustic analysis of suprasegmental
information of tones is preferably processed in the right hemisphere, but is influenced by phonological and lexical semantic processes residing in the left hemisphere.
The ear preference in dichotic listening depends on the levels of speech and linguistic analysis and preferentially lateralizes across the different hemispheres. That is,
the manifestation of functional lateralization depends on the integration of information across the two hemispheres.