Visual backward masking


We can generally recognize an object, even if it is presented for a very brief time. However, if another object appears immediately following the first object, the perception on the first object is impaired such that we do not notice its existence.

This perceptual phenomenon, called “visual backward masking,” is used in vision science to study how visual perception is processed in the brain. Interestingly, this phenomenon occurs even if the second object does not spatially overlap the first object, such as a contour or four dots surrounding the object.

The occurrence of this phenomenon is assumed to be due to a disruption of “feedback processing.” When we see something, visual information is serially processed from lower to higher visual areas in the brain in a bottom-up manner. However, top-down feedback processing, in which visual signals are sent back from higher to lower areas, also plays a critical role in visual perception. Visual backward masking is thought to occur owing to interference with feedback processing.

“We applied backward masking to infants aged 3-8 months to examine the development of feedback processing,” says Yusuke Nakashima, a postdoctoral fellow at Chuo University in Tokyo and the study’s lead author.

“Recent studies in vision science revealed the importance of feedback processing in visual perception, but its development is poorly understood.”

To test whether backward masking occurs in infants, the researchers presented images of faces on a computer screen and measured the length of time that infants spent looking at them. As infants tend to look longer at faces, researchers can test whether infants perceive faces by measuring their looking time.

The faces were presented in two ways. In one condition, a face was followed by a mask image, in which infants would not see the face if backward masking occurred. In another condition, nothing appeared after the face; thus, infants would be able to see the face.

The researchers found that infants aged 7-8 months could not see faces followed by the mask, indicating that backward masking occurred, similar to adults. In contrast, infants aged 3-6 months could perceive faces even when the faces were followed by the mask image, indicating that masking did not occur and that younger infants could see faces that older infants could not.

“These results suggest that feedback processing is immature in infants younger than 7 months,” says Nakashima. “That is, younger infants do not have feedback processing that backward masking should interfere, and thus, masking is ineffective for them.” The results of the study demonstrated that the mechanisms for visual perception change drastically in the second half of the first year of life, from the bottom-up system to the system incorporating top-down processing.

The results also showed that objects that can be perceived in early infancy become imperceptible during development. “This might seem counterintuitive,” says Masami Yamaguchi, a professor at Chuo University. “Instead, important visual abilities would be acquired by the maturation of feedback processing.”

For example, feedback processing is essential for robustly perceiving ambiguous visual images, such as occluded objects. “Younger infants whose feedback processing is immature might perceive the external world ambiguously,” says Yamaguchi. “In return for susceptibility to visual masking, we acquire the ability to robustly perceive ambiguous visual scenes.”

Schizophrenia is associated with marked impairment across a variety of information processing domains, spanning from very early stages of perceptual processing, through complex, higher-order cognitive processes. Deficits in early-stage visual processing have consistently been reported in chronic schizophrenia (1–6).

Consistent with a cascade model of information processing, whereby disruptions in early perceptual processes have downstream consequences for higher-order cognition and functioning, impaired visual processing is associated with deficits in social cognition (i.e., processing of social stimuli including emotion identification and mental state attribution) in this clinical population (7–14).

Moreover, structural equation modeling analyses have demonstrated that social cognition mediates the relationship between visual processing and community functioning in people with schizophrenia (7, 12, 15). Thus, visual processing and social cognitive abilities are important components of the pathway toward functional recovery in schizophrenia.

Social cognitive deficits are well-documented in people with recent-onset schizophrenia (ROSz), with meta-analytic reviews reporting large effect sizes that are on par with those obtained from chronic phase schizophrenia samples (16–18). In contrast, considerably less is known about visual perception abnormalities in the early phase of illness. Similarly, the nature of the relationship between visual processing and social cognition in the early phase of illness is unknown.

The available evidence strongly suggests visual processing abnormalities in ROSz (19–23), with patients exhibiting significantly impaired contour integration (19), visual perception organization (20), and motion processing (21) relative to healthy adults. However, the magnitude of impairment may be attenuated relative to what is observed in chronic phase schizophrenia (19, 24, 25).

The earliest stages of visual processing can be probed behaviorally with visual masking tasks (see (26) for a comprehensive review). In these tasks, a rapidly presented target stimulus is either shortly preceded by (for forward masking) or shortly followed by (for backward masking) a masking stimulus which interferes with processing of the target. Depending on the type of paradigm used, the masking stimuli may spatially overlap the target, or it may surround, but not touch, the target.

The duration of the interval between the target and mask is brief (i.e., 0–500 ms), and is varied across trials. Accuracy for identifying the target, or some aspect of the target (e.g., target location, a feature of the target), is assessed yielding a masking function. For backward masking, the typical response function is S-shaped, with very poor accuracy at short intervals between target and mask, and improved performance as the interval between target and mask increases.

Prior studies of visual backward masking in ROSz indicate impaired performance relative to healthy adults (22, 25), an association with duration of untreated psychosis (i.e., short duration of untreated psychosis associated with better performance; (27)), and stability of performance over 6–24 months (22, 23).

Here, we assessed visual backward masking and test the association between early visual processing and performance on social cognitive tasks that involve processing of visual cues in people with ROSz and healthy adults. We hypothesized that visual backward masking performance and social cognitive task performance would be significantly impaired in the ROSz sample compared to healthy adults. In addition, we hypothesized that visual backward masking performance would be significantly correlated with social cognitive task performance in the patient group.

reference link :

More information: Yusuke Nakashima et al, Perception of invisible masked objects in early infancy, Proceedings of the National Academy of Sciences (2021). DOI: 10.1073/pnas.2103040118


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