Neural fate of seen and unseen faces in visuospatial neglect: A combined event-related functional MRI and event-related potential study
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Summary
This study investigates the neural mechanisms underlying visual extinction in patients with right parietal damage, specifically addressing whether stimuli that escape conscious awareness still undergo cortical processing. Visual extinction is a deficit where a patient fails to perceive a stimulus in the contralesional field when it is presented simultaneously with an ipsilesional stimulus, despite intact early visual areas. The authors hypothesized that residual perceptual and semantic processing might occur in occipital and temporal cortices without awareness, but that integration with parietal regions is necessary for conscious perception. To test this, the researchers combined event-related functional MRI (fMRI) and event-related potentials (ERPs) in a single patient with chronic neglect and extinction caused by focal right parietal damage. The experimental design involved presenting schematic faces or shapes in the right visual field, left visual field, or both fields simultaneously. The critical condition involved bilateral simultaneous stimulation where a left face could be either perceived or extinguished. The patient underwent fMRI scanning using a 1.5-T scanner and ERP recording from 31 scalp locations. Stimulus duration was titrated to ensure a balanced number of extinguished and perceived trials. The fMRI analysis utilized the general linear model to compare brain activity during unilateral trials, extinguished bilateral trials, and perceived bilateral trials. Additionally, effective connectivity analysis was performed to assess how activity in visual areas coupled with other brain regions depending on awareness. ERP analysis focused on early visual components (P1, N1) and face-specific potentials (N170). The results demonstrated that extinguished faces still activated right primary visual cortex (V1) and inferior temporal cortex, indicating that early visual processing occurs without awareness. ERPs confirmed this, showing that extinguished faces elicited early occipital responses and a preserved face-specific N170 potential at 170 ms, similar to seen faces. However, when faces were perceived, there was significantly greater activity in a distributed network including right V1, bilateral fusiform gyri, and left parietal cortex. Crucially, effective connectivity analysis revealed that awareness of faces was associated with increased coupling between visual areas (V1 and fusiform gyrus) and dorsal parietal and frontal regions. In contrast, extinguished stimuli lacked this long-range connectivity. These findings suggest that neural activity in V1 and ventral temporal cortex can occur without conscious awareness, supporting the existence of separate cortical streams for feature extraction and spatial attention. The study concludes that while early visual processing remains intact in neglect patients, the coupling of these areas with dorsal parietal and frontal networks is critical for transforming neural activity into conscious perception. This provides evidence that visual extinction results from a failure of attentional integration rather than a complete loss of sensory input processing.
Provenance
The full processing record for this entry. Every stage of this paper's journey through the pipeline is logged — what ran, with which tool and model, how many attempts it took, and when it last completed. Discovered via author_sweep_intake on 2026-05-28.
| Stage | Outcome | Tool | Model | Prompt | Attempts | Completed |
|---|---|---|---|---|---|---|
| discover | success | author_sweep | — | — | 2 | 2026-05-28 |
| archive | success | semantic_scholar | — | — | 22 | 2026-06-09 |
| extract | success | cached | — | — | 2 | 2026-06-09 |
| clean | success | clean | — | — | 1 | 2026-06-04 |
| chunk | success | chunk | — | — | 1 | 2026-06-04 |
| embed | success | embed | Qwen/Qwen3-Embedding-8B | — | 1 | 2026-06-04 |
| enrich | success | — | — | — | 1 | 2026-05-28 |
| promote | success | — | — | — | 1 | 2026-06-04 |
| summarize | success | llm | qwen3.6-27b-prismaquant | summ-v5 | 1 | 2026-06-09 |
| tag | success | vector_similarity | — | — | 15 | 2026-06-11 |
| verify | success | — | — | — | 1 | 2026-06-09 |
Summary generated by qwen3.6-27b-prismaquant on 2026-06-09; verification: verified.
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