総論・運転中の脳機能画像〈総説〉

The Neural Substrates while Operating a Driving Simulator

はじめに

　脳卒中や脳外傷などによる脳損傷者が社会復帰をしていく上で，そのひとつの手段として自動車を自ら運転できることの意義は大きい．しかし身体障害，視覚障害に加え，注意障害，遂行機能障害，記憶障害，空間認知障害，失語症，失行症，判断力の低下，視覚－運動変換の障害等の高次脳機能障害により，運転を断念しなければならない例が多い．また，わが国では，2007年の改正道路交通法により，2009年から75歳以上の高齢運転者の免許証更新時には，講習予備検査として認知機能検査が導入された．高齢者の免許保有率が増加し，しかも交通事故件数が加齢とともに急激に多発する事実が背景にあると思われる．したがって，個々の脳損傷者や高齢者が安全に運転を再開できるかどうかを判断する上で，自動車運転に必須と考えられる高次脳機能を確認しておくことは重要となる．

Abstract : Driving is an important activity of daily living. However, the ability to drive is often affected after brain injury. The aim of this study was to investigate the fundamental region of neural activity in healthy subjects, which is believed to be necessary for driving ability and to examine the effect of brain injury on driving safety. Experimental studies were performed on 7 normal right-handed adults and 6 patients with brain injury (3 resumed driving, 3 did not resume driving). The participants were asked to turn to the left or right from a straight road in a driving simulator. During driving, changes in oxy-Hb levels were measured using functional near-infrared spectroscopy at 34 sites including both hemispheres. The areas measured included the dorsolateral frontal cortex in the anterior region, the inferior parietal lobule in the posterior region, and the superior temporal gyrus in the inferior region. The areas that showed significant activity in the healthy subjects spanned from the frontal region to the temporal and parietal regions, and were more prominent in the right cerebral hemisphere than in the left. Patients who resumed driving showed similar patterns as healthy subjects ; cortical activations near damaged regions were retained as seen on CT or MRI. However, the patients who could not resume driving showed no cortical activation near the lesions. Our results provide further evidence that driving a car is a complex cognitive skill, and we believe that it is important to check the site of brain injury and the brain region where the damage has occurred before providing sufficient real car driving practice to patients with brain injury.