Featured Research

from universities, journals, and other organizations

Seeing A Brain As It Learns To See

Date:
November 6, 2008
Source:
Duke University
Summary:
A brain isn't born fully organized. It builds its abilities through experience, making physical connections between neurons and organizing circuits to store and retrieve information in milliseconds for years afterwards. Now that process has been caught in the act for the first time by a research team that watched a nave brain organize itself to interpret images of motion.

The above figure shows the directional preferences of individual neurons before and after experience with moving patterns of light.
Credit: Courtesy of Duke University

A brain isn't born fully organized. It builds its abilities through experience, making physical connections between neurons and organizing circuits to store and retrieve information in milliseconds for years afterwards.

Now that process has been caught in the act for the first time by a Duke University research team that watched a nave brain organize itself to interpret images of motion.

"This is the first time that anyone has been able to watch as visual experience selectively shapes the functional properties of individual neurons," said David Fitzpatrick, professor of neurobiology and director of the Duke Institute for Brain Sciences. "These results emphasize just how important experience is for the early development of brain circuits."

The group's findings appear online Oct. 22 in the journal Nature.

Using an advanced imaging system that can see changes in calcium levels within individual neurons as an indication of electrical activity, the team has been able to see inside the brain of a one-month old ferret as it opened its eyes for the first time and learned how to interpret moving images.

They watched the brain learning how to see. As a ferret learned to discriminate one pattern of motion from another over the course of a few hours, the researchers could see large numbers of individual neurons in the visual cortex develop specific responses and become organized into functional assemblies called cortical columns. Additional experiments confirmed that the changes were dependent on the neurons being activated by the animal's experience with moving visual images.

The measurements were made using something called "in vivo two-photon laser scanning microscopy," which allows researchers to focus on a virtual slice of living tissue a few microns thick, and up to 300 microns below the surface of the brain. By scanning at multiple depths, the researchers were able to examine the properties of hundreds of neurons in a single animal. A fluorescent dye sensitive to calcium allowed the scientists to detect changes in the activity of individual neurons as the learning occurred.

Ferrets are born with their eyes closed and remain so for the first 30 days or so, Fitzpatrick explained. What the Duke team saw happening as the animals opened their eyes and watched moving images for the first time was the emergence of columns of neurons sensitive to a particular feature of the visual stimulus: its direction of motion.

In visual areas of the mature brain, individual neurons are programmed to be most responsive to a particular direction of motion. Some are most responsive to left-to-right motion, for example, and others will be most responsive to down-to-up or right-to-left and so on. As signals from a visual stimulus enter these brain centers for interpretation, the entire collection of neurons that has been programmed to detect motion will fire signals to cast their votes, in effect, on which direction the stimulus is moving. Those neurons which are programmed to be most responsive to the direction the stimulus is actually moving cast the loudest votes.

"Before experience with a moving stimulus, individual neurons respond almost equally to opposite directions of motion and there is little order in the way they are arranged," Fitzpatrick said. "But as a result of experience with moving images, their response to a particular direction of motion strengthens and they begin to act like their neighbors, forming columns of neurons with similar preferences. We have been able to visualize the self-organizing process by which the brain uses experience to guide the construction of circuits that are critical for interpreting moving stimuli."

The scientists next have to figure out how neurons end up preferring one motion direction over another, and what aspects of the circuit are altered to create the direction-selective responses.

Fitzpatrick is confident that the findings from these experiments can be generalized to other brain regions and will be of value in understanding neurological and psychiatric disorders.

"Many people don't realize that the vast majority of cortical connections are being formed at a time when experience can influence neural activity," he said. "Understanding how experience shapes the architecture of developing neural circuits, and identifying the underlying cellular and molecular mechanisms could provide the key to a number of developmental brain disorders."

Funding for the research was provided by grants from the National Institutes of Health and the Whitehall Foundation. Other authors include assistant professor Leonard White and postdoctoral fellows Ye Li, Stephen Van Hooser and Mark Mazurek, all of Duke.


Story Source:

The above story is based on materials provided by Duke University. Note: Materials may be edited for content and length.


Journal Reference:

  1. Ye Li, Stephen D. Van Hooser, Mark Mazurek, Leonard E. White, David Fitzpatrick. Experience with moving visual stimuli drives the early development of cortical direction selectivity. Nature, 2008; DOI: 10.1038/nature07417

Cite This Page:

Duke University. "Seeing A Brain As It Learns To See." ScienceDaily. ScienceDaily, 6 November 2008. <www.sciencedaily.com/releases/2008/10/081022135431.htm>.
Duke University. (2008, November 6). Seeing A Brain As It Learns To See. ScienceDaily. Retrieved July 28, 2014 from www.sciencedaily.com/releases/2008/10/081022135431.htm
Duke University. "Seeing A Brain As It Learns To See." ScienceDaily. www.sciencedaily.com/releases/2008/10/081022135431.htm (accessed July 28, 2014).

Share This




More Health & Medicine News

Monday, July 28, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Traditional African Dishes Teach Healthy Eating

Traditional African Dishes Teach Healthy Eating

AP (July 28, 2014) Classes are being offered nationwide to encourage African Americans to learn about cooking fresh foods based on traditional African cuisine. The program is trying to combat obesity, heart disease and other ailments often linked to diet. (July 28) Video provided by AP
Powered by NewsLook.com
West Africa Gripped by Deadly Ebola Outbreak

West Africa Gripped by Deadly Ebola Outbreak

AFP (July 28, 2014) The worst-ever outbreak of the deadly Ebola epidemic grips west Africa, killing hundreds. Duration: 00:48 Video provided by AFP
Powered by NewsLook.com
Trees Could Save More Than 850 Lives Each Year

Trees Could Save More Than 850 Lives Each Year

Newsy (July 27, 2014) A national study conducted by the USDA Forest Service found that trees collectively save more than 850 lives on an annual basis. Video provided by Newsy
Powered by NewsLook.com
Google's Next Frontier: The Human Body

Google's Next Frontier: The Human Body

Newsy (July 27, 2014) Google is collecting genetic and molecular information to paint a picture of the perfectly healthy human. 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:
from the past week

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