The effect of prism adaptation on state estimates of eye position in the orbit

Abstract

Prism adaptation (PA) after-effects are assessed using tests that measure changes in sensorimotor systems. After-effects on pointing without feedback to a visual target (open loop pointing -OLP) are traditionally described as being larger than those measured by straight ahead pointing (SAP) with eyes closed, and the difference between them is attributed to a shift in visual localisation. However, neither differences between OLP and SAP, nor shifts in perceptual judgement of visual straight ahead (VSA), are consistently reported. Moreover, since very few studies have directly recorded direction of gaze, an effect of PA on the state estimate of gaze direction has not been reliably documented. The current research aimed to isolate the effects of PA on state estimates of eye position. We measured sensorimotor aftereffects through common (OLP, SAP, and VSA) measures, and also recorded eye position and additional after-effect measures to interrogate changes to the oculomotor system and how these might relate to other measures of sensorimotor change. To ascertain if PA's effects on estimates of eye position could be attributed to eye muscle potentiation, we compared the effects of PA to sustained gaze deviation without adaptation. PA induced no effect on visual straight-ahead and no change in direction of gaze, when measured while positioning a target, looking straight ahead in the dark, or looking toward the passively positioned and occluded unexposed hand. We also found that after-effects measured by SAP with the eyes open were larger than SAP with the eyes closed and equal to those observed with OLP. The findings challenge the concept that total adaptation after-effect is a direct sum of arm proprioceptive and visual after-effects as conventionally measured, and suggest that the oculomotor system is altered by prism adaptation only in interaction with an arm motor command when vision is available. Highlights• No evidence of a shift of visual straight-ahead or of gaze direction following prism adaptation.• Active arm movement under the availability of vision produced largest after-effect.• Findings challenge the concept of linear additivity of arm proprioceptive and visual after-effects of prism adaptation.

Associations and Dissociations between Oculomotor Readiness and Covert Attention

“…In order to address these issues and provide a more rigorous test of exogenous-only version of OMRH/PMT we developed a new variant of the Posner cueing task in which cues and targets were presented within or beyond the effective oculomotor range (EOMR) [104]. Eye-abduction is thought to induce biased proprioception [105], which could lead to a bias in attention, although a recent study has cast some doubt on this claim [106]; we nevertheless used Presentation in Extreme Periphery (PEP), which has the advantage of presenting stimuli in the far periphery (up to 44° of visual angle) while keeping the participant’s eye and trunk in their canonical, natural position. Each participant’s Effective Oculomotor Range (EOMR) was computed in order to define the location of the placeholders in the different cueing tasks.…”

Virtual reality-based sensorimotor adaptation shapes subsequent spontaneous and naturalistic stimulus-driven brain activity

“…Unfortunately, we could not monitor eye movements in the scanner, so we cannot directly confirm, nor exclude this hypothesis. However, a recent study by Gilligan et al . (2019) found that PA had no effect on subsequent gaze directions in healthy individuals during passive gazing, but only when gazing involved active arm movements.…”

“…Unfortunately, we could not monitor eye movements in the scanner, so we cannot directly confirm, nor exclude this hypothesis. However, a recent study by Gilligan et al (2019) found that PA had no effect on subsequent gaze directions in healthy individuals during passive gazing, but only when gazing involved active arm movements. Moreover, theoretically, only videos that presented bilateral salient objects actually lead to a competition between execution of left or right saccades (Nardo et al, 2016).…”

Patients with lesions to the intraparietal cortex show greater proprioceptive realignment after prism adaptation: Evidence from open-loop pointing and manual straight ahead

“…One possibility is that lesions to the IPS could disrupt the calibration of corollary discharge, preventing any adjustment in visual reference frames that would normally occur during prism exposure. However, previous research has disputed the role of felt eye position in visual realignment during prism adaptation (Gilligan et al, 2019;Newport et al, 2009).…”

“…We chose to focus on the intraparietal cortex given its importance for the spatial transformations that occur during goal-directed pointing and reaching (Culham and Kanwisher, 2001;Vingerhoets, 2014). We predicted that control participants would show smaller MSA shifts than OLP shifts consistent with previous evidence (reviewed by Facchin et al, 2019;and Gilligan et al, 2019) and the idea that the former measures only limb proprioceptive shift and the latter measures both visual and limb proprioceptive shifts. If IPS lesions alter the way in which sensory-motor realignment occurs during prism adaptation, then the difference in the magnitude of the MSA versus OLP shifts for the patients would be altered compared to controls.…”