Paired chirp evoked cortical inhibition and its behavioral correlates in a speech intelligibility task

Successful auditory stream segregation depends on correctly inhibiting irrelevant stimuli being perceived in parallel with relevant information. Here, we analyze the behavioral correlates of inhibitory processing in healthy subjects, by first calculating the percentage of inhibition elicited through a paired-chirp auditory stimulation paradigm and then analyzing its correlation to the score in a speech intelligibility task. Analysis of cortical inhibition was made both in amplitude and phase, focusing on the N1-P2 complex. Significant inhibition between the condition and the test chirp in both of the inter stimulus intervals (ISIs) used and both N1 and P2 waves was observed. Inhibition in phase synchronization stability (PSS) showed a positive correlation to scores obtained in the task for all given modalities of the study, while amplitude analysis showed a correlation for the N1 wave with 500 ms ISI only. It was shown that the PSS analysis provides a more reliable representation of cortical inhibition, able to correlate to the attentional task. It is concluded that the given paradigm allows to assess inhibitory processing, vital to the allocation of attention.