Attentional load modifies early activity in human primary visual cortex

Rauss, Karsten; Pourtois, Gilles; Vuilleumier, Patrik; Schwartz, Sophie · 2008 · OpenAlex-citations

DOI: 10.1002/hbm.20636

archive: archived pipeline: cataloged verified

Get this paper ↗ (DOI — opens at the source; we link to it, we don't host it)

Summary

This study investigates whether attentional load modulates the earliest stages of visual processing in the human primary visual cortex (V1). Guided by Lavie’s load theory of selective attention, which posits that the locus of attentional filtering shifts based on cognitive demands, the authors sought to determine if high attentional load suppresses early neural responses to irrelevant peripheral distractors. While previous functional MRI studies indicated reduced V1 activation under high load, they could not distinguish between early feedforward processing and later feedback mechanisms. This research addresses that gap by using high-density electroencephalography (EEG) to track the precise time course of attention-related effects on the C1 component, the earliest visual evoked potential associated with V1 activity. The experiment involved 28 healthy volunteers divided into two groups: one tested with stimuli in the upper visual field (VF) and the other in the lower VF. Participants performed a rapid serial visual presentation task at fixation, alternating between low attentional load (simple color detection) and high attentional load (complex conjunction discrimination). During these tasks, task-irrelevant distractors were flashed in the periphery. EEG data were recorded from 62 electrodes, and analyses included peak amplitude measurements, microstate segmentation to assess topographical stability, and local autoregressive average (LAURA) source localization to identify neural generators. Behavioral performance confirmed that the high-load condition significantly increased reaction times and error rates, validating the manipulation of attentional demands. The results demonstrated that attentional load significantly modulated the amplitude of the C1 component, but only for distractors presented in the upper VF. Under high attentional load, C1 amplitudes were significantly reduced for upper VF distractors compared to low load, whereas no such modulation occurred for lower VF distractors. Microstate analyses revealed significant topographical differences between load conditions within the first 100 ms post-stimulus for the upper VF group, indicating early changes in neural generator configuration. Source localization confirmed that distractor-related activity originated primarily in early visual areas near the occipital pole. Notably, while prefrontal activity differed between load conditions, the early visual modulation was specific to the upper VF. These findings provide evidence that attentional load can filter irrelevant information at the very earliest stages of cortical processing, supporting models of flexible attentional selection. The study confirms that top-down influences can impact initial sensory inputs in V1, rather than merely reshaping later representations. However, the pronounced asymmetry between upper and lower visual fields suggests that attentional mechanisms are not uniform across the visual cortex. This functional asymmetry implies that the efficiency or mechanism of early attentional filtering may depend on the specific retinotopic location of the stimulus, offering new insights into the spatial constraints of attentional selection in humans.

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.

Summary generated by qwen3.6-27b-prismaquant on 2026-06-26; verification: verified.

Topics

Ranked by relevance to this paper. Hover a topic for its definition.

• attention selective divided