Proprioceptive and Retinal Afference Modify Postsaccadic Ocular Drift

Abstract

Drift of the eyes after saccades produces motion of images on the retina (retinal slip) that degrades visual acuity. In this study, we examined the contributions of proprioceptive and retinal afference to the suppression of postsaccadic drift induced by a unilateral ocular muscle paresis. Eye movements were recorded in three rhesus monkeys with a unilateral weakness of one vertical extraocular muscle before and after proprioceptive deafferentation of the paretic eye. Postsaccadic drift was examined in four visual states: monocular viewing with the normal eye (4-wk period); binocular viewing (2-wk period); binocular viewing with a disparity-reducing prism (2-wk period); and monocular viewing with the paretic eye (2-wk period). The muscle paresis produced vertical postsaccadic drift in the paretic eye, and this drift was suppressed in the binocular viewing condition even when the animals could not fuse. When the animals viewed binocularly with a disparity-reducing prism, the drift in the paretic eye was suppressed in two monkeys (with superior oblique pareses) but generally was enhanced in one animal (with a tenotomy of the inferior rectus). When drift movements were enhanced, they reduced the retinal disparity that was present at the end of the saccade. In the paretic-eye-viewing condition, postsaccadic drift was suppressed in the paretic eye and was induced in the normal eye. After deafferentation in the normal-eye-viewing state, there was a change in the vertical postsaccadic drift of the paretic eye. This change in drift was idiosyncratic and variably affected the amplitude and velocity of the postsaccadic drift movements of the paretic eye. Deafferentation of the paretic eye did not affect the postsaccadic drift of the normal eye nor did it impair visually mediated adaptation of postsaccadic drift. The results demonstrate several new findings concerning the roles of visual and proprioceptive afference in the control of postsaccadic drift: disconjugate adaptation of postsaccadic drift does not require binocular fusion; slow, postsaccadic drift movements that reduce retinal disparity but concurrently increase retinal slip can be induced in the binocular viewing state; postsaccadic drift is modified by proprioception from the extraocular muscles, but these modifications do not serve to minimize retinal slip or to correct errors in saccade amplitude; and visually mediated adaptation of postsaccadic drift does not require proprioceptive afference from the paretic eye.

The functions of the proprioceptors of the eye muscles

“…Compensation for postsaccadic drift develops over time and adjustment is required to each eye separately (disconjugate adaptation). Lewis et al (1999) produced postsaccadic drift in monkeys by unilateral surgical paralysis of a vertical eye muscle. The e¡ects of various viewing regimes and of dea¡erentation of the paretic eye on the development of compensation were then studied in an elaborate series of experiments.…”

Effect of tongue stimulation on nystagmus eye movements in blind patients

“…A deafferentation procedure that sections ophthalmic division of the trigeminal nerve failed to reveal any proprioceptive influence on eye movements in monkeys (Guthrie et al 1983;Lewis et al 1994Lewis et al , 1999Lewis et al , 2001; but positive effects on vestibular ocular responses in pigeons (Donaldson and Knox 2000) and on saccades and pursuits in human (Knox 2008), although some recent findings showed that there is proprioceptive representation at the cortex level in monkeys and human being (Zhang et al 2008;Balslev and Miall 2008;Balslev et al 2011). It is not clear where the effect of the tongue stimulation on nystagmus takes place.…”

Posturografia em idosos com distúrbios vestibulares e quedas

“…O sistema sacádico consiste em movimentos rápidos dos olhos, quando o RVO e a perseguição ocular lenta não conseguem manter o objeto de interesse na fóvea, para visualizá-lo nitidamente 31 . No envelhecimento, há diminuição do ganho dos movimentos sacádicos 32 .…”

“…Trata-se de um reflexo que estabiliza as imagens na retina durante o movimento cefálico, ao produzir um movimento ocular na direção oposta, preservando a nitidez visual durante a locomoção 32 . Apresenta comprometimento relacionado à senescência vestibular 1,31 , decorrente da redução da sensibilidade dos canais semicirculares às estimulações angulares de alta Macedo C, Gazzola JM, Caovilla HH, Ricci NA, Doná F, Ganança FF frequência, interferindo nas respostas reflexas aos movimentos rápidos do segmento cefálico 34 .…”