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.
Les zones de la vision étant normales, la vision est normale, ses émotions sont normales -- il peut rire, pleurer, ainsi de suite -- mais la connexion qui relie la vision aux émotions est rompue, et, par conséquent, il a l'illusion que sa mère est un imposteur.