**A few hours of monocular patching temporarily enhances the deprived eye's contribution to binocular vision, constituting a form of adult brain plasticity. Although the mechanism for this plasticity is currently unknown, several imaging studies present evidence that monocular deprivation achieves its effects by changing excitatory–inhibitory balance in the visual cortex. Much of the past work on adult monocular patching utilized binocular rivalry to quantify the patching-induced shift in perceptual eye dominance, extracting periods of exclusive visibility (in which one eye's signal is suppressed from perception) to assess each eye's contribution to binocular vision while overlooking the occurrence of mixed visibility (in which information from both eyes is combined). In this paper, we discuss two experiments to investigate the effects of short-term monocular occlusion on the relative predominance of mixed and exclusive percepts during binocular rivalry. In addition to the known perceptual eye-dominance shift, we hypothesized patching would also increase the perception of mixtures during rivalry due to deprivation-induced changes in excitatory–inhibitory balance. Our data point to two previously unknown effects of monocular deprivation: (a) a significant increase in the overall fraction and median duration of mixed visibility during rivalry that is detectable up to at least an hour after removing the patch and (b) the overall fraction of superimposition; rather than piecemeal, mixed percepts are specifically enhanced after monocular deprivation. In addition to strengthening the contribution of the deprived eye, our results show that temporary monocular patching enhances the visibility of fused binocular percepts, likely the result of attenuated interocular inhibition.**

*deprived*eye that is observable up to at least an hour after deprivation (Lunghi, Burr, & Morrone, 2011). The ability of the adult visual system to temporarily shift perceptual eye dominance points to a latent functional plasticity whose mechanism is currently unknown although there is empirical evidence implicating changes in excitatory–inhibitory (E-I) balance in V1 (Chadnova, Reynaud, Clavagnier, & Hess, 2017; Lunghi, Emir, Morrone, & Bridge, 2015).

*SD*of the group mean. In sum, 13 individuals participated in the study. A subset of our participants (

*N*= 5, three women, 24 ± 1.3) completed additional postdeprivation measurements that were taken over the course of an hour after removing the eye patch to evaluate the decay of the patching-induced changes in rivalry dynamics.

^{2}. Subjects viewed the stimuli at a viewing distance of 70 cm with passive polarized 3-D glasses so that the left image was only seen by the left eye and the right image by the right eye. The polarized filters had the effect of reducing the luminance to about 40%, measured with a photometer.

*SEM*).

*d*variables are the overall fractions for the exclusive percepts from the nondeprived and deprived eyes. This ratio computed a value between −1 and 1, the extreme values indicating completely monocular vision from the nondeprived and deprived eyes, respectively. To evaluate deprivation-induced changes in these indices, we subtracted the baseline ratio from each postpatching ODI measure.

*t*tests on these normalized post/baseline values that determined whether deprivation significantly shifted the mean with respect to baseline (zero). We used the initial postdeprivation value for each dependent variable under the a priori assumption that the effect was maximal immediately after removing the patch.

*P*values were corrected for multiple comparisons using the false discovery rate (FDR) correction method outlined in Benajmini and Hochberg (1995). We obtained 95% confidence intervals and the standard deviation of a distribution of 1,000 bootstrapped resamples (each drawing 13 subjects with replacement) of the normalized post/baseline values for each dependent variable. All

*SEM*s in the current paper are equivalent to the standard deviation of the respective bootstrap distribution.

*t*tests to determine which time points were significantly shifted with respect to baseline.

*p*< 0.0001); therefore, a PCA transformation of the data would assist in mining statistically uncorrelated latent variables from the data that are arguably more informative of the neural processes underlying rivalry than the original task response variables used for analysis (Reynaud & Hess, 2017).

**A**

*is the representation of median duration data*

_{i}**X**

*at time point*

_{i}*i*(baseline or postpatching) in the PC space defined at baseline by the PC coefficient matrix

**C**. Both

**A**

*and*

_{i}**X**

*are*

_{i}*N*× 3 matrices, where

*N*represents the total number of participants. The columns of

**X**

*correspond to the median durations of the three percept categories (exclusive left, mixed, exlcusive right), and the columns of*

_{i}**A**

*correspond to the PC scores for the three PCs extracted at baseline defined by coefficient matrix*

_{i}**C**. We then conducted FDR-corrected pair-wise

*t*tests on the postbaseline values for each PC column

*j*in

**A**

*(i.e.,*

_{i}**A**

_{2}

*−*

_{j}**A**

_{1}

*) to evaluate patching-induced changes in the relative weight of each component's influence on binocular rivalry dynamics with respect to baseline. Importantly, PCA does not rely on our a priori assumptions (and subsequent dependent variables of interest) of the underlying processes driving rivalry phase durations. On the contrary, PCA uncovers statistically uncorrelated components of rivalry phase-duration data that may then map onto our understanding of the neural mechanisms involved in binocular rivalry, allowing us to evaluate patching-induced changes within those components.*

_{j}*M*= 0.03, 95% CI: [−0.10, 0.16], FDR-corrected

*p*> 0.05; median duration:

*M*= 0.06, 95% CI: [−0.05, 0.18], FDR-corrected

*p*> 0.05). However, we do find that the fraction and median duration of the exclusive percept of the nondeprived eye decrease significantly: fraction,

*M*= −0.31, 95% CI: [−0.41, −0.20],

*t*(12) = −5.41, FDR-corrected

*p*< 0.001; median duration,

*M*= −0.15, 95% CI: [−0.24, −0.04],

*t*(12) = −2.91, FDR-corrected

*p*< 0.05. This implies that the shift in perceptual eye dominance observed after patching may be driven by a decrease in the input strength of the nondeprived eye's image rather than a reciprocal increase in the deprived eye's contribution.

*t*(12) = −4.09, FDR-corrected

*p*< 0.01, as did that of the deprived eye's image, mean difference = 0.28, 95% CI: [0.09, 0.51], FDR-corrected

*p*> 0.05. Increases in the overall fractions of all three mixed percepts were also observed: fraction mixed (nondeprived eye),

*M*= 0.46, 95% CI: [0.15, 0.89],

*t*(12) = 3.19, FDR-corrected

*p*< 0.05; fraction mixed (balanced),

*M*= 0.72, 95% CI: [0.11, 1.55], FDR-corrected

*p*> 0.05; fraction mixed (deprived eye),

*M*= 0.47, 95% CI: [0.21, 0.75],

*t*(12) = 3.19, FDR-corrected

*p*< 0.05. These results indicate that the mixed percepts were enhanced without the introduction of eye-specific bias.

*M*= 0.33, bootstrapped 95% CI: [0.19, 0.52],

*t*(12) = 3.51, FDR-corrected

*p*< 0.01, and the median duration of mixed visibility, Figure 4B,

*M*= 0.30, bootstrapped 95% CI: [0.17, 0.44],

*t*(12) = 4.17, FDR-corrected

*p*< 0.01. The shift in perceptual eye dominance (using the exclusive percepts) was also highly significant,

*M*= 0.20, 95% CI: [0.11, 0.29],

*t*(12) = 4.42,

*p*< 0.001, Figure 4C. Interestingly, we did not observe a significant shift in perceptual eye dominance within the mixed percepts, mean difference = 0.03, 95% CI: [−0.04, 0.11],

*t*(13) = 0.78,

*p*> 0.05, further suggesting that the shift in perceptual eye dominance and the increase in mixed visibility may be separate effects of patching.

*F*(2, 10) = 1.30,

*p*< 0.05,

*M*= 0.74, 95% CI: [−0.22, 1.71]; t30:

*M*= 0.65, 95% CI: [0.06, 1.23]; t60:

*M*= 0.31, 95% CI: [−0.37, 0.99]).

*F*(2, 8) = 1.55,

*p*> 0.05,

*M*= 1.18, 95% CI: [0.06, 2.30]; t30:

*M*= 0.64, 95% CI: [−0.43, 1.74]; t60:

*M*= 0.28, 95% CI: [−0.55, 1.13]).

*F*(2, 8) = 1.78,

*p*> 0.05,

*M*= 0.12, 95% CI: [0.10, 0.23],

*t*(4) = 3.1, FDR-corrected

*p*< 0.05), as well at 30 min after removing the patch,

*M*= 0.08, 95% CI: [0.05, 0.11],

*t*(4) = 7.37, FDR-corrected

*p*< 0.01, but not at 60 min (FDR-corrected

*p*> 0.05), suggesting a gradual recovery to baseline levels.

*p*< 0.001). This finding inspired us to utilize a PCA to transform the variables in our median duration data set (exclusive left, mixed, exclusive right) into a new set of statistically uncorrelated variables that were possibly more informative of neural processes underlying rivalry. We administered a descriptive PCA on the baseline median durations extracted from the processed time series illustrated in Figure 2C to uncover three PCs that explained 100% of the variability in our data (Figure 5A). The PCA coefficients indicate the degree to which each PC (PCs 1–3) is associated with the original rivalry percept variables. PC 1 is most closely associated with the median duration of mixed visibility and explains 70.10% of the variability in the baseline data. For the purpose of this analysis, PC 1 can be interpreted as the binocular combination component underlying rivalry phase durations. For PC 2, the PCA extracted the correlation between the two exclusive percept variables; PC 2 is most closely associated with the median duration of both exclusive percepts and explains 28.94% of variability in the data. PC 2 can then be feasibly regarded as the perceptual suppression component underlying rivalry phase durations. Finally, PC 3 is anticorrelated between the two exclusive percepts and uncorrelated with mixed visibility; this PC explains the remaining 0.95% of the variability in the data. PC 3 points to interocular balance, or perceptual eye dominance, as a small underlying component influencing the baseline rivalry phase duration data.

*z*-normalized (mean = 0, standard deviation = 1) both the PC scores and their corresponding features in the original data set to ensure both sets were scaled similarly for comparison. The PC scores were all significantly correlated with the features we extracted from the original data set,

*F*s(1, 12) ≥ 21.4,

*p*s < 0.001, adjusted

*R*

^{2}≥ 0.61, indicating the PCA successfully extracted meaningful components underlying the phase-duration data at baseline (Figure 5C).

*t*tests were conducted on the postbaseline PC scores. We found that patching significantly increased the mean score of PC 1,

*M*= 0.65, 95% CI: [0.09, 1.21],

*t*(13) = 2.52, FDR-corrected

*p*< 0.05, and PC 3,

*M*= 0.33, 95% CI: [0.11, 0.55],

*t*(13) = 3.31, FDR-corrected

*p*< 0.05, but not PC 2,

*M*= −0.06, 95% CI: [−0.44, 0.30],

*t*(13) = −0.40; FDR-corrected

*p*> 0.05. Notably, the PCA uncovered statistically uncorrelated components of rivalry phase duration data that map on quite well to our understanding of several factors involved in binocular rivalry: binocular combination, perceptual suppression, and perceptual eye dominance. This approach allowed us to evaluate patching-induced changes within these mechanistic components, extending the insights of the previous analyses. Specifically, our results indicate that MD affects putative neural mechanisms responsible for binocular combination and perceptual eye dominance rather than those responsible for exclusive dominance.

^{2}, driven at a resolution of 960 × 1,080 per eye, with a refresh rate of 60 Hz and a nominal field of view of 100°. The left- and right-eye images were separated by a divider such that the left eye only viewed the left side of the goggles and the right eye only viewed the right side.

*d*variables indicate the overall fraction reported for seeing superimposition and piecemeal percepts, respectively. Negative values in the MPR indicated bias in favor of superimposition percepts, and positive values indicated bias in favor of piecemeal percepts. Patching-induced changes in the MPR were obtained by subtracting baseline from postpatching values.

*t*tests on the first postpatching measurement and baseline for (a) the overall fraction of mixed visibility, (b) the median duration of mixed visibility, (c) the mixed percept ratio (MPR), and (d) the eye dominance index (ODI). We also conducted a repeated-measures ANOVA with complementary post hoc paired

*t*tests on the MPR and ODI values to determine the time course of the decay of the effect of patching on these variables.

*M*= 1.09, 95% CI: [0.24, 1.93],

*t*(9) = 2.98,

*p*< 0.05, and median duration,

*M*= 0.24, 95% CI: [0.04, 0.43],

*t*(9) = 2.74,

*p*< 0.05, of mixed visibility during rivalry. Perceptual eye dominance was also significantly shifted in favor of the deprived eye with respect to baseline,

*M*= 0.12, 95% CI: [0.01, 0.23],

*t*(9) = 2.52,

*p*< 0.05.

*M*= −0.25, 95% CI: [−0.62, −0.12],

*t*(9) = −2.75,

*p*< 0.05. This indicates that the increase in mixed visibility observed in this experiment and in Experiment 1 is likely due to increases in the superimposition percepts rather than piecemeal percepts. This was confirmed by separate paired

*t*tests on the normalized postbaseline fractions for both superimposition and piecemeal percepts immediately after deprivation: superimposition,

*M*= 0.08, 95% CI: [0.03, 0.12],

*t*(9) = 4.01, FDR-corrected

*p*< 0.01; piecemeal,

*M*= −0.02, 95% CI: [−0.07, 0.02],

*t*(9) = −1.06, FDR-corrected

*p*> 0.05.

*F*(3, 27) = 0.38,

*p*> 0.05,

*p*s < 0.05.

*F*(3, 27) = 1.30,

*p*> 0.05,

*M*= 0.31, 95% CI: [0.06, 0.56],

*t*(9) = 2.8, FDR-corrected

*p*< 0.05, as well as at 15 min after removing the patch,

*M*= 0.30, 95% CI: [0.15, 0.45],

*t*(9) = 4.65, FDR-corrected

*p*< 0.01.

*F*(3, 27) = 0.70,

*p*> 0.05,

*t*(9) > 2.98, FDR-corrected

*p*s < 0.05.

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