Aging, Spatial Disparity, and the Sound-Induced Flash Illusion.

Sound-induced flash illusion (SiFI) refers to an auditory dominance effect in which observers misperceive the number of visual flashes due to the simultaneous presentation of a different number of auditory beeps. Although the SiFI remains robust despite many factors, little is known about how the dominance of audition over vision changes as a function of spatial location in 3D space and how this corresponds with aging. In the present study, we recruited younger (18-26 years old) and older adults (60-76 years old) and presented visual stimuli in near space and auditory stimuli in far space (Vnear_Afar) or visual stimuli in far space and auditory stimuli in near space (Vfar_Anear), with the aim of exploring the effect of aging on spatial dominance in SiFI. The results showed that both participant groups exhibited a SiFI auditory dominance effect; however, older adults were more susceptible to illusions than younger adults. More importantly, for younger adults, when auditory stimuli were presented in far space, the accuracy and d' indicated that SiFI was significantly enhanced in the fission illusion, and the reaction time (RT) results showed that RT became longer in the fusion illusion. However, for older adults, the SiFI was not affected by the spatial location. Therefore, the present results reveal for the first time that the SiFI effect is modulated by the depth of auditory stimuli. Moreover, older adults were not susceptible to the depth dimension, thus showing age-related sensory decline and specifically showing a decreased ability to localize visual and auditory stimuli.

Sound-induced flash illusion (SiFI) is the illusion that participants perceive incorrectly that the number of visual flashes is equal to the number of auditory beeps when presented within 100 ms. Although previous studies found that repetition suppression can reduce an individual's perceptual sensitivity to the SiFI, there is not yet a consensus as to how visual adaptation affects the SiFI. In the present study, we added prolonged adapting visual stimuli prior to the presentation of audiovisual stimuli to investigate whether the bottom-up factor of adaptation affects the SiFI. The adapting visual stimuli consisted of one or two of the same visual stimuli that lasted for 2 minutes in succession, followed by the audiovisual stimuli. Both adaptation conditions showed SiFI effects. The accuracy of adapting double-flashes was significantly lower than that of in adapting a single flash for the fission illusion. Our analyses indicated that such a pattern could be attributed to a lower d' in adapting double-flashes than in adapting a single flash. However, the accuracy, discriminability and criterion were not significantly different between the two adaptation conditions because of the instability of the fusion illusion. Thus, the present study indicated that the reduced perceptual sensitivity based on visual adaptation could enhance the fission illusion in multisensory integration.

Sound-induced flash illusion (SIFI) is an auditory-dominated multisensory integration phenomenon in which flashes presented in conjunction with an unequal number of auditory sounds are illusorily perceived as equal in number to the auditory sounds. Previous studies on the factors that impact SIFI have mainly focused on top-down and bottom-up factors. This study aimed to explore the effects of top-down cognitive expectations on the SIFI by manipulating the proportion of trial types. The results showed that the accuracy of judgment was improved and reaction times were shortened when the instructions were consistent with the actual proportion of trial type. When the instructions were not consistent with the actual proportion of trial types, the instructions could still regulate the accuracy and reaction times in judging the fission illusion (i.e., a brief flash accompanied by two auditory stimuli tends to be perceived as two flashes) regardless of the actual proportion of trial types. The results indicated that top-down cognitive expectations could significantly reduce the fission illusion and accelerate the judgment, but the effect was not significant in the fusion illusion (i.e., two brief flashes accompanied by single auditory stimuli tend to be perceived as a single flash) due to the instability of the illusion.

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.

Multisensorial Perception in Chronic Migraine and the Role of Medication Overuse

A single flash accompanied by two auditory beeps tends to be perceived as two flashes (Shams et al. Nature 408:788, 2000, Cogn Brain Res 14:147–152, 2002). This phenomenon is known as ‘sound-induced flash illusion.’ Previous neuroimaging studies have shown that this illusion is correlated with modulation of activity in early visual cortical areas (Arden et al. Vision Res 43(23):2469–2478, 2003; Bhattacharya et al. NeuroReport 13:1727–1730, 2002; Shams et al. NeuroReport 12(17):3849–3852, 2001, Neurosci Lett 378(2):76–81, 2005; Watkins et al. Neuroimage 31:1247–1256, 2006, Neuroimage 37:572–578, 2007; Mishra et al. J Neurosci 27(15):4120–4131, 2007). We examined how robust the illusion is by testing whether the frequency of the illusion can be reduced by providing feedback. We found that the sound-induced flash illusion was resistant to feedback training, except when the amount of monetary reward was made dependent on accuracy in performance. However, even in the latter case the participants reported that they still perceived illusory two flashes even though they correctly reported single flash. Moreover, the feedback training effect seemed to disappear once the participants were no longer provided with feedback suggesting a short-lived refinement of discrimination between illusory and physical double flashes rather than vanishing of the illusory percept. These findings indicate that the effect of sound on the perceptual representation of visual stimuli is strong and robust to feedback training, and provide further evidence against decision factors accounting for the sound-induced flash illusion.

The effect of eye disease, cataract surgery and hearing aid use on multisensory integration in ageing

This study investigated the effect of variable interstimulus intervals (ISIs) on behavioral reaction time (RT) and on the latency and amplitude of the auditory P300 using an auditory continuous performance task (ACPT) paradigm. Twenty subjects were instructed to respond to common stimuli and ignore a rare stimulus. Common stimuli were 1000-, 1500-, and 2000-Hz pure tones. The rare stimulus was a 250-Hz pure tone. ISIs of 1, 2, and 4 seconds were used for this investigation. A significant correlation between ISI, reaction time, P300 latency, correct rejections, and false alarm rates was found. A significant correlation between P300 latency, P300 amplitude, correct rejections, and false alarm rates was also observed. Likewise, a statistically significant increase in reaction time (RT) was observed as ISI increased. The ACPT paradigm in conjunction with the auditory P300 response can measure both behavioral and electrophysiologic changes that occur during active auditory attention and auditory cognitive processing tasks.

It has been suggested that interference in symbolically cued bimanual reaction time tasks is caused primarily by the perceptual processing of stimuli and not by motor preparation of the required movements. Here subjects made movements of the right and left index fingers that varied in their spatial and motor congruence. Spatial congruence was manipulated by presenting symbolic cues (i.e., pairs of letters) on a computer screen cueing the required movement directions. Motor congruence was manipulated by altering hand orientation. Results showed that interference occurs at both the stage of stimulus processing and the stage of motor preparation. These effects were reflected in the latencies of the different bimanual movements with both motor incongruence and spatial incongruence causing significant increases in reaction time. However, spatially incongruent movements that were made in response to incongruent visual cues demonstrated changes in reaction time that were more than double those of movements that required simultaneous activation of nonhomologous muscles. Therefore in symbolically cued bimanual reaction-time tasks, although both motor and spatial constraints operate, there is a clear dominance of spatial incongruence on performance. While motor congruence effects are likely due to cross-facilitation in corticospinal pathways, spatial incongruence effects are probably due to interference between the mechanisms that identify incongruent stimuli and translate these cues into the appropriate movements.

Detecting signs for an increased level of risk during driving are critical for the effective prevention of road traffic accidents. The current study searched for literature through major databases such as PubMed, EBSCO, IEEE, and ScienceDirect. A total of 14 articles that measured P300 components in relation to driving tasks were included for a systematic review and meta-analysis. The risk factors investigated in the reviewed articles were summarized in five categories, including reduced attention, distraction, alcohol, challenging situations on the road, and negative emotion. A meta-analysis was conducted at both behavioral and neural levels. Behavioral performance was measured by the reaction time and driving performance, while the neural response was measured by P300 amplitude and latency. A significant increase in reaction time was identified when drivers were exposed to the risk factors. In addition, the significant effects of a reduced P300 amplitude and prolonged P300 latency indicated a reduced capacity for cognitive information processing. There was a tendency of driving performance decrement in relation to the risk factors, however, the effect was non-significant due to considerable variations and heterogeneity across the included studies. The results led to the conclusion that the P300 amplitude and latency are reliable indicators and predictors of the increased risk in driving. Future applications of the P300-based brain–computer interface (BCI) system may make considerable contributions toward preventing road traffic accidents.

Impaired temporal perception of multisensory cues is a common phenomenon observed in older adults that can lead to unreliable percepts of the external world. For instance, the sound induced flash illusion (SIFI) can induce an illusory percept of a second flash by presenting a beep close in time to an initial flash-beep pair. Older adults that have enhanced susceptibility to a fall demonstrate significantly stronger illusion percepts during the SIFI task compared to those older adults without any history of falling. We hypothesize that a global inhibitory deficit may be driving the impairments across both postural stability and multisensory function in older adults with a fall history (FH). We investigated oscillatory activity and perceptual performance during the SIFI task, to understand how active sensory processing, measured by gamma (30–80 Hz) power, was regulated by alpha activity (8–13 Hz), oscillations that reflect inhibitory control. Compared to young adults (YA), the FH and non-faller (NF) groups demonstrated enhanced susceptibility to the SIFI. Further, the FH group had significantly greater illusion strength compared to the NF group. The FH group also showed significantly impaired performance relative to YA during congruent trials (2 flash-beep pairs resulting in veridical perception of 2 flashes). In illusion compared to non-illusion trials, the NF group demonstrated reduced alpha power (or diminished inhibitory control). Relative to YA and NF, the FH group showed reduced phase-amplitude coupling between alpha and gamma activity in non-illusion trials. This loss of inhibitory capacity over sensory processing in FH compared to NF suggests a more severe change than that consequent of natural aging.

Monkeys have been introduced as model organisms to study neural correlates of numerical competence, but many of the behavioral characteristics of numerical judgments remain speculative. Thus, we analyzed the behavioral performance of two rhesus monkeys judging the numerosities 1 to 7 during a delayed match-to-sample task. The monkeys showed similar discrimination performance irrespective of the exact physical appearance of the stimuli, confirming that performance was based on numerical information. Performance declined smoothly with larger numerosities, and reached discrimination threshold at numerosity "4." The nonverbal numerical representations in monkeys were based on analog magnitudes, object tracking process ("subitizing") could not account for the findings because the continuum of small and large numbers shows a clear Weber fraction signature. The lack of additional scanning eye movements with increasing set sizes, together with indistinguishable neuronal response latencies for neurons with different preferred numerosities, argues for parallel encoding of numerical information. The slight but significant increase in reaction time with increasing numerosities can be explained by task difficulty and consequently time-consuming decision processes. The behavioral results are compared to single-cell recordings from the prefrontal cortex in the same subjects. Models for numerosity discrimination that may account for these results are discussed.

Memory load and the similarity between positive and negative sets were varied orthogonally in an information-reduction task which required S to respond either “yes” or “no” to the question of whether or not a visually displayed two-dimensional pattern had been contained in a previously memorized set of patterns. Six Sa were given 8 days of practice. The results showed that throughout practice, there was a significant increase in reaction time with increaaes in the similarity of positive and neptive sets. The memory load differences sipificantly decreaaed to zero with practice, and this drop was independent of the similarity effect.. It was concluded that extended practice influences memory load differences and effects that reflect the complexity of the memory comparison process differentially.

Ensemble perception-the encoding of objects by their group properties-is known to be resistant to outlier noise. However, this resistance is somewhat paradoxical: how can the visual system determine which stimuli are outliers without already having derived statistical properties of the ensemble? A simple solution would be that ensemble perception is not a simple, one-step process; instead, outliers are detected through iterative computations that identify items with high deviance from the mean and reduce their weight in the representation over time. Here we tested this hypothesis. In Experiment 1, we found evidence that outliers are discounted from mean orientation judgments, extending previous results from ensemble face perception. In Experiment 2, we tested the timing of outlier rejection by having participants perform speeded judgments of sets with or without outliers. We observed significant increases in reaction time (RT) when outliers were present, but a decrease compared to no-outlier sets of matched range suggesting that range alone did not drive RTs. In Experiment 3 we tested the timing by which outlier noise reduces over time. We presented sets for variable exposure durations and found that noise decreases linearly over time. Altogether these results suggest that ensemble representations are optimized through iterative computations aimed at reducing noise. The finding that ensemble perception is an iterative process provides a useful framework for understanding contextual effects on ensemble perception. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Network pharmacology, in-silico and in-vivo studies for analgesic and antipyretic activities of Haplanthodes tentaculata (L) leaves.