The timing of visual selective attention in fronto-parietal network: TMS behavioral and brain structural evidence.

Neuronal activation within the fronto-parietal network (FPN) exhibits distinct time windows during bottom-up and top-down attention. Previous studies have shown that transcranial magnetic stimulation (TMS) applied to the FPN can have inhibitory effects on attention performance. However, whether the timing of TMS over the FPN differentially inhibits bottom-up and top-down behaviors requires further investigation. Here, we examined how the timing of TMS delivery to FPN nodes affects visual selective attention. The single-pulse TMS was applied to the right dorsolateral prefrontal cortex (rDLPFC) and right superior parietal lobule (rSPL) in both active and sham groups, with different timings (early: 33 ms, 50 ms, 66 ms, 83 ms; late: 216 ms, 233 ms, 250 ms, 266 ms) of TMS pulses after stimulus onset. Behavioral results showed that late TMS over the rDLPFC impaired top-down attention by decreasing accuracy and prolonged reaction times (RTs). Late TMS over the rSPL enhanced top-down attention by increasing accuracy and reducing the RT/Accuracy index. Late TMS over the rDLPFC and rSPL respectively enhanced and reduced the cognitive load difference between bottom-up and top-down attention. Voxel-based morphometry further revealed that RTs in the active group were correlated with gray matter volume (GMV) in the fronto-parietal cortex. Predictive analysis confirmed the stability of the associations between regional GMV and attention. These findings provide causal behavioral evidence that the FPN contributes to visual selective attention during the late time window, and the brain structure results further support the relationship between fronto-parietal structure and the behavioral regulation of visual selective attention.