So his vision is normal because the visual areas are normal, his emotions are normal -- he'll laugh, he'll cry, so on and so forth -- but the wire from vision to emotions is cut and therefore he has this delusion that his mother is an impostor.
視覚エリアは正常なので視覚も正常で 感情も正常です　笑いますし泣きもします しかし視覚から感情への線が切れているので 母親がニセモノだという妄想を抱いてしまうのです