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zoom RSS 脳の「不適切情報除去フィルタ」発見

<<   作成日時 : 2007/12/13 22:21   >>

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脳の「不適切情報除去フィルタ」発見
「不適切フィルタ」というべきか、良い記憶にとって必須の新たな脳部位が見つかった。
画像 邪魔する物があっても記憶が得意な人々は、基底核での活動性が高いことが脳スキャンから見つかったとスウェーデンのカロリンスカ研究所からの報告。
 なぜ記憶が得意な人がいるのかを説明できるかもしれないし、ADHDの理解にも役立つ可能性がある。直ちにアクセス可能な情報を保持する能力は「working memory」と呼ばれる。他の仕事をしているときも情報を保持し、知的な活動場所を提供しているので、学習にとって不可欠のものである。この能力は、人によって異なり、違いは大きさではなく、どれほど効果的に不適切なことを排除できるかどうかにかかっているという。
 25人のボランティアを使って、タスク時の機能的MRI(fMRI)検査を施行した。不適切な惑わせる物が後から出てくると予知させるような視覚的ノイズを与えると、基底核と前頭前野の神経活動が活発となり、不適切な情報を取り除くことを準備することがわかった。
 また、基底核の淡蒼球の強い活動が、記憶に保持された情報量に敏感な頭頂葉後部のより少ない貯蔵と関連していた(?)。ADHDの小児において注意力やworking memory の改善方法を開発中である。基底核は注意力制御が困難な病気の有力原因候補である。ただ、他の脳の場所もこうしたフィルターの役割を果たしている可能性がある。
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Last Updated: Monday, 10 December 2007, 00:04 GMT
Brain 'irrelevance filter' found
http://news.bbc.co.uk/2/hi/health/7132829.stm

画像brain activity
Memory capacity may be linked to filtering out irrelevant information

Scientists believe they have located a new brain area essential for good memory - the "irrelevance filter".

People who are good at remembering things, even with distractions, have more activity in the basal ganglia on brain scans, the Swedish team found.

The work in Nature Neuroscience could help explain why some people are better at remembering things than others.

Clinically, it could also aid the understanding of attention deficit hyperactivity disorder (ADHD).

The ability to hold information in the mind so that it is immediately accessible is known as working memory.

We use working memory all of the time - for example, when doing a simple maths calculation in our head or recalling a telephone number.


There will be many brain regions that filter irrelevant information, so it is too early to tell if these findings will have a bearing on conditions such as ADHD
John Duncan
Medical Research Council scientist
Working memory is important because it gives a mental workspace in which we can hold information whilst mentally engaged in other relevant tasks, which is crucial for learning.

Its capacity is limited and seems to vary from person to person.

These variations are not just due to having a larger or smaller memory store, but also due to differences in how effectively irrelevant items are kept out of memory, the Karolinksa Institute researchers believe.

Distracters

Dr Torkel Klingberg and colleague Fiona McNab used a special brain scan called functional magnetic resonance imaging (fMRI) to track what was happening in the brains of 25 healthy volunteers.

The volunteers were asked to perform a computer-based task that required them to respond to target visual images, with or without distractions.

A noise informed subjects when an upcoming visual display would contain irrelevant distracters along with the targets.

When this cue occurred, neural activity increased in the basal ganglia and the prefrontal cortex before the visual display appeared, suggesting the brain was preparing to "filter out" the upcoming distracters.

Also, greater activity in a specific part of the basal ganglia - the globus pallidus - correlated with less unnecessary storage in another part of the brain, the posterior parietal cortex, which is sensitive to the amount of information held in memory.

The team is currently investigating methods of improving attention and working memory in children with ADHD and monitoring any changes with fMRI.

Medical Research Council scientist John Duncan said: "This is very interesting work and gives a window on important parts of the brain.

"The basal ganglia are very strong candidates for involvement in brain disorders where people have difficulty with attentional control.

"But there will be many brain regions that filter irrelevant information, so it is too early to tell if these findings will have a bearing on conditions such as ADHD."

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Nature Neuroscience
Published online: 9 December 2007 | doi:10.1038/nn2024

Prefrontal cortex and basal ganglia control access to working memory

Fiona McNab1 & Torkel Klingberg1
Abstract

Our capacity to store information in working memory might be determined by the degree to which only relevant information is remembered. The question remains as to how this selection of relevant items to be remembered is accomplished. Here we show that activity in the prefrontal cortex and basal ganglia preceded the filtering of irrelevant information and that activity, particularly in the globus pallidus, predicted the extent to which only relevant information is stored. The preceding frontal and basal ganglia activity were also associated with inter-individual differences in working memory capacity. These findings reveal a mechanism by which frontal and basal ganglia activity exerts attentional control over access to working memory storage in the parietal cortex in humans, and makes an important contribution to inter-individual differences in working memory capacity.
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1. Developmental Cognitive Neuroscience, Stockholm Brain Institute, Karolinska Institutet, MR Centrum, N8:00, 17176 Stockholm, Sweden.

Correspondence to: Torkel Klingberg1 e-mail: Torkel.Klingberg@ki.se

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