Neural noise created during binocular rivalry

June 19, 2009,

Neural "noise" may cause you to miss important changes in your environment when you are concentrating on something else, new research indicates.

The research by Sam Ling, a postdoctoral researcher in Vanderbilt University's Psychology Department, and Randolph Blake, Centennial Professor of Psychology, is currently in press at Psychological Science.

"We found that when the brain actively ignores the presence of an object in the environment, it does so in a way that weakens and degrades residual information about that object," Ling said. "We found that the brain's neural representation of an object outside your window of awareness is not only weaker, but also 'noisier.' It's as if the brain turns down the contrast on your mental television and also adds static noise into the image."

The new research explored what is happening to an ignored stimulus during binocular rivalry, which occurs when the two eyes view radically different images. The brain temporarily rejects, or suppresses, one of those images in favor of the other. The image that commands our visual awareness switches between the two over time. This fluctuation in visual awareness enables cognitive to study the neural correlates of awareness and consciousness.

It has been known for years that the neural representation of a temporarily erased from awareness during binocular rivalry is weaker in strength as a result. Ling and Blake set out to discover if there were other consequences associated with this weakening process.

To do so, the researchers tested people on a simple task that required them to judge the orientation of a pattern, called a grating, composed of parallel contours that tilted either clockwise or counterclockwise. Ordinarily, people are able to distinguish tilts as small as a few degrees. However, when the pattern was presented to an eye that was in this suppressed state, people were significantly worse at the task, sometimes confusing orientations that differed by 10 degrees.

"The problem wasn't that people couldn't see the gratings, because we made them sufficiently high contrast so they could overcome suppression and break into consciousness," Blake said. "Nonetheless, because it was going to a suppressed eye, the grating underwent some sort of general degradation in the fidelity with which it was being registered. Neural noise could explain this."

In an attempt to identify the source of the added noise, Ling and Blake performed a second experiment where observers were asked simply to detect a grating of a given orientation presented within a band of visual noise that the investigators themselves produced on the testing monitor. Ordinarily, observers are able to ignore noise that differs in orientation from a test grating, indicating that the brain cells detecting the grating are responsive to only a limited range of orientations. During suppression, however, the range of interfering orientations was widened considerably, thereby expanding the range of noise orientations that interfered with detection of the test grating.

"We believe this temporary broadening of the 'tuning' of orientation during suppression is a prime candidate as the cause of the reduced fidelity of the neural representation of orientation during suppression," Ling said.

Source: Vanderbilt University (news : web)

Related Stories

Recommended for you

Suicide risk in abused teen girls linked to mother-daughter conflict

October 18, 2018
Teenage girls who were maltreated as children are more likely to entertain suicidal thoughts if the relationship with their mother is poor and the degree of conflict between the two of them high.

Study shows how bias can influence people estimating the ages of other people

October 17, 2018
A trio of researchers from the University of New South Wales and Western Sydney University has discovered some of the factors involved when people make errors in estimating the ages of other people. In their paper published ...

Infants are more likely to learn when with a peer

October 16, 2018
Infants are more likely to learn from on-screen instruction when paired with another infant as opposed to viewing the lesson alone, according to a new study.

Researchers use brain cells in a dish to study genetic origins of schizophrenia

October 16, 2018
A study in Biological Psychiatry has established a new analytical method for investigating the complex genetic origins of mental illnesses using brain cells that are grown in a dish from human embryonic stem cells. Researchers ...

Income and wealth affect the mental health of Australians, study shows

October 16, 2018
Australians who have higher incomes and greater wealth are more likely to experience better mental health throughout their lives, new research led by the Bankwest Curtin Economics Centre has found.

Study suggests biological basis for depression, anxiety, sleep disturbances in older adults

October 15, 2018
UC San Francisco researchers, in collaboration with the unique Brazilian Biobank for Aging Studies (BBAS) at the University of São Paulo, have shown that the earliest stages of the brain degeneration associated with Alzheimer's ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.