Orientational asymmetries in small-field optokinetic nystagmus in human infants

Horizontal and Vertical Optokinetic Eye Movements in Macaque Monkeys With Infantile Strabismus: Directional Bias and Crosstalk

“…In some normal infants, downward OKN is absent altogether. 19 Downward OKN gain improves from age 1 month to 1 year, but at age 1 year is still only~50% that of normal adults. Children and adults who had infantile-onset strabismus may retain the deficit of downward OKN, as their up-down OKN asymmetries can exceed those of control subjects.…”

“…Upward stimulus motion evokes more robust OKN than downward motion. [19][20][21][22][23][24][25][26][27] An upward bias of vertical OKN in humans has been reported consistently in studies using magnetic search coil eye movement recordings. Conflicting results have been reported when EOG or infrared recording methods are used, which are subject to eyelid interference artifact during vertical eye motion.…”

“…Hainline et al 19 used the term ''crosstalk'' to describe diagonal slow-phase eye movement evoked during strictly horizontal or vertical stimulus motion in healthy human infants: ''In many infant records, we saw evidence that OKN in one direction was 'contaminated' by movements in the orthogonal dimension.'' They reported that crosstalk was prominent only during trials of downward OKN; horizontal eye movement averaged 61% of the amplitude of downward eye movement.…”

“…Upward (UW) stimulus motion evokes more robust OKN than downward (DW) motion. [19][20][21][22][23][24][25][26][27] In children and adults with strabismus and/or amblyopia, the asymmetry favoring upward OKN may be more pronounced. 25,28,29 Behavioral studies have shown that the postnatal development of binocular sensory and motor functions in infant NHPs parallels closely that of infant humans, but on a compressed time scale (i.e., 1 week of monkey development is equivalent to 1 month of human).…”

Visual Perception

“…These are called "step-like" saccades. However, not all studies have found this apparent immaturity (Hainline & Abramov, 1985). Hainline (1998) points out that adults will occasionally produce step-like saccades when they are tired or inattentive, and suggests that perhaps the frequency of such saccades in infants might also be caused by lack of attention to the stimuli that are shown them in laboratory tests.…”