Long-term Tai Chi training reduces the fusion illusion in older adults.

Sound-induced flash illusion (SiFI) is an auditory-dominated audiovisual integration phenomenon that can be used as a reliable indicator of audiovisual integration. Although previous studies have found that Tai Chi exercise has a promoting effect on cognitive processing, such as executive functions, the effect of Tai Chi exercise on early perceptual processing has yet to be investigated. This study used the classic SiFI paradigm to investigate the effects of long-term Tai Chi exercise on multisensory integration in older adults. We compared older adults with long-term Tai Chi exercise experience with those with long-term walking exercise. The results showed that the accuracy of the Tai Chi group was higher than that of the control group under the fusion illusion condition, mainly due to the increased perceptual sensitivity to flashes. However, there was no significant difference between the two groups in the fission illusion. These results indicated that the fission and fusion illusions were affected differently by Tai Chi exercise, and this was attributable to the association of the participants' flash discriminability with them. The present study provides preliminary evidence that long-term Tai Chi exercise improves older adults' multisensory integration, which occurs in early perceptual processing.

Age-related impairment of navigation and strategy in virtual star maze.

BACKGROUND: Although it is well known that aging impairs navigation performance, the underlying mechanisms remain largely unknown. Egocentric strategy requires navigators to remember a series of body-turns without relying on the relationship between environmental cues. Previous study suggested that the egocentric strategy, compared with non-egocentric strategy, was relatively unimpaired during aging. In this study, we aimed to examine strategy use during virtual navigation task and the underlying cognitive supporting mechanisms in older adults. METHODS: Thirty young adults and thirty-one older adults were recruited from the local community. This study adapted star maze paradigm using non-immersive virtual environment. Participants moved freely in a star maze with adequate landmarks, and were requested to find a fixed destination. After 9 learning trials, participants were probed in the same virtual star maze but with no salient landmarks. Participants were classified as egocentric or non-egocentric strategy group according to their response in the probe trial. RESULTS: The results revealed that older adults adopting egocentric strategy completed the navigation task as accurate as young adults, whereas older adults using non-egocentric strategy completed the navigation task with more detours and lower accuracy. The relatively well-maintained egocentric strategy in older adults was related to better visuo-spatial ability. CONCLUSIONS: Visuo-spatial ability might play an important role in navigation accuracy and navigation strategy of older adults. This study demonstrated the potential value of the virtual star maze in evaluating navigation strategy and visuo-spatial ability in older adults.

Environmentally Benign, Rapid, and Selective Extraction of Gold from Ores and Waste Electronic Materials.

The extraction of gold from ores and electronic waste is an important topic worldwide, as this precious metal has immense value in a variety of fields. However, serious environmental pollution and high energy consumption due to the use of toxic oxidation reagents and harsh reaction conditions is a well-known problem in the gold industry. Herein, we report a new chemical method based on the combined use of N-bromosuccinimide (NBS) and pyridine (Py), which has a greatly decreased environmental impact and reagent cost, as well as mild reaction requirements. This method can directly leach Au0 from gold ore and electronic waste to form AuIII in water. The process is achieved in a yield of approximately 90 % at room temperature and a nearly neutral pH. The minimum dose of NBS/Py is as low as 10 mm, which exhibits low toxicity towards mammalian cells and animals as well as aquatic creatures. The high leaching selectivity of Au over other metals during gold leaching is demonstrated, showing that this method has great potential for practical industrial application towards the sustainable refining of gold from ores and electronic waste.

Toward systems neuroscience in mild cognitive impairment and Alzheimer's disease: a meta-analysis of 75 fMRI studies.

Most of the previous task functional magnetic resonance imaging (fMRI) studies found abnormalities in distributed brain regions in mild cognitive impairment (MCI) and Alzheimer's disease (AD), and few studies investigated the brain network dysfunction from the system level. In this meta-analysis, we aimed to examine brain network dysfunction in MCI and AD. We systematically searched task-based fMRI studies in MCI and AD published between January 1990 and January 2014. Activation likelihood estimation meta-analyses were conducted to compare the significant group differences in brain activation, the significant voxels were overlaid onto seven referenced neuronal cortical networks derived from the resting-state fMRI data of 1,000 healthy participants. Thirty-nine task-based fMRI studies (697 MCI patients and 628 healthy controls) were included in MCI-related meta-analysis while 36 task-based fMRI studies (421 AD patients and 512 healthy controls) were included in AD-related meta-analysis. The meta-analytic results revealed that MCI and AD showed abnormal regional brain activation as well as large-scale brain networks. MCI patients showed hypoactivation in default, frontoparietal, and visual networks relative to healthy controls, whereas AD-related hypoactivation mainly located in visual, default, and ventral attention networks relative to healthy controls. Both MCI-related and AD-related hyperactivation fell in frontoparietal, ventral attention, default, and somatomotor networks relative to healthy controls. MCI and AD presented different pathological while shared similar compensatory large-scale networks in fulfilling the cognitive tasks. These system-level findings are helpful to link the fundamental declines of cognitive tasks to brain networks in MCI and AD.

Multisensory working memory capture of attention.

During visual search, representations in working memory (WM) can guide the deployment of attention toward memory-matching visual input. Although previous studies have demonstrated that multisensory interactions facilitate WM and visual search, it remains unclear whether multisensory interaction influences attentional capture by WM. To address this issue, the present study adopted a dual-task paradigm, pairing a visual search task with a WM task, in which the memory modality was manipulated to be either visual or audiovisual. The results revealed that memory-driven attentional capture was observed under the visual and the audiovisual condition. Additionally, the capture effects and response time (RT) costs under the audiovisual condition were weaker than those under the visual condition, even on the trials with the earliest RTs. Furthermore, RT benefits under the audiovisual condition were comparable with those under the visual condition. These findings suggest that multisensory interactions can enhance cognitive control, leading to robust strategic effects and improved search performance. In this process, cognitive control tends to suppress the attentional capture by WM-matching distractors rather than enhance the attentional capture by WM-matching targets. The present study offers new insights into the influence of multisensory interactions on attentional capture by WM.

Effect of Target Semantic Consistency in Different Sequence Positions and Processing Modes on T2 Recognition: Integration and Suppression Based on Cross-Modal Processing.

In the rapid serial visual presentation (RSVP) paradigm, sound affects participants' recognition of targets. Although many studies have shown that sound improves cross-modal processing, researchers have not yet explored the effects of sound semantic information with respect to different locations and processing modalities after removing sound saliency. In this study, the RSVP paradigm was used to investigate the difference between attention under conditions of consistent and inconsistent semantics with the target (Experiment 1), as well as the difference between top-down (Experiment 2) and bottom-up processing (Experiment 3) for sounds with consistent semantics with target 2 (T2) at different sequence locations after removing sound saliency. The results showed that cross-modal processing significantly improved attentional blink (AB). The early or lagged appearance of sounds consistent with T2 did not affect participants' judgments in the exogenous attentional modality. However, visual target judgments were improved with endogenous attention. The sequential location of sounds consistent with T2 influenced the judgment of auditory and visual congruency. The results illustrate the effects of sound semantic information in different locations and processing modalities.

Compensation Mechanisms May Not Always Account for Enhanced Multisensory Illusion in Older Adults: Evidence from Sound-Induced Flash Illusion.

Sound-induced flash illusion (SiFI) is typical auditory dominance phenomenon in multisensory illusion. Although a number of studies have explored the SiFI in terms of age-related effects, the reasons for the enhanced SiFI in older adults are still controversial. In the present study, older and younger adults with equal visual discrimination were selected to explore age differences in SiFI effects, and to explore the neural indicators by resting-state functional magnetic resonance imaging (rs-fMRI) signals. A correlation analysis was calculated to examine the relationship between regional homogeneity (ReHo) and the SiFI. The results showed that both younger and older adults experienced significant fission and fusion illusions, and fission illusions of older adults were greater than that of younger adults. In addition, our results showed ReHo values of the left middle frontal gyrus (MFG), the right inferior frontal gyrus (IFG) and right superior frontal gyrus (SFG) were significantly positively correlated with the SiFI in older adults. More importantly, the comparison between older and younger adults showed that ReHo values of the right superior temporal gyrus (STG) decreased in older adults, and this was independent of the SiFI. The results indicated that when there was no difference in unisensory ability, the enhancement of multisensory illusion in older adults may not always be explained by compensation mechanisms.

Sound-induced flash illusion is modulated by the depth of auditory stimuli: Evidence from younger and older adults.

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.

Regular Tai Chi Practice Is Associated With Improved Memory as Well as Structural and Functional Alterations of the Hippocampus in the Elderly.

OBJECTIVE: The current study aimed at comparing the effects of Tai Chi (a motor-cognitive exercise) with walking (an exercise without cognitive demands) on cognitive performance, brain structure, and brain function in the elderly. METHODS: This cross-sectional study included 42 healthy elderly women within two groups: Tai Chi (n = 20; mean age = 62.90 ± 2.38 years) and brisk walking exercise (n = 22; mean age = 63.27 ± 3.58 years). All the participants underwent a cognitive assessment via the Montreal Cognitive Assessment and brain structural and resting state functional magnetic resonance imaging (rsfMRI) assessments. RESULTS: Episodic memory in the Tai Chi group was superior to that of the walking group. Higher gray matter density in the inferior and medial temporal regions (including the hippocampus) and higher ReHo in temporal regions (specifically the fusiform gyrus and hippocampus) were found in the Tai Chi group. Significant partial correlations were found between the gray matter density of the left hippocampus and episodic memory in the whole sample. Significant partial correlations were observed between the ReHo in left hippocampus, left parahippocampal, left fusiform, and delayed memory task, which was observed among all subjects. CONCLUSION: The present study suggests that long-term Tai Chi practice may improve memory performance via remodeling the structure and function of the hippocampus.

Differential Effects of Tai Chi Chuan (Motor-Cognitive Training) and Walking on Brain Networks: A Resting-State fMRI Study in Chinese Women Aged 60.

Background: This cross-sectional study aimed to investigate whether a long-term engagement in different types of physical exercise may influence resting-state brain networks differentially. In particular, we studied if there were differences in resting-state functional connectivity measures when comparing older women who are long-term practitioners of tai chi chuan or walking. Method: We recruited 20 older women who regularly practiced tai chi chuan (TCC group), and 22 older women who walked regularly (walking group). Both the TCC group and the walking group underwent a resting-state functional magnetic resonance imaging (rs-fMRI) scan. The acquired rs-fMRI data of all participants were analyzed using independent component analysis. Age and years of education were added as co-variables. Results: There were significant differences in default network, sensory-motor network, and visual network of rs-fMRI between the TCC group and walking group (p < 0.05). Conclusions: The findings of the current study suggested that long-term practice of different types of physical exercises (TCC vs. walking) influenced brain functional networks and brain functional plasticity of elderly women differentially. Our findings encourage further research to investigate whether those differences in resting-state functional connectivity as a function of the type of physical exercise have implications for the prevention of neurological diseases.

Tai Chi Training Evokes Significant Changes in Brain White Matter Network in Older Women.

Background: Cognitive decline is age relevant and it can start as early as middle age. The decline becomes more obvious among older adults, which is highly associated with increased risk of developing dementia (e.g., Alzheimer's disease). White matter damage was found to be related to cognitive decline through aging. The purpose of the current study was to compare the effects of Tai Chi (TC) versus walking on the brain white matter network among Chinese elderly women. Methods: A cross-sectional study was conducted where 42 healthy elderly women were included. Tai Chi practitioners (20 females, average age: 62.9 ± 2.38 years, education level 9.05 ± 1.8 years) and the matched walking participants (22 females, average age: 63.27 ± 3.58 years, educational level: 8.86 ± 2.74 years) underwent resting-state functional magnetic resonance imaging (rsfMRI) scans. Diffusion tensor imaging (DTI) and graph theory were employed to study the data, construct the white matter matrix, and compare the brain network attributes between the two groups. Results: Results from graph-based analyses showed that the small-world attributes were higher for the TC group than for the walking group (p < 0.05, Cohen's d = 1.534). Some effects were significant (p < 0.001) with very large effect sizes. Meanwhile, the aggregation coefficient and local efficiency attributes were also higher for the TC group than for the walking group (p > 0.05). However, no significant difference was found between the two groups in node attributes and edge analysis. Conclusion: Regular TC training is more conducive to optimize the brain functioning and networking of the elderly. The results of the current study help to identify the mechanisms underlying the cognitive protective effects of TC.

[Comparison of visual evoked related potentials in healthy young adults of different COMT genotypes by using a 3-back paradigm during a continuous mental arithmetic task].

To explore the change of numerical working memory ability in healthy young adults, continuous mental arithmetic task were performed for 3 hours and a numerical working memory paradigm was determined at 5 min intervals according to different COMT genotypes of young adults. Twenty subjects of different genotypes were chosen from 115 healthy young adults, P3 event-related potentials was utilized to observe the relationship between this COMT polymorphism and cortical physiology in a continuous working memory task. The results demonstrate that subjects bearing the Val/Val homozygote have significantly higher mean P3 amplitudes than Val/Met heterozygote (P<0.01), however, insignificant differences in comparison to Met/Met homozygote. Mean P3 amplitudes tended to sharply increase among different genotype subjects are observe in different Blocks. We suggest that numerical working memory ability was associated with P3 amplitude evoked from centro-parietal area of brain, which indicate the degree of influence of task on different subjects.

Putting age-related task activation into large-scale brain networks: A meta-analysis of 114 fMRI studies on healthy aging.

Normal aging is associated with cognitive decline and underlying brain dysfunction. Previous studies concentrated less on brain network changes at a systems level. Our goal was to examine these age-related changes of fMRI-derived activation with a common network parcellation of the human brain function, offering a systems-neuroscience perspective of healthy aging. We conducted a series of meta-analyses on a total of 114 studies that included 2035 older adults and 1845 young adults. Voxels showing significant age-related changes in activation were then overlaid onto seven commonly referenced neuronal networks. Older adults present moderate cognitive decline in behavioral performance during fMRI scanning, and hypo-activate the visual network and hyper-activate both the frontoparietal control and default mode networks. The degree of increased activation in frontoparietal network was associated with behavioral performance in older adults. Age-related changes in activation present different network patterns across cognitive domains. The systems neuroscience approach used here may be useful for elucidating the underlying network mechanisms of various brain plasticity processes during healthy aging.

Comparison of visual evoked-related potentials in healthy young adults of different catechol-O-methyltransferase genotypes in a continuous 3-back task.

We further support the notion that the catechol-O-methyltransferase (COMT) polymorphism may play a role in cognitive function. A continuous visual 3-back numerical working memory task was performed for an hour among 21 patients with different COMT genotypes. P300 visual event-related potentials evoked from the 3-back task were first utilized to observe the relationship between this COMT polymorphism and cortical physiology. The results showed that Val/Met heterozygous individuals show poorer performance, lower P300 amplitude, and higher P300 latency than those bearing the Val/Val homozygote on the task. This visual 3-back paradigm is a promising tool to examine continuous working memory capacity. The role of the COMT gene in dopamine catabolism makes for the influence of COMT polymorphism on P300 endophenotypes.

[Study on visual evoked related potentials in young adults of different COMT genotypes by using a numeric working memory task].

AIM: To explore the change of number working memory ability in healthy young adults, a continuous 3-back number working memory task were performed for an hour and 12 Blocks according to different COMT genotypes of young adults. METHODS: 18 different genotype subjects were chosen from 112 healthy young adults, P3 event-related potentials was utilized to observe the relationship between this COMT polymorphism and cortical physiology in a continuous working memory task. RESULTS: Subjects bearing the Val/Val homozygote had significantly higher mean P3 amplitudes than Val/Met heterozygote (P < 0.01), however, no significant differences in comparison to Met/Met homozygote. CONCLUSION: Val/Met Heterozygote subjects are associated with the poorest performance of working memory. There is a relationship between COMT genotype and P3 visual event-related potentials evoked from 3-back task.