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Reactive and Proactive Response Inhibition in Neurodevelopmental Stuttering
- Author / Creator
- Tendera, Anna
The present doctoral thesis focused on understanding the potential imbalance of inhibitory control in neurodevelopmental stuttering. Inhibitory control is defined as an ability to suppress behaviours that are no longer needed. Two types of inhibitory control were of particular interest - reactive inhibition, the ability to rapidly cancel an ongoing motor behaviour that is no longer required in reaction to a particular external cue; and proactive inhibition, the ability to anticipate the potential necessity of a withhold response and to make an intrinsically-generated decision to stop.
Using a behavioural reactive inhibition task (Study 1), we found that AWS showed a similar point of subjective equality, a psychometric measure of stopping effectiveness when compared to AWNS. The probability of stopping for AWS was also similar to AWNS. Similar probability of stopping for AWS and AWNS was evident in both speech and manual response conditions. Response times (RTs) were comparable across conditions. In the behavioural proactive inhibition task (Study 2), we found some subtle dysregulation in proactive stopping processes in AWS, which influenced the overall accuracy of stopping and decreased its probability in both speech and manual response conditions. However, PSE was similar in AWS and AWNS. Additionally, AWS tended to respond faster in failed STOP trials and in correct GO trials in manual and speech conditions. Finally, a faster RT of GO trials after a failed STOP trials (adjRT) was present in AWS, indicating faster RT adjustments after an error, but only when a manual response was required. In the electroencephalographic (EEG) reactive inhibition task (Study 3), we found that AWS had a shallower P3 amplitude in trials when a stop signal was presented compared to AWNS. AWS also showed an earlier P3 peak than AWNS. The N2 component, however, was not sensitive to group differences. The EEG results demonstrate the utility of P3 as a temporally precise neural marker of stuttering.
Taken together, these findings suggest that behavioural measurements in proactive inhibition were sensitive to stuttering, while reactive behavioural measurements showed that stopping in AWS was as effective as in AWNS. However, the ERP findings of stopping in AWS showed important latency and amplitude differences, consistent with the idea that the neural correlates of inhibition are dysregulated in AWS.
- Graduation date
- Fall 2019
- Type of Item
- Doctor of Philosophy
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