這實驗透過切除orbitotforntal cortex和thalamic submedius以及健康老鼠比較, 在訓練
階段三組老鼠都可以學習聲音和食物的關聯.但在切除兩個腦區的兩個實驗組都發現, 他們
無法更新或適應新的情況, 例如某個聲音和食物無關聯了. OFC是傳統就知道和決策有關的
腦區, 但thalamic submedius卻是首次發現.
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http://medicalxpress.com/news/2015-09-decision-making-involves-brain-region.htm
l ( http://tinyurl.com/pqbgl33 )
Decision-making involves a little known brain region
When faced with a change to our environment, we have to make appropriate
decisions, which usually involves the orbitofrontal cortex. Yet unexpectedly,
scientists at the Institut de Neurosciences Cognitives et Intégratives
d'Aquitaine (INCIA, CNRS/Université de Bordeaux) have discovered that a
brain region located in the thalamus also plays a crucial role in using these
evolved skills. Tested in the rat, this work is published on 23 September
2015 in The Journal of Neuroscience.
All living organisms must take appropriate decisions to meet their own needs.
In particular, the ability to take account of abrupt environmental changes
represents a significant challenge for the survival of a species. Such
decision-making is considered as an evolved cognitive function. It involves
the orbitofrontal cortex, one of the most developed brain structures, known
to perform decision-making processes.
The "Décision et Adaptation" team at the INCIA first of all focused on the
brain regions connected to the orbitofrontal cortex. Using a labeling
technique, the scientists evidenced a specific area, the thalamic submedius
nucleus, which is closely linked to the orbitofrontal cortex and whose
functional role is unknown.
The team then tested the role of these two brain structures (the submedius
thalamic nucleus and orbitofrontal cortex) in decision-making and adaptive
behavior. To achieve this, they studied three groups of rats: the first
presented lesions to the orbitofrontal cortex, the second had lesions on the
submedius nucleus and the third was made up of lesion-free control animals.
The objective was to test their ability to establish a link between an
auditory cue and obtaining a food reward.
The experiment was organized in two phases. The initial learning phase
allowed the animals to learn that two different sounds (S1 and S2) each
signaled a specific food reward. The three groups of animals thus visited the
food dispenser as soon as an auditory stimulus was perceived. The lesions did
not prevent the animals from learning that an auditory stimulus predicts a
reward. During the second phase, the procedure remained unchanged for the
first cue, but for S2, the scientists distributed food rewards during, and
mostly outside, cue test periods. This sound thus lost its predictive value
and lesion-free animals started to take no account of the S2 auditory
stimulus, only visiting the dispenser when they heard S1. On the other hand,
animals with a lesion - of either the orbitofrontal cortex or the submedius
thalamic nucleus - proved incapable of making this distinction, and thus of
adapting.
This study therefore identified the existence of a circuit between the
thalamus and the cortex, which proved crucial to adaptive decision-making.
The originality of this discovery lies in the key role that scientists
attribute to the submedius thalamic nucleus, a structure hitherto poorly
known in the field of adaptive behavior. These findings suggest that numerous
functional circuits underlying this type of behavior may involve a
contribution from the thalamus. The team is now planning to explore these
"thalamocortical" circuits, whose understanding could shed light on numerous
diseases, such as schizophrenia or addiction.
Explore further: Study pinpoints brain area's role in learning
More information: "Flexible Use of Predictive Cues beyond the Orbitofrontal
Cortex: Role of the Submedius Thalamic Nucleus." Journal of Neuroscience, 23
September 2015, 35(38): 13183-13193; DOI: 10.1523/JNEUROSCI.1237-15.2015
http://dx.doi.org/10.1523/JNEUROSCI.1237-15.2015
Journal reference: Journal of Neuroscience search and more info website
Provided by: CNRS search and more info website
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