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The C1 ERP component reflects the earliest visual processing in V1. However, it remains debated whether attentional load can influence it or not. We conducted two EEG experiments to investigate the effect of attentional load on the C1. Task difficulty was manipulated at fixation using an oddball detection task that was either easy (low load) or difficult (high load), while the distractor was presented in the upper visual field (UVF) to score the C1. In Experiment 1, we used a block design and the stimulus onset asynchrony (SOA) between the central stimulus and the peripheral distractor was either short or long. In Experiment 2, task difficulty was manipulated on a trial‐by‐trial basis using a visual cue, and the peripheral distractor was presented either before or after the central stimulus. The results showed that the C1 was larger in the high compared to the low load condition irrespective of SOA in Experiment 1. In Experiment 2, no significant load modulation of the C1 was observed. However, we found that the contingent negative variation (CNV) was larger in the low compared to the high load condition. Moreover, the C1 was larger when the peripheral distractor was presented after than before the central stimulus. Combined together, these results suggest that different top‐down control processes can influence the initial feedforward stage of visual processing in V1 captured by the C1 ERP component. Our new ERP findings inform about top‐down modulatory effects created by attentional load on early visual processing in the primary visual cortex (V1). In two experiments, we found that V1 activity was not reduced when attentional load increased. However, this lack of modulation could be explained by the likely contribution of other cognitive processes, including working memory, which could mask or interfere with the early gating of sensory processing in V1 created by attentional load. [ABSTRACT FROM AUTHOR]

The C1 event‐related potential (ERP) captures the earliest stage of feedforward processing in the primary visual cortex (V1). An ongoing debate is whether top‐down selective attention can modulate the C1. One side of the debate pointed out that null findings appear to outnumber positive findings; thus, selective attention does not seem to influence the C1. However, this suggestion is not based on a valid approach to summarizing evidence across studies. Therefore, we conducted a systematic review and meta‐analysis investigating the effects of selective attention on the C1, involving 47 experiments and 794 subjects in total. Despite heterogeneity across studies, results suggested that attention has a moderate effect on the C1 (Cohen's dz = 0.33, p <.0001); that is, C1 amplitude is larger for visual stimuli that are attended than unattended. These results suggest that C1 is affected by top‐down selective attention. This is the first systematic review and meta‐analysis for the effects of selective attention on the C1 ERP component. We showed statistical evidence in favor of an effect of selective attention on the C1 and no difference of modulation by different types of attention. [ABSTRACT FROM AUTHOR]

Selective attention is essential when we face sensory inputs with distractions. In the past decades, Lavie's load theory of selective attention delineates a complete picture of distractor suppression under different attentional control load. The present study was originally designed to explore how reward modulates the load effect of attentional selection. Unexpectedly, it revealed new findings under extended attentional load that was not involved in previous work. Participants were asked to complete a rewarded attentive visual tracking task while presented with irrelevant auditory oddball stimuli, with their behavioral performance, event‐related potentials and pupillary responses recorded. We found that although the behavioral performance and pupil sizes varied unidirectionally with the attentional load, the processing of distractors as reflected by the mismatch negativity (MMN) increased first and then decreased. In contrast to the prediction of Lavie's theory that attentional control fails to effectively suppress distractor processing under high attentional control load, our finding suggests that extremely high attentional control load may instead require suppression of distractor processing at a stage as early as possible. Besides, P3a, a positive‐polarity response sometimes following the MMN, was not affected by the attentional load, but both N1 (a negative‐polarity component peaking ~100 ms from sound onset) and P3a were weakened at higher reward, indicating that reward leads to attenuated early processing of distractor and thus suppresses the attentional orienting towards distractors. These findings altogether complement Lavie's load theory of selective attention, presenting a more complex picture of how attentional load and reward affects selective attention. In a rewarded attentive tracking task with auditory distractors, the processing of distractors was found to increase first and then decrease with attentional load, and also weakened with higher reward. This contradicts the prediction of previous theory that attentional control fails to suppress distractor processing under high attentional control load. Instead, it suggests that extremely high attentional control load may require suppression of distractor processing at an early stage, presenting a more complex picture of how attentional load and reward affect selective attention. [ABSTRACT FROM AUTHOR]