IN ordinary visual searching or scanning of the environment the eyes and head move together whereas in reading or scrutinizing an object at a near point the eyes move saccadically and the head is still. During visual pursuit the eye movements are conjugate and precede those of the head. In contrast, during active or passive head turning the eyes move conjugately but in a direction opposite to the head. Thus, when the head is turned to the left the eyes deviate conjugately to the right. Clockwise tilting of the head results in counterclockwise rotation of the eyes; when the head moves up the eyes move down. Similar dissociation in direction between head and eyes occurs during headbody rotation in a swivel or Bárány chair and during head tremor. This vestibulo-ocular effect on body rotation occurs without optic fixation, eg, in the dark or in subjects who are drowsy, but
Bender MB, Feldman M. Visual Illusions During Head Movement in Lesions of the Brain Stem. Arch Neurol. 1967;17(4):354–364. doi:10.1001/archneur.1967.00470280020003
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