Organizer: Jeannette R. Mahoney, Albert Einstein College of Medicine
Abstract: The ability to successfully integrate simultaneous information relayed across multiple sensory systems is an integral aspect of daily functioning. Unisensory impairments have been individually linked to slower gait, functional decline, increased risks of falls, cognitive decline, and worse quality of life in the elderly. To date, however, relatively few studies have set out to determine how multisensory integration processes change with increasing age. In what follows, we will discuss recent aging work investigating: 1) the temporal binding window of integration; 2) susceptibility to the sound-induced flash illusion; and 3) differential visual-somatosensory integration effects. Our overall objective is to demonstrate the clinical-translational value of multisensory integration effects in predicting important motor outcomes like balance and falls.
S6.1 Temporal Integration of Multisensory Events in Later Years
Michael Barnett-Cowan University of Waterloo
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To safely interact with the environment, the brain must quickly make sense of converging multisensory information in order to form a reliable and accurate percept with which to guide decision-making and behaviour. As we age, however, natural changes occurring in the brain affect the way the senses provide accurate and reliable information about the world in timely fashion. While it is well understood that the senses become less sharp as we age, how the brain continues to integrate multisensory cues with unreliable sensory information available in later life is less clear. Older adults have trouble separating multisensory events in time, an observation that cannot be entirely accounted for by an age-related reduction in unisensory detection thresholds, potentially explaining why many sensory-related challenges experienced in later life (e.g., decision-making, communication, balance control) persist despite the use of corrective devices designed to address unisensory loss. Given that sensory-related challenges in the elderly can dramatically affect later life functional independence, lead to isolation, impaired communication, and increased fall rates, a shift in the paradigm for assessing and treating sensory impairment in the elderly is needed. Here I review work in our lab that has shown that i) older adults have an extended temporal binding window compared to younger adults, but which is task-specific, ii) older adults are less aware of the perceived onset of a fall compared to younger adults, and iii) the representation of the duration of multisensory events during a fall is distorted during a fall, particularly for older adults. These results and future work will be discussed in the context of informing falls prevention strategies to help prevent falls in later life.
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S6.2 Simultaneity and temporal order judgments are coded differently and change with age: an event-related potential study
Aysha Basharat*, Meaghan S. Adams, W. Richard Staines, Michael Barnett-Cowan University of Waterloo
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Multisensory integration is required for a number of tasks of daily living where the inability to accurately identify simultaneity and temporality of multisensory events results in errors in judgment and can lead to poor decision-making and dangerous behaviour. Previously, our lab discovered that older adults exhibited impaired timing of audiovisual events, particularly when making temporal order judgments (TOJ). Simultaneity judgments (SJ) however were preserved across the lifespan. Recently, we investigated the difference between the TOJ and SJ tasks in younger and older adults to assess neural processing differences between the two tasks and across the lifespan. Event related potentials (ERPs) were studied to determine between-task and between-age differences. Results revealed task specific differences in perceiving simultaneity and temporal order, suggesting that each task may be subserved via different neural mechanisms. The auditory N1 and visual P1 ERP amplitudes confirmed that unisensory processing of audiovisual stimuli did not differ between the two tasks within both younger and older groups, indicating that performance differences between tasks arise either from multisensory integration or higher-level decision-making. Compared to younger adults, older adults showed a sustained higher auditory N1 ERP amplitude response across SOAs, suggestive of an extended temporal binding window. Our work provides compelling evidence that different neural mechanisms subserve the SJ and TOJ tasks and that simultaneity and temporal order perception are coded differently and change with age.
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S6.3 A population study of multisensory perception in middle-aged and older adults: The Sound-Induced Flash Illusion in The Irish Longitudinal Study on Ageing (TILDA)
Annalisa Setti*, Belinda Hernández, Rose Anne Kenny, Fiona N. Newell University College Cork
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Population studies such as the Berlin Ageing Study and the Health and Retirement Study have provided strong evidence for the link between sensory perception and ageing. Emerging evidence from the experimental literature shows that multisensory perception also changes with ageing, and it is associated with an enlarged temporal window of integration between visual and auditory inputs. A test emerging as robust indicator of such age-related changes is the Sound-Induced Flash Illusion. Older adults are more susceptible to this illusion over larger stimulus onset asynchronies; this higher susceptibility is, in turn, associated with cognitive and functional disabilities. While multisensory perception has been vastly studied experimentally, there are currently no population data available. Here we present the protocol for the introduction of the Sound-Induced Flash Illusion in the Irish Longitudinal Study on Ageing, a population representative study of 50+ in Ireland. Data on the Sound-Induced Flash Illusion on a sample of 4000 individuals, showing the association between susceptibility at different stimulus onset asynchronies and ageing, will be discussed in light of the experimental literature and the potential contribution of population-level data on multisensory perception to the study of healthy and pathological ageing.
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S6.4 Intra- and inter-individual differences in susceptibility to the Sound-Induced Flash illusion
Jason Chan* & Annalisa Setti University College Cork
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The Sound-Induced Flash illusion (SIFI) is a robust multisensory phenomenon occurring when one visual stimulus, for example a flash, is perceived as two flashes when paired with two auditory stimuli in close temporal proximity. Older adults are more susceptible to this illusion than younger adults at longer stimulus on-set asynchronies (SOAs). However, differences in the susceptibility to the illusion occur depending on the population considered (e.g. fallers or active older people who exercise) and on the experimental context (e.g, the number of SOAs) available to the participants during the task. Given that previous research has shown that older adults are a heterogeneous population, these individual differences need to be considered. The SIFI could be potentially part of a non-verbal diagnostic toolkit to assess multisensory integration, however operational standards need to be considered. Furthermore, many studies have used the SIFi to investigate multisensory temporal integration, largely showing the same pattern of results. However, the number of perceived illusions vary between these studies. We will discuss work that shows changing the number of SOAs presented will affect the number of perceived illusions. This suggests the SOAs are modulating the perceived illusion. We will discuss these intra and inter-individual differences in light of temporal integration deficits and prospective use of SIFI to assess such deficits.
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S6.5 Understanding Differential Visual-Somatosensory Integration Effects in Aging
Jeannette R. Mahoney* Albert Einstein College of Medicine
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Successful integration of concurrent information across multiple sensory modalities is crucial for functioning in the real world, completion of activities of daily living, and mobility. Yet, research investigating age-related changes in multisensory integration (MSI) processes still remains scarce. To date, there has been converging evidence for larger behavioral MSI effects in older compared to younger adults; however, the question of whether “larger” effects are actually “better” for seniors remains largely unanswered. Findings from our recent visual-somatosensory (VS) multisensory studies provide support for differential patterns of multisensory processing in aging that are associated with static balance, falls, and physical activities. In an attempt to identify potential mechanisms behind these age-related VS integrative effects, we investigated constituent unisensory visual and somatosensory functioning. Results revealed that older adults with poor somatosensory sensitivity demonstrated larger VS integrative effects; however, the largest VS integrative effects were found in seniors with both poor somatosensory sensitivity and poor visual acuity. Collectively, these results shed light on the idea that VS integration is likely a compensatory process used to overcome age-related physiological declines in unisensory processing. While the effect of MSI has been attributed to basic degenerative changes in neuronal architecture during the aging process, this speculative interpretation has yet to be empirically tested. Future studies are clearly needed to establish the structural and functional correlates of multisensory integration in aging, specifically visual-somatosensory integration, in order to further establish the link between differential MSI effects with other important age-related clinical motor outcomes.
