Navigation Links
Changes in brain chemicals mark shifts in infant learning
Date:10/26/2009

When do you first leave the nest? Early in development infants of many species experience important transitionssuch as learning when to leave the protective presence of their mother to start exploring the wider world. Neuroscientists have now pinpointed molecular events occurring in the brain during that turning point.

Based on animal studies, the findings may shed light on the strength of attachments in many speciesincluding the conundrum of why human children form strong attachments to even abusive caregivers.

"This is one of the few times we know what causes this type of early transition," said psychologist Gordon A. Barr, Ph.D., of The Children's Hospital of Philadelphia, co-author of a study that appeared online Sept. 27 in Nature Neuroscience. Barr performed the studies in rats with a longtime collaborator, neuroscientist Regina M. Sullivan, Ph.D., of the Nathan Kline Institute and New York University Langone Medical Center.

The youngest rats, called pups, first experience the mother's presence with both positive and negative stimuli. Even if the mother does something unpleasant, like stepping on or biting a pup, the baby rat stays close by the mother, something called preference learning. "From an evolutionary standpoint, this makes sense," said Barr. "The dependent baby has a better chance of survival if it doesn't stray from the mother's side."

However, at about ten days of age, the rat pups experience a transition to so-called aversion learning, in which they learn to avoid unpleasant stimuli. Said Barr, "Once an animal is better able to move around, it needs to be able to escape from stressful situations, again in the interests of its survival." The maturing rat learns a type of safe behavior while away from parental protection.

For neuroscientists, one puzzle has been how to understand the underlying biological events in the changeover from preference learning to aversion learning. In a series of studies reported in the current paper, the authors focused on neurotransmitters in the brain, then manipulated those chemical messages to mimic their natural effects in rats.

They conditioned the rat pups to associate a new odor with a negative eventa mild electric shock. In adult rats, but not in immature rats, a shock induces a telltale increase in levels of the stress hormone corticosterone. Increased corticosterone, in turn, causes the amygdala, a learning center in the brain, to have increased levels of the neurotransmitter dopamine.

Using microarrays (to detect changes in dopamine-related gene expression) and microdialysis (to measure changes in dopamine levels), the study team confirmed that changes in dopamine levels were linked to changes in learning patterns.

On about their tenth day of life, rat pups start to make the transition from preference learning to aversion learning. Based on their corticosterone/dopamine findings, Barr and Sullivan were able to chemically manipulate the learning transition. By injecting eight-day-old rat pups with corticosterone, the scientists advanced the animals' learning behaviorsthe young rats avoided the new (shock-associated) odor, just as older rats did. Eight-day-old control rats did not show such avoidance behavior.

Injecting dopamine directly into an eight-day-old rat's amygdala had a similar effect, switching their usual preference learning to aversion learning typical of older animals. The researchers also toggled the switch in the other direction. By blocking dopamine receptors in eight-day-old rats already treated with corticosterone, the rats showed preference learning instead of the aversion learning induced by corticosterone.

The neural mechanisms they found, said Barr, may also apply to infant behavior in dogs, rats and people. "For humans," said Barr, "the findings may shed light on the pathologically strong attachment that children are known to have even for abusive caretakers." In addition, he said, the findings suggest that scientists may detect neural mechanisms at the heart of other developmental transitions, such as an infant's switch from breastfeeding to eating solid food.


'/>"/>

Contact: John Ascenzi
Ascenzi@email.chop.edu
267-426-6055
Children's Hospital of Philadelphia
Source:Eurekalert

Related biology news :

1. Old developmental pathways spawn revolutionary evolutionary changes
2. New study shows fish respond quickly to changes in mercury deposition
3. New study shows fish respond quickly to changes in mercury deposition
4. Great Plains historical stability vulnerable to future changes
5. New technique reveals subtle force-induced changes in biomolecules conformation
6. Tolerance to inhalants may be caused by changes in gene expression
7. A new explanation for evolutionary changes in genetic sex-determination systems
8. Hearing changes how we perceive gender
9. UC Davis bird-flu expert calls for changes in early-warning system
10. Elevated carbon dioxide changes soil microbe mix below plants
11. Humans have caused profound changes in Caribbean coral reefs
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:2/3/2016)... 2016 --> ... "Automated Fingerprint Identification System Market by Component (Hardware and ... & Finance, Government, Healthcare, and Transportation) and Geography - ... is expected to be worth USD 8.49 Billion by ... and 2020. The transformation and technology evolution from the ...
(Date:2/2/2016)... 2, 2016  BioMEMS devices deployed in ... on medical screening and diagnostic applications, such ... devices that facilitate and assure continuous monitoring ... are being bolstered through new opportunities offered ... acquisition coupled with wireless connectivity and low ...
(Date:2/2/2016)... Technology Enhancements Accelerate Growth of X-ray Imaging ... and computed radiography markets in Thailand ... Indonesia (TIM). It provides an in-depth analysis ... as regional market drivers and restraints. The study offers ... market attractiveness, both for digital and computed radiography. Market ...
Breaking Biology News(10 mins):
(Date:2/9/2016)... NJ (PRWEB) , ... February 09, 2016 , ... ... Dorman, former Vice President for Public Policy for the National Organization for Rare ... patient advocacy groups to ensure their voices are heard throughout the drug regulatory ...
(Date:2/9/2016)... Feb. 9, 2016 This market research report ... and future prospects of the market in terms of ... companies engaged in the manufacture of microbiology culture media ... with a market snapshot providing the overall information of ... report. This section also provides the overall information and ...
(Date:2/9/2016)... -- Three-Year Initiative Supports Next Generation of Medical ... Life-Changing Camp Experiences ... the lives of children born with rare diseases, as well as ... is announcing a new initiative designed to positively affect the lives ... of rare disease care. --> To mark the company,s ...
(Date:2/9/2016)... Feb. 9, 2016 ... 2016", report provides in depth insights on ... around the Protein-Tyrosine Phosphatase 1B (PTP1B) Inhibitors. ... in various stages of development including Discovery, ... III and Preregistration. Report covers the product ...
Breaking Biology Technology: