Doruk Deniz, Chanes Lorena, Malavera Alejandra, Merabet Lotfi B, Valero-Cabré Antoni, Fregni Felipe
Neuromodulation Center, Spaulding Rehabilitation Hospital, Harvard Medical School, Charlestown, MA 02129, USA.
Université Pierre et Marie Curie, CNRS UMR 7225-INSERM UMRS S975, Centre de Recherche de l'Institut du Cerveau et la Moelle (ICM), 75013 Paris, France.
Heliyon. 2018 Apr 30;4(4):e00595. doi: 10.1016/j.heliyon.2018.e00595. eCollection 2018 Apr.
The impact of visuospatial attention on perception with supraliminal stimuli and stimuli at the threshold of conscious perception has been previously investigated. In this study, we assess the cross-modal effects of visuospatial attention on conscious perception for near-threshold somatosensory stimuli applied to the face.
Fifteen healthy participants completed two sessions of a near-threshold cross-modality cue-target discrimination/conscious detection paradigm. Each trial began with an endogenous visuospatial cue that predicted the location of a weak near-threshold electrical pulse delivered to the right or left cheek with high probability (∼75%). Participants then completed two tasks: first, a forced-choice (felt once or twice?) and then, a (did you feel the stimulus and, if yes, where (left/right)?). Somatosensory discrimination was evaluated with the response reaction times of correctly detected targets, whereas the somatosensory conscious detection was quantified using perceptual sensitivity (d') and response bias (beta). A 2 × 2 repeated measures ANOVA was used for statistical analysis.
In the somatosensory discrimination task (1 task), participants were significantly faster in responding to correctly detected targets (p < 0.001). In the somatosensory conscious detection task (2 task), a significant effect of visuospatial attention on response bias (p = 0.008) was observed, suggesting that participants had a less strict criterion for stimuli preceded by spatially valid than invalid visuospatial cues.
We showed that spatial attention has the potential to modulate the discrimination and the conscious detection of near-threshold somatosensory stimuli as measured, respectively, by a reduction of reaction times and a shift in response bias toward less conservative responses when the cue predicted stimulus location. A shift in response bias indicates possible effects of spatial attention on internal decision processes. The lack of significant results in perceptual sensitivity (d') could be due to weaker effects of endogenous attention on perception.
以往曾研究过视觉空间注意对阈上刺激和意识知觉阈值处刺激的感知的影响。在本研究中，我们评估视觉空间注意对施加于面部的近阈值体感刺激的意识知觉的跨模态效应。
15名健康参与者完成了两阶段的近阈值跨模态线索-目标辨别/意识检测范式。每个试验开始时会有一个内源性视觉空间线索，该线索以高概率（约75%）预测将传递到右脸颊或左脸颊的微弱近阈值电脉冲的位置。参与者随后完成两项任务：首先，进行强制选择（感觉了一次还是两次？），然后，进行一项（你感觉到刺激了吗？如果是，在哪里（左/右）？）。通过正确检测到的目标的反应时间来评估体感辨别，而使用知觉敏感性（d'）和反应偏差（β）来量化体感意识检测。采用2×2重复测量方差分析进行统计分析。
在体感辨别任务（任务1）中，参与者对正确检测到的目标的反应明显更快（p<0.001）。在体感意识检测任务（任务2）中，观察到视觉空间注意对反应偏差有显著影响（p = 0.008），这表明与无效的视觉空间线索相比，参与者对由空间有效线索之前的刺激的标准不那么严格。
我们表明，当线索预测刺激位置时，空间注意有可能分别通过减少反应时间和将反应偏差转向不太保守的反应来调节近阈值体感刺激的辨别和意识检测。反应偏差的变化表明空间注意对内部决策过程可能产生影响。知觉敏感性（d'）缺乏显著结果可能是由于内源性注意对知觉的影响较弱。
