Effects of attentional instructions on neural and behavioral correlates of vocal auditory feedback control in post-stroke aphasia.

Existing evidence supports the notion that feedback-based attentional instructions can modulate vocal sensorimotor control mechanisms. Here, we investigated whether such instructions can improve the neural and behavioral functions for vocal auditory feedback control in individuals with aphasia. A total of 66 participants with post-stroke aphasia and 64 age-matched controls performed steady vocalizations of the speech vowel sound /a/ while their real-time auditory feedback was randomly altered by ±100 cents pitch-shift stimuli during electro-encephalography (EEG) recordings. Two conditions were tested: 1) participants received instructions to monitor their feedback and press buttons to indicate the detection of pitch-shift alterations, and 2) participants performed the same task without such instructions. Results indicated significantly lower accuracy of pitch shift detection in aphasia vs. controls. Event-related potential (ERP) analysis revealed that the amplitude of P2 neural component was increased under instructions in both groups, with stronger effects in controls than aphasia. We also found that the magnitude of vocal compensations was reduced under instructions in controls without such an effect for aphasia. In addition, attentional instructions resulted in reconfiguration of neural-behavioral coupling: under instructions, larger P2 activities were associated with smaller vocal compensations whereas no such relationship was observed without instructions. Moreover, larger P2 amplitudes predicted better detection accuracies in aphasia. These findings provide evidence that attention to auditory feedback modulates speech error detection while stabilizing vocal motor output. In aphasia, attentional modulation provide a potential mechanism to support speech monitoring and improve communicative outcomes via linking cortical error processing to conscious feedback awareness.