Visual-Somatosensory Integration in Older Adults: Links to Sensory and Motor Functioning

Abstract

Every day we receive information from each of our sensory systems. The synergistic processing of this information is referred to as multisensory integration (MSI). Research examining MSI in older adults is still in its infancy. There, however, appears to be an emerging consensus indicating larger behavioral MSI effects in older compared to younger adults. To date, the mechanisms behind increased MSI in the elderly are not well understood. Given the inherent decline in sensory functioning in the elderly, the current study aimed to examine whether the effect of visual acuity and somatosensory sensitivity on visualsomatosensory integration (VSI) in aging could explain increased MSI RT benefits.;Additionally, the relationships among visual acuity and somatosensory sensitivity, VSI, and balance were also examined given the adverse effects of sensory decline on motor outcomes. 163 non-demented participants ( M= 77 years, 56% female) without any medical or psychiatric conditions that could affect their performance were included in the current study. Participants received three randomly presented stimulus conditions (two unisensory and one multisensory) in a simple reaction time paradigm. They were instructed to make speeded foot-pedal responses as soon as they detected any stimulation. Vision was assessed using Snellen eye chart while somatosensory sensitivity was determined by lowest vibration threshold on the Vibratron II test. Participants were assigned into either low or high sensory functioning combination groups. Results from linear mixed effect models, adjusted for age, gender, ethnicity, health comorbidities, visual correction, and presence of neuropathy revealed a main effect of stimulus condition on reaction time (RT). Specifically, the RTs to multisensory stimulation were significantly faster than RTs in visual (p < .001) and somatosensory (p < .001) alone conditions. While vision did not influence VS RT facilitation, there was a significant interaction between somatosensory sensitivity and stimulus condition, indicating larger VS RT facilitation in individuals with lower somatosensory sensitivity in the comparison between RTs in multisensory and somatosensory alone stimulus conditions (p < .001). Additionally, there was a significant interaction between stimulus condition and sensory functioning group, where the group with low sensory functioning in both modalities demonstrated the largest difference between RTs in multisensory compared to somatosensory alone condition relative to the other three groups (p < .001). Neither visual acuity, somatosensory sensitivity, nor their combination moderated the relationship between VSI and balance or falls. In summary, the current results indicated a significant role for somatosensory functioning on VSI in the elderly.;Keywords: multisensory integration, visual acuity, somatosensory sensitivity, aging.