Zoom Brown Bag: Studying sensory reweighting via the perception of gravity in aging with central vision loss

Abstract:To interact with the world around us, we must accurately perceive our environment and how we are moving within it. For this, visual, vestibular, and somatosensory (proprioceptive and tactile) inputs must be integrated and appropriately (re)weighted depending on signal reliability and environmental and task demands. This sensory reweighting process is therefore dynamic. Age-related sensory deficits are thought to lead older adults to systematically up-weight visual information, however. This visual dependence in older age is associated with alterations in body coordination, adaptation difficulties, balance, and falls, among others, and such limitations can be debilitating when visual information is reduced and unreliable, as in the case of central visual field loss due to age-related macular degeneration (AMD). It is unclear whether aging allows for sensory adaptations to compensate for vision loss in AMD, and it is possible that visual dependence persists, whereby affected individuals are relying more on the sense that is failing them. We are therefore examining sensory reweighting in AMD with classic measures of subjective visual vertical estimation, an essential aspect of space perception and postural control. Prior to studying the complex case of AMD, where aging, vision loss, and an eccentric oculomotor reference frame may all play a part, we first examine whether the use of eccentric viewing strategies alone may affect verticality judgments. Since individuals with binocular central field loss commonly employ an eccentric preferred retinal locus (PRL) in their better eye, and given that eye position signals also contribute to individuals’ space perception and postural orientation and control, the consequences of AMD may extend beyond visual and oculomotor tasks. Thus, in addition to investigating the potential influence of eye eccentricity on verticality judgments in younger adults with no vision deficits, we look at individuals with monocular AMD who can serve as their own controls. Preliminary results seem to indicate that older adults with AMD rely on visual context in their subjective vertical estimation, despite their vision loss, and that eccentric viewing alters one's verticality perception. The potential interaction of eye orientation and contextual visual information will be essential to consider further in designing rehabilitation protocols for individuals with AMD. https://www.ski.org/users/catherine-agathos

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