Subcortical sources dominate the neuroelectric auditory frequency-following response to speech.
Neuroimage
; 175: 56-69, 2018 07 15.
Article
em En
| MEDLINE
| ID: mdl-29604459
ABSTRACT
Frequency-following responses (FFRs) are neurophonic potentials that provide a window into the encoding of complex sounds (e.g., speech/music), auditory disorders, and neuroplasticity. While the neural origins of the FFR remain debated, renewed controversy has reemerged after demonstration that FFRs recorded via magnetoencephalography (MEG) are dominated by cortical rather than brainstem structures as previously assumed. Here, we recorded high-density (64 ch) FFRs via EEG and applied state-of-the art source imaging techniques to multichannel data (discrete dipole modeling, distributed imaging, independent component analysis, computational simulations). Our data confirm a mixture of generators localized to bilateral auditory nerve (AN), brainstem inferior colliculus (BS), and bilateral primary auditory cortex (PAC). However, frequency-specific scrutiny of source waveforms showed the relative contribution of these nuclei to the aggregate FFR varied across stimulus frequencies. Whereas AN and BS sources produced robust FFRs up to â¼700â¯Hz, PAC showed weak phase-locking with little FFR energy above the speech fundamental (100â¯Hz). Notably, CLARA imaging further showed PAC activation was eradicated for FFRs >150â¯Hz, above which only subcortical sources remained active. Our results show (i) the site of FFR generation varies critically with stimulus frequency; and (ii) opposite the pattern observed in MEG, subcortical structures make the largest contribution to electrically recorded FFRs (ANâ¯≥â¯BSâ¯>â¯PAC). We infer that cortical dominance observed in previous neuromagnetic data is likely due to the bias of MEG to superficial brain tissue, underestimating subcortical structures that drive most of the speech-FFR. Cleanly separating subcortical from cortical FFRs can be achieved by ensuring stimulus frequencies are >150-200â¯Hz, above the phase-locking limit of cortical neurons.
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Texto completo:
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Base de dados:
MEDLINE
Assunto principal:
Córtex Auditivo
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Percepção da Fala
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Processamento de Imagem Assistida por Computador
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Colículos Inferiores
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Eletroencefalografia
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Potenciais Evocados Auditivos
Limite:
Adult
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Female
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Humans
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Male
Idioma:
En
Revista:
Neuroimage
Assunto da revista:
DIAGNOSTICO POR IMAGEM
Ano de publicação:
2018
Tipo de documento:
Article