Vision and touch in ageing: Crossmodal selective attention and visuotactile spatial interactions

Age-related changes to the attentional modulation of temporal binding

During multisensory integration, the time range within which visual and auditory information can be perceived as synchronous and bound together is known as the temporal binding window (TBW). With increasing age, the TBW becomes wider, such that older adults erroneously, and often dangerously, integrate sensory inputs that are asynchronous. Recent research suggests that attentional cues can narrow the width of the TBW in younger adults, sharpening temporal perception and increasing the accuracy of integration. However, due to their age-related declines in attentional control, it is not yet known whether older adults can deploy attentional resources to narrow the TBW in the same way as younger adults. This study investigated the age-related changes to the attentional modulation of the TBW. Thirty younger and 30 older adults completed a cued-spatial-attention version of the stream-bounce illusion, assessing the extent to which the visual and auditory stimuli were integrated when presented at three different stimulus-onset asynchronies, and when attending to a validly cued or invalidly cued location. A 2 × 2 × 3 mixed ANOVA revealed that when participants attended to the validly cued location (i.e., when attention was present), susceptibility to the stream-bounce illusion decreased. However, crucially, this attentional manipulation significantly affected audiovisual integration in younger adults, but not in older adults. These findings suggest that older adults have multisensory integration-related attentional deficits. Directions for future research and practical applications surrounding treatments to improve the safety of older adults' perception and navigation through the environment are discussed.

Perceptual training narrows the temporal binding window of audiovisual integration in both younger and older adults

There is a growing body of evidence to suggest that multisensory processing changes with advancing age-usually in the form of an enlarged temporal binding window-with some studies linking these multisensory changes to negative clinical outcomes. Perceptual training regimes represent a promising means for enhancing the precision of multisensory integration in ageing; however, to date, the vast majority of studies examining the efficacy of multisensory perceptual learning have focused solely on healthy young adults. Here, we measured the temporal binding windows of younger and older participants before and after training on an audiovisual temporal discrimination task to assess (i) how perceptual training affected the shape of the temporal binding window and (ii) whether training effects were similar in both age groups. Our results replicated previous findings of an enlarged temporal binding window in older adults, as well as providing further evidence that both younger and older participants can improve the precision of their audiovisual timing estimation via perceptual training. We also show that this training protocol led to a narrowing of the temporal binding window associated with the sound-induced flash illusion in both age groups indicating a general refinement of audiovisual integration. However, while younger adults also displayed a general reduction in crossmodal interactions following training, this effect was not observed in the older adult group. Together, our results suggest that perceptual training narrows the temporal binding window of audiovisual integration in both younger and older adults but has less of an impact on prior expectations regarding the source of audiovisual signals in older adults.

Age-related changes in visuo-proprioceptive processing in perceived body position

This study investigated age-related change in visuo-proprioceptive processing in the perceived body position using mirror hand/foot illusions, focusing on its temporal characteristics, its dependency on body parts, and its association with older adults’ fall risk. Either immediately or 15 s after the exposure to the mirror-induced inconsistency of visuo-proprioceptive signals regarding the right hand or foot position, participants performed a reaching task using the unseen, illusion-affected hand or foot. Results showed clear age group differences. Specifically, older adults exhibited larger reaching errors than younger adults in the hand condition, and after the 15 s delay in the foot condition. Further, the reaching errors were constant across time for older adults but decreased after the delay in young adults, regardless of the tested body part. Particularly, older adults’ risk of falling, which was assessed by the timed up-and-go test, was negatively correlated with the reduction of reaching error across time. This suggests that older adults, especially those with a high risk of falling, face difficulties in appropriately processing visual and proprioceptive information for body perception in accordance with their external environment.

Audiovisual Integration for Saccade and Vergence Eye Movements Increases with Presbycusis and Loss of Selective Attention on the Stroop Test

Multisensory integration is a capacity allowing us to merge information from different sensory modalities in order to improve the salience of the signal. Audiovisual integration is one of the most used kinds of multisensory integration, as vision and hearing are two senses used very frequently in humans. However, the literature regarding age-related hearing loss (presbycusis) on audiovisual integration abilities is almost nonexistent, despite the growing prevalence of presbycusis in the population. In that context, the study aims to assess the relationship between presbycusis and audiovisual integration using tests of saccade and vergence eye movements to visual vs. audiovisual targets, with a pure tone as an auditory signal. Tests were run with the REMOBI and AIDEAL technologies coupled with the pupil core eye tracker. Hearing abilities, eye movement characteristics (latency, peak velocity, average velocity, amplitude) for saccade and vergence eye movements, and the Stroop Victoria test were measured in 69 elderly and 30 young participants. The results indicated (i) a dual pattern of aging effect on audiovisual integration for convergence (a decrease in the aged group relative to the young one, but an increase with age within the elderly group) and (ii) an improvement of audiovisual integration for saccades for people with presbycusis associated with lower scores of selective attention in the Stroop test, regardless of age. These results bring new insight on an unknown topic, that of audio visuomotor integration in normal aging and in presbycusis. They highlight the potential interest of using eye movement targets in the 3D space and pure tone sound to objectively evaluate audio visuomotor integration capacities.

A Scoping Review of Audiovisual Integration Methodology: Screening for Auditory and Visual Impairment in Younger and Older Adults

With the rise of the aging population, many scientists studying multisensory integration have turned toward understanding how this process may change with age. This scoping review was conducted to understand and describe the scope and rigor with which researchers studying audiovisual sensory integration screen for hearing and vision impairment. A structured search in three licensed databases (Scopus, PubMed, and PsychInfo) using the key concepts of multisensory integration, audiovisual modality, and aging revealed 2,462 articles, which were screened for inclusion by two reviewers. Articles were included if they (1) tested healthy older adults (minimum mean or median age of 60) with younger adults as a comparison (mean or median age between 18 and 35), (2) measured auditory and visual integration, (3) were written in English, and (4) reported behavioral outcomes. Articles that included the following were excluded: (1) tested taste exclusively, (2) tested olfaction exclusively, (3) tested somatosensation exclusively, (4) tested emotion perception, (5) were not written in English, (6) were clinical commentaries, editorials, interviews, letters, newspaper articles, abstracts only, or non-peer reviewed literature (e.g., theses), and (7) focused on neuroimaging without a behavioral component. Data pertaining to the details of the study (e.g., country of publication, year of publication, etc.) were extracted, however, of higher importance to our research question, data pertaining to screening measures used for hearing and vision impairment (e.g., type of test used, whether hearing- and visual-aids were worn, thresholds used, etc.) were extracted, collated, and summarized. Our search revealed that only 64% of studies screened for age-abnormal hearing impairment, 51% screened for age-abnormal vision impairment, and that consistent definitions of normal or abnormal vision and hearing were not used among the studies that screened for sensory abilities. A total of 1,624 younger adults and 4,778 older participants were included in the scoping review with males composing approximately 44% and females composing 56% of the total sample and most of the data was obtained from only four countries. We recommend that studies investigating the effects of aging on multisensory integration should screen for normal vision and hearing by using the World Health Organization's (WHO) hearing loss and visual impairment cut-off scores in order to maintain consistency among other aging researchers. As mild cognitive impairment (MCI) has been defined as a “transitional” or a “transitory” stage between normal aging and dementia and because approximately 3–5% of the aging population will develop MCI each year, it is therefore important that when researchers aim to study a healthy aging population, that they appropriately screen for MCI. One of our secondary aims was to determine how often researchers were screening for cognitive impairment and the types of tests that were used to do so. Our results revealed that only 55 out of 72 studies tested for neurological and cognitive function, and only a subset used standardized tests. Additionally, among the studies that used standardized tests, the cut-off scores used were not always adequate for screening out mild cognitive impairment. An additional secondary aim of this scoping review was to determine the feasibility of whether a meta-analysis could be conducted in the future to further quantitatively evaluate the results (i.e., are the findings obtained from studies using self-reported vision and hearing impairment screening methods significantly different from those measuring vision and hearing impairment in the lab) and to assess the scope of this problem. We found that it may not be feasible to conduct a meta-analysis with the entire dataset of this scoping review. However, a meta-analysis can be conducted if stricter parameters are used (e.g., focusing on accuracy or response time data only).

Systematic Review Registration:https://doi.org/10.17605/OSF.IO/GTUHD.

Evidence-Based Communication with Critically Ill Older Adults

Communication is a critical component of patient-centered care. Critically ill, mechanically ventilated patients are unable to speak and this condition is frightening, frustrating, and stressful. Impaired communication in the intensive care unit (ICU) contributes to poor symptom identification and restricts effective patient engagement. Older adults are at higher risk for communication impairments in the ICU because of pre-illness communication disorders and cognitive dysfunction that often accompanies or precedes critical illness. Assessing communication disorders and developing patient-centered strategies to enhance communication can lessen communication difficulty and increase patient satisfaction.

Estimation of Torso Vibrotactile Thresholds Using Eccentric Rotating Mass Motors

The characterization of vibrotactile perception is crucial to accurately configure haptic devices and create appropriate stimuli for improving user performance in human-machine interaction systems. This article presents a study aiming to determine the absolute and differential vibrotactile thresholds in different areas of the torso to develop reliable haptic patterns to be displayed using a haptic vest. In the 'absolute threshold' experiment, we measure the minimum detectable vibration using a forced-choice task. Furthermore, in the 'differential threshold' experiment, we measure the minimum frequency change needed for users to discriminate two successive vibrotactile stimuli using a vibration matching task. The first experiment does not show differences between absolute thresholds, opening up the possibility of setting a unique minimal vibration for creating haptic patterns. Similarly, the second experiment does not show differences between differential thresholds. Moreover, as these thresholds follow Weber's law, it is viable to estimate any upper or lower differential threshold for any reference stimulus using a K-value. These results are a first step for creating vibrotactile patterns over the torso with the employed eccentric rotating mass motors. Moreover, the whole study provides a method to obtain these psychophysical values since the usage of different motors can change these results.

Effect of timing delay between visual and vestibular stimuli on heading perception

Heading direction is perceived based on visual and inertial cues. The current study examined the effect of their relative timing on the ability of offset visual headings to influence inertial perception. Seven healthy human subjects experienced 2 s of translation along a heading of 0°, ±35°, ±70°, ±105°, or ±140°. These inertial headings were paired with 2-s duration visual headings that were presented at relative offsets of 0°, ±30°, ±60°, ±90°, or ±120°. The visual stimuli were also presented at 17 temporal delays ranging from -500 ms (visual lead) to 2,000 ms (visual delay) relative to the inertial stimulus. After each stimulus, subjects reported the direction of the inertial stimulus using a dial. The bias of the inertial heading toward the visual heading was robust at ±250 ms when examined across subjects during this period: 8.0° ± 0.5° with a 30° offset, 12.2° ± 0.5° with a 60° offset, 11.7° ± 0.6° with a 90° offset, and 9.8° ± 0.7° with a 120° offset (mean bias toward visual ± SE). The mean bias was much diminished with temporal misalignments of ±500 ms, and there was no longer any visual influence on the inertial heading when the visual stimulus was delayed by 1,000 ms or more. Although the amount of bias varied between subjects, the effect of delay was similar.NEW & NOTEWORTHY The effect of timing on visual-inertial integration on heading perception has not been previously examined. This study finds that visual direction influence inertial heading perception when timing differences are within 250 ms. This suggests visual-inertial stimuli can be integrated over a wider range than reported for visual-auditory integration and may be due to the unique nature of inertial sensation, which can only sense acceleration while the visual system senses position but encodes velocity.

Repeated Exposure to Illusory Sense of Body Ownership and Agency Over a Moving Virtual Body Improves Executive Functioning and Increases Prefrontal Cortex Activity in the Elderly

We previously showed that the illusory sense of ownership and agency over a moving body in immersive virtual reality (displayed in a first-person perspective) can trigger subjective and physiological reactions on the real subject’s body and, therefore, an acute improvement of cognitive functions after a single session of high-intensity intermittent exercise performed exclusively by one’s own virtual body, similar to what happens when we actually do physical activity. As well as confirming previous results, here, we aimed at finding in the elderly an increased improvement after a longer virtual training with similar characteristics. Forty-two healthy older subjects (28 females, average age = 71.71 years) completed a parallel-group randomized controlled trial (RCT; UMIN000039843, umin.ac.jp) including an adapted version of the virtual training previously used: while sitting, participants observed the virtual body in a first-person perspective (1PP) or a third-person perspective (3PP) performing 20 min of virtual high-intensity intermittent exercise (vHIE; the avatar switched between fast and slow walking every 2 min). This was repeated twice a week for 6 weeks. During the vHIE, we measured the heart rate and administered questionnaires to evaluate illusory body ownership and agency. Before the beginning of the intervention, immediately after the first session of vHIE, and at the end of the entire intervention, we evaluated the cognitive performance at the Stroop task with online recording of the hemodynamic activity over the left dorsolateral prefrontal cortex. While we confirm previous results regarding the virtual illusion and its physiological effects, we did not find significant cognitive or neural improvement immediately after the first vHIE session. As a novelty, in the 1PP group only, we detected a significant decrease in the response time of the Stroop task in the post-intervention assessment compared to its baseline; coherently, we found an increased activation on left dorsolateral prefrontal cortex (lDLPFC) after the entire intervention. While the current results strengthen the impact of the virtual full-body illusion and its physiological consequences on the elderly as well, they might have stronger and more established body representations. Perhaps, a longer and increased exposure to those illusions is necessary to initiate the cascade of events that culminates to an improved cognitive performance.

Ageing and multisensory integration: A review of the evidence, and a computational perspective

The processing of multisensory signals is crucial for effective interaction with the environment, but our ability to perform this vital function changes as we age. In the first part of this review, we summarise existing research into the effects of healthy ageing on multisensory integration. We note that age differences vary substantially with the paradigms and stimuli used: older adults often receive at least as much benefit (to both accuracy and response times) as younger controls from congruent multisensory stimuli, but are also consistently more negatively impacted by the presence of intersensory conflict. In the second part, we outline a normative Bayesian framework that provides a principled and computationally informed perspective on the key ingredients involved in multisensory perception, and how these are affected by ageing. Applying this framework to the existing literature, we conclude that changes to sensory reliability, prior expectations (together with attentional control), and decisional strategies all contribute to the age differences observed. However, we find no compelling evidence of any age-related changes to the basic inference mechanisms involved in multisensory perception.

Crossmodal spatial distraction across the lifespan

The ability to resist distracting stimuli whilst voluntarily focusing on a task is fundamental to our everyday cognitive functioning. Here, we investigated how this ability develops, and thereafter declines, across the lifespan using a single task/experiment. Young children (5-7 years), older children (10-11 years), young adults (20-27 years), and older adults (62-86 years) were presented with complex visual scenes. Endogenous (voluntary) attention was engaged by having the participants search for a visual target presented on either the left or right side of the display. The onset of the visual scenes was preceded - at stimulus onset asynchronies (SOAs) of 50, 200, or 500 ms - by a task-irrelevant sound (an exogenous crossmodal spatial distractor) delivered either on the same or opposite side as the visual target, or simultaneously on both sides (cued, uncued, or neutral trials, respectively). Age-related differences were revealed, especially in the extreme age-groups, which showed a greater impact of crossmodal spatial distractors. Young children were highly susceptible to exogenous spatial distraction at the shortest SOA (50 ms), whereas older adults were distracted at all SOAs, showing significant exogenous capture effects during the visual search task. By contrast, older children and young adults' search performance was not significantly affected by crossmodal spatial distraction. Overall, these findings present a detailed picture of the developmental trajectory of endogenous resistance to crossmodal spatial distraction from childhood to old age and demonstrate a different efficiency in coping with distraction across the four age-groups studied.

When irrelevant information helps: Extending the Eriksen-flanker task into a multisensory world

Charles W. Eriksen dedicated much of his research career to the field of cognitive psychology, investigating human information processing in those situations that required selection between competing stimuli. Together with his wife Barbara, he introduced the flanker task, which became one of the standard experimental tasks used by researchers to investigate the mechanisms underpinning selection. Although Eriksen himself was primarily interested in investigating visual selection, the flanker task was eventually adapted by other researchers to investigate human information processing and selection in a variety of nonvisual and multisensory situations. Here, we discuss the core aspects of the flanker task and interpret the evidence of the flanker task when used in crossmodal and multisensory settings. "Selection" has been a core topic of psychology for nearly 120 years. Nowadays, though, it is clear that we need to look at selection from a multisensory perspective-the flanker task, at least in its crossmodal and multisensory variants, is an important tool with which to investigate selection, attention, and multisensory information processing.

Multisensory integration involved in the body perception of community-dwelling older adults

This study investigates how the multisensory integration in body perception changes with increasing age, and whether it is associated with older adults’ risk of falling. For this, the rubber hand illusion (RHI) and rubber foot illusion (RFI) were used. Twenty-eight community-dwelling older adults and 25 university students were recruited. They viewed a rubber hand or foot that was stimulated in synchrony or asynchrony with their own hidden hand or foot. The illusion was assessed by using a questionnaire, and measuring the proprioceptive drift and latency. The Timed Up and Go Test was used to classify the older adults into lower and higher fall-risk groups. No difference was observed in the RHI between the younger and older adults. However, several differences were observed in the RFI. Specifically, the older adults with a lower fall-risk hardly experienced the illusion, whereas those with a higher fall-risk experienced it with a shorter latency and no weaker than the younger adults. These results suggest that in older adults, the mechanism of multisensory integration for constructing body perception can change depending on the stimulated body parts, and that the risk of falling is associated with multisensory integration.

Sensory capability and information integration independently explain the cognitive status of healthy older adults

While there is evidence that sensory processing and multisensory integration change with age, links between these alterations and their relation to cognitive status remain unclear. In this study, we assessed sensory thresholds and performance of healthy younger and older adults in a visuotactile delayed match-to-sample task. Using Bayesian structural equation modelling (BSEM), we explored the factors explaining cognitive status in the group of older adults. Additionally, we applied transcranial alternating current stimulation (tACS) to a parieto-central network found to underlie visuotactile interactions and working memory matching in our previous work. Response times and signal detection measures indicated enhanced multisensory integration and enhanced benefit from successful working memory matching in older adults. Further, tACS caused a frequency-specific speeding (20 Hz) and delaying (70 Hz) of responses. Data exploration suggested distinct underlying factors for sensory acuity and sensitivity d’ on the one side, and multisensory and working memory enhancement on the other side. Finally, BSEM showed that these two factors labelled ‘sensory capability’ and ‘information integration’ independently explained cognitive status. We conclude that sensory decline and enhanced information integration might relate to distinct processes of ageing and discuss a potential role of the parietal cortex in mediating augmented integration in older adults.

Evidence-Based Communication with Critically Ill Older Adults

Communication is a critical component of patient-centered care. Critically ill, mechanically ventilated patients are unable to speak and this condition is frightening, frustrating, and stressful. Impaired communication in the intensive care unit (ICU) contributes to poor symptom identification and restricts effective patient engagement. Older adults are at higher risk for communication impairments in the ICU because of pre-illness communication disorders and cognitive dysfunction that often accompanies or precedes critical illness. Assessing communication disorders and developing patient-centered strategies to enhance communication can lessen communication difficulty and increase patient satisfaction.

Impaired Multisensory Integration Predisposes the Elderly People to Fall: A Systematic Review

Background: This systematic review pooled all the latest data and reviewed all the relevant studies to look into the effect of multisensory integration on the balance function in the elderly.

Methods: PubMed, Web of Science and Scopus were searched to find eligible studies published prior to May 2019. The studies were limited to those published in Chinese and English language. The quality of the included studies was assessed against the Newcastle-Ottawa Scale or an 11-item checklist, as recommended by Agency for Healthcare Research and Quality (AHRQ). Any disagreement among reviewers was resolved by comparing notes and reaching a consensus.

Results: Eight hundred thirty-nine records were identified and 17 of them were included for systematic review. The result supported our assumption that multisensory integration works on balance function in the elderly. All the 17 studies were believed to be of high or moderate quality.

Conclusions: The systematic review found that the impairment of multisensory integration could predispose elderly people to fall. Accurate assessment of multisensory integration can help the elderly identify the impaired balance function and minimize the risk of fall. And our results provide a new basis for further understanding of balance maintenance mechanism. Further research is warranted to explore the change in brain areas related to multisensory integration in the elderly.

Crossmodal Congruency Enhances Performance of Healthy Older Adults in Visual-Tactile Pattern Matching

One of the pivotal challenges of aging is to maintain independence in the activities of daily life. In order to adapt to changes in the environment, it is crucial to continuously process and accurately combine simultaneous input from different sensory systems, i.e., crossmodal or multisensory integration. With aging, performance decreases in multiple domains, affecting bottom-up sensory processing as well as top-down control. However, whether this decline leads to impairments in crossmodal interactions remains an unresolved question. While some researchers propose that crossmodal interactions degrade with age, others suggest that they are conserved or even gain compensatory importance. To address this question, we compared the behavioral performance of older and young participants in a well-established crossmodal matching task, requiring the evaluation of congruency in simultaneously presented visual and tactile patterns. Older participants performed significantly worse than young controls in the crossmodal task when being stimulated at their individual unimodal visual and tactile perception thresholds. Performance increased with adjustment of stimulus intensities. This improvement was driven by better detection of congruent stimulus pairs, while the detection of incongruent pairs was not significantly enhanced. These results indicate that age-related impairments lead to poor performance in complex crossmodal scenarios and demanding cognitive tasks. Crossmodal congruency effects attenuate the difficulties of older adults in visuotactile pattern matching and might be an important factor to drive the benefits of older adults demonstrated in various crossmodal integration scenarios. Congruency effects might, therefore, be used to develop strategies for cognitive training and neurological rehabilitation.

The Effect of Ageing on Optimal Integration of Conflicting and Non-Conflicting Visual–Haptic Stimuli

Multisensory integration typically follows the predictions of a statistically optimal model whereby the contribution of each sensory modality is weighted according to its reliability. Previous research has shown that multisensory integration is affected by ageing, however it is less certain whether older adults follow this statistically optimal model. Additionally, previous studies often present multisensory cues which are conflicting in size, shape or location, yet naturally occurring multisensory cues are usually non-conflicting. Therefore, the mechanisms of integration in older adults might differ depending on whether the multisensory cues are consistent or conflicting. In the current experiment, young () and older () adults were asked to make judgements regarding the height of wooden blocks using visual, haptic or combined visual–haptic information. Dual modality visual–haptic blocks could be presented as equal or conflicting in size. Young and older adults’ size discrimination thresholds (i.e., precision) were not significantly different for visual, haptic or visual–haptic cues. In addition, both young and older adults’ discrimination thresholds and points of subjective equality did not follow model predictions of optimal integration, for both conflicting and non-conflicting cues. Instead, there was considerable between subject variability as to how visual and haptic cues were processed when presented simultaneously. This finding has implications for the development of multisensory therapeutic aids and interventions to assist older adults with everyday activities, where these should be tailored to the needs of each individual.

Crossmodal congruency effect scores decrease with repeat test exposure

The incorporation of feedback into a person’s body schema is well established. The crossmodal congruency task (CCT) is used to objectively quantify incorporation without being susceptible to experimenter biases. This visual-tactile interference task is used to calculate the crossmodal congruency effect (CCE) score as a difference in response time between incongruent and congruent trials. Here we show that this metric is susceptible to a learning effect that causes attenuation of the CCE score due to repeated task exposure sessions. We demonstrate that this learning effect is persistent, even after a 6 month hiatus in testing. Two mitigation strategies are proposed: 1. Only use CCE scores that are taken after learning has stabilized, or 2. Use a modified CCT protocol that decreases the task exposure time. We show that the modified and shortened CCT protocol, which may be required to meet time or logistical constraints in laboratory or clinical settings, reduced the impact of the learning effect on CCT results. Importantly, the CCE scores from the modified protocol were not significantly more variable than results obtained with the original protocol. This study highlights the importance of considering exposure time to the CCT when designing experiments and suggests two mitigation strategies to improve the utility of this psychophysical assessment.

Preserved multisensory body representations in advanced age

The internal representation of the body emerges via the integration of multisensory body cues. Sensory signal transfer and the ability to integrate multisensory information deteriorate significantly with increasing age. However, there is little empirical evidence on age-related changes in body representations based on multisensory integration. Here, we used a standard paradigm for evaluating body representations based on multisensory integration, the rubber hand illusion, and compared the amount of proprioceptive drift and changes in perceived body ownership triggered by the integration of visual, tactile, and proprioceptive cues between younger and older adults. To account for potential age-related differences in the temporal stability of the illusion, proprioceptive drift was measured at five different time points. Our results show that older adults used synchronous visuo-tactile cues similarly to younger adults to update both the position of their own hand, and their feeling of ownership over the artificial hand. Independent of visuo-tactile synchrony, older adults perceived their hand as closer to their body than younger adults did, and showed a less stable representation of this in-depth hand position. This proprioceptive bias towards the body did not correlate with the strength of the illusion. Our results indicate that the integration of visual and tactile cues is largely preserved in advanced age when used to update limb position, whereas proprioception worsens with age. This may be linked to two different pathways that underlie changes in body representations over the life span.

Developmental Differences in Filtering Auditory and Visual Distractors During Visual Selective Attention

The current experiment examined changes in visual selective attention in young children, older children, young adults, and older adults while participants were instructed to ignore auditory and visual distractors. The aims of the study were to: (a) determine if the Perceptual Load Hypothesis (PLH) (distraction greater under low perceptual load) could predict which irrelevant stimuli would disrupt visual selective attention, and (b) if auditory to visual shifts found in modality dominance research could be extended to selective attention tasks. Overall, distractibility decreased with age, with incompatible distractors having larger costs in young and older children than adults. In regard to accuracy, visual distractibility did not differ across age nor load, whereas, auditory interference was more pronounced early in development and correlated with age. Auditory and visual distractors also slowed down responses in young and older children more than adults. Finally, the PLH did not predict performance. Rather, children often showed the opposite pattern, with visual distractors having a greater cost in the high load condition (older children) and auditory distractors having a greater cost in the high load condition (young children). These findings are consistent with research examining the development of modality dominance and shed light on changes in multisensory processing and selective attention across the lifespan.

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

Research investigating multisensory integration (MSI) processes in aging is scarce, but converging evidence for larger behavioral MSI effects in older compared to younger adults exists. The current study employed a three-prong approach to determine whether inherent age-related sensory processing declines were associated with larger (i.e., worse) visual-somatosensory (VS) reaction time (RT) facilitation effects. Non-demented older adults ( n = 156 ; mean age = 77 years; 55% female) without any medical or psychiatric conditions were included. Participants were instructed to make speeded foot-pedal responses as soon as they detected visual, somatosensory, or VS stimulation. Visual acuity was assessed using the Snellen test while somatosensory sensitivity was determined using vibration thresholds. The aims of the current study were to: (1) replicate a reliable MSI effect; (2) investigate the effect of unisensory functioning on VS RT facilitation; and (3) determine whether sensory functioning combination groups manifested differential MSI effects. Results revealed a significant VS RT facilitation effect that was influenced by somatosensory sensitivity but not visual acuity. That is, older adults with poor somatosensory sensitivity demonstrated significantly larger MSI effects than those with intact somatosensory sensitivity. Additionally, a significant interaction between stimulus condition and sensory functioning group suggested that the group with poor visual acuity and poor somatosensory functioning demonstrated the largest MSI effect compared to the other groups. In summary, the current study reveals that worse somatosensory functioning is associated with larger MSI effects in older adults. To our knowledge, this is first study to identify potential mechanisms behind increased RT facilitation in aging.

Does hearing aid use affect audiovisual integration in mild hearing impairment?

There is converging evidence for altered audiovisual integration abilities in hearing-impaired individuals and those with profound hearing loss who are provided with cochlear implants, compared to normal-hearing adults. Still, little is known on the effects of hearing aid use on audiovisual integration in mild hearing loss, although this constitutes one of the most prevalent conditions in the elderly and, yet, often remains untreated in its early stages. This study investigated differences in the strength of audiovisual integration between elderly hearing aid users and those with the same degree of mild hearing loss who were not using hearing aids, the non-users, by measuring their susceptibility to the sound-induced flash illusion. We also explored the corresponding window of integration by varying the stimulus onset asynchronies. To examine general group differences that are not attributable to specific hearing aid settings but rather reflect overall changes associated with habitual hearing aid use, the group of hearing aid users was tested unaided while individually controlling for audibility. We found greater audiovisual integration together with a wider window of integration in hearing aid users compared to their age-matched untreated peers. Signal detection analyses indicate that a change in perceptual sensitivity as well as in bias may underlie the observed effects. Our results and comparisons with other studies in normal-hearing older adults suggest that both mild hearing impairment and hearing aid use seem to affect audiovisual integration, possibly in the sense that hearing aid use may reverse the effects of hearing loss on audiovisual integration. We suggest that these findings may be particularly important for auditory rehabilitation and call for a longitudinal study.

Using Race Model Violation to Explore Multisensory Responses in Older Adults: Enhanced Multisensory Integration or Slower Unisensory Processing?

Older adults exhibit greater multisensory reaction time (RT) facilitation than young adults. Since older adults exhibit greater violation of the race model (i.e., cumulative distribution functions for multisensory RTs are greater than that of the summed unisensory RTs), this has been attributed to enhanced multisensory integration. Here we explored whether (a) individual differences in RT distributions within each age group might drive this effect, and (b) the race model is more likely to be violated if unisensory RTs are slower. Young () and older adults () made speeded responses to visual, auditory or tactile stimuli, or any combination of these (bi-/tri-modal). The test of the race model suggested greater audiovisual integration for older adults, but only when accounting for individual differences in RT distributions. Moreover, correlations in both age groups showed that slower unisensory RTs were associated with a greater degree of race model violation. Therefore, greater race model violation may be due to greater ‘room for improvement’ from unisensory responses in older adults compared to young adults, and thus could falsely give the impression of enhanced multisensory integration.

Aging Effect on Audiovisual Integrative Processing in Spatial Discrimination Task

Multisensory integration is an essential process that people employ daily, from conversing in social gatherings to navigating the nearby environment. The aim of this study was to investigate the impact of aging on modulating multisensory integrative processes using event-related potential (ERP), and the validity of the study was improved by including “noise” in the contrast conditions. Older and younger participants were involved in perceiving visual and/or auditory stimuli that contained spatial information. The participants responded by indicating the spatial direction (far vs. near and left vs. right) conveyed in the stimuli using different wrist movements. electroencephalograms (EEGs) were captured in each task trial, along with the accuracy and reaction time of the participants’ motor responses. Older participants showed a greater extent of behavioral improvements in the multisensory (as opposed to unisensory) condition compared to their younger counterparts. Older participants were found to have fronto-centrally distributed super-additive P2, which was not the case for the younger participants. The P2 amplitude difference between the multisensory condition and the sum of the unisensory conditions was found to correlate significantly with performance on spatial discrimination. The results indicated that the age-related effect modulated the integrative process in the perceptual and feedback stages, particularly the evaluation of auditory stimuli. Audiovisual (AV) integration may also serve a functional role during spatial-discrimination processes to compensate for the compromised attention function caused by aging.

Effects of Aging in Multisensory Integration: A Systematic Review

Multisensory integration (MSI) is the integration by the brain of environmental information acquired through more than one sense. Accurate MSI has been shown to be a key component of successful aging and to be crucial for processes underlying activities of daily living (ADLs). Problems in MSI could prevent older adults (OA) to age in place and live independently. However, there is a need to know how to assess changes in MSI in individuals. This systematic review provides an overview of tests assessing the effect of age on MSI in the healthy elderly population (aged 60 years and older). A literature search was done in Scopus. Articles from the earliest records available to January 20, 2016, were eligible for inclusion if assessing effects of aging on MSI in the healthy elderly population compared to younger adults (YA). These articles were rated for risk of bias with the Newcastle-Ottawa quality assessment. Out of 307 identified research articles, 49 articles were included for final review, describing 69 tests. The review indicated that OA maximize the use of multiple sources of information in comparison to YA (20 studies). In tasks that require more cognitive function, or when participants need to adapt rapidly to a situation, or when a dual task is added to the experiment, OA have problems selecting and integrating information properly as compared to YA (19 studies). Additionally, irrelevant or wrong information (i.e., distractors) has a greater impact on OA than on YA (21 studies). OA failing to weigh sensory information properly, has not been described in previous reviews. Anatomical changes (i.e., reduction of brain volume and differences of brain areas' recruitment) and information processing changes (i.e., general cognitive slowing, inverse effectiveness, larger time window of integration, deficits in attentional control and increased noise at baseline) can only partly explain the differences between OA and YA regarding MSI. Since we have an interest in successful aging and early detection of MSI issues in the elderly population, the identified tests form a good starting point to develop a clinically useful toolkit to assess MSI in healthy OA.

Are Older Adults Less Embodied? A Review of Age Effects through the Lens of Embodied Cognition

Embodied cognition is a theoretical framework which posits that cognitive function is intimately intertwined with the body and physical actions. Although the field of psychology is increasingly accepting embodied cognition as a viable theory, it has rarely been employed in the gerontological literature. However, embodied cognition would appear to have explanatory power for aging research given that older adults typically manifest concurrent physical and mental changes, and that research has indicated a correlative relationship between such changes. The current paper reviews age-related changes in sensory processing, mental representation, and the action-perception relationship, exploring how each can be understood through the lens of embodied cognition. Compared to younger adults, older adults exhibit across all three domains an increased tendency to favor visual processing over bodily factors, leading to the conclusion that older adults are less embodied than young adults. We explore the significance of this finding in light of existing theoretical models of aging and argue that embodied cognition can benefit gerontological research by identifying further factors that can explain the cause of age-related declines.

Investigating visual-tactile interactions over time and space in adults with autism

It has been suggested that the sensory symptoms which affect many people with autism spectrum conditions (ASC) may be related to alterations in multisensory processing. Typically, the likelihood of interactions between the senses increases when information is temporally and spatially coincident. We explored visual-tactile interactions in adults with ASC for the first time in two experiments using low-level stimuli. Both participants with ASC and matched neurotypical controls only produced crossmodal interactions to near simultaneous stimuli, suggesting that temporal modulation is unaffected in the adult population. We also provide preliminary evidence that visual-tactile interactions may occur over greater spatial distances in participants with ASC, which merits further exploration.

Spatial representations in older adults are not modified by action: Evidence from tool use

Theories of embodied perception hold that the visual system is calibrated by both the body schema and the action system, allowing for adaptive action-perception responses. One example of embodied perception involves the effects of tool use on distance perception, in which wielding a tool with the intention to act upon a target appears to bring that object closer. This tool-based spatial compression (i.e., tool-use effect) has been studied exclusively with younger adults, but it is unknown whether the phenomenon exists with older adults. In this study, we examined the effects of tool use on distance perception in younger and older adults in 2 experiments. In Experiment 1, younger and older adults estimated the distances of targets just beyond peripersonal space while either wielding a tool or pointing with the hand. Younger adults, but not older adults, estimated targets to be closer after reaching with a tool. In Experiment 2, younger and older adults estimated the distance to remote targets while using either a baton or a laser pointer. Younger adults displayed spatial compression with the laser pointer compared to the baton, although older adults did not. Taken together, these findings indicate a generalized absence of the tool-use effect in older adults during distance estimation, suggesting that the visuomotor system of older adults does not remap from peripersonal to extrapersonal spatial representations during tool use.

The sound-induced flash illusion reveals dissociable age-related effects in multisensory integration

While aging can lead to significant declines in perceptual and cognitive function, the effects of age on multisensory integration, the process in which the brain combines information across the senses, are less clear. Recent reports suggest that older adults are susceptible to the sound-induced flash illusion (Shams et al., 2000) across a much wider range of temporal asynchronies than younger adults (Setti et al., 2011). To assess whether this cost for multisensory integration is a general phenomenon of combining asynchronous audiovisual input, we compared the time courses of two variants of the sound-induced flash illusion in young and older adults: the fission illusion, where one flash accompanied by two beeps appears as two flashes, and the fusion illusion, where two flashes accompanied by one beep appear as one flash. Twenty-five younger (18–30 years) and older (65+ years) adults were required to report whether they perceived one or two flashes, whilst ignoring irrelevant auditory beeps, in bimodal trials where auditory and visual stimuli were separated by one of six stimulus onset asynchronies (SOAs). There was a marked difference in the pattern of results for the two variants of the illusion. In conditions known to produce the fission illusion, older adults were significantly more susceptible to the illusion at longer SOAs compared to younger participants. In contrast, the performance of the younger and older groups was almost identical in conditions known to produce the fusion illusion. This surprising difference between sound-induced fission and fusion in older adults suggests dissociable age-related effects in multisensory integration, consistent with the idea that these illusions are mediated by distinct neural mechanisms.

Hypothesis-driven methods to augment human cognition by optimizing cortical oscillations

Cortical oscillations have been shown to represent fundamental functions of a working brain, e.g., communication, stimulus binding, error monitoring, and inhibition, and are directly linked to behavior. Recent studies intervening with these oscillations have demonstrated effective modulation of both the oscillations and behavior. In this review, we collect evidence in favor of how hypothesis-driven methods can be used to augment cognition by optimizing cortical oscillations. We elaborate their potential usefulness for three target groups: healthy elderly, patients with attention deficit/hyperactivity disorder, and healthy young adults. We discuss the relevance of neuronal oscillations in each group and show how each of them can benefit from the manipulation of functionally-related oscillations. Further, we describe methods for manipulation of neuronal oscillations including direct brain stimulation as well as indirect task alterations. We also discuss practical considerations about the proposed techniques. In conclusion, we propose that insights from neuroscience should guide techniques to augment human cognition, which in turn can provide a better understanding of how the human brain works.

Aging and response interference across sensory modalities

Advancing age is associated with decrements in selective attention. It was recently hypothesized that age-related differences in selective attention depend on sensory modality. The goal of the present study was to investigate the role of sensory modality in age-related vulnerability to distraction, using a response interference task. To this end, 16 younger (mean age = 23.1 years) and 24 older (mean age = 65.3 years) adults performed four response interference tasks, involving all combinations of visual and auditory targets and distractors. The results showed that response interference effects differ across sensory modalities, but not across age groups. These results indicate that sensory modality plays an important role in vulnerability to distraction, but not in age-related distractibility by irrelevant spatial information.

A standing posture is associated with increased susceptibility to the sound-induced flash illusion in fall-prone older adults

Recent research has provided evidence suggesting a link between inefficient processing of multisensory information and incidence of falling in older adults. Specifically, Setti et al. (Exp Brain Res 209:375-384, 2011) reported that older adults with a history of falling were more susceptible than their healthy, age-matched counterparts to the sound-induced flash illusion. Here, we investigated whether balance control in fall-prone older adults was directly associated with multisensory integration by testing susceptibility to the illusion under two postural conditions: sitting and standing. Whilst standing, fall-prone older adults had a greater body sway than the age-matched healthy older adults and their body sway increased when presented with the audio-visual illusory but not the audio-visual congruent conditions. We also found an increase in susceptibility to the sound-induced flash illusion during standing relative to sitting for fall-prone older adults only. Importantly, no performance differences were found across groups in either the unisensory or non-illusory multisensory conditions across the two postures. These results suggest an important link between multisensory integration and balance control in older adults and have important implications for understanding why some older adults are prone to falling.

Susceptibility to a multisensory speech illusion in older persons is driven by perceptual processes

Recent studies suggest that multisensory integration is enhanced in older adults but it is not known whether this enhancement is solely driven by perceptual processes or affected by cognitive processes. Using the “McGurk illusion,” in Experiment 1 we found that audio-visual integration of incongruent audio-visual words was higher in older adults than in younger adults, although the recognition of either audio- or visual-only presented words was the same across groups. In Experiment 2 we tested recall of sentences within which an incongruent audio-visual speech word was embedded. The overall semantic meaning of the sentence was compatible with either one of the unisensory components of the target word and/or with the illusory percept. Older participants recalled more illusory audio-visual words in sentences than younger adults, however, there was no differential effect of word compatibility on recall for the two groups. Our findings suggest that the relatively high susceptibility to the audio-visual speech illusion in older participants is due more to perceptual than cognitive processing.

Multisensory integration, aging, and the sound-induced flash illusion

The present study examined age-related differences in multisensory integration and the role of attention in age-related differences in multisensory integration. The sound-induced flash illusion--the misperception of the number of visual flashes due to the simultaneous presentation of a different number of auditory beeps--was used to examine the strength of multisensory integration in older and younger observers. The effects of integration were examined when discriminating 1-3 flashes, 1-3 beeps, or 1-3 flashes presented with 1-3 beeps. Stimulus conditions were blocked according to these conditions with baseline (unisensory) performance assessed during the multisensory block. Older participants demonstrated greater multisensory integration--a greater influence of the beeps when judging the number of visual flashes--than younger observers. In a second experiment, the role of attention was assessed using a go/no-go paradigm. The results of Experiment 2 replicated those of Experiment 1. In addition, the strength of the illusion was modulated by the sensory domain of the go/no-go task, though this did not differ by age group. In the visual go/no-go task we found a decrease in the illusion, yet in the auditory go/no-go task we found an increase in the illusion. These results demonstrate that older individuals exhibit increased multisensory integration compared with younger individuals. Attention was also found to modulate the strength of the sound-induced flash illusion. However, the results also suggest that attention was not likely to be a factor in the age-related differences in multisensory integration.

The effect of multisensory cues on attention in aging

The attention network test (ANT) assesses the effect of alerting and orienting cues on a visual flanker task measuring executive attention. Previous findings revealed that older adults demonstrate greater reaction times (RT) benefits when provided with visual orienting cues that offer both spatial and temporal information of an ensuing target. Given the overlap of neural substrates and networks involved in multisensory processing and cueing (i.e., alerting and orienting), an investigation of multisensory cueing effects on RT was warranted. The current study was designed to determine whether participants, both old and young, benefited from receiving multisensory alerting and orienting cues. Eighteen young (M=19.17 years; 45% female) and eighteen old (M=76.44 years; 61% female) individuals that were determined to be non-demented and without any medical or psychiatric conditions that would affect their performance were included. Results revealed main effects for the executive attention and orienting networks, but not for the alerting network. In terms of orienting, both old and young adults demonstrated significant orienting effects for auditory-somatosensory (AS), auditory-visual (AV), and visual-somatosensory (VS) cues. RT benefits of multisensory compared to unisensory orienting effects differed by cue type and age group; younger adults demonstrated greater RT benefits for AS orienting cues whereas older adults demonstrated greater RT benefits for AV orienting cues. Both groups, however, demonstrated significant RT benefits for multisensory VS orienting cues. These findings provide evidence for the facilitative effect of multisensory orienting cues, and not multisensory alerting cues, in old and young adults.

Multisensory integration across the senses in young and old adults

Stimuli are processed concurrently and across multiple sensory inputs. Here we directly compared the effect of multisensory integration (MSI) on reaction time across three paired sensory inputs in eighteen young (M=19.17 years) and eighteen old (M=76.44 years) individuals. Participants were determined to be non-demented and without any medical or psychiatric conditions that would affect their performance. Participants responded to randomly presented unisensory (auditory, visual, somatosensory) stimuli and three paired sensory inputs consisting of auditory-somatosensory (AS) auditory-visual (AV) and visual-somatosensory (VS) stimuli. Results revealed that reaction time (RT) to all multisensory pairings was significantly faster than those elicited to the constituent unisensory conditions across age groups; findings that could not be accounted for by simple probability summation. Both young and old participants responded the fastest to multisensory pairings containing somatosensory input. Compared to younger adults, older adults demonstrated a significantly greater RT benefit when processing concurrent VS information. In terms of co-activation, older adults demonstrated a significant increase in the magnitude of visual-somatosensory co-activation (i.e., multisensory integration), while younger adults demonstrated a significant increase in the magnitude of auditory-visual and auditory-somatosensory co-activation. This study provides first evidence in support of the facilitative effect of pairing somatosensory with visual stimuli in older adults.