Serial Subtraction Task Research Articles

Dual-task performance during the Timed Up and Go test in Parkinson's disease - the impact of freezing and cognition

BackgroundDual-task interference (DTI) on gait is well documented in Parkinson’s disease (PD), but how dual-tasks affect functional mobility is less known. Understanding how cognition and freezing of gait (FOG) further impact dual-task ability is important for risk assessment and subsequent delivery of targeted rehabilitation. Research questionWhat is the DTI on completion time of the Timed Up and Go, and DTI on response rate of a serial subtraction task when performed simultaneously, and is DTI impacted by FOG or cognition? MethodsA cross-sectional study design was used. Demographic and clinical characteristics of participants were collected, including global cognition and self-reported FOG. The TUG test was performed with and without a serial subtraction task. Completion times on TUG and response rates on the serial subtraction task was compared between single and dual-task performance using paired samples t-test or Wilcoxon signed rank test as appropriate. Prioritization between tasks was compared with one-sample Wilcoxon signed rank test. The impact of FOG and cognition was investigated with multiple linear regression, controlling for age, sex, and disease severity. ResultsA total of 77 people with mild to moderate PD were included. Significant DTI was observed for both the gait (TUG) and cognitive (response rate) tasks. No statistically significant pattern of prioritization was observed between motor and cognitive tasks. Global cognition was significantly related to both completion time and response rate in single and dual-tasking, whereas FOG was not found to be associated to the outcomes in either condition. SignificanceCognition appears to significantly relate to performance of functional mobility in single and dual-task conditions, which should be considered during routine mobility assessments in people with PD.

Dual-task performance and brain morphologic characteristics in Parkinson's disease.

Introduction Parkinson's disease (PD) reduces an individual's capacity for automaticity which limits their ability to perform two tasks simultaneously, negatively impacting daily function. Understanding the neural correlates of dual-tasks (DT) may pave the way for targeted therapies. To better understand automaticity in PD, we aimed to explore whether individuals with differing DT performances possessed differences in brain morphologic characteristics. Methods Data were obtained from 34 individuals with PD and 47 healthy older adults including: 1) demographics (age, sex), 2) disease severity (Movement Disorder Society - Unified Parkinson's Disease Rating Scale (MDS-UPDRS), Hoehn & Yahr, levodopa equivalent daily dose (LEDD)), 3) cognition (Montreal Cognitive Assessment), 4) Levodopa Equivalent Daily Dose, 5) single task- and DT- performance during a DT-Timed-Up-and-Go test utilizing a serial-subtraction task, and 6) Cortical thicknesses and subcortical volumes obtained from volumetric MRI. Participants were categorized as low or high DT performers if their combined DT-effect was greater than the previously determined mean value for healthy older adults (μ=74.2). Nonparametric testing using Quade's ANCOVA was conducted to compare cortical thicknesses and brain volumes between the highDT and lowDT groups while controlling for covariates: age, sex, MDS-UPDRS part III, LEDD, and intracranial volume. Secondarily, similar comparisons were made between the healthy older adult group the highDT and lowDT groups. Lastly, a hierarchical linear regression model was conducted regressing combined DT-effect on covariates (block one) and cortical thicknesses (block 2) in stepwise fashion. Results The highDT group had thicker cortices than the lowDT group in the right primary somatosensory (p=0.001), bilateral primary motor (p=<0.001, left; p=0.002, right), bilateral supplementary motor area (p=0.001, left; p<0.001, right), and mean of the bilateral hemispheres (p=0.001, left; p<0.001, right). Of note, left primary cortex thickness (p=0.002), left prefrontal cortex thickness (p<0.001), and right supplementary motor area thickness (p=0.003) differed when adding a healthy comparison group. Additionally, the regression analysis found that the left paracentral lobule thickness explained 20.8% of the variability in combined DT-effect (p=0.011) beyond the influence of covariates. Conclusions These results suggest regions underlying dual-task performance; specifically, a convergence of neural control relying sensorimotor integration, motor planning, and motor activation to achieve higher levels of DT performance for individuals with PD.

Impaired Neuromotor Control During Gait in Concussed Adolescents-A Frequency Analysis.

Disruptions in gait function are common after concussion in adolescents; however, the neuromotor control deficits driving these gait disruptions are not well known. Fifteen concussed (age mean [SD]): 17.4 [0.6], 13 females, days since injury: 26.3 [9.9]) and 17 uninjured (age: 18.0 [0.7], 10 females) adolescents completed 3 trials each of single-task gait and dual-task gait (DT). During DT, participants simultaneously walked while completing a serial subtraction task. Gait metrics and variability in instantaneous mean frequency in lower extremity muscles were captured by inertial sensors and surface electromyography, respectively. A 2-way analysis of covariance was used to compare gait metrics across groups and conditions. Functional principal components analysis was used to identify regions of variability in instantaneous mean frequency curves. Functional principal component scores were compared across groups using a Welch statistic. Both groups displayed worse performance on gait metrics during DT condition compared to single-task, with no differences between groups (P < .001). Concussed adolescents displayed significantly greater instantaneous mean frequency, indicated by functional principal component 1, in the tibialis anterior, biceps femoris, and semitendinosus (P < .05) during single-task and DT compared with uninjured adolescents. Our observations suggest that concussed adolescents display inefficient motor unit recruitment lasting longer than 2weeks following injury, regardless of the addition of a secondary task.

Speaking demands: concurrent visuomotor rotor pursuit tracking measures cognitive load for speech

ABSTRACT Purpose The purpose of this proof-of-principle study was to determine the extent to which concurrent tracking in a visuomotor rotor pursuit task is a feasible task for inferring the attentional load of clinical speaking tasks. The central predictions of the concurrent dual-task paradigm suggest that participants would exhibit performance change on a visuomotor rotor pursuit task during concurrent speech task performance, particularly when performing an attention-demanding speech task. Method Twenty-five participants performed common speech clinical assessment tasks that included syllable repetition, sentence repetition, counting forward by one, or serial subtraction by three, which requires a higher working memory load. All speech tasks were performed as a single-task and under dual-task conditions with a concurrent visuomotor rotor pursuit task. Results Compared to performing the attention-demanding visuomotor rotor pursuit task as a single-task, participants exhibited clear reductions in tracking accuracy (percent time-on-target) when performing under dual-task conditions with a concurrent speech task. A significantly greater reduction in tracking accuracy was observed during dual-task performance with a serial subtraction task than during the more automatic speaking tasks that involved repetition and counting forward. Conclusion These data suggest that dual-task performance of even repetitive speaking tasks introduces an attentional demand that is reflected in dual-task performance of a concurrent visuomotor rotor pursuit task and that this interference may be greater for speech tasks that require more cognitive resources.

Depression of dynamic cerebral autoregulation during neural activation: The role of responders and non-responders

Neurovascular coupling (NVC) interaction with dynamic cerebral autoregulation (dCA) remains unclear. We investigated the effect of task complexity and duration on the interaction with dCA. Sixteen healthy participants (31.6 ± 11.6 years) performed verbal fluency (naming-words (NW)) and serial subtraction (SS) paradigms, of varying complexity, at durations of 05, 30 and 60 s. The autoregulation index (ARI), was estimated from the bilateral middle cerebral artery blood velocity (MCAv) step response, calculated by transfer function analysis (TFA), for each paradigm during unstimulated (2 min) and neuroactivated (1 min) segments. Intraclass correlation (ICC) and coefficient of variation (CV) determined reproducibility for two visits and objective criteria were applied to classify responders (R) and non-responders (NoR) to task-induced MCAv increase. ICC values demonstrated fair reproducibility in all tasks. ARI decreased in right (RH) and left (LH) hemispheres, irrespective of paradigm complexity and duration (p < 0.0001). Bilateral ARI estimates were significantly decreased during NW for the R group only (p < 0.0001) but were reduced in both R (p < 0.0001) and NoR (p = 0.03) groups for SS tasks compared with baseline. The reproducible attenuation of dCA efficiency due to paradigm-induced NVC response, its interaction, and different behaviour in R and NoR, warrant further research in different physiological and clinical conditions.

The Effects of Polyphenol Supplementation on BDNF, Cytokines and Cognition in Trained Male Cyclists following Acute Ozone Exposure during High-Intensity Cycling.

The neurotoxic effects of ozone exposure are related to neuroinflammation and increases in reactive oxygen species (ROS). This study aimed to assess inflammation, Brain-Derived Neurotrophic Factor (BDNF), and cognition in healthy male cyclists following polyphenol supplementation and exercise in an ozone-polluted environment. Ten male cyclists initially completed a maximal incremental test and maximal effort 4 km time trial in ambient air. Cyclists then completed two trials in an ozone-polluted environment (0.25 ppm) following 7 days of supplementation with either polyphenol (POLY) or placebo (PL). Experimental trials consisted of a three-stage submaximal test followed by a 4 km time trial. Blood samples were drawn pre- and post-exercise, and analyzed for BDNF, interleukin 6 (IL-6), interleukin 10 (IL-10) and tumor necrosis factor (TNF-α). The Stroop test and serial subtraction task were performed before ozone exposure and again after the 4 km TT. Serum BDNF increased post-exercise (p < 0.0001), and positive differences were observed post-exercise in the ozone POLY group relative to PL (p = 0.013). Plasma IL-6 increased post-exercise (p = 0.0015), and TNF-α increased post-ozone exposure (p = 0.0018). There were no differences in Stroop or serial subtraction tasks pre- or post-exercise. Exercise increases BDNF in ozone.

Cognitive-motor interference during walking with modified leg mechanics: a dual-task walking study.

The use of mobile exoskeletons as assistive walking devices has the potential to affect the biomechanics of the musculoskeletal system due to their weight and restricted range of motion. This may result in physical and cognitive load for the user. Understanding how lower extremity loading affects cognitive-motor interference is crucial for the design of wearable devices, including powered exoskeletons, and the development of effective training interventions. This study aims to examine the effects of modified leg mechanics on cognitive-motor interference in dual-task walking. Gait variability, as an indicator of motor control, was analyzed to investigate its relation to cognitive task difficulty and to determine whether lower extremity loading modifies this relationship. Additionally, the impact on the gait pattern, as represented by the mean values of spatio-temporal gait parameters were investigated. Fifteen healthy young adults walked on a treadmill with and without weight cuffs bilaterally attached to their thighs and shanks while performing a visual-verbal Stroop test (simple task) and a serial subtraction task (difficult task). Dependent variables include mean values and variability (coefficients of variation) of step length, step width, stride time and double support time. Additionally, secondary task performance as correct response rates and perceived workload were assessed. Double support time variability decreased during dual-task walking, but not during walking with modified leg mechanics while performing the difficult secondary task. Walking with modified leg mechanics resulted in increased gait variability compared to normal walking, regardless of cognitive load. During walking with modified leg mechanics, step length, step width, and stride time increased, while double support time decreased. The secondary tasks did not affect the gait pattern. The interplay between an external focus of attention and competition for attentional resources may influence the variability of double support time. The findings suggest that walking with modified leg mechanics could increase cognitive-motor interference for healthy young adults in demanding dual-task situations. Therefore, it is important to analyze the underlying mechanisms of cognitive-motor interference in the context of human-exoskeleton interaction.

Lower back muscle activity during weight-shifting is affected by ageing and dual-tasking

PurposePostural control deteriorates with age, especially under dual-task conditions. It is currently unknown how a challenging virtual reality weight-shifting task affects lower back muscle activity. Hence, this study investigated erector spinae neuromuscular control during mediolateral weight-shifting as part of an exergame during single- (ST) and dual-task (DT) conditions in young and older adults. MethodsSeventeen young and 17 older adults performed mediolateral weight-shifts while hitting virtual wasps in a virtual environment with and without a serial subtraction task (DT). Center of mass position was recorded in real-time using 3D motion capturing. Electromyography recorded bilateral activation of the lumbar longissimus and iliocostalis muscles. ResultsWeight-shifting (p < 0.03) and targeting the wasps (p < 0.005) deteriorated with age and DT. Relative muscle activation during both quiet stance and weight-shifting increased with age, while the DT-effect did not differ consistently between age-groups. However, bilateral muscle co-contraction decreased with DT in young adults only. When switching direction and targeting the wasps, variability of muscle activation increased with age and DT and proved related to worse targeting performance. These effects were mainly visible at the non-dominant body side. ConclusionOlder adults showed a higher erector spinae muscle contribution to perform weight-shifts with increased variability at the end of a shift, whereby muscle activity was modulated less well in older than in young adults in response to DT. Hence, the current findings point to the potential for developing postural training in which older adults learn to fine-tune trunk muscle activity to improve weight-shifting and reduce fall risk.

Does GERAS DANCE improve gait in older adults?

BackgroundOlder adults at increased fall risk walk slower with less rhythm and coordination. This study explored the effect of dance on spatiotemporal gait parameters in older adults. MethodsParticipants (N = 23) in a single-arm trial were enrolled in the 12-week GERAS DANCE program (total dose of 36 h). Gait was assessed at baseline and 12-weeks under two experimental conditions: normal walking or walking while performing serial subtraction by 3. Outcome measures were gait speed, stride length time, double support time, stride length and stride width. Separate two-way repeated measures ANOVAs were used to determine estimates of the magnitude of effect of GERAS DANCE on spatiotemporal gait parameters and a paired t-test was used to examine differences in cognitive performance before and after dance. ResultsOlder adults (72.50 ± 7.13 years; 75% female) had excellent attendance (82.73% adherence). GERAS DANCE resulted in increased gait speed (p<0.001), reduced stride length time (p = 0.034), reduced double support time (p = 0.001), increased stride length (p = 0.003) and marginally reduced stride width (p = 0.064), regardless of the experimental condition. Improvements in walking performance were observed with sustained performance on the serial subtraction task before and after GERAS DANCE. ConclusionsGERAS DANCE may be a safe and feasible program to help improve spatiotemporal gait parameters in older adults with early memory or mobility impairments. Next steps include testing the efficacy for fall prevention to help inform clinical practice guidelines and virtual intervention implementation.

Using synchronized eye movements to assess attentional engagement.

The gradual emergence of online education in China in recent years requires new means of real-time monitoring and timely feedback to students. This research examines the effectiveness of synchronized eye movement assessment of attention engagement through two experiments. The first experiment used 24 university students in school as participants and made them watch the same video in high and low attentional engagement states (serial subtraction task) to compare the Inter-Subject Correlation (ISC) of participants' eye movements in different conditions. The results showed that the ISC of eye movements was significantly higher for participants in a high attentional engagement state than for participants in a low attentional engagement state. The second experiment had 26 university students in school as participants, as part of which they were made to watch video materials under the condition of having eye movement modeling examples. The results showed that the ISC of eye movements was significantly lower for participants in the group with eye movement modeling examples than those without eye movement modeling examples. However, overall test scores were significantly higher in the former than the latter. The first experiment showed that the eye movement trajectories of participants with high attentional engagement were more consistent than of those with low attentional engagement. Therefore, the ISC of participants' eye movements could be used as an objective indicator to assess and predict students' attentional conditions during online education. The second experiment showed that the eye movement modeling examples interfered with the participants' attention distribution to some extent; nevertheless, they positively affected the improvement in teaching effectiveness. Overall, the studies showed that the Inter-Subject Correlation is reliable to assess attentional engagement status in domestic online education.

Dividing attention during the Timed Up and Go enhances associations of several subtask performances with MCI and cognition.

We tested the hypothesis that dividing attention would strengthen the ability to detect mild cognitive impairment (MCI) and specific cognitive abilities from Timed Up and Go (TUG) performance in the community setting. While wearing a belt-worn sensor, 757 dementia-free older adults completed TUG during two conditions, with and without a concurrent verbal serial subtraction task. We segmented TUG into its four subtasks (i.e., walking, turning, and two postural transitions), and extracted 18 measures that were summarized into nine validated sensor metrics. Participants also underwent a detailed cognitive assessment during the same visit. We then employed a series of regression models to determine the combinations of subtask sensor metrics most strongly associated with MCI and specific cognitive abilities for each condition. We also compared subtask performances with and without dividing attention to determine whether the costs of divided attention were associated with cognition. While slower TUG walking and turning were associated with higher odds of MCI under normal conditions, these and other subtask associations became more strongly linked to MCI when TUG was performed under divided attention. Walking and turns were also most strongly associated with executive function and attention, particularly under divided attention. These differential associations with cognition were mirrored by performance costs. However, since several TUG subtasks were more strongly associated with MCI and cognitive abilities when performed under divided attention, future work is needed to determine how instrumented dual-task TUG testing can more accurately estimate risk for late-life cognitive impairment in older adults.

Influence of serial subtraction tasks on transient characteristics of postural control

Influence of serial subtraction tasks on transient characteristics of postural control

Influence of serial subtraction tasks on transient characteristics of postural control.

We sought to better understand the influence of cognitive perturbations on transient aspects of postural control. Twenty healthy, younger adults had their postural control assessed during eyes open quiet stance. Participants completed three different conditions that either had no cognitive perturbation present, an easy cognitive perturbation (i.e., serial subtraction by ones), or a more difficult cognitive perturbation (i.e., serial subtraction by sevens). All trials finished with 60s of undisturbed eyes open quiet stance, which was the focus of the balance assessment. 95% confidence ellipse area (EA) was calculated for 5-s epochs throughout the trial. The difference in EA from the first epoch after participants started (onset) or stopped (offset) the cognitive task to the last epoch of the trial (i.e., 55-60s after perturbation) was used to characterize transient postural control behavior. Functional near-infrared spectroscopy was also used to quantify changes in prefrontal cortex activation during the counting tasks to support interpretation of the transient balance findings. There was a significant effect of condition for transient balance characteristics following a cognitive perturbation (P<0.001), with greater transient increases in postural sway for both difficult (Cohen's d=0.40, P<0.001) and easier (Cohen's d=0.29, P=0.013) cognitive perturbations relative to no cognitive perturbation. The onset of cognitive tasks was also associated with greater transient increases in postural sway than the offset of the cognitive tasks (Cohen's d=0.24, P=0.019). The functional near-infrared spectroscopy data indicated that a significant decrease in deoxygenated hemoglobin was observed for left Brodmann area 46 for both the subtraction by ones (T=-3.97; Benjamini-Hochberg significance value (q)=0.008) and subtraction by sevens (T=-3.11; q=0.036) conditions relative to the baseline condition. The subtraction by sevens condition was also associated with a relative increase in deoxygenated hemoglobin for the right Brodmann area 9 (T=3.36; q=0.026) compared to the subtraction by ones condition. In conclusion, serial subtraction can elicit transient increases in postural sway, with more difficult tasks and the onset of the cognitive-motor challenge exhibiting magnified effects. Additionally, even the cessation of a cognitive task (i.e., serial subtraction) can be associated with lingering perturbing effects on balance control.

A Novel Way of Measuring Dual-Task Interference: The Reliability and Construct Validity of the Dual-Task Effect Battery in Neurodegenerative Disease

Background. Decreased automaticity is common among individuals with neurodegenerative disease and is often assessed using dual-task (DT) paradigms. However, the best methods for assessing performance changes related to DT demands remain inconclusive. Objective. To investigate the reliability and validity of a novel battery of DT measures (DT Effect—Battery (DTE-B)) encompassing three domains: task-specific interference, task prioritization, and automaticity. Methods. Data for this retrospective cross-sectional study included 125 participants with Parkinson’s disease (PD), 127 participants with Alzheimer’s disease (AD), and 84 healthy older adults. Reliability analyses were conducted using a subset of each population. DTE-B measures were calculated from single and DT performance on the Timed Up and Go test and a serial subtraction task. Construct validity was evaluated via associations within the DTE-B and with theoretically supported measures as well as known-groups validity analyses. Results. Good to excellent reliability was found for DTE-B measures of task interference (motor and cognitive DT effects) (ICCs≥.658) and automaticity (combined DT effect (cDTE)) (ICCs≥.938). Evidence for convergent validity was found with associations within the hypothesized constructs. Known-groups validity analyses revealed differences in the DTE-B among the healthy group and PD and AD groups (ps≤.001), excepting task prioritization (ps≥.061). Conclusions. This study provides evidence to support the DTE-B as a reliable measure of multiple constructs pertinent to DT performance. The cDTE demonstrated evidence to support its validity as a measure of automaticity. Further investigation of the utility of the DTE-B in both PD and AD, as well as other populations, is warranted.

Cardiovascular reactivity, stress, and personal emotional salience: Choose your tasks carefully.

Both greater cardiovascular reactivity and lesser reactivity ("blunting") to laboratory stressors are linked to poor health outcomes, including among people who have a history of traumatic experiences. In a sample of recently separated and divorced adults (N=96), this study examined whether differences in cardiovascular reactivity might be explained by differences in the personal emotional salience of the tasks and trauma history. Participants were assessed for trauma history, current distress related to their marital dissolution, and cardiovascular reactivity during two tasks, a serial subtraction math stressor task and a divorce-recall task. Participants with a greater trauma history evidenced less blood pressure reactivity to the serial subtraction task (a low personal emotional salience task) when compared to participants with less trauma history. In contrast, participants with a greater trauma history evidenced higher blood pressure reactivity to the divorce-recall task, but only if they also reported more divorce-related distress (high personal emotional salience). These associations were not significant for heart rate reactivity. Among people with a history of more traumatic experiences, a task with low personal salience was associated with a lower blood pressure response, whereas a task with higher personal emotional salience was associated with a higher blood pressure response. Future studies examining cardiovascular reactivity would benefit from determining the personal emotional salience of tasks, particularly for groups that have experienced stressful life events or trauma.

Effects of Age on Dual Task Walking Performance as Measured Using a Smartphone Application in Middle-Aged Adults

After the age of 65, one’s ability to walk while performing an additional cognitive task (i.e., dual-tasking) is predictive of both future falls and cognitive decline. However, while it is well-known that older adults exhibit diminished dual-task performance, the time course of age-related dual-task decline has not been established. We thus conducted an analysis of data collected within the ongoing Barcelona Brain Health Initiative, a prospective population-based study characterizing the determinants of brain health maintenance in middle-aged adults. Cognitively-unimpaired participants (n=655) aged 40-65 years without neuro-psychiatric disease completed laboratory-based trials of walking normally (single-task) and walking while performing a verbalized serial subtraction task (dual-task). A smartphone-based gait assessment application was used to capture data and derive both the mean stride time (ST) and stride time variability (STV, defined as the coefficient of variation about the mean stride time) of each trial. The dual-task costs (DTC) to each gait metric were obtained by calculating the percent change from single- to dual-task conditions. We categorized participants into five groups according to age (e.g. Group 1: 40-45 years; Group 5: 60-65 years). Age group did not have an effect on single-task gait outcomes (p>0.51). However, the oldest age group, as compared to each of the other groups, exhibited greater DTC to both ST and STV (p<0.03). These results indicate that dual-task walking performance in particular may begin to diminish in late middle age even in the absence of detectable cognitive issues, DTC may offer a sensitive metric to age-related change in cognitive function.

Postural Control under Cognitive Load: Evidence of Increased Automaticity Revealed by Center-of-Pressure and Head Kinematics

How postural responses change with sensory perturbations while also performing a cognitive task is still debatable. This study investigated this question via comprehensive assessment of postural sway, head kinematics and their coupling. Twenty-three healthy young adults stood in tandem with eyes open or wearing the HTC Vive Head-Mounted Display (HMD) with a static or dynamic (i.e., movement in the anterior-posterior direction at 5 mm or 32 mm at 0.2 Hz) 3-wall stars display. On half of the trials, participants performed a cognitive serial subtraction task. Medio-lateral center-of-pressure (COP) path significantly increased with the cognitive task, particularly with dynamic visuals whereas medio-lateral variance decreased with the cognitive task. Head path and velocity significantly increased with the cognitive task in both directions while variance decreased. Head-COP cross-correlations ranged between 0.78 and 0.66. These findings, accompanied by frequency analysis, suggest that postural control switched to primarily relying on somatosensory input under challenging cognitive load conditions. Several differences between head and COP suggest that head kinematics contribute an important additional facet of postural control and the relationship between head and COP may depend on task and stance position. The potential of HMDs for clinical assessments of balance needs to be further explored.

Modifying the Mini-Cog to Screen for Cognitive Impairment in Nonliterate Individuals.

Objectives The Mini-Cog, a rapid, valid, and reliable screening tool for cognitive impairment, consists of 3-word recall and an executive clock drawing test (CDT). However, CDT requires at least basic literacy and cultural exposure to analog clocks, conditions not met in many population groups around the world. We developed a modification of the Mini-Cog (MMC) for use with nonliterate and literate individuals. Methods Participants were adults (≥60 years) with no neurological diagnosis, with known cognitive impairment due to stroke, Parkinsonism, traumatic brain injury, or Alzheimer's disease, and whose family members were able to read and write. We replaced the CDT with two tasks of everyday life: a serial subtraction task or a multistep performance task. Family members rated the acceptability and feasibility of the Mini-Cog versions using a 6-point scale and completed a proxy-rated cognitive staging tool, the Dementia Severity Rating Scale (DSRS). Spearman's rho, Mann-Whitney U, and chi-square tests were used to evaluate group differences and associations between measures. Results Data were collected from 63 participants (75% ≥ 60 years, 67% nonliterate). Literacy was associated with CDT (chi-square strength 0.9, p < 0.001). Both MMC versions correlated with DSRS in healthy adults and patients (rho 0.6-0.7, p < 0.05). In literate individuals, the acceptability and feasibility of CDT and both alternate distractors were similarly high (5/6). Conclusions Two alternate distractor tasks may successfully replace CDT in the Mini-Cog. The MMC versions are promising and deserve further study as screening tools for cognitive impairment in larger and more fully characterized samples.

Targeted tDCS Mitigates Dual-Task Costs to Gait and Balance in Older Adults.

Among older adults, the ability to stand or walk while performing cognitive tasks (ie, dual-tasking) requires coordinated activation of several brain networks. In this multicenter, double-blinded, randomized, and sham-controlled study, we examined the effects of modulating the excitability of the left dorsolateral prefrontal cortex (L-DLPFC) and the primary sensorimotor cortex (SM1) on dual-task performance "costs" to standing and walking. Fifty-seven older adults without overt illness or disease completed 4 separate study visits during which they received 20 minutes of transcranial direct current stimulation (tDCS) optimized to facilitate the excitability of the L-DLPFC and SM1 simultaneously, or each region separately, or neither region (sham). Before and immediately after stimulation, participants completed a dual-task paradigm in which they were asked to stand and walk with and without concurrent performance of a serial-subtraction task. tDCS simultaneously targeting the L-DLPFC and SM1, as well as tDCS targeting the L-DLPFC alone, mitigated dual-task costs to standing and walking to a greater extent than tDCS targeting SM1 alone or sham (p < 0.02). Blinding efficacy was excellent and participant subjective belief in the type of stimulation received (real or sham) did not contribute to the observed functional benefits of tDCS. These results demonstrate that in older adults, dual-task decrements may be amenable to change and implicate L-DPFC excitability as a modifiable component of the control system that enables dual-task standing and walking. tDCS may be used to improve resilience and the ability of older results to walk and stand under challenging conditions, potentially enhancing everyday functioning and reducing fall risks. ANN NEUROL 2021;90:428-439.

Brain Activation Changes While Walking in Adults with and without Neurological Disease: Systematic Review and Meta-Analysis of Functional Near-Infrared Spectroscopy Studies.

(1) Functional near-infrared spectroscopy (fNIRS) provides a useful tool for monitoring brain activation changes while walking in adults with neurological disorders. When combined with dual task walking paradigms, fNIRS allows for changes in brain activation to be monitored when individuals concurrently attend to multiple tasks. However, differences in dual task paradigms, baseline, and coverage of cortical areas, presents uncertainty in the interpretation of the overarching findings. (2) Methods: By conducting a systematic review of 35 studies and meta-analysis of 75 effect sizes from 17 studies on adults with or without neurological disorders, we show that the performance of obstacle walking, serial subtraction and letter generation tasks while walking result in significant increases in brain activation in the prefrontal cortex relative to standing or walking baselines. (3) Results: Overall, we find that letter generation tasks have the largest brain activation effect sizes relative to walking, and that significant differences between dual task and single task gait are seen in persons with multiple sclerosis and stroke. (4) Conclusions: Older adults with neurological disease generally showed increased brain activation suggesting use of more attentional resources during dual task walking, which could lead to increased fall risk and mobility impairments. PROSPERO ID: 235228.