Multisensory integration precision is associated with better cognitive performance over time in older adults: A large-scale exploratory study

The cost effectiveness of a multidomain intervention on physical, cognitive, vascular, dietary and psychosocial outcomes among community dwelling older adults with cognitive frailty in Malaysia: The AGELESS Trial

BACKGROUND

Cognitive frailty (CF) in older adults is a potentially reversible syndrome that may benefit from lifestyle-based multidomain interventions. This study assessed the AGELESS intervention's impact on cognitive, physical, vascular, dietary, and psychosocial outcomes, along with its cost-effectiveness, in a Low-Middle-Income Country (LMIC).

METHODS

The AGELESS randomized controlled trial recruited 106 older adults (above 60 years) from Klang Valley, Malaysia, with (pre)-CF (≥ 1 Fried's criteria and Clinical Dementia Rating scale = 0.5). Participants were randomly assigned to a 24-month multidomain intervention (physical activity, cognitive training, nutritional and psychological counselling, cardiovascular care) or control group (educational module). Primary outcomes, assessed at baseline, 12 and 24 months, included the modified Neuropsychological Tests Battery (mNTB) and physical performance measures. Intervention costs were calculated to determine Incremental Cost-Effectiveness Ratios (ICERs). An intention-to-treat analysis was conducted to account for attrition.

RESULTS

The trial occurred during the COVID-19 pandemic. Despite a 50% dropout rate, adherence among remaining participants was over 50% for all intervention components (range 53%-91%). The intervention led to significant improvements in selected parameters of cognitive function, physical performance, anthropometry, and dietary patterns (for all parameters, p < 0.05 for interaction time*group in repeat-measures ANOVA). The cost per participant was RM 1592.74 (≈USD 355.05) in the multidomain arm, and RM 488.21 (≈USD 108.83) in the control arm. The ICER computation indicated the 2-min step test as the most cost-effective measure (ICER RM 149.19 ≈USD33.26).

CONCLUSION

The AGELESS trial demonstrates that a multidomain, lifestyle-based intervention can improve cognitive and physical function in older adults with (pre)-CF. This cost-effective approach highlights CF as a modifiable health condition and supports its potential inclusion in health policy to promote healthy aging and reduce health risks in LMICs, where there is a larger prevention potential due to prevalent lifestyle-related risk factors.

A systematic review of the relationships amongst older adults' cognitive and motor speech abilities

Age-related differences in motor speech performance may be only partially explained by physiological factors. In this systematic review we investigated the extent to which cognition is related to older adults' motor speech production. PsycInfo, PubMed, Web of Science, and the Cochrane Library were last searched on 1st October 2024. Eligible studies involved healthy older adults, and/or those with mild cognitive impairment (MCI), with an average age of 60 or above. Study quality was formally evaluated and results presented via a narrative synthesis. In total, there were 22 eligible studies identified including 747 older adults. Ten of eighteen studies investigating attention/executive abilities reported significant relationships with motor speech subprocesses in 571 of 661 participants. Relationships between other cognitive abilities and motor speech outcomes were also reported, however, there were significant gaps in the literature and heterogeneity in the measurements used. In addition, only five studies contained the highest quality evidence. Cognition, and potentially executive abilities specifically, may affect speech articulation in healthy aging and in MCI. Further research implementing a range of tasks is required to better understand the trajectory of age-related changes to cognition and motor speech production.

Visual experience affects neural correlates of audio-haptic integration: A case study of non-sighted individuals

The ability to reduce sensory uncertainty by integrating information across different senses develops late in humans and depends on cross-modal, sensory experience during childhood and adolescence. While the dependence of audio-haptic integration on vision suggests cross-modal neural reorganization, evidence for such changes is lacking. Furthermore, little is known about the neural processes underlying audio-haptic integration even in sighted adults. Here, we examined electrophysiological correlates of audio-haptic integration in sighted adults (n = 29), non-sighted adults (n = 7), and sighted adolescents (n = 12) using a data-driven electrical neuroimaging approach. In sighted adults, optimal integration performance was predicted by topographical and super-additive strength modulations around 205-285 ms. Data from four individuals who went blind before the age of 8-9 years suggests that they achieved optimal integration via different, sub-additive mechanisms at earlier processing stages. Sighted adolescents showed no robust multisensory modulations. Late-blind adults, who did not show behavioral benefits of integration, demonstrated modulations at early latencies. Our findings suggest a critical period for the development of optimal audio-haptic integration dependent on visual experience around the late childhood and early adolescence.

Beyond facilitating unisensory processing: Crossmodal associative memory training further modulates sensory integration

Audiovisual associative memory and audiovisual integration involve common behavioral processing components and significantly overlap in their neural mechanisms. This suggests that training on audiovisual associative memory may have the potential to improve audiovisual integration. The current study tested this hypothesis by applying a 2 (group: audiovisual training group, unimodal control group) × 2 (time: pretest, posttest) design. The audiovisual training group received an adaptive audiovisual associative memory training protocol, whereas the active control group undertook an adaptive unimodal item memory training protocol. The training duration for both protocols was seven days, with one and a half hours per day. Before and after training, both groups underwent testing for audiovisual integration through event-related potential (ERP) measures in a detection task that required rapid detection of auditory, visual, or audiovisual stimuli. Behavioral results revealed a training-general effect, as both groups exhibited faster response times in unimodal stimulus detection after 7-day training. EEG results revealed a consistent pattern in which the amplitudes of both visual and auditory evoked components decreased following the training. Moreover, a training-specific effect was found for sensory integration, with the effect of audiovisual integration being modulated in the earlier stage of processing for the audiovisual training group. Such a modulation was not found in the unimodal control group. These findings indicate that training on higher cognitive functions could penetrate to both unisensory processing and the integration of sensory information, which may potentially aid in the development of more targeted and efficient interventions for perceptual processes.

Preliminary report: Reduced hand sensory and motor function in persons living with heart failure

Despite the growing evidence highlighting reduced functional independence in persons living with heart failure (PwHF), the underlying mechanisms that lead to reduced functional independence in this patient population are unknown. Given the association between functional independence and fine motor skills, which are functionally related to hand sensory and motor functions, we hypothesized that PwHF exhibit reduced sensory and motor function of hands compared to healthy individuals. We recruited a total of 10 PwHF (age: 57.6 ± 12.5 years old, four females) and a total of age- & sex-matched healthy control individuals (age: 58.2 ± 12.2 years old, four females). Participants performed a wide range of tests assessing the level of independence, fitness, cognitive function, and hand sensorimotor function. While the level of independence was comparable between two groups, PwHF exhibited reduced sensory and motor function. Compared to healthy participants, the ability to identify an object via tactile and proprioceptive inputs was reduced in PwHF, though the tactile mechanoreceptor function showed normal integrity. Similarly, PwHF exhibited a decline in manipulating small objects and steady grip force production. Heart failure seems to have repercussions that extend to the sensorimotor control of hand actions in advance to a decline in functional independence. These results underscore the need of further investigation as to the underlying mechanisms of reduced sensorimotor function, potential intervention targets, and determine whether assessments of hand sensorimotor function can serve as a vehicle to quantify restoration of self-care functionality.

Nutrition is associated with differences in multisensory integration in healthy older adults

Diet can influence cognitive functioning in older adults and is a modifiable risk factor for cognitive decline. However, it is unknown if an association exists between diet and lower-level processes in the brain underpinning cognition, such as multisensory integration. We investigated whether temporal multisensory integration is associated with daily intake of fruit and vegetables (FV) or products high in fat/sugar/salt (FSS) in a large sample (N = 2,693) of older adults (mean age = 64.06 years, SD = 7.60; 56% female) from The Irish Longitudinal Study on Ageing (TILDA). Older adults completed a Food Frequency Questionnaire from which the total number of daily servings of FV and FSS items respectively was calculated. Older adults' susceptibility to the Sound Induced Flash Illusion (SIFI) measured the temporal precision of audio-visual integration, which included three audio-visual Stimulus Onset Asynchronies (SOAs): 70, 150 and 230 ms. Older adults who self-reported a higher daily consumption of FV were less susceptible to the SIFI at the longest versus shortest SOAs (i.e. increased temporal precision) compared to those reporting the lowest daily consumption (p = .013). In contrast, older adults reporting a higher daily consumption of FSS items were more susceptible to the SIFI at the longer versus shortest SOAs (i.e. reduced temporal precision) compared to those reporting the lowest daily consumption (p < .001). The temporal precision of multisensory integration is differentially associated with levels of daily consumption of FV versus products high in FSS, consistent with broader evidence that habitual diet is associated with brain health.

Impacts of audiovisual simultaneity perception on single-task and dual-task gaits in middle-aged and older adults

BACKGROUND

While dual-task walking requires the ability to integrate sensory information from multiple ongoing sources, it remains unknown whether dual-task walking is more affected than single-task walking by the multisensory integration ability.

RESEARCH QUESTION

How does the audiovisual temporal integration ability affect single-task and dual-task gaits in the aging population?

METHODS

One hundred and thirty healthy middle-aged and older adults (age = 64.7 ± 6.4 years) completed an audiovisual simultaneity judgment (AVSJ) task and underwent single-task, motor dual-task, and cognitive dual-task gait assessments. In the AVSJ task, participants judged whether a flash and an auditory stimulus presented at different stimulus onset asynchronies were simultaneous. The accuracy and precision of the AVSJ performance were assessed using the point of subjective simultaneity (PSS) and the temporal binding window (δ), respectively. A lower absolute PSS and δ indicated better performance. Participants held a cup of water and performed serial-7 subtraction for motor and cognitive dual-task gait assessments, respectively. The spatiotemporal gait parameters and their variability were calculated. The influences of PSS and δ on the gait parameters of the three gaits were examined with multiple hierarchical regressions.

RESULTS

Only the cognitive dual-task gait was significantly affected by PSS and δ. Greater PSS predicted a longer single support time (β = 0.195, p = 0.024) and its variability (β = 0.224, p = 0.011). Greater δ predicted greater step time variability (β = 0.198, p = 0.022).

SIGNIFICANCE

Declined perception of audiovisual simultaneity particularly degrades temporal control of cognitive dual-task walking, highlighting the importance of assessing and training this ability after midlife.

The emergence of the multisensory brain: From the womb to the first steps

The becoming of the human being is a multisensory process that starts in the womb. By integrating spontaneous neuronal activity with inputs from the external world, the developing brain learns to make sense of itself through multiple sensory experiences. Over the past ten years, advances in neuroimaging and electrophysiological techniques have allowed the exploration of the neural correlates of multisensory processing in the newborn and infant brain, thus adding an important piece of information to behavioral evidence of early sensitivity to multisensory events. Here, we review recent behavioral and neuroimaging findings to document the origins and early development of multisensory processing, particularly showing that the human brain appears naturally tuned to multisensory events at birth, which requires multisensory experience to fully mature. We conclude the review by highlighting the potential uses and benefits of multisensory interventions in promoting healthy development by discussing emerging studies in preterm infants.

Individual differences in seated resting heart rate are associated with multisensory perceptual function in older adults

There is evidence that cardiovascular function can influence sensory processing and cognition, which are known to change with age. However, whether the precision of unisensory and multisensory temporal perception is influenced by cardiovascular activity in older adults is uncertain. We examined whether seated resting heart rate (RHR) was associated with unimodal visual and auditory temporal discrimination as well as susceptibility to the audio-visual Sound Induced Flash Illusion (SIFI) in a large sample of older adults (N = 3232; mean age = 64.17 years, SD = 7.74, range = 50-93; 56% female) drawn from The Irish Longitudinal Study on Ageing (TILDA). Faster seated RHR was associated with better discretization of two flashes (but not two beeps) and increased SIFI susceptibility when the audio-visual stimuli were presented close together in time but not at longer audio-visual temporal offsets. Our findings suggest a significant relationship between cardiovascular activity and the precision of visual and audio-visual temporal perception in older adults, thereby providing novel evidence for a link between cardiovascular function and perceptual function in aging.

Evidence for an association between allostatic load and multisensory integration in middle-aged and older adults

Multisensory integration, the ability of the brain to integrate information from different sensory modalities, is critical for responding to environmental stimuli. While older adults show changes in multisensory integration with age, the impact of allostatic load (AL) (i.e., the effect of exposure to chronic stress, which can accelerate ageing) on multisensory perception remains understudied. We explored the relationship between multisensory integration and AL in 1,358 adults aged 50+ from The Irish Longitudinal Study on Ageing by performing a Sound Induced Flash Illusion (SIFI) task at multiple audio-visual temporal asynchronies. The AL score was created using a battery of biomarkers representing the activity of four major physiological systems: immunological, cardiovascular, metabolic, and renal. The number of biomarkers for which a participant was categorised in the highest risk quartile using sex-specific cutoffs was used to produce an overall AL score. We accounted for medication use when calculating our AL score. We analysed the accuracy of illusion trials on a SIFI task using generalised logistic mixed effects regression models adjusted for a number of covariates. Observation of cross-sectional and longitudinal results revealed that lower accuracy in integration (i.e., higher SIFI susceptibility with larger temporal asynchronies) was associated with higher AL. This confirmed the distinct patterns of multisensory integration in ageing.

Audio-visual integration is more precise in older adults with a high level of long-term physical activity

It is well established that physical activity leads to numerous health, cognitive, and psychological benefits. However, to date, very few studies have investigated the impact of physical activity on multisensory perception, that is, the brain's capacity to integrate information across sensory modalities. Furthermore, it is unknown what level of long-term physical activity is associated with multisensory integration in adults. We explored the relationship between multisensory integration and a ten-year physical activity trajectory in 2,974 adults aged 50+ from The Irish Longitudinal Study on Ageing by measuring susceptibility to the Sound Induced Flash Illusion (SIFI) at multiple audio-visual temporal asynchronies. Physical activity was measured using the International Physical Activity Questionnaire (IPAQ-SF) at 2 years intervals over ten years. We used latent class trajectory modelling to identify latent growth classes of individuals following a similar trajectory of physical activity over time. We analysed the association of this trajectory with performance accuracy to the illusion trials of the SIFI task with generalized logistic mixed effects regression models, adjusted for several covariates. Results showed that more precise integration (i.e., lower SIFI susceptibility with larger temporal asynchronies) was associated with a higher level of sustained physical activity across ten years. Although the use of self-reported physical activity and a short version of the SIFI task limit our conclusions to some extent, nonetheless, the results suggest that sustained physical activity is associated with more precise multisensory integration, which in turn is linked to better balance and a lower risk of falling in older adults.

Age-Related Changes to Multisensory Integration and Audiovisual Speech Perception

Multisensory integration is essential for the quick and accurate perception of our environment, particularly in everyday tasks like speech perception. Research has highlighted the importance of investigating bottom-up and top-down contributions to multisensory integration and how these change as a function of ageing. Specifically, perceptual factors like the temporal binding window and cognitive factors like attention and inhibition appear to be fundamental in the integration of visual and auditory information-integration that may become less efficient as we age. These factors have been linked to brain areas like the superior temporal sulcus, with neural oscillations in the alpha-band frequency also being implicated in multisensory processing. Age-related changes in multisensory integration may have significant consequences for the well-being of our increasingly ageing population, affecting their ability to communicate with others and safely move through their environment; it is crucial that the evidence surrounding this subject continues to be carefully investigated. This review will discuss research into age-related changes in the perceptual and cognitive mechanisms of multisensory integration and the impact that these changes have on speech perception and fall risk. The role of oscillatory alpha activity is of particular interest, as it may be key in the modulation of multisensory integration.

Older adults with slow sit to stand times show reduced temporal precision of audio-visual integration

Sustained integration of sensory inputs over increased temporal delays is associated with reduced cognitive and physical functioning in older adults and adverse outcomes such as falls. Here, we explored the relationship between multisensory integration and a clinically relevant measure of balance/postural control; Sit-to-Stand Time, the efficiency with which an older adult can transition between a seated and a standing posture. We investigated whether temporal multisensory integration was associated with performance on the Five-Times Sit-to-Stand Test (FTSST) in a large sample of 2556 older adults (mean age = 63.62 years, SD = 7.50; 55% female) drawn from The Irish Longitudinal Study on Ageing (TILDA). K-means clustering was applied to FTSST data, yielding three clusters characterised by fast (mean = 10.88 s; n = 1122), medium (mean = 14.34 s; n = 1133) and slow (mean = 18.97 s; n = 301) sit-to-stand times. At wave 3 of TILDA, older adults participated in the Sound Induced Flash Illusion (SIFI), a measure of the precision of temporal audio-visual integration, which included three audio-visual stimulus onset asynchronies (SOAs): 70, 150 and 230 ms. Older adults with the slowest sit-to-stand times were more susceptible to the SIFI at the longest SOA (230 ms) compared to the shortest SOA (70 ms) relative to those with the fastest times (p = 0.02). Older adults who take longer to repeatedly transition from a seated to a standing posture exhibit an expanded temporal binding window for audio-visual events, supporting a link between multisensory perception and balance/postural control in ageing.

Longitudinal grip strength is associated with susceptibility to the Sound Induced Flash Illusion in older adults

The precision of temporal multisensory integration is associated with specific aspects of physical functioning in ageing, including gait speed and incidents of falling. However, it is unknown if such an association exists between multisensory integration and grip strength, an important index of frailty and brain health and predictor of disease and mortality in older adults. Here, we investigated whether temporal multisensory integration is associated with longitudinal (eight-year) grip strength trajectories in a large sample of 2,061 older adults (mean age = 64.42 years, SD = 7.20; 52% female) drawn from The Irish Longitudinal Study on Ageing (TILDA). Grip strength (kg) for the dominant hand was assessed with a hand-held dynamometer across four testing waves. Longitudinal k-means clustering was applied to these data separately for sex (male, female) and age group (50-64, 65-74, 75+ years). At wave 3, older adults participated in the Sound Induced Flash Illusion (SIFI), a measure of the precision of temporal audio-visual integration, which included three audio-visual stimulus onset asynchronies (SOAs): 70, 150 and 230 ms. Results showed that older adults with a relatively lower (i.e., weaker) grip strength were more susceptible to the SIFI at the longer SOAs compared to those with a relatively higher (i.e., stronger) grip strength (p <.001). These novel findings suggest that older adults with relatively weaker grip strength exhibit an expanded temporal binding window for audio-visual events, possibly reflecting a reduction in the integrity of the central nervous system.

The temporal precision of audiovisual integration is associated with longitudinal fall incidents but not sensorimotor fall risk in older adults

Sustained multisensory integration over long inter-stimulus time delays is typically found in older adults, particularly those with a history of falls. However, the extent to which the temporal precision of audio-visual integration is associated with longitudinal fall or fall risk trajectories is unknown. A large sample of older adults (N = 2319) were grouped into longitudinal trajectories of self-reported fall incidents (i.e., decrease, stable, or increase in number) and, separately, their performance on a standard, objective measure of fall risk, Timed Up and Go (TUG; stable, moderate decline, severe decline). Multisensory integration was measured once as susceptibility to the Sound-Induced Flash Illusion (SIFI) across three stimulus onset asynchronies (SOAs): 70 ms, 150 ms and 230 ms. Older adults with an increasing fall number showed a significantly different pattern of performance on the SIFI than non-fallers, depending on age: For adults with increasing incidents of falls, those aged 53-59 years showed a much smaller difference in illusion susceptibility at 70 ms versus 150 ms than those aged 70 + years. In contrast, non-fallers showed a more comparable difference between these SOA conditions across age groups. There was no association between TUG performance trajectories and SIFI susceptibility. These findings suggests that a fall event is associated with distinct temporal patterns of multisensory integration in ageing and have implications for our understanding of the mechanisms underpinning brain health in older age.

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.