我今天真的太無聊了,所以逛到哈佛醫學院網站

除了看他們的新聞之外,　

還順便看一下他們的PhD program,以及postdoctoral felowships

因為這次的哈佛新聞是我有興趣的東西,就會對那內容特別有印象

後來在看雅虎新聞的時候意外的發現居然也有報導這個

我真是覺得台灣媒體其實也很不錯; 很認真的在關心一般人不會注意的新知

光是這一點就要給他們好好鼓勵鼓勵

腦內聯繫差…人真的愈老愈糊塗

更新日期:2007/12/07 04:39 　楊明暐／綜合報導

　隨著一個人變老，他的心智也會愈來愈遲鈍。一項研究發現，正常的老化確實會使人的頭腦逐漸朽壞。

　美國哈佛大學科學家利用醫學影像技術對93名年齡介於18歲到93歲之間的健康成年人腦部進行掃描。

　過去相關研究多集中在老化對腦部特殊結構造成的影響。哈佛研究人員則把重點擺在腦內不同區域間的溝通聯繫，他們利用「功能性磁共振造影技術」（fMRI）掃描腦部，以了解老化對這種活動產生的影響。

　研究人員對充斥神經細胞的「腦白質」進行追蹤，「腦白質」負責腦內連線工作，可讓腦部不同區域進行溝通並分享資訊。

　研究人員發現，「腦白質」會隨人老化而跟著退化，尤其前、後腦區域間的聯繫會因「腦白質」退化而減少。因此，年輕人腦部各區域可以維持同步，老年人大多沒辦法。

　能維持腦部同步運作的老年人，在接受一系列心智能力測驗時，表現往往比那些腦內聯繫受到破壞的同輩好很多。不過，受破壞的程度因人而異，就像測驗結果也是各不相同。

　研究人員還發現，負責掌管人們內心思維的系統，特別容易被破壞。當人們未集中注意力在處理來自外在世界的資訊時，這套系統往往就會介入。科學家表示，這項研究可能有助於從生理學角度去了解知能退化的問題。

　主持這項研究的潔西卡．安德魯斯─漢納表示，有人到90多歲還很精明，其他人則愈老愈糊塗，喪失心智能力的原因之一，有可能是腦內各個系統已無法同步運作。

　美國阿茲海默氏症學會的巴拉德教授認為，有必要進行更多研究，以驗證研究正確無誤。

December 06, 2007

(Image: Courtesy of Randy L. Buckner, Howard Hughes Medical Institute at Harvard University )

The image in the background shows that distant regions of the brain show correlated activity in young adults. The foreground image shows that in advanced aging, coordinated activity among regions of the brain decreases (and is associated with cognitive decline). Brain activity was measured using functional magnetic resonance imaging, which can precisely map increased blood flow in the brain. Increased blood flow (orange and yellow colors) reflects greater activity in regions of the brain that are utilized during mental tasks.

A team of Howard Hughes Medical Institute researchers has shown that normal aging disrupts communication between different regions of the brain. The new research, which used advanced medical imaging techniques to look at the brain function of 93 healthy individuals from 18 to 93 years old, shows that this decline happens even in the absence of serious pathologies like Alzheimer's disease.

Researchers have known for quite some time that normal aging slowly degrades bundles of axons in the central nervous system that transmit critical signals. “Our study now shows that cognitive decline in aging may be linked to disruption of communication between different regions of the brain,” said Buckner, who is a Howard Hughes Medical Institute investigator at Harvard University. He is also affiliated with the Athinoula A. Martinos Center for Biomedical Imaging at Massachusetts General Hospital/Harvard Medical School.

“Our study now shows that cognitive decline in aging may be linked to disruption of communication between different regions of the brain.”
Randy L. Buckner

The new research, published December 6, 2007, in the journal Neuron, begins to reveal how simply growing old can affect the higher-level brain systems that govern cognition. “We may have caught the failure of communication in the act,” said Buckner.

The human brain can be divided into major functional regions, each responsible for different kinds of “applications,” such as memory, sensory input and processing, executive function or even one's own internal musing. The functional regions of the brain are linked by a network of white matter conduits. These communication channels help the brain coordinate and share information from the brain's different regions. White matter is the tissue through which messages pass from different regions of the brain.

Scientists have known that white matter degrades with age, but they did not understand how that decline contributes to the degradation of the large-scale systems that govern cognition.

“The crosstalk between the different parts of the brain is like a conference call,” said Jessica Andrews-Hanna, a graduate student in Buckner's lab and the lead author of the study. “We were eavesdropping on this crosstalk and we looked at how activity in one region of the brain correlates with another.”

Buckner, Andrews-Hanna, and their colleagues looked at crosstalk in the brains of 93 people aged 18 to 93, divided roughly into a young adult group (18-34 years old) and an old adult group (60-93 years old). The older participants were given a battery of tests to measure their cognitive abilities — including memory, executive function and processing speed. Each person was studied using functional magnetic resonance imaging (fMRI) exams to measure activity in different parts of the brain. fMRI can precisely map enhanced blood flow in specific regions of the brain. Increased blood flow reflects greater activity in regions of the brain that are utilized during mental tasks.

For the task used in the Neuron study, subjects were presented words and were asked to decide whether each word represented a living (e.g., dog) or nonliving (e.g., house) object. “Such a task requires the participants to meaningfully process the words,” said Buckner.

Buckner's group explored whether aging in the older group caused a loss of correlation between the regions of the brain that — at least in young adults — engage in robust neural crosstalk.

They focused on the links within two critical networks, one responsible for processing information from the outside world and one, known as the default network, which is more internal and kicks in when we muse to ourselves. For example, the default network is presumed to depend on two regions of the brain linked by long-range white matter pathways. The new study revealed a dramatic difference in these regions between young and old subjects. “We found that in young adults, the front of the brain was pretty well in sync with the back of the brain,” said Andrews-Hanna. “In older adults this was not the case. The regions became out of sync and they were less correlated with each other.” Interestingly, the older adults with normal, high correlations performed better on cognitive tests.

According to Buckner, it is inferred that in a young, healthy brain, signals are readily transmitted by white-matter conduits. As we age, those conduits are compromised. “Measures of white matter integrity in the older adults point to decline,” he said. Depending on the networks at play, the result may be impaired memory, reasoning or other important cognitive functions.

Buckner and Andrews-Hanna emphasized that other changes in the aging brain may contribute to cognitive decline. For example, cells' ability to express chemical neurotransmitters may also be compromised.

In general, the new work promises a better physiological understanding of cognitive decline in the elderly and may help explain differences among individuals. “It may help explain why some people are just as sharp in their 90s as they were in their 40s,” noted Andrews-Hanna. “We all age differently and cognitive abilities vary considerably among individuals.”

Typically, said Buckner, as individuals get into their 70s and 80s, you see some degree of change. “We can use this new approach (correlating the activities of different regions of the brain) as a tool to understand variation between individuals. We can also explore risk factors for breakdowns (in these pathways) like cardiovascular health.”