Abstract
Introduction The subjective visual vertical (SVV) measures the perception of a person's spatial orientation relative to gravity. Weighted central integration of vestibular, visual, and proprioceptive inputs is essential for SVV perception. Without any visual references and minimal proprioceptive contribution, the static SVV reflects balance of the otolith organs. Normal aging is associated with bilateral and progressive decline in otolith organ function, but age-dependent effects on SVV are inconclusive. Studies on sensory reweighting for visual vertical and multisensory integration strategies reveal age-dependent differences, but most studies have included elderly participants in comparison to younger adults. The aim of this study was to compare young adults with older adults, an age group younger than the elderly. Methods Thirty-three young and 28 older adults (50–65 years old) adjusted a tilted line accurately to their perceived vertical. The rod's final position from true vertical was recorded as tilt error in degrees. For otolithic balance, visual vertical was recorded in the dark without any visual references. The rod and frame task (RFT) with tilted disorienting visual frames was used for creating visuovestibular conflict. We adopted Nyborg's analysis method to derive the rod and frame effect (RFE) and trial-to-trial variability measures. Rod alignment times were also analyzed. Results There was no age difference in signed tilts of SVV without visual reference. There was an age effect on RFE and on overall trial-to-trial variability of rod tilt, with older adults displaying larger frame effects and greater variability in rod tilts. Alignment times were longer in the tilted-frame conditions for both groups and in the older adults compared to their younger counterparts. The association between tilt accuracy and tilt precision was significant for older adults only during visuovestibular conflict, revealing an increase in RFE with an increase in tilt variability. Correlation of σSVV, which represents vestibular input precision, with RFE yielded exactly the same contribution of σSVV to the variance in RFE for both age groups. Conclusions Older adults have balanced otolithic input in an upright position. Increased reliance on visual cues may begin at ages younger than what is considered elderly. Increased alignment times for older adults may create a broader time window for integration of relevant and irrelevant sensory information, thus enhancing their multisensory integration. In parallel with the elderly, older adults may differ from young adults in their integration of sensory cues for visual vertical perception.
Highlights
Introduction. e subjective visual vertical (SVV) measures the perception of a person’s spatial orientation relative to gravity
Age-related vestibular changes start from an age well below 50 years [59], and vestibular impairments begin in the fifth decade of life [20]
We investigated whether SVV, a spatial orientation task, and visual dependence on the rod and frame test (RFT) may differ between a group of young and another group of older adults, less than 65 years of age, in order to identify whether performances in this age group are in parallel with those of the elderly
Summary
Introduction. e subjective visual vertical (SVV) measures the perception of a person’s spatial orientation relative to gravity. Studies on sensory reweighting for visual vertical and multisensory integration strategies reveal age-dependent differences, but most studies have included elderly participants in comparison to younger adults. E static SVV is tested in complete darkness, in order to exclude visual references, and in an upright sitting position, so that proprioceptive inputs contribute only minimally Assessed in such conditions, the Journal of Aging Research static SVV reflects tonic otolithic input differences between the two ears [13, 14]. E functional consequence of decline in the function of the otolith organs includes age-dependent reduction in afferent signals to the integrating centers for SVV within the central nervous system, and reduced sensitivity to gravity and linear acceleration [22, 23]. By using Bayesian inference, the authors deduced that, for perception of vertical with visual contextual information, there is an age-dependent reweighting of sensory information and shift in its sensory weights favoring visual contextual information and downweighting of unreliable and noisy vestibular signals
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