Subjects: Psychology >> Social Psychology submitted time 2023-03-27 Cooperative journals: 《心理学报》
Abstract： Continuous flash suppression (CFS) is one of the common methods to study unconscious visual processing. In the regular CFS paradigms used in previous studies, dynamic or high contrast image sequences (such as the Mondrian pattern sequences) are presented to one eye as masks. Meanwhile, a static or lower contrast target is presented to the opposite eye, which can be rendered invisible by the masks for a short period of time. The present study was designed to explore whether the CFS can effectively block the conscious processing of multiple moving targets. Inspired by the camouflage of chameleons in the nature, we proposed a novel CFS paradigm (which we call the “chameleon” paradigm). By using the alpha blending algorithm, we ensured the color of the targets to be consistent with the corresponding regions of the CFS masks at any moment. We then tested whether the “chameleon” paradigm can obscure the targets’ motion information from awareness more effectively than the regular CFS paradigm. We randomly recruited eight participants. Their dominant eyes were presented with the regular CFS masks, meanwhile the nondominant eyes were presented with ten spatially non-overlapping squares as the targets which moved either upwards or downwards at a constant velocity. Each square had one second of lifetime. Thus, for each square, after every one second of movement, its position was reset, and then it continued to move in the same direction at the same speed. In each trial, the target squares were presented for ten seconds (refreshing their positions ten times) at most. By manipulating the degree of color consistency between the targets and the masks, a total of four experimental conditions were included, with a “chameleon” condition and three control conditions. Participants were instructed to report the moving direction of the targets on seeing the targets by pressing a corresponding button. The program recorded both the response accuracy and the response time since the start of a trial (i.e. the time required for the targets to break into awareness, aka the breakthrough time). We also calculated the percentage of trials where the targets broke into awareness, which was called the breakthrough rate. The results showed that the “chameleon” paradigm allowed the CFS masks to efficiently block the conscious processing of multiple moving targets. Specifically, as compared to the three control conditions with less degree of color consistency between the targets and the CFS masks, the breakthrough rate was significantly lower under the “chameleon” condition where the color of the targets was fully consistent with the CFS masks. No significant differences were found for the breakthrough rate between the three control conditions. Moreover, according to the grand average data, in the “chameleon” condition the moving targets could break into awareness within 10 s in only about 25% of the trials. For the three control conditions, this probability increased to more than 80%, suggesting an overwhelming advantage of the “chameleon” paradigm in rendering multiple moving targets invisible. Another advantage of the “chameleon” paradigm is that it does not require the CFS masks to contain any motion information resembling the targets, thereby it ensures that the measurement of unconscious visual motion processing is exclusively from the target. Compared with the idea of modifying CFS masks in the literature, our method is believed to have broader applicability. Therefore, we recommend the “chameleon” paradigm a useful tool for future investigations of unconscious visual motion information processing.
Subjects: Psychology >> Cognitive Psychology submitted time 2022-01-21
Abstract：
Continuous flash suppression (CFS) is one of the common methods to study unconscious visual processing. In the regular CFS paradigms used in previous studies, dynamic or high contrast image sequences (such as the Mondrian pattern sequences) are presented to one eye as masks. Meanwhile, a static or lower contrast target is presented to the opposite eye, which can be rendered invisible by the masks for a short period of time. The present study was designed to explore whether the CFS can effectively block the conscious processing of multiple moving targets. Inspired by the camouflage of chameleons in the nature, we proposed a novel CFS paradigm (which we call the "chameleon" paradigm). By using the alpha blending algorithm, we ensured the color of the targets to be consistent with the corresponding regions of the CFS masks at any moment. We then tested whether the “chameleon” paradigm can obscure the targets’ motion information from awareness more effectively than the regular CFS paradigm.
We randomly recruited eight participants. Their dominant eyes were presented with the regular CFS masks, meanwhile the nondominant eyes were presented with ten spatially non-overlapping squares as the targets which moved either upwards or downwards at a constant velocity. Each square had one second of lifetime. Thus, for each square, after every one second of movement, its position was reset, and then it continued to move in the same direction at the same speed. In each trial, the target squares were presented for ten seconds (refreshing their positions ten times) at most. By manipulating the degree of color consistency between the targets and the masks, a total of four experimental conditions were included, with a “chameleon” condition and three control conditions. Participants were instructed to report the moving direction of the targets on seeing the targets by pressing a corresponding button. The program recorded both the response accuracy and the response time since the start of a trial (i.e. the time required for the targets to break into awareness, aka the breakthrough time). We also calculated the percentage of trials where the targets broke into awareness, which was called the breakthrough rate.
The results showed that the "chameleon" paradigm allowed the CFS masks to efficiently block the conscious processing of multiple moving targets. Specifically, as compared to the three control conditions with less degree of color consistency between the targets and the CFS masks, the breakthrough rate was significantly lower under the “chameleon” condition where the color of the targets was fully consistent with the CFS masks. No significant differences were found for the breakthrough rate between the three control conditions. Moreover, according to the grand average data, in the “chameleon” condition the moving targets could break into awareness within 10s in only ~25% of the trials. For the three control conditions, this probability increased to more than 80%, suggesting an overwhelming advantage of the “chameleon” paradigm in rendering multiple moving targets invisible.
Another advantage of the "chameleon" paradigm is that it does not require the CFS masks to contain any motion information resembling the targets, thereby it ensures that the measurement of unconscious visual motion processing is exclusively from the target. Compared with the idea of modifying CFS masks in the literature, our method is believed to have broader applicability. Therefore, we recommend the “chameleon” paradigm a useful tool for future investigations of unconscious visual motion information processing.
Peer Review Status:
Awaiting Review
Subjects: Psychology >> Cognitive Psychology submitted time 2023-10-13
Abstract： Patching one eye of an adult human for a few hours has been found to promote the dominance of the patched eye, which is called short-term monocular deprivation effect. Interestingly, recent work has reported that prolonged eye-specific attention can also cause a shift of ocular dominance towards the unattended eye though visual inputs during adaptation are balanced across the eyes. Considering that patching blocks all input information from one eye, attention is undoubtedly deployed to the opposite eye. Therefore, the short-term monocular deprivation effect might to some extent be contributed by the eye-specific attentional modulation, which remains largely unknown. The goal of the present study was to investigate whether attention can modulate the short-term monocular deprivation effect in adults.
Twenty adult participants took part in the present study. We asked participants to perform an attentive tracking task throughout the monocular patching. During the tracking, the primary stimuli consisted of two types of chromatic gratings, red-green gratings (R-G) and yellow-blue (Y-B) gratings, one of which was defined as the target gratings (attended stimuli) and the other as the distractor gratings (unattended stimuli). Target gratings and distractor gratings were distinct from each other in fundamental visual features such as color, shape, and spatial frequency. We instructed participants to continuously attend to and track the movement of the target grating in the attentive tracking task. Before and after one hour of monocular patching, we measured participants’ ocular dominance using a binocular rivalry task in which both target gratings and distractor gratings served as testing stimuli.
In case there lacks of comparability in binocular rivalry performance measured with different types of testing stimuli, we focused on the comparison of the monocular deprivation effect for the same testing stimuli between different attention conditions. Our results generally support the notion of attentional modulation on the monocular deprivation effect. To be specific, we observed a larger shift of ocular dominance towards the deprived eye when the binocular rivalry testing gratings shared features with the target gratings during the tracking compared to when they shared features with the distractor gratings. For testing with Y-B gratings, there was a significantly greater monocular deprivation effect when Y-B gratings were attended during the patching compared to when R-G gratings were attended. For testing with R-G gratings, we detected a similar trend, though it did not reach statistical significance.
In conclusion, the present study provides some preliminary evidence supporting the modulatory role of attention in the effect of typical monocular deprivation. Our work suggests that short-term ocular dominance plasticity is not solely determined by imbalanced visual feedforward inputs, but also affected by top-down attentional feedbacks, discovering potential interplays between higher-level cognitive functions and lower-level visual processing in this phenomenon. Because monocular deprivation has recently been used to treat amblyopia, our finding of attentional modulation on this effect may provide useful clues on how to optimize such treatment in future work.
Peer Review Status:Awaiting Review
Subjects: Other Disciplines >> Synthetic discipline submitted time 2023-10-09 Cooperative journals: 《心理科学进展》
Abstract： During the development, the structure and functions of the visual system can be affected by visual experiences and environments. This is called visual plasticity which is most prominent during the critical period of development after birth. Although the structures and functions of neural circuits tend to be stable in adult visual cortex, mounting evidence has shown that adult visual cortex still retains a certain degree of plasticity, including ocular dominance plasticity. Ocular dominance in humans refers to a phenomenon that one eye is functionally superior to the other eye. A common method for measuring perceptual ocular dominance is the binocular rivalry task. The typical stimuli in this task are two spatially overlapped but incompatible images, with one presented to each eye. At any moment, observer is usually aware of only one of the images which remains visible for a while before being consciously replaced by the other one. The ratio of dominance duration for each eye in a binocular rivalry task can be used to quantitatively assess observer's ocular dominance.One of the most commonly used ways to modulate ocular dominance in adults is monocular deprivation, which shifts ocular dominance to the deprived eye through the temporary occlusion of one eye. In recent decades, researchers have extensively investigated the monocular deprivation effect and its underlying mechanism by constantly changing the way of monocular deprivation, such as depriving the energy information (e.g. contrast) or phase information (e.g. contour) of monocular images. A consistent finding is that the imbalance of visual input between two eyes, whether achieved through complete or partial deprivation of visual information to one eye, leads to a shift of ocular dominance towards the deprived eye. The shift of ocular dominance may reflect neural plasticity in the early stages of visual processing, which is closely related to the reduction of GABA inhibition in the primary visual cortex. Meanwhile, one suggested mechanism for monocular deprivation is homeostatic plasticity, an inherent mechanism that stabilizes neuronal activity and prevents the neuronal system from becoming hyperactive or hypoactive. In the context of short-term monocular deprivation, an imbalance in visual input between the two eyes may trigger a homeostatic upregulation of neural response in the deprived eye to maintain a balance of neural activity within the visual system. This can lead to a shift in ocular dominance towards the deprived eye following the monocular deprivation. More recently, it has been found that even in the absence of visual input deprivation, directing a greater amount of attention towards one eye can effectively induce an effect of ocular dominance shift. For example, a “dichoptic-backward-movie” adaptation paradigm was invented to study eye-based attention induced ocular dominance shift. The ocular dominance is biased in favor of the eye (unattended eye) that has viewed a backward movie for long during which time the opposite eye (attended eye) is presented with a regular movie. This phenomenon indicates that the neural mechanisms of short-term ocular dominance plasticity not only occur at the lower level of visual processing stage but also receive feedback regulations from higher cortical sites. Notably, the boost of the unattended eye was not observed when testing stimuli were binocularly compatible. Therefore, the attention-induced ocular dominance shift may not be explicable solely by means of the homeostatic plasticity mechanism, because the involvement of homeostasis is not specific to binocular rivalry. Given the crucial role of interocular competition in attention-induced ocular dominance shift, this effect is currently explained by the adaptation of ocular opponency neurons that represents interocular conflict by computing differences between the input signals from the two eyes. Despite significant advancements in the investigation of short-term ocular dominance plasticity, there are many promising research directions for future studies, especially those that may further our understanding of the complicated mechanisms for short-term ocular dominance plasticity. The article then ends with the outlook in this regard. Key words
Subjects: Psychology >> Cognitive Psychology submitted time 2023-05-15
Abstract： During the development, the structure and functions of the visual system can be affected by visual experiences and environments. This is called visual plasticity which is most prominent during the critical period of development after birth. Although the structures and functions of neural circuits tend to be stable in adult visual cortex, mounting evidence has shown that adult visual cortex still retains a certain degree of plasticity, including ocular dominance plasticity. In recent decades, it has been found that perceptual ocular dominance in adults can be biased by adjusting the input information or attentional allocation between the two eyes. However, the neural mechanisms underlying these different types of ocular dominance plasticity may have multiple origins. Monocular deprivation due to imbalanced visual inputs may be accounted for by the homeostatic plasticity mechanism of the visual cortex. However, the shift of ocular dominance caused by imbalanced attentional allocations between the two eyes reflects the feedbacks from higher cortical sites, which is currently explained by the adaptation of ocular opponency neurons. Future studies may provide more direct evidence for the ocular-opponency-neuron account and explore the likely interactions between attention and visual input that reshape ocular dominance.
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