| Summary: | 碩士 === 國立中央大學 === 認知與神經科學研究所 === 102 === The presupplementary motor area (pre-SMA) and the right inferior frontal gyrus
(rIFG) are critical for successful response inhibition. However, different conclusions
regarding their roles have been made. Since stop signals usually appear abruptly and
infrequently, it has been argued that attentional capture may be involved in the task. To
dissociate inhibition and attentional capture, an “ignore” condition in a stimulus selective
stop-signal task was introduced. Because the ignore signal shares all but one feature with
the stop signal but does not require stopping, performance in the ignore conditions can be
contrasted to that in the stop conditions. However, some argued that the role of the ignore
signal might not be as straightforward as it seems.
The current study aimed to examine how ignore trials may affect the inhibitory
process and the causal relations of pre-SMA and rIFG in implementing such trials by using
theta burst TMS (cTBS). The objective of Experiment 1 was to testify whether “ignore”
trials affect performance by comparing participants’ performances in both simple and
selective stop-signal tasks by strategy classifications. Results showed that ignore trials also
influenced the stop process, indicating that ignore trials may not only represent attentional
capture but also partial inhibition (i.e. response slowing). In Experiment 2, cTBS was
applied over the pre-SMA and rIFG to further examine their roles in partial inhibition in
participants whose ignore RTs were fast and those who were slow. Results showed a
double dissociation between brain regions. cTBS over the rIFG showed a decrease in RT in
the slow ignore RT group, indicating the involvement of rIFG in partial inhibition. On the
other hand, cTBS over the pre-SMA showed an escalated ignore RT, suggesting that the ! iii
pre-SMA might play a role in suppressing inhibitory function in order to respond fast in
ignore trials.
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