The Role Of The Fronto-parietal Network On Attentional Control:A TMS Study

Attentional is a fundamental cognitive activity in human. Attention can improve the detection ability of behavior and shorten the reaction. Many study have shown that attentional deficit is related with many clinical disorders, such as attention deficit hyperactivity disorder, Alzheimer’s disease and schizophrenias, then it is very important to study neural mechanism of attention in normal human. Behavior and neuroimaging studies have shown that when human attended to a visual stimuli, there were many brain areas tend to activity. But how do those active brain areas connect and communicative to represent the visual attention and modulated different kind of attention control? The answers of these question will be depending on the research of visual attention network.The present research using Transcranial Magnetic Stimulation technology to study the role of fronto-parietal attentional control network in visual attention. Here we used TMS to interfere with the activity of the right dorsal prefrontal cortex(DLPFC) or the right posterior parietal cortex(PPC), during the performance of a visual search task. Performance was evaluated at baseline, during TMS session.In the experiment of section 2, the paradigm included pop-out task and search task as well as the objects in working memory was updating in every trial. The result showed the performance of participants were improved in both pop-out and search task when TMS applied to DLPFC and PPC. The DLPFC involved top-down process in visual search. However the PPC have involved both pop-out and search task.In the experiment of section 3, the paradigm was similar to experiment of section 2, the difference is that the target object was invariable. However, in contrast to the result of experiment 1, the TMS disturbed the performance of participants whatever in pop-out or search task. RTs were prolonged when TMS was applied over the DLPFC in the search, but not in the pop-out condition, relative to the baseline session. It means that the DLPFC which is higher-level cognition areas really act crucial role in attention. In comparison, TMS over the PPC prolonged RTs in both the pop-out condition, and when the target appeared in the left visual field in the search condition. This result indicated that the PPC modulated bottom-up process and top-down process in visual attentionIn the summar, taken together these findings provide evidence for a differential role of DLPFC and PPC in the visual search, indicating that DLPFC has a specific involvement in the “search” condition, while PPC is mainly involved in detecting “popout” targets and search condition where target present in left visual field.