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A crossing over or decussation of two structures, as in the fibres of the nerves in the optic chiasm, which in humans and other animals with forward-pointing eyes and therefore overlapping visual fields are only partly crossed or decussated. Also called a chiasma. chiasms, chiasmata, or chiasmas pl. chiasmic or chiasmal adj. [From Greek chiasma a cross, named after the shape of the upper-case letter chi (X)]

Subjects: Psychology.

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