Cortical activity evoked by voice pitch changes: A combined fNIRS and EEG study

Functional near-infrared spectroscopy (fNIRS) and electroencephalography (EEG) data were simultaneously obtained from normal-hearing listeners presented with continuous natural vowel sequences to study the interrelation of the haemodynamic and electrophysiological cortical responses evoked by voice pitch changes. fNIRS topographies and distributed ERP source reconstructions both indicated additional activity in the right superior temporal cortex if the prosodic contours varied between successive vowels, rather than being the same throughout the sequences. The source-level ERPs furthermore revealed two temporally and spatially separable adaptation processes in superior temporal cortex: Firstly, the early P1 component was bilaterally attenuated when vowels with the same prosodic contours were presented repeatedly, reflecting sensory adaptation. Secondly, the later P2 and sustained potential components were smaller in the right hemisphere during sequences without prosodic changes, which is taken to represent an attention-based adaptation effect. The present results demonstrate the convergence of both methods and demonstrate which ERPs underlie the right-lateralised activity in superior temporal cortex evoked in response to pitch changes that has been observed in many neuroimaging studies.