左半側空間無視患者における縦書き文の読み誤りに関する検討

A study on reading errors in Japanese vertically printed sentences in patients with left unilateral spatial neglect

目的：左半側空間無視患者における縦書き文にみられる左側の読み落としの特徴，および文の改行位置が読み落としの現れ方に与える影響について検討を行った．

対象：右大脳半球に病変を有する左半側空間無視患者8例（男性5例，女性3例）．

方法：縦書き文の音読課題を行った．課題文は2行からなる縦書き文を4文配置（左側に2文，右側に2文を配置）したものである．縦書き文は4文字の複合語の語中で改行が行われるように作成した．

結果：8例中4例に左側の読み落としが認められた．左側の読み落としは，縦書き文の文頭から生じることが多かった．左半側空間無視が最も重度の1例では，左側の読み落としが行の途中から生じることもあった．4例中3例は改行時に次の行頭の文字を推測しやすい文で，読み落としが少なかった．

結論：左側の読み落としの生じやすさに大きくかかわるのは，左側に文が存在することを示す文脈的手がかりの有無であると考えられた．

Purpose：This study examined the characteristics of left-side omissions and the effect of line-break positions when patients with left unilateral spatial neglect read vertically printed sentences.

Subjects：Eight patients with left unilateral spatial neglect due to lesions in the right hemisphere (5 males, 3 females).

Methods：Participants performed a task requiring them to read vertically printed sentences aloud. The text was composed of four vertically written sentences, with two sentences on the left and two on the right. Each sentence consisted of two lines. The sentences were designed so that line breaks occurred within four-character compound words.

Results：Left-side omissions were observed in four of the eight patients. In most cases, these omissions occurred from the beginning of the vertically printed sentences. In one patient with the most severe left unilateral spatial neglect, left-side omissions also occurred from the middle of lines. In three of the four patients, fewer omissions were observed when the first character of the following line could be easily predicted at the point of the line break.

Conclusion：Contextual cues signaling the presence of sentences on the left side have a major influence on left-side omissions.