アリゾナ州立大学の神経科学者William Tyler氏は、数年前から、米陸軍研究所から資金提供を受けて神経科学技術の研究に取り組んできたが、今回、その研究が米国防総省の国防高等研究計画庁(DARPA)の目に留まった。DARPAは、非侵襲的脳刺激法を改良する研究として、同氏の研究所に『Young Faculty Award』賞を授与したのだ。
すでに科学者たちは最先端の脳刺激法を考案し、パーキンソン病や鬱病などの疾患の治療に利用している(日本語版記事)。だが、現在の脳深部刺激療法には、電極や電池を体内に移植する侵襲的手術が必要だ。また、外部からの超音波刺激は、通常は「多くの罹患部が存在する脳深部の回路」まで届かない、とTyler氏は『Armed With Science』に書いている。
Tyler氏が率いる研究チームは、外部から多数の脳回路を刺激できる『経頭蓋パルス超音波』を開発した。この装置は、既存の方法と違って、脳深部の部位に的を絞って超音波を照射できることがすでに分かっている。また、2〜3ミリメートルしかない脳の特定ゾーンに照準を合わせることができる。しかも、試作品の装置は、標準的なヘルメットの中に収まるくらい十分小さい。
このマイクロ・コントローラー装置を利用すれば、超音波で脳の様々な部位を刺激して、兵士の注意力や認識力を向上させたり、ストレスや痛みを緩和させるほか、外傷性脳損傷(Traumatic brain injury, TBI)を防いだりすることができると期待されている。
「外傷性脳損傷で実際に損傷を与えるのは、最初の損傷ではなく、数時間後に発生する代謝性障害やフリーラジカル、腫れだ。リモコン操作で直ちに介入することができれば、生涯にわたる脳損傷を防ぐことが可能になるだろう」とTyler氏は述べている。
[外傷性脳損傷は、脳の一部が局所的にダメージを受ける脳挫傷とは異なり、脳の軸索が広範囲に損傷を受けるもの。高次脳機能障害に至った場合、記憶力、注意力の低下や人格やコミュニケーション能力等に問題が生じる。外見上、健常人と何ら変化は無いが、社会適応性が損なわれるため苦しむ患者が多い。
地雷や携帯型小型ミサイルを改造した即席爆発装置(IED)では、爆風は音速を超える。外見上は無傷に近いものの、帰還後に記憶障害や歩行障害に苦しむ例が増えたため、米国政府は2009年に診断基準を変更。2001年から2009年10月まで約14万人が受傷したとの結果をまとめている
A device that fits in a helmet and can irradiate each part of the deep brain with pinpoint ultrasonic waves. In addition to improving the attention and cognitive ability of soldiers, it is expected to help prevent brain damage.
William Tyler, a neuroscientist at Arizona State University, has been working on neuroscience and technology research funded by the U.S. Army Institute for several years, and this time the research is the Defense Advanced Research Projects of the US Department of Defense. It caught the eye of the Planning Agency (DARPA). DARPA has awarded his laboratory the "Young Faculty Award" for research to improve non-invasive brain stimulation.
Scientists have already devised state-of-the-art brain stimulation methods and are using them to treat diseases such as Parkinson's disease and depression. However, current deep brain stimulation requires invasive surgery to transplant electrodes and batteries into the body. Also, external ultrasound stimuli usually do not reach the "deep circuit of the brain, where many affected areas are present," Tyler wrote in Armed With Science.
A research team led by Tyler has developed "transcranial pulse ultrasound" that can stimulate a large number of brain circuits from the outside. It has already been found that this device, unlike existing methods, can irradiate deep-brain areas with ultrasound. It can also be aimed at specific zones of the brain that are only a few millimeters. What's more, the prototype device is small enough to fit in a standard helmet.
With this microcontroller device, ultrasound stimulates various parts of the brain to improve the attention and cognition of soldiers, relieve stress and pain, and traumatic brain injury (Traumatic brain). It is expected to be able to prevent injury, TBI).
"It's not the first injury that actually causes traumatic brain injury, but the metabolic disorders, free radicals, and swelling that occur hours later. If you can intervene immediately with remote control, you'll have lifelong brain injury. It will be possible to prevent it, "said Tyler.
[Traumatic brain injury is a widespread damage to the axons of the brain, unlike a cerebral contusion in which part of the brain is locally damaged. When higher brain dysfunction occurs, problems occur in memory, attention, personality, communication ability, and so on. Apparently, there is no difference from healthy people, but many patients suffer from impaired social adaptability.
In an improvised explosive device (IED), which is a modification of a land mine or a small portable missile, the blast exceeds the speed of sound. Although seemingly intact, the US government changed its diagnostic criteria in 2009 as more and more people suffered from memory and gait disorders after returning. It summarizes the results that about 140,000 people were injured from 2001 to October 2009]
