Department of Psychiatry and Psychotherapy, Multisensory Integration Lab, Charité - Universitätsmedizin Berlin, Berlin, Germany.
Biological Psychology, Christian-Albrechts-University, Kiel, Germany.
Eur J Neurosci. 2022 Jun;55(11-12):3141-3153. doi: 10.1111/ejn.15169. Epub 2021 Mar 18.
Occipital oscillations in the alpha band are closely related to visual perception and attention. In multiple studies, increased alpha power has been shown to reduce detection rates of hard-to-detect visual stimuli. Recent studies explain this finding by a shift in perceptual bias. Moreover, the phase of alpha oscillations prior to stimulus onset appears to be critical for the detection of visual stimuli. This is explained by a shift in cortical excitability over the course of each alpha cycle. However, prior studies often used short presentation times of visual stimuli at the perceptual threshold. Here, we use longer presentation times to elucidate whether the same mechanisms hold for the perception of salient but challenging visual stimuli presented for up to 1,500 ms. To this end, we presented participants with hard to distinguish but salient upright or tilted Gaussian gratings in a two-alternative forced choice task, while recording occipital electroencephalographic activity. Previous reports link alpha power to stimulus detection hit rates, and we found that low prestimulus power at the individual alpha frequency relates to higher perceptual accuracy. Contrary to recent findings, we neither found an influence of alpha power on criterion, nor an influence of alpha phase on perception or response speed. We argue that longer presentation times might attenuate a possible response bias, and increased excitability might sharpen the discrimination ability, thereby leading to increased perceptual accuracy and unaffected response criterion.
枕部α波段的振荡与视觉感知和注意力密切相关。在多项研究中，增加α波功率已被证明会降低难以察觉的视觉刺激的检测率。最近的研究通过感知偏差的转变来解释这一发现。此外，刺激前α振荡的相位似乎对视觉刺激的检测至关重要。这可以通过每个α周期中皮质兴奋性的变化来解释。然而，之前的研究通常使用接近感知阈的视觉刺激的短呈现时间。在这里，我们使用更长的呈现时间来阐明相同的机制是否适用于感知突出但具有挑战性的视觉刺激，这些刺激呈现时间长达 1500 毫秒。为此，我们在二选一强制选择任务中向参与者呈现难以区分但突出的垂直或倾斜的高斯光栅，同时记录枕部脑电图活动。先前的报告将α波功率与刺激检测命中率联系起来，我们发现个体α频率的预刺激功率低与更高的感知准确性相关。与最近的发现相反，我们既没有发现α波功率对标准的影响，也没有发现α相位对感知或反应速度的影响。我们认为，更长的呈现时间可能会减弱可能的反应偏差，而增加的兴奋性可能会提高辨别能力，从而导致感知准确性提高，而反应标准不受影响。
