Regular Show: The Movie (2015)
As voluntary attention can increase the proportion of time of perceiving inputs to the attended eye in binocular rivalry (Chong et al. 2005; Zhang et al. 2012; Marx and Einhauser 2015), we hypothesized that prolonged top-down eye-specific attention by watching the dichoptic movie would increase the probability of perceiving the regular movie images and boost the neural responses to signals from the attended eye. This would cause sustained unbalanced responses in the 2 monocular pathways to some degree resembling the neural activity pattern during short-term monocular deprivation (Lunghi et al. 2015; Lyu et al. 2020). We surmised that prolonged watching the dichoptic movie might also cause a shift of perceptual ocular dominance, as often seen in monocular deprivation studies (for review, see Basgoze et al. 2018; Bao and Engel 2019).
Regular Show: The Movie (2015)
Diagram of the experimental session in experiment 2. A binocular rivalry pre-test preceded a preadaptation SSVEP test. After 60 min of adaption, a post-adaptation SSVEP test was completed followed by a binocular rivalry post-test. For the control session, the only difference was the adaptation phase, where both eyes viewed identical regular movie images though still flickering at the frequencies specified in the experimental session.
In the EEG formal experiment, subjects first performed 2 binocular rivalry tests (Fig. 2). Each included 5 trials. The first 5 trials served as a warm-up test which were not analyzed (Bai et al. 2017; Bao et al. 2018). The second 5 trials were the binocular rivalry pre-test measuring the perceptual ocular dominance before adaptation. Subjects then performed an EEG pre-test measuring the neural ocular dominance when they watched natural scene stimuli before adaptation. This was followed by a 1-h dichoptic-backward-movie adaption. During adaptation, the primary task was still to follow the logic of the regular movie. The dichoptic movie was played with sound (synchronized with the regular movie) for ease of eye-specific attentional allocation. Meanwhile, subjects had to detect infrequent blob targets as in experiment 1b. To prevent fatigue, the 1-h adaptation was divided into two 30-min sections. Subjects were allowed to rest for 5 min with their eyes closed between the 2 sections. At the end of adaptation, subjects performed an EEG post-test followed by a binocular rivalry post-test.
Illustration of the blob detection results for the 3 adaptation conditions of experiment 1b. The bars show the grand average detection percentages for each eye and each condition. D and ND mean presenting the regular movie to the dominant or nondominant eye, respectively. The circles show the individual data. Error bars represent standard errors of means.
Illustration of the normalized detection percentages for the 3 adaptation conditions of experiment 1b. The bars show the grand average normalized detection percentages for each eye and each condition. D and ND mean presenting the regular movie to the dominant or nondominant eye, respectively. The circles show the individual data. Error bars represent standard errors of means.
One thing unclear is to what extent this attention-driven ocular dominance plasticity is related to binocular rivalry mechanisms, considering that dissimilar movie images in the two eyes always rivaled. Therefore, experiment 3 adopted video-alternating stimuli presented monocularly to reduce interocular competition (Fig. 4a), with the regular movie always presented to the dominant eye and the backward movie to the opposite eye. 041b061a72