Modulation of the spatial attention network by incentives in healthy aging and mild cognitive impairment

What do functional neuroimaging studies tell us about the association between falls and cognition in older adults? A systematic review

Impaired cognition is a known risk factor for falls in older adults. To enhance prevention strategies and treatment of falls among an aging global population, an understanding of the neural processes and networks involved is required. We present a systematic review investigating how functional neuroimaging techniques have been used to examine the association between falls and cognition in seniors. Peer-reviewed articles were identified through searching five electronic databases: 1) Medline, 2) PsycINFO, 3) CINAHL, 4) EMBASE, and 5) Pubmed. Key author, key paper, and reference searching was also conducted. Nine studies were included in this review. A questionnaire composed of seven questions was used to assess the quality of each study. EEG, fMRI, and PET were utilized across studies to examine brain function in older adults. Consistent evidence demonstrates that cognition is associated with measures of falls/falls risk, specifically visual attention and executive function. Our results show that falls/falls risk may be implicated with specific brain regions and networks. Future studies should be prospective and long-term in nature, with standardized outcome measures. Mobile neuroimaging techniques may also provide insight into brain activity as it pertains to cognition and falls in older adults in real-world settings.

Differences in Rhythmic Neural Activity Supporting the Temporal and Spatial Cueing of Attention

The neural processes serving the orienting of attention toward goal-relevant stimuli are generally examined with informative cues that direct visual attention to a spatial location. However, cues predicting the temporal emergence of an object are also known to be effective in attentional orienting but are implemented less often. Differences in the neural oscillatory dynamics supporting these divergent types of attentional orienting have only rarely been examined. In this study, we utilized magnetoencephalography and an adapted Posner cueing task to investigate the spectral specificity of neural oscillations underlying these different types of attentional orienting (i.e., spatial vs. temporal). We found a spectral dissociation of attentional cueing, such that alpha (10-16 Hz) oscillations were central to spatial orienting and theta (3-6 Hz) oscillations were critical to temporal orienting. Specifically, we observed robust decreases in alpha power during spatial orienting in key attention areas (i.e., lateral occipital, posterior cingulate, and hippocampus), along with strong theta increases during temporal orienting in the primary visual cortex. These results suggest that the oscillatory dynamics supporting attentional orienting are spectrally and anatomically specific, such that spatial orienting is served by stronger alpha oscillations in attention regions, whereas temporal orienting is associated with stronger theta responses in visual sensory regions.

A Cross-sectional Study of Attention Bias for Facial Expression Stimulation in Patients with Stroke at the Convalescence Stage

BACKGROUND

Post-stroke depression increases the likelihood of adverse physical symptoms. Attentional bias (AB) for negative stimuli is important in depression onset, maintenance, and remission. Stroke is more likely in older adults, who can have reduced cognitive function. Individuals with mild cognitive impairment (MCI) can have delayed reaction times (RTs). We hypothesized that RT to select neutral facial expression is affected by depressive symptoms and cognitive function in patients with stroke.

METHODS

This study analyzed 61 patients with stroke. Beck Depression Inventory-Second Edition (BDI-II) and Profile of Mood States (short version) scores were determined. Task stimuli comprised eight pairs of facial expressions containing affective (angry) and neutral faces. AB was measured as the RT to select the neutral face in two simultaneously presented images using attention bias modification (ABM) software. Patients were grouped according to depressive symptoms using BDI-II scores. Between-subject factors of depressive symptoms and cognitive function were determined by ANCOVA.

RESULTS

No significant interaction was found between depressive symptoms and cognitive function on RT. There was a main effect of cognitive function, but not depressive symptoms. In patients with hemiparesis and depressive symptoms, RT was significantly shorter in patients without MCI compared with patients with MCI.

CONCLUSIONS

People with stroke and elevated depression symptoms with hemiparesis but without MCI quickly selected neutral facial expressions from neutral and aversive expressions, and thus do not need ABM to escape aversive stimuli. ABM in response to aversive stimuli may be useful in evaluating negative emotions in individuals with post-stroke depression without MCI.

Losing Money and Motivation: Effects of Loss Incentives on Motivation and Metacognition in Younger and Older Adults

Incentives are usually expected to increase motivation and cognitive control and to thereby improve performance. A small but growing number of studies have begun to investigate whether the effects of incentive on cognitive performance differ for younger vs. older adults. Most have used attention and cognitive control paradigms, trial-wise implementation of incentive condition, and gain incentives (reward), with only a very few investigating the effects of loss incentives. The present study takes a complementary approach: We tested younger and older adults in a working memory paradigm with loss incentives implemented session-wide (between subjects). We also included self-report measures to ask how loss incentive affected participants’ perceptions of the mental demand of the task, as well as their perceived effort, frustration, motivation, distraction, and metacognitive judgments of how well they had performed. This allowed us to test the disparate predictions of different theoretical views: the intuitive hypothesis that incentive should increase motivation and performance, the motivational shift proposal that older adults are especially motivated to avoid losses (Freund and Ebner, 2005), a heuristic “positivity effect” perspective that older adults ignore losses (Brassen et al., 2012; Williams et al., 2017), and a more nuanced view that suggests that when negative information is unavoidable and increases perceived costs, older adults may instead disengage from the situation (Charles, 2010; Hess, 2014). The results seemed most consistent with the more nuanced view of the positivity effect. While neither group showed incentive-related performance differences, both younger and older adults reported greater perceived demand and frustration under loss incentive, especially in the most challenging conditions. Loss incentive increased the accuracy of immediate metacognitive judgments, but reduced the accuracy of later, more global judgments of competency for older adults. Self-report measures suggested that the loss incentive manipulation was distracting to young adults and demotivating for older adults. The results suggest a need for caution in generalizing from existing studies to everyday life, and that additional studies parameterizing critical aspects of task design and incentive manipulation are needed to fully understand how incentives affect cognition and motivation in younger and older adults.

Effects of an extrinsic motivator on the evaluation of cognitive and daily living functions in patients with schizophrenia

We investigated the effect of an extrinsic motivator on the MATRICS Consensus Cognitive Battery (MCCB) and UCSD Performance-Based Skills Assessment (UPSA) scores, which assess cognitive and daily living functions, in patients with schizophrenia. We enrolled 60 clinically stable patients with schizophrenia and allocated them to the motivator or control group. We conducted baseline assessments of cognitive function using the MCCB, daily living function using the UPSA, clinical symptoms, and psychosocial characteristics in both groups. In the retrial, we initially evaluated clinical symptoms. Next, we assigned an extrinsic motivator to the motivator group and again assessed cognitive function and daily living function using the MCCB and UPSA. Statistical analyses were performed using t-tests, Chi-square tests, Fisher's exact test, repeated measures analysis of variance, and logistic regression analysis. We found significant time × group interactions in processing speed, verbal learning, visual learning, and composite scores of MCCB. There were no significant interactions in UPSA scores. The meaningful change rates of social cognition and composite scores in MCCB were significantly higher in the motivator group than in the control group. After adjusting for additional variables, the extrinsic motivator had a significant effect on the meaningful MCCB composite score change. Conclusively, our findings suggest beneficial effects of extrinsic motivator on the MCCB score in patients with schizophrenia. In the future, the implementation and interpretation of the MCCB considering the motivation is necessary.

Construction and evaluation of multidomain attention training to improve alertness attention, sustained attention, and visual-spatial attention in older adults with mild cognitive impairment: A randomized controlled trial

OBJECTIVES

We aimed to analyze the effects of multidomain attention training on alertness, sustained attention, and visual-spatial attention in older adults with mild cognitive impairment (MCI).

DESIGN

The design used in this study was a two-arm, parallel group, double-blind randomized controlled trial.

SETTING AND PARTICIPANTS

The participants of the study were seventy-eight older adults with MCI (mean age: 79.5 ± 7.9 years) from retirement centers and community housing for the elderly.

INTERVENTION

The participants were randomly assigned to an experimental group (multidomain attention training, n = 39) or an active control group (n = 39). Both groups underwent training sessions for 45 minutes three times per week for 6 weeks (18 sessions in total).

MEASURES

The main efficacy indicator was alertness (Trail Making Test Part B), sustained attention (Digit Vigilance Test), and visual-spatial attention (Trail Making Test Part A). The secondary outcome indicators were other cognitive functions (Mini-Mental State Examination [MMSE] and Montreal Cognitive Assessment [MoCA] subscales). Measurements were obtained at pretest, posttest, and 3 and 6 months after training.

RESULTS

The results were analyzed by a generalized estimating equation (GEE), which indicated that attention outcomes (alertness, sustained attention, and visual-spatial attention) of the experimental group did not improve after training. However, the experimental group displayed a significant improvement in the attention, memory, and orientation of MMSE and MoCA subscales over a period of 6 months and also showed superior results compared with the control group.

CONCLUSIONS

Multidomain attention training demonstrated improved alertness and visual-spatial attention for posttest after 6 months. We also outline potential future advances in attention training for improving attention in older adults with MCI.

Reward sensitivity predicts dopaminergic response in spatial neglect

It has recently been revealed that spatial neglect can be modulated by motivational factors including anticipated monetary reward. A number of dopaminergic agents have been evaluated as treatments for neglect, but the results have been mixed, with no clear anatomical or cognitive predictors of dopaminergic responsiveness. Given that the effects of incentive motivation are mediated by dopaminergic pathways that are variably damaged in stroke, we tested the hypothesis that the modulatory influences of reward and dopaminergic drugs on neglect are themselves related. We employed a single-dose, double-blind, crossover design to compare the effects of Co-careldopa and placebo on a modified visual cancellation task in patients with neglect secondary to right hemisphere stroke. Whilst confirming that reward improved visual search in this group, we showed that dopaminergic stimulation only enhances visual search in the absence of reward. When patients were divided into REWARD-RESPONDERs and REWARD-NON-RESPONDERs, we found an interaction, such that only REWARD-NON-RESPONDERs showed a positive response to reward after receiving Co-careldopa, whereas REWARD-RESPONDERs were not influenced by drug. At a neuroanatomical level, responsiveness to incentive motivation was most associated with intact dorsal striatum. These findings suggest that dopaminergic modulation of neglect follows an 'inverted U' function, is dependent on integrity of the reward system, and can be measured as a behavioural response to anticipated reward.

Computerized Dual-Task Testing of Gait and Visuospatial Cognitive Functions; Test-Retest Reliability and Validity

The common occurrence of age decline in mobility and cognition does cause a decrease in the level of physical activity and an increased falls risk. Consequently, dual -task (DT) assessment that simultaneously addresses both mobility skills and cognitive functions are important because, continued difficulties and fall injuries will have a sizable impact in this population. The first objective of the present study was to assess test-retest reliability of a computerized DT treadmill walking protocol and concurrent outcome measures of gait and visuospatial executive function in a group of healthy older adults. Secondly, discriminative validity was evaluated by examining the effect of DT conditions (single task vs. dual-task) on; (a) spatiotemporal gait measures (average and coefficient of variation) and (b) visuomotor and visuospatial executive performance measures. Twenty-five community-dwelling individuals median age 65 (range 61-67) were recruited from a Fitness Facility. Participants performed a computerized visuomotor tracking task and a visuospatial executive game task in standing and while treadmill walking. Testing was conducted on two occasions, 1 week apart. Moderate to high test-retest reliability (ICC values of 0.65-0.88) were observed for spatiotemporal gait variables. No significant differences between the group means were observed between test periods in any gait variable. Moderate test-retest reliability (ICC values of 0.6-0.65) was observed for measures of visuomotor and visuospatial executive performance during treadmill walking. Significant DT effects were observed for both spatiotemporal gait variables and visuospatial executive performance measures. This study demonstrates the reliability and reproducibility of the computer-based assessment tool for dual task treadmill walking. The high to moderate ICC values and the lack of systematic errors in the measures indicate that this tool has the ability to repeatedly record reliable data from community-dwelling older adults. The present computerized dual-task protocols broaden the types of standardized visuomotor and visuospatial executive activities for use with DT treadmill walking that has previously been reported.

Reward processing in neurodegenerative disease

Representation of reward value involves a distributed network including cortical and subcortical structures. Because neurodegenerative illnesses target specific anatomic networks that partially overlap with the reward circuit, they would be predicted to have distinct impairments in reward processing. This review presents the existing evidence of reward processing changes in neurodegenerative diseases including mild cognitive impairment (MCI), Alzheimer's disease, frontotemporal dementia, amyotrophic lateral sclerosis (ALS), Parkinson's disease, and Huntington's disease, as well as in healthy aging. Carefully distinguishing the different aspects of reward processing (primary rewards, secondary rewards, reward-based learning, and reward-based decision-making) and using tasks that differentiate the stages of processing reward will lead to improved understanding of this fundamental process and clarify a contributing cause of behavioral change in these illnesses.

Closed-loop rehabilitation of age-related cognitive disorders

Cognitive deficits are common in older adults, as a result of both the natural aging process and neurodegenerative disease. Although medical advancements have successfully prolonged the human lifespan, the challenge of remediating cognitive aging remains. The authors discuss the current state of cognitive therapeutic interventions and then present the need for development and validation of more powerful neurocognitive therapeutics. They propose that the next generation of interventions be implemented as closed-loop systems that target specific neural processing deficits, incorporate quantitative feedback to the individual and clinician, and are personalized to the individual's neurocognitive capacities using real-time performance-adaptive algorithms. This approach should be multimodal and seamlessly integrate other treatment approaches, including neurofeedback and transcranial electrical stimulation. This novel approach will involve the generation of software that engages the individual in an immersive and enjoyable game-based interface, integrated with advanced biosensing hardware, to maximally harness plasticity and assure adherence. Introducing such next-generation closed-loop neurocognitive therapeutics into the mainstream of our mental health care system will require the combined efforts of clinicians, neuroscientists, bioengineers, software game developers, and industry and policy makers working together to meet the challenges and opportunities of translational neuroscience in the 21st century.

A systematic review of type 2 diabetes mellitus and hypertension in imaging studies of cognitive aging: time to establish new norms

The rising prevalence of type 2 diabetes (T2DM) and hypertension in older adults, and the deleterious effect of these conditions on cerebrovascular and brain health, is creating a growing discrepancy between the "typical" cognitive aging trajectory and a "healthy" cognitive aging trajectory. These changing health demographics make T2DM and hypertension important topics of study in their own right, and warrant attention from the perspective of cognitive aging neuroimaging research. Specifically, interpretation of individual or group differences in blood oxygenation level dependent magnetic resonance imaging (BOLD MRI) or positron emission tomography (PET H2O(15)) signals as reflective of differences in neural activation underlying a cognitive operation of interest requires assumptions of intact vascular health amongst the study participants. Without adequate screening, inclusion of individuals with T2DM or hypertension in "healthy" samples may introduce unwanted variability and bias to brain and/or cognitive measures, and increase potential for error. We conducted a systematic review of the cognitive aging neuroimaging literature to document the extent to which researchers account for these conditions. Of the 232 studies selected for review, few explicitly excluded individuals with T2DM (9%) or hypertension (13%). A large portion had exclusion criteria that made it difficult to determine whether T2DM or hypertension were excluded (44 and 37%), and many did not mention any selection criteria related to T2DM or hypertension (34 and 22%). Of all the surveyed studies, only 29% acknowledged or addressed the potential influence of intersubject vascular variability on the measured BOLD or PET signals. To reinforce the notion that individuals with T2DM and hypertension should not be overlooked as a potential source of bias, we also provide an overview of metabolic and vascular changes associated with T2DM and hypertension, as they relate to cerebrovascular and brain health.

The interacting effect of cognitive and motor task demands on performance of gait, balance and cognition in young adults

Mobility limitations and cognitive impairments, each common with aging, reduce levels of physical and mental activity, are prognostic of future adverse health events, and are associated with an increased fall risk. The purpose of this study was to examine whether divided attention during walking at a constant speed would decrease locomotor rhythm, stability, and cognitive performance. Young healthy participants (n=20) performed a visuo-spatial cognitive task in sitting and while treadmill walking at 2 speeds (0.7 and 1.0 m/s).Treadmill speed had a significant effect on temporal gait variables and ML-COP excursion. Cognitive load did not have a significant effect on average temporal gait variables or COP excursion, but variation of gait variables increased during dual-task walking. ML and AP trunk motion was found to decrease during dual-task walking. There was a significant decrease in cognitive performance (success rate, response time and movement time) while walking, but no effect due to treadmill speed. In conclusion walking speed is an important variable to be controlled in studies that are designed to examine effects of concurrent cognitive tasks on locomotor rhythm, pacing and stability. Divided attention during walking at a constant speed did result in decreased performance of a visuo-spatial cognitive task and an increased variability in locomotor rhythm.

Impaired choice stepping in response to a visual-spatial attention demanding task among older adults at high risk of falling: a pilot study

BACKGROUND AND AIMS

Impairment in visual-spatial attention can cause difficulties in planning and guiding movements, leading to falls in older adults .The purpose of this study was to investigate the relationship between visual-spatial attention during movement and the risk of falling in older adults.

METHODS

Thirty-six elderly volunteers (mean age, 73.2±6.8 years) performed a rapid choice stepping task in response to flanker task stimuli. Step errors in congruent or incongruent conditions were recorded as a measure of the accuracy of choice stepping. Four clinical measurements were also assessed: 10-min walking time, timed up and go test, functional reach test and 5- chair stand test.

RESULTS

High-risk (HR) participants showed a significantly higher rate of step errors in the incongruent condition than low-risk (LR) ones (HR: 55.5%, LR: 18.5%; p =0.032). Step error in the incongruent condition [odds ratio (OR)=5.5; p=0.041] was the only independent variable which remained significant in the final step of the logistic regression model.

CONCLUSION

Impaired choice stepping in response to a visual-spatial attention-demanding task was associated with the risk of falling in older adults.

Are impairments in visual-spatial attention a critical factor for increased falls risk in seniors? An event-related potential study

Falls are experienced annually by approximately one third of community dwellers over the age of 65, and while neuro-cognitive deficits have been shown to increase falls risk, the specific nature of these deficits remain unspecified. Here we examined whether visual-spatial attention may be a core neuro-cognitive system showing abnormal function in fallers. Using a between-groups design, we recorded event-related potentials in a canonical spatial cuing task performed by two groups of senior (aged 65+ years old) participants: those with a recent history of falls and those with no such history. In terms of attentional control systems in cortex, we found no significant differences in function between groups. However, in terms of attentional facilitation of cortical processing, we found that fallers manifest specific abnormalities in the sensory/perceptual processing of targets in the left visual field. Our findings thus suggest that fallers have specific deficits in visuocortical systems associated with attentional enhancement of events on the left side of visual space.

Combined effects of attention and motivation on visual task performance: transient and sustained motivational effects

We investigated how the brain integrates motivational and attentional signals by using a neuroimaging paradigm that provided separate estimates for transient cue- and target-related signals, in addition to sustained block-related responses. Participants performed a Posner-type task in which an endogenous cue predicted target location on 70% of trials, while motivation was manipulated by varying magnitude and valence of a cash incentive linked to task performance. Our findings revealed increased detection performance (d′) as a function of incentive value. In parallel, brain signals revealed that increases in absolute incentive magnitude led to cue- and target-specific response modulations that were independent of sustained state effects across visual cortex, fronto-parietal regions, and subcortical regions. Interestingly, state-like effects of incentive were observed in several of these brain regions, too, suggesting that both transient and sustained fMRI signals may contribute to task performance. For both cue and block periods, the effects of administering incentives were correlated with individual trait measures of reward sensitivity. Taken together, our findings support the notion that motivation improves behavioral performance in a demanding attention task by enhancing evoked responses across a distributed set of anatomical sites, many of which have been previously implicated in attentional processing. However, the effect of motivation was not simply additive as the impact of absolute incentive was greater during invalid than valid trials in several brain regions, possibly because motivation had a larger effect on reorienting than orienting attentional mechanisms at these sites.