Cortico-Cortical Interactions in Spatial Attention: A Combined ERP/TMS Study
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Summary
This study investigates the neural mechanisms underlying spatial attention during visual search, specifically examining the role of the right posterior parietal cortex (rPPC) in cortico-cortical interactions. While functional imaging has identified a dorsal frontoparietal network involved in visual search, the specific functions of areas like the rPPC and their interactions with sensory cortex remain poorly understood. To address this, the authors combined transcranial magnetic stimulation (TMS) and event-related potentials (ERPs) to assess how disrupting rPPC activity affects both behavioral performance and the timing of attentional shifts. The experimental design involved seven healthy participants performing a conjunction visual search task, where targets were defined by a combination of color and orientation. Single-pulse TMS was delivered 100 ms after the onset of the search array, targeting either the rPPC or a control site at the vertex. Simultaneously, EEG was recorded to measure the N2pc component, an ERP marker associated with the focusing of attention on target locations. The study compared reaction times (RTs) and ERP waveforms between rPPC and vertex stimulation conditions to determine if rPPC disruption specifically impaired attentional selectivity. The results demonstrated that TMS over the rPPC significantly delayed reaction times on target-present trials compared to vertex stimulation, indicating an impairment in search performance. Crucially, this behavioral deficit had a direct neural correlate: the early phase of the N2pc component (250–300 ms post-stimulus) was eliminated over the right hemisphere when TMS was applied to the rPPC, whereas it remained present during vertex stimulation. Later phases of the N2pc (363–413 ms) were unaffected by the stimulation. No significant effects were observed over the unstimulated left hemisphere. These findings provide evidence that the rPPC plays a critical role in the initiation of attentional shifts. The elimination of the early N2pc suggests that TMS-induced disruption of rPPC interferes with top-down control signals sent to remote extrastriate visual areas. This supports the hypothesis that cortico-cortical links implement rapid, top-down attentional modulations of sensory processing, with the rPPC facilitating the initial selection of target locations within 250 ms of stimulus onset.
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| Stage | Outcome | Tool | Model | Prompt | Attempts | Completed |
|---|---|---|---|---|---|---|
| discover | success | OpenAlex-citations | — | — | 1 | 2026-06-17 |
| archive | success | semantic_scholar | — | — | 6 | 2026-06-25 |
| extract | success | cached | — | — | 2 | 2026-06-25 |
| clean | success | clean | — | — | 1 | 2026-06-18 |
| chunk | success | chunk | — | — | 1 | 2026-06-18 |
| embed | success | embed | Qwen/Qwen3-Embedding-8B | — | 1 | 2026-06-18 |
| promote | success | — | — | — | 1 | 2026-06-17 |
| summarize | success | llm | qwen3.6-27b-prismaquant | summ-v5 | 1 | 2026-06-25 |
| tag | success | vector_similarity | — | — | 6 | 2026-06-18 |
| verify | success | — | — | — | 1 | 2026-06-26 |
Summary generated by qwen3.6-27b-prismaquant on 2026-06-25; verification: verified.
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