关键词: 双眼竞争, 神经位点, tDCS, 刺激依赖性, 灵活配置机制

Abstract: Binocular rivalry occurs when the two eyes receive conflicting visual images, resulting in alternating perceptual dominance rather than image fusion. This phenomenon provides a unique window into the neural basis of visual consciousness, as the visual input remains constant while subjective awareness fluctuates. A fundamental question in binocular rivalry research is: where along the visual pathway does the competition occur? Early theories proposed that rivalry primarily involves monocular neurons in primary visual cortex (V1) or the lateral geniculate nucleus through interocular inhibition mechanisms. However, electrophysiological studies in monkeys revealed stronger correlations between neural activity in higher visual areas (e.g., inferotemporal cortex) and perceptual states, suggesting competition at object-level representations. The hybrid model emerged to reconcile these findings, proposing that rivalry occurs across multiple hierarchical levels through reciprocal interactions. Yet a critical question remains inadequately addressed: How might different visual conditions alter the sites at which rivalry competition is most prevalent? While neuroimaging studies hint at this possibility, systematic causal evidence has been lacking, preventing us from understanding whether the brain flexibly recruits different neural resources based on stimulus characteristics. This study employed transcranial direct current stimulation (tDCS) to systematically examine the causal roles of four candidate brain regions—occipital cortex, right parietal cortex, left parietal cortex, and prefrontal cortex—across two stimulus types representing distinct representational levels. We conducted eight independent experiments following a 2×4 design: two stimulus types (orthogonal gratings as local-feature stimuli vs. face/house images as object-level stimuli) × four brain regions. Each experiment used a within-subjects design with three tDCS conditions (anodal, cathodal, and sham stimulation). A total of 160 participants were recruited across experiments (18–22 per experiment; mean age = 20.8 years; all right-handed with normal or corrected-to-normal vision). We used high-definition tDCS with a 4×1 electrode montage (one central electrode and four return electrodes) positioned over target regions based on the international 10-10 system. Stimulation intensity did not exceed 1.00 mA and lasted 20 minutes during each session. Participants completed binocular rivalry tasks using a mirror stereoscope while continuously reporting their perceptual states via key presses. We measured two dependent variables: eye dominance strength (reflecting competitive bias and relative gain) and perceptual alternation rate (reflecting destabilization and switching frequency). Results revealed a robust stimulus-dependent pattern of regional involvement. For grating stimuli (Experiments 1–4), occipital tDCS significantly change eye dominance strength, F(2, 38) = 7.637, p = 0.002, η_p^2= 0.287, 1-β > 0.999. Right parietal tDCS also change eye dominance, F(2, 38) = 5.355, p = 0.009, η_p^2= 0.220, 1-β = 0.999, while change alternation rate, F(2, 38) = 3.706，p = 0.034, η_p^2= 0.163, 1-β = 0.990. Neither left parietal nor prefrontal tDCS affected grating rivalry. In striking contrast, for face/house stimuli (Experiments 5–8), left parietal significantly change eye dominance, F(2, 38) = 3.974, p = 0.027, η_p^2= 0.173, 1-β = 0.994. prefrontal tDCS change eye dominance, F(2, 38) = 4.062, p = 0.025, η_p^2= 0.176, 1-β = 0.995. Notably, neither occipital nor right parietal stimulation affected face/house rivalry. This double dissociation demonstrates that simple grating rivalry predominantly engages occipital cortex (early interocular competition) and right parietal cortex (spatial attention modulation), whereas object-level rivalry recruits prefrontal cortex (cognitive control) and left parietal cortex (object feature integration). This study provides the causal evidence for stimulus-dependent flexible configuration of rivalry sites. Rather than employing a fixed neural network, the brain flexibly allocates different hierarchical neural resources based on stimulus representational level. These findings advance the hybrid model from a descriptive multi-site framework to a predictive theory specifying how stimulus properties determine dominant competitive loci, offering new insights into the flexible neural architecture underlying visual consciousness.

Key words: Binocular rivalry, Neural sites, tDCS, Stimulus-dependent patterns, Flexible site configuration