Featured Research

from universities, journals, and other organizations

Brain area attacked by Alzheimer's links learning, rewards

Date:
December 18, 2013
Source:
Duke University
Summary:
One of the first areas of the brain to be attacked by Alzheimer's disease, the posterior cingulate cortex, or PCC, has been found to step in during a cognitive challenge to improve the brain's performance. This small study in monkeys establishes a role for the PCC in learning and its connection to the brain's reward system.

One of the first areas of the brain to be attacked by Alzheimer's disease is more active when the brain isn't working very hard, and quiets down during the brain's peak performance.

The question that Duke University graduate student Sarah Heilbronner wanted to resolve was whether this brain region, called the posterior cingulate cortex, or PCC, actively dampens cognitive performance, say by allowing the mind to wander, or is instead monitoring performance and trying to improve it when needed.

If the PCC were monitoring and improving performance, increased activity there would be the result of poor performance, not the cause of it.

The PCC connects to both learning and reward systems, Heilbronner said, and is a part of the "default mode network." It lies along a mid-line between the ears, where many structures related to rewards can be found. "It's kind of a nexus for multiple systems," said Heilbronner, who is currently a postdoctoral researcher in neuroanatomy at the University of Rochester.

"As this area begins to deteriorate, people begin to show the early signs of cognitive decline -- problems learning and remembering things, getting lost, trouble planning -- that ultimately manifest as outright dementia," said Michael Platt, director of the Duke Institute for Brain Sciences, who supervised Heilbronner's 2012 dissertation. Their findings appear Dec. 18 in the journal Neuron.

Heilbronner's experiment to better understand the PCC's role in learning and remembering relied on two rhesus macaque monkeys fitted with electrodes to read out the activity of individual neurons in their brains. Their task was akin to playing video games with their eyes. The monkeys were shown a series of photographs each day marked with dots at the upper left and lower right corners. To get a rewarding squirt of juice, they had to move their gaze to the correct target dot on a photo, and they learned by trial and error which dot would yield the reward for each photo.

Each day, they were shown up to 12 photos from an assortment of Heilbronner's vacation snaps at Yellowstone National Park and the Grand Canyon. Some of each day's images were familiar with a known reward target, and others were new. As the monkeys responded with their gaze, the researchers watched the activity of dozens of neurons in each monkey's brain immediately following correct and incorrect responses. They also altered the amount of juice dispensed in some cases, creating a sense of high-reward and low-reward answers.

If the PCC actively dampened performance, the researchers would expect to see it active before a choice is made or the feedback is received. Instead, they saw it working after the feedback, lasting sometimes until the next image was presented. Neurons in the PCC responded strongly when the monkeys needed to learn something new, especially when they made errors or didn't earn enough reward to keep motivated.

The researchers also ran the task after administering a drug, muscimol, that impaired the function of the PCC temporarily during testing. With the center inactivated by the drug, the monkeys could recall earlier learning regardless of the size of the reward. Learning a new item was still possible when the reward was large, but the monkeys couldn't learn anything new when rewards were small. "Maybe it didn't seem worth it," Heilbronner said.

The dampening experiment also reinforced what the researchers had seen in the timing of the PCC's response. If this center's role is to let the mind wander, performance should have improved when the muscimol was administered, but the opposite was true.

Heilbronner concludes that the PCC summons more resources for a challenging cognitive task. So rather than being the cause of poor performance on a task, PCC actually steps in during a challenge to improve the situation.

"This study tells us that a healthy PCC is required for monitoring performance and keeping motivated during learning, particularly when problems are challenging," Platt said.

Heilbronner is now interested in finding out whether the PCC is more important to learning than it is to recall, and how motivation interacts with PCC abnormalities seen in Alzheimer's disease.


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. SarahR. Heilbronner, MichaelL. Platt. Causal Evidence of Performance Monitoring by Neurons in Posterior Cingulate Cortex during Learning. Neuron, 2013; 80 (6): 1384 DOI: 10.1016/j.neuron.2013.09.028

Cite This Page:

Duke University. "Brain area attacked by Alzheimer's links learning, rewards." ScienceDaily. ScienceDaily, 18 December 2013. <www.sciencedaily.com/releases/2013/12/131218130259.htm>.
Duke University. (2013, December 18). Brain area attacked by Alzheimer's links learning, rewards. ScienceDaily. Retrieved July 23, 2014 from www.sciencedaily.com/releases/2013/12/131218130259.htm
Duke University. "Brain area attacked by Alzheimer's links learning, rewards." ScienceDaily. www.sciencedaily.com/releases/2013/12/131218130259.htm (accessed July 23, 2014).

Share This




More Mind & Brain News

Wednesday, July 23, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Idaho Boy Helps Brother With Disabilities Complete Triathlon

Idaho Boy Helps Brother With Disabilities Complete Triathlon

Newsy (July 23, 2014) An 8-year-old boy helped his younger brother, who has a rare genetic condition that's confined him to a wheelchair, finish a triathlon. Video provided by Newsy
Powered by NewsLook.com
Huge Schizophrenia Study Finds Dozens Of New Genetic Causes

Huge Schizophrenia Study Finds Dozens Of New Genetic Causes

Newsy (July 22, 2014) The 83 new genetic markers could open dozens of new avenues for schizophrenia treatment research. Video provided by Newsy
Powered by NewsLook.com
Why Do People Believe We Only Use 10 Percent Of Our Brains?

Why Do People Believe We Only Use 10 Percent Of Our Brains?

Newsy (July 22, 2014) The new sci-fi thriller "Lucy" is making people question whether we really use all our brainpower. But, as scientists have insisted for years, we do. Video provided by Newsy
Powered by NewsLook.com
Do Obese Women Have 'Food Learning Impairment'?

Do Obese Women Have 'Food Learning Impairment'?

Newsy (July 18, 2014) Yale researchers tested 135 men and women, and it was only obese women who were deemed to have "impaired associative learning." 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