Featured Research

from universities, journals, and other organizations

Brain's Visual Cortex Doesn't "Tell" All It Knows

Date:
May 31, 2001
Source:
University Of California, San Diego
Summary:
The print on a page may be too fine to read, but that doesn't mean your brain can't discern the pattern of lines. New research by scientists at the University of Minnesota and the University of California, San Diego has shown that neurons in the human visual cortex, a brain center that processes visual information, can respond to patterns of lines too fine for subjects to resolve.

The print on a page may be too fine to read, but that doesn't mean your brain can't discern the pattern of lines. New research by scientists at the University of Minnesota and the University of California, San Diego has shown that neurons in the human visual cortex, a brain center that processes visual information, can respond to patterns of lines too fine for subjects to resolve.

Related Articles


The work reveals that some types of visual information, while not consciously perceived, are still conveyed closer to the brain's center(s) of consciousness than was previously thought. The discovery contributes to the understanding of vision and has implications for the age-old question of consciousness. The work will be published in the May 24 issue of Nature.

"This is probably the first demonstration that visual cortical neurons are capable of resolving fine lines past the limits previously thought to exist," said Sheng He, assistant professor of psychology at the University of Minnesota and first author of the Nature paper. His coauthor is Donald MacLeod, a psychologist at UC San Diego.

Everyone with normal vision can perceive patterns of lines up to a certain point. But when the spacing of lines becomes too fine, the lines seem to disappear and only a uniform blur is seen. Previously, vision researchers thought this limitation was due to optical blurring in the eye--that is, a failure of the retina to resolve the lines. Now, at least some of the blurring has been shown to occur in the visual cortex, said He.

The researchers studied the responses of two subjects to patterns of lines projected directly onto their retinas by lasers. The lines were either horizontal or vertical.

It has been known for some time that certain neurons in the visual cortex respond preferentially to either vertical lines, horizontal lines or in- between orientations. With enough neurons responding to every conceivable orientation, humans can perceive lines that run in any direction.

It has also been known that when human subjects are shown a pattern of vertical or horizontal lines for several seconds and then shown a second grid of lines, they are better able to perceive the orientation of the second grid if it is perpendicular to the original one. The reason is that the neurons responding to, say, a vertical grid become fatigued and have trouble perceiving a second vertical grid. But the neurons that respond to horizontal lines are fresh and respond strongly.

He and MacLeod observed this phenomenon in their subjects. But when they projected lines so fine that they were slightly, but definitely, past the subjects' ability to resolve, the subjects exhibited the same difficulty perceiving a second grid of clearly visible lines with the same orientation. This, said He, is evidence that the cortical neurons geared to that orientation were perceiving the lines the first time, when the lines were invisible to the subjects. Therefore, the subjects' inability to see the too-fine lines must be due to a blurring that occurs after the visual cortex receives input.

The visual cortex lies in the rear of the cerebrum. He said that researchers elsewhere have hypothesized that people cannot become aware of optical information unless it reaches the frontal area of the cortex. The work of He and MacLeod is consistent with this theory, He said. The blurring of lines appears to be due to processes inside the visual cortex that prevent some information from other cortical areas and consciousness.

"This suggests that not everything in the cortex can become conscious knowledge," said He. "Your visual cortex isn’t telling you everything." The work was supported by the National Institutes of Health and the Alfred P. Sloan Foundation.


Story Source:

The above story is based on materials provided by University Of California, San Diego. Note: Materials may be edited for content and length.


Cite This Page:

University Of California, San Diego. "Brain's Visual Cortex Doesn't "Tell" All It Knows." ScienceDaily. ScienceDaily, 31 May 2001. <www.sciencedaily.com/releases/2001/05/010529070018.htm>.
University Of California, San Diego. (2001, May 31). Brain's Visual Cortex Doesn't "Tell" All It Knows. ScienceDaily. Retrieved December 21, 2014 from www.sciencedaily.com/releases/2001/05/010529070018.htm
University Of California, San Diego. "Brain's Visual Cortex Doesn't "Tell" All It Knows." ScienceDaily. www.sciencedaily.com/releases/2001/05/010529070018.htm (accessed December 21, 2014).

Share This


More From ScienceDaily



More Mind & Brain News

Sunday, December 21, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Researchers Test Colombian Village With High Alzheimer's Rates

Researchers Test Colombian Village With High Alzheimer's Rates

AFP (Dec. 19, 2014) In Yarumal, a village in N. Colombia, Alzheimer's has ravaged a disproportionately large number of families. A genetic "curse" that may pave the way for research on how to treat the disease that claims a new victim every four seconds. Duration: 02:42 Video provided by AFP
Powered by NewsLook.com
Double-Amputee Becomes First To Move Two Prosthetic Arms With His Mind

Double-Amputee Becomes First To Move Two Prosthetic Arms With His Mind

Buzz60 (Dec. 19, 2014) A double-amputee makes history by becoming the first person to wear and operate two prosthetic arms using only his mind. Jen Markham has the story. Video provided by Buzz60
Powered by NewsLook.com
Prenatal Exposure To Pollution Might Increase Autism Risk

Prenatal Exposure To Pollution Might Increase Autism Risk

Newsy (Dec. 18, 2014) Harvard researchers found children whose mothers were exposed to high pollution levels in the third trimester were twice as likely to develop autism. Video provided by Newsy
Powered by NewsLook.com
Yoga Could Be As Beneficial For The Heart As Walking, Biking

Yoga Could Be As Beneficial For The Heart As Walking, Biking

Newsy (Dec. 17, 2014) Yoga can help your weight, blood pressure, cholesterol and heart just as much as biking and walking does, a new study suggests. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Health & Medicine

Mind & Brain

Living & Well

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins