Inefficient response inhibition in individuals with mild cognitive impairment

Dynamic modulation of spatial selection: Online and anticipatory adjustments in the flanker task

To track the spatiotemporal dynamics of selective attention, we constructed four theory-driven variants of Eriksen's flanker task. In each, subjects made speeded binary categorizations of target arrowhead direction while ignoring surrounding flanker arrowheads, whose direction was either congruent or incongruent to the target. Experiment 1 tracked the temporal evolution of target selection by systematically manipulating onset asynchrony between the target and flankers. In Experiments 2A and 2B, we increased flanker strength (both experiments) and reduced target strength (Experiment 2B only) at various times relative to target onset, exploring the effects of dynamic perceptual inputs on flanker congruency effects. Experiment 3 measured how uncertainty about stimulus location impeded spatial selection. Our findings demonstrate that spatial selection in the flanker task is dynamically modulated by both intra- and supra-trial factors.

The added value of metadata on test completion time for the quantification of cognitive functioning in survey research

OBJECTIVE

Information on the time spent completing cognitive testing is often collected, but such data are not typically considered when quantifying cognition in large-scale community-based surveys. We sought to evaluate the added value of timing data over and above traditional cognitive scores for the measurement of cognition in older adults.

METHOD

We used data from the Longitudinal Aging Study in India-Diagnostic Assessment of Dementia (LASI-DAD) study (N = 4,091), to assess the added value of timing data over and above traditional cognitive scores, using item-specific regression models for 36 cognitive test items. Models were adjusted for age, gender, interviewer, and item score.

RESULTS

Compared to Quintile 3 (median time), taking longer to complete specific items was associated (p < 0.05) with lower cognitive performance for 67% (Quintile 5) and 28% (Quintile 4) of items. Responding quickly (Quintile 1) was associated with higher cognitive performance for 25% of simpler items (e.g., orientation for year), but with lower cognitive functioning for 63% of items requiring higher-order processing (e.g., digit span test). Results were consistent in a range of different analyses adjusting for factors including education, hearing impairment, and language of administration and in models using splines rather than quintiles.

CONCLUSIONS

Response times from cognitive testing may contain important information on cognition not captured in traditional scoring. Incorporation of this information has the potential to improve existing estimates of cognitive functioning.

Computational modeling of selective attention differentiates subtypes of amnestic mild cognitive impairment

Individuals with amnestic mild cognitive impairment (aMCI), a prodromal stage of Alzheimer's disease and other dementias, show inhibition deficits in addition to episodic memory. How the latent processes of selective attention (i.e., from perception to motor response) contribute to these inhibition deficits remains unclear. Therefore, the present study examined contributions of selective attention to aMCI-related inhibition deficits using computational modeling of attentional dynamics. Two models of selective attention - the dual-stage two-phase model and the shrinking spotlight model - were fitted to individual participant data from a flanker task completed by 34 individuals with single-domain aMCI (sdaMCI, 66-86 years), 20 individuals with multiple-domain aMCI (mdaMCI, 68-88 years), and 52 healthy controls (64-88 years). Findings showed greater commission errors in the mdaMCI group compared to controls. Final-fitting model parameters indicated inhibitory and early perceptual deficits in mdaMCI , and impaired spatial allocation of attention in both MCI groups. Model parameters differentiated mdaMCI from sdaMCI and controls with moderate-to-high sensitivity and specificity. Impairments in perception and selective attention may contribute to inhibition deficits in both aMCI subtypes.

Abnormal resting-state functional connectivity of hippocampal subregions in type 2 diabetes mellitus-associated cognitive decline

Objective

Type 2 diabetes mellitus (T2DM) over time predisposes to inflammatory responses and abnormalities in functional brain networks that damage learning, memory, or executive function. The hippocampus is a key region often reporting connectivity abnormalities in memory disorders. Here, we investigated peripheral inflammatory responses and resting-state functional connectivity (RSFC) changes characterized of hippocampal subregions in type 2 diabetes-associated cognitive decline (T2DACD).

Methods

The study included 16 patients with T2DM, 16 patients with T2DACD and 25 healthy controls (HCs). Subjects were assessed for cognitive performance, tested for the expression of inflammatory factors IL-6, IL-10 and TNF-α in peripheral serum, underwent resting-state functional magnetic resonance imaging scans, and analyzed for RSFC using the hippocampal subregions as seeds. We also calculated the correlation between cognitive performance and RSFC of hippocampal subregion, and analyzed the significantly altered RSFC values of T2DACD for Receiver Operating Characteristic (ROC) analysis.

Results

T2DACD patients showed a decline in their ability to complete cognitive assessment scales and experimental paradigms, and T2DM did not show abnormal cognitive performance. IL-6 expression was increased in peripheral serum in both T2DACD and T2DM. Compared with HCs, T2DACD showed abnormalities RSFC of the left anterior hippocampus with left precentral gyrus and left angular gyrus. T2DM showed abnormalities RSFC of the left middle hippocampus with right medial frontal gyrus, right anterior and middle hippocampus with left precuneus, left anterior hippocampus with right precuneus and right posterior middle temporal gyrus. Compared with T2DM, T2DACD showed abnormalities RSFC of the left posterior hippocampus and right middle hippocampus with left precuneus. In addition, RSFC in the left posterior hippocampus with left precuneus of T2DACD was positively correlated with Flanker conflict response time (r=0.766, P=0.001). In the ROC analysis, the significantly altered RSFC values of T2DACD achieved significant performance.

Conclusions

T2DACD showed a significant decrease in attentional inhibition and working memory, peripheral pro-inflammatory response increased, and abnormalities RSFC of the hippocampal subregions with default mode network and sensory-motor network. T2DM did not show a significant cognitive decline, but peripheral pro-inflammatory response increased and abnormalities RSFC of the hippocampus subregions occurred in the brain. In addition, the left precuneus may be a key brain region in the conversion of T2DM to T2DACD. The results of this study may provide a basis for the preliminary diagnosis of T2DACD.

Decisional components of motor responses are not related to online response control: Evidence from lexical decision and speed-accuracy tradeoff manipulations

Evidence suggests that decision processes can propagate to motor-response execution. However, the functional characterization of motor decisional components is not yet fully understood. By combining a classic lexical decision experiment with manipulations of speed-accuracy tradeoff (SAT), the present experiment assessed the hypothesis that decisional effects on chronometric measures of motor-response execution are related to online response control. The electromyographic (EMG) signal associated with manual button-press responses was used to dissociate the premotor component (from stimulus onset until the onset of the EMG activity) from the motor component (from EMG onset until the button-press), thus enabling the assessment of decision-related effects in terms of motor-response duration within single-trial reaction times. Other than replicating all the previously reported SAT effects, the experiment revealed hindered control processes when the instructions emphasized speed over accuracy, as indicated by measures of response control such as partial errors, fast errors, and correction likelihood. Nonetheless, the lexicality effect on motor responses, consisting of slower motor times for pseudowords compared to words, was impervious to any SAT modulation. The results suggest that SAT-induced variations in decision and response control policies may not be the prominent determinant of decision-related effects on motor times, highlighting the multiple "cognitive" components that affect peripheral response execution.

Effects of stimulus onset asynchrony on cognitive control in healthy adults

The efficiency of cognitive control in healthy adults can be influenced by various factors, including the stimulus onset asynchrony (SOA) effect and strategy training. To address these issues, our study aims to investigate the impact of SOA on single-mode cognitive control using the Go/No-Go task, as well as the manifestation of proactive control within dual mechanisms of cognitive control through the AX-CPT task. In single-mode cognitive control, extending SOA led to significantly enhanced reaction times (RTs) during Go trials, suggesting improved task performance with increased preparation time. Moreover, the analysis revealed consistently higher accuracy rates in No-Go trials than to Go trials across all SOA levels, indicating robust inhibition processes unaffected by SOA variations. In the dual mechanisms of cognitive control, significant variations in RT and accuracy were observed among different trial types. Notably, participants exhibited superior performance in detecting targets during BY trials and shorter RTs in BX trials, indicative of efficient processing of target stimuli. Conversely, prolonged RTs in AY trials suggest proactive control strategies aimed at maintaining task-relevant information and inhibiting irrelevant responses. Overall, these findings highlight the effect of SOA on single-mode cognitive control and the emergence of proactive control within dual mechanisms of cognitive control in healthy adults.

The assessment of executive function abilities in healthy and neurodegenerative aging-A selective literature review

Numerous studies have examined executive function (EF) abilities in cognitively healthy older adults and those living with mild cognitive impairment (MCI) and Alzheimer's disease (AD). Currently, there are no standard accepted protocols for testing specific EFs; thus, researchers have used their preferred tool, which leads to variability in assessments of decline in a particular ability across studies. Therefore, there is a need for guidance as to the most sensitive tests for assessing EF decline. A search of the most current literature published between 2000 and 2022 on EF studies assessing cognitively healthy older adults and individuals living with MCI and AD was conducted using PubMed/Medline, PsycINFO, Embase, Web of Science, and Google Scholar. Emphasis was placed on the EF's dual-tasking, inhibition, shifting or switching, and working memory updating. Many tasks and their outcomes were reviewed. Of particular importance was the difference in outcomes for tasks applied to the same group of participants. These various EF assessment tools demonstrate differences in effectively identifying decline in EF ability due to the aging process and neurodegenerative conditions, such as MCI and AD. This review identifies various factors to consider in using particular EF tasks in particular populations, including task demand and stimuli factors, and also when comparing differing results across studies.

Relationship between cardiorespiratory fitness and executive function of Chinese Tibetan adolescents aged 13-18

OBJECTIVES

Explore the correlation between cardiorespiratory fitness (CRF) and execution function (EF) of Chinese Tibetan adolescents at high altitude (HA) areas.

DESIGN

A cross-sectional survey was used to study 1138 participants aged 13-18 (47.72% boys) at baseline.

METHODS

Lhasa (3650 m), Nagqu (4500 m), Qamdo (3500 m), and Nyingchi (3100 m) in China were chosen. CRF was measured by the 20 m shuttle run test (20mSRT) and a subsequent estimation of their maximal oxygen consumption (V̇O2max) was calculated using the Léger equations. The three core EFs (inhibition, working memory, and cognitive flexibility) were tested by a modified Eriksen flanker, N-back, and a more-odd shifting. The association between CRF and EF was explored by Pearson correlation, one-way ANOVA, and stratified regression.

RESULTS

The reaction time (RT) of 1-back, cognitive flexibility with V̇O2max showed a declining trend, (F = 34.475, 27.498, P < 0.01). Interestingly, 2-back RT went up and then went down with V̇O2max. (F = 29.55, P < 0.01). After increasing V̇O2max as a variable, a stratified regression analysis with the RT for 1-back, 2-back, and cognitive flexibility showed that ΔR2 equaled 0.107 ms, 0.071 ms, and 0.091 ms, respectively (P < 0.01). With V̇O2max increased by 1 mL/kg/min, the RT of 1-back, 2-back, and cognitive flexibility shortened 14.697 ms, 15.689 ms, and 11.771 ms, respectively.

CONCLUSIONS

CRF was positively associated with working memory, and cognitive flexibility development among Chinese Tibetan adolescents living at HA areas, respectively.

Huntington disease exacerbates action impulses

Background

Impulsivity is a common clinical feature of Huntington disease (HD), but the underlying cognitive dynamics of impulse control in this population have not been well-studied.

Objective

To investigate the temporal dynamics of action impulse control in HD patients using an inhibitory action control task.

Methods

Sixteen motor manifest HD patients and seventeen age-matched healthy controls (HC) completed the action control task. We applied the activation-suppression theoretical model and distributional analytic techniques to differentiate the strength of fast impulses from their top-down suppression.

Results

Overall, HD patients produced slower and less accurate reactions than HCs. HD patients also exhibited an exacerbated interference effect, as evidenced by a greater slowing of RT on non-corresponding compared to corresponding trials. HD patients made more fast, impulsive errors than HC, evidenced by significantly lower accuracy on their fastest reaction time trials. The slope reduction of interference effects as reactions slowed was similar between HD and controls, indicating preserved impulse suppression.

Conclusion

Our results indicate that patients with HD show a greater susceptibility to act rapidly on incorrect motor impulses but preserved proficiency of top-down suppression. Further research is needed to determine how these findings relate to clinical behavioral symptoms.

Biomechanical Analysis of Unplanned Gait Termination According to a Stop-Signal Task Performance: A Preliminary Study

There is a correlation between cognitive inhibition and compensatory balance response; however, the correlation between response inhibition and gait termination is not clear.

OBJECTIVES

The purpose of this study was to investigate the gait parameters of the lower extremity that occurred during unplanned gait termination (UGT) in two groups classified by the stop-signal reaction time (SSRT).

METHODS

Twenty young adults performed a stop-signal task and an unplanned gait termination separately. UGT required subjects to stop on hearing an auditory cue during randomly selected trials. The spatiotemporal and kinematic gait parameters were compared between the groups during UGT.

RESULTS

In phase one, the fast group had a significantly greater angle and angular velocity of knee flexion and ankle plantar flexion than the slow group (p < 0.05). Phase two showed that the fast group had a significantly greater angle and angular velocity of knee extension than the slow group (p < 0.05). Concerning the correlation analysis, the angle and angular velocity of knee flexion and ankle plantar flexion showed a negative correlation with the SSRT during UGT in phase one (p < 0.05). Phase two showed that the angle and angular velocity of knee extension was negatively correlated with the SSRT during UGT (p < 0.05).

CONCLUSION

The shorter the SSRT, the greater the angle and joint angular velocity of the ankle or knee joint that were prepared and adjusted for gait termination. The correlation between the SSRT and UGT suggests that a participant's capacity to inhibit an incipient finger response is associated with their ability to make a corrective gait pattern in a choice-demanding environment.

Associations between waist circumference and executive function among Chinese Tibetan adolescents living at high altitude

Background

Associations between body composition and execution function (EF) were currently studied in low altitude (LA) areas. However, the research on the correlation between waist circumference (WC) and EF among adolescents living at high altitude (HA) was limited.

Objective

We sought to explore the association between WC and EF in Chinese Tibetan adolescents aged 13-18 years in HA areas.

Methods

After excluding invalid data and extreme values, 1,228 participants (583 boys and 645 girls) were eventually included. The areas of Lhasa (average elevation of 3650 m), Nagqu (4500 m), Qamdo (3500 m), and Nyingchi (3100 m) in China were chosen as study sites. Participants completed tasks to measure inhibitory control, working memory, and cognitive flexibility. The predictive association between WC and EF was explored by One-way ANOVA, Pearson correlation, and linear regression analysis.

Results

After controlling for concomitant variables, the reaction time (RT) of responding to inhibitory control (difference incongruent and congruent), working memory (1-back, 2-back), and cognitive flexibility (heterogeneous, difference in heterogeneous and homogeneous) stimuli in subjects with WC ≥ 85th percentile was longer than that in those with WC of the 15th percentile or below [by 1.785 ms (95% CI: 0.078, 3.491), 208.734 ms (95% CI: 96.886, 320.582), 106.679 ms (95% CI: 16.485, 196.873), 82.307 ms (95% CI: 19.171, 145.442), and 58.397 ms (95% CI: 0.343,116.452), respectively], (P < 0.05).

Conclusion

After adjustment for concomitant variables, WC was significantly positively associated with the RT of inhibitory control, working memory, and cognitive flexibility among Chinese Tibetan adolescents in HA areas.

Time of Day Effects on Inhibitory Functioning: Cognitive and Neural Evidence of Sundowning in Amnestic Mild Cognitive Impairment

Background: Amnestic mild cognitive impairment (aMCI), a prodromal phase of Alzheimer’s disease (AD), is characterized by episodic memory dysfunction, but inhibitory deficits have also been commonly reported. Time of day (TOD) effects have been confirmed in 1) healthy aging on cognitive processes such as inhibitory control, and 2) on behavior in AD (termed the sundowning effect), but no such research has addressed aMCI. Objective: The present study examined the impact of TOD on the behavioral and electrophysiological correlates of inhibition in 54 individuals with aMCI and 52 healthy controls (HCs), all of morning chronotype. Methods: Participants were randomly assigned to complete two inhibition tasks (Go-NoGo and Flanker) during their optimal (morning) or non-optimal (evening) TOD, while electroencephalography was recorded. Results: Both tasks elicited changes in N2 and P3 event-related potential (ERP) components, which commonly index inhibitory functioning. Analyses showed that the Go-NoGo difference in P3 amplitude was reduced in individuals with aMCI relative to HCs. Compared to HCs, the Flanker difference in P3 amplitude was also reduced and coincided with more errors in the aMCI group. Notably, these behavioral and ERP differences were exaggerated in the non-optimal TOD relative to the optimal TOD. Conclusion: Findings confirm the presence of inhibition deficits in aMCI and provide novel evidence of sundowning effects on inhibitory control in aMCI. Results reinforce the need to consider the influences of TOD in clinical assessments involving individuals with aMCI.

Disrupted Value-Directed Strategic Processing in Individuals with Mild Cognitive Impairment: Behavioral and Neural Correlates

Value-directed strategic processing involves attending to higher-value information while inhibiting lower-value information. This preferential processing is relatively preserved in cognitively normal older adults but is impaired in individuals with dementia. No studies have investigated whether value-directed strategic processing is disrupted in earlier stages of cognitive decline, namely, mild cognitive impairment (MCI). The current study examined behavioral and EEG differences in value-directed strategic processing between 18 individuals with MCI and 18 cognitively normal older controls using a value-directed list learning task. Behaviorally, individuals with MCI recalled fewer total and high-value words compared to controls, but no group differences were observed in low-value word recall. Neurally, individuals with MCI had reduced theta synchronization relative to controls between 100 and 200 ms post-stimulus. Greater alpha desynchronization was observed for high- versus low-value words between 300 and 400 ms in controls but not in the MCI group. The groups showed some processing similarities, with greater theta synchronization for low-value words between 700 and 800 ms and greater alpha desynchronization for high-value words between 500 and 1100 ms. Overall, value-directed strategic processing was compromised in individuals with MCI on both behavioral and neural measures relative to controls. These findings add to the growing body of literature on differences between typical cognitive aging and MCI.

The Effects of a Magic Intervention Program on Cognitive Function and Neurocognitive Performance in Elderly Individuals With Mild Cognitive Impairment

Objectives

Cognitive training is one of the management options for elderly individuals who suffer from mild cognitive impairment (MCI) and an effective way to improve executive function. This study aimed to evaluate the effectiveness of a magic intervention program as a method of cognitive training in improving cognitive function and neurocognitive performance in this group.

Methods

Twenty-four participants aged 60-80 years with MCI were recruited and randomly assigned to a magic intervention group or a control group. The magic intervention group received a 6-week magic intervention program. The primary endpoints were the scores for the cognitive assessment tests [e.g., Mini-Mental State Examination (MMSE) and Montreal Cognitive Assessment (MoCA)] for general cognitive function. The secondary endpoints were the behavioral [e.g., accuracy and reaction times] and the electroencephalographic [e.g., event-related potential (ERP) P3 amplitudes] performance during the Flanker task to assess attention and inhibitory control. All variables were measured before and after the magic intervention.

Results

The results showed that the 6-week magic intervention significantly improved the MoCA scores in the cognitive assessment tests although no significant pre-post intervention difference was observed in the MMSE scores. In terms of neurocognitive performance, the magic intervention had significantly positive effects on the accuracy, reaction times, and P3 amplitudes when performing the Flanker task.

Conclusion

The results of the present study showed that the 6-week magic intervention had beneficial effects on the cognitive and electrophysiological performance in the elderly subjects with MCI. For such a group, lifestyle intervention programs that encourage participation such as the magic practice and performance may be a viable suggestion to prevent the progression of MCI to Alzheimer's disease.

Baseline Global Cognitive Function Affects Cognitive and Functional Outcomes of Combined Physical and Cognitive Training Among Older Adults With Cognitive Decline

IMPORTANCE

Baseline global cognitive function may affect cognitive and functional outcomes during combined physical and cognitive training; however, how it influences the effects of combined training remains uncertain.

OBJECTIVE

To determine the impact of baseline global cognitive function on cognitive and functional outcomes after combined physical and cognitive training among older adults with cognitive decline.

DESIGN

Observational.

SETTING

Local communities and senior centers.

PARTICIPANTS

Older adults with mild cognitive decline (MCD; n = 51) and moderate to severe cognitive decline (MSCD; n = 40).

INTERVENTION

Participants received 45 to 55 min of physical exercise training followed by 45 to 55 min of cognitive training in one session per week for 12 wk. Outcomes and Measures: Montreal Cognitive Assessment (MoCA), Lawton-Brody Instrumental Activities of Daily Living Scale (Lawton-Brody IADL), Word Recall Test (WRT), Stroop Color and Word Test (SCWT), Digital Symbol Substitution Test (DSST), and Trail Making Test (TMT) scores were assessed and compared between the MCD and MSCD groups.

RESULTS

Significant interaction effects were found for the WRT, SCWT, MoCA, and Lawton-Brody IADL. WRT and SCWT scores significantly improved in the MCD group, whereas MoCA and Lawton-Brody IADL scores significantly improved in the MSCD group. DSST scores increased among all participants, but TMT scores improved only in the MCD group.

CONCLUSIONS AND RELEVANCE

Older adults' baseline global cognitive function affected cognitive and instrumental activities of daily living (IADL) outcomes regarding combined training. High-level cognitive function, including inhibition and shifting abilities and working memory capacity, improved among older adults with MCD, whereas general cognitive function and IADLs improved among older adults with MSCD. What This Article Adds: Findings revealed domain-specific changes with respect to baseline cognitive function, which may help to refine current combined training protocols and facilitate development of personalized combined training programs for older adults with cognitive impairments.

Two sides of the same coin: ADHD affects reactive but not proactive inhibition in children

Children with attention-deficit/hyperactivity disorder (ADHD) present a deficit in inhibitory control. Still, it remains unclear whether it comes from a deficit in reactive inhibition (ability to stop the action in progress), proactive inhibition (ability to exert preparatory control), or both.We compared the performance of 39 children with ADHD and 42 typically developing children performing a Simon choice reaction time task. The Simon task is a conflict task that is well-adapted to dissociate proactive and reactive inhibition. Beyond classical global measures (mean reaction time, accuracy rate, and interference effect), we used more sophisticated dynamic analyses of the interference effect and accuracy rate to investigate reactive inhibition. We studied proactive inhibition through the congruency sequence effect (CSE).Our results showed that children with ADHD had impaired reactive but not proactive inhibition. Moreover, the deficit found in reactive inhibition seems to be due to both a stronger impulse capture and more difficulties in inhibiting impulsive responses. These findings contribute to a better understanding of how ADHD affects inhibitory control in children.

EEG theta and alpha oscillations in early versus late mild cognitive impairment during a semantic Go/NoGo task

Amnestic mild cognitive impairment (aMCI) is marked by episodic memory deficits, which can be used to classify individuals into early MCI (EMCI) and late MCI (LMCI). Although mounting evidence suggests that individuals with aMCI have additional cognitive alterations including deficits in cognitive control, few have examined if EMCI and LMCI differ on processes other than episodic memory. Using a semantic Go/NoGo task, we examined differences in cognitive control between EMCI and LMCI on behavioral (accuracy and reaction time) and neural (scalp-recorded event-related oscillations in theta and alpha band) measures. Although no behavioral differences were observed between the EMCI and LMCI groups, differences in neural oscillations were observed. The LMCI group had higher theta synchronization on Go trials at central electrodes compared to the EMCI group. In addition, the EMCI group showed differences in theta power at central electrodes and alpha power at central and centro-parietal electrodes between Go and NoGo trials, while the LMCI group did not exhibit such differences. These findings suggest that while behavioral differences may not be observable, neural changes underlying cognitive control processes may differentiate EMCI and LMCI stages and may be useful to understand the trajectory of aMCI in future studies.

Decline in the integration of top-down and bottom-up attentional control in older adults with mild cognitive impairment

Individuals with mild cognitive impairment (MCI) have deficits in goal-directed top-down and stimulus-driven bottom-up attentional control. However, it remains unclear whether and how the interaction between the two processes is altered in individuals with MCI. We collected electroencephalography (EEG) data from 30 older adults with MCI and 30 demographically matched healthy controls (HCs) when they were performing a perceptual decision-making task, in which we manipulated the cognitive load involved in task-relevant top-down processing and the surprise level involved in task-irrelevant bottom-up processing. We found the significant group difference in the interaction between top-down and bottom-up processes. HCs showed enlarged P3 and strengthened event-related microstate C on high (vs. low) surprise level trials under high cognitive load, while there was no such surprise effect suggesting distraction under low cognitive load. In contrast, participants with MCI showed increased P2 and P3 amplitudes and strengthened microstates C and D on high (vs. low) surprise level trials under low cognitive load yet no surprise effect under high load. These results suggested that participants with MCI were distracted by task-irrelevant information under low cognitive load, while under high load, they might experience a passive inhibition on the task-irrelevant bottom-up processing because of the exhaustion of attentional resources; in addition, this altered interaction observed in the MCI group occurred at the stages of selective attention and uncertainty reduction.

Acute Exercise and Cognitive Function in Alzheimer's Disease

BACKGROUND

Many studies have shown the impact of acute aerobic exercises (AAE) on cognition in healthy adults or at a pre-dementia stage. Few studies, however, have explored the positive effects of AAE in moderate Alzheimer's disease (ADM) patients.

OBJECTIVE

Evaluating the effect of AAE on cognitive functions in ADM patients.

METHODS

Overall, 79 (age: 69.62±0.99) ADM patients were recruited. Participants were divided into three groups according to the task: aerobic exercises done alone or combined with cognitive games presented on a screen, and a control group who performed a reading task. The aerobic exercise protocol consisted of a 20-min cycling exercise of moderate intensity, corresponding to 60%of the individual target maximal heart rate recorded in a 6-minute walking test. The participants' cognition was monitored before and after the intervention using the Tower of Hanoi, Digit Span, and Stroop tasks.

RESULTS

After the exercise, the participants' attention in both the physical and combined groups improved for the Stroop, the forward and backward Digit Span tasks, as well as the time taken to solve the Tower of Hanoi, although no significant differences were found in the number of moves taken in the latter. By contrast, the control group did not show any significant improvement for most of the cognitive tasks after the reading session.

CONCLUSION

Current evidence suggests that AAE may help to improve cognitive functions in ADM patients. This improvement is enhanced when the exercise is combined with cognitive games. Safe and progressive types of exercises should be promoted among ADM patients.

Value of Neuropsychological Tests to Identify Patients with Depressive Symptoms on the Alzheimer's Disease Continuum

Background:

Depressive symptoms often co-occur with Alzheimer’s disease (AD) and can impact neuropsychological test results. In early stages of AD, disentangling cognitive impairments due to depression from those due to neurodegeneration often poses a challenge.

Objective:

We aimed to identify neuropsychological tests able to detect AD-typical pathology while taking into account varying degrees of depressive symptoms.

Methods:

A battery of neuropsychological tests (CERAD-NP) and the Geriatric Depression Scale (GDS) were assessed, and cerebrospinal fluid (CSF) biomarkers were obtained. After stratifying patients into CSF positive or negative and into low, moderate, or high GDS score groups, sensitivity and specificity and area under the curve (AUC) were calculated for each subtest.

Results:

497 participants were included in the analyses. In patients with low GDS scores (≤10), the highest AUC (0.72) was achieved by Mini-Mental State Examination, followed by Constructional Praxis Recall and Wordlist Total Recall (AUC = 0.714, both). In patients with moderate (11–20) and high (≥21) GDS scores, Trail Making Test-B (TMT-B) revealed the highest AUCs with 0.77 and 0.82, respectively.

Conclusion:

Neuropsychological tests showing AD-typical pathology in participants with low GDS scores are in-line with previous results. In patients with higher GDS scores, TMT-B showed the best discrimination. This indicates the need to focus on executive function rather than on memory task results in depressed patients to explore a risk for AD.

Reaction time intra-individual variability reveals inhibitory deficits in single- and multiple-domain amnestic mild cognitive impairment

OBJECTIVES

Amnestic mild cognitive impairment (aMCI), a prodromal stage of Alzheimer's disease and other dementias, is characterized by episodic memory impairment. Recent evidence has shown inhibitory control deficits in aMCI, but the extent of these deficits across inhibitory domains (i.e., response inhibition and interference control) and aMCI subtypes (i.e., single- versus multiple-domain) remains unclear. Few studies have included response time intra-individual variability (RT IIV) in these efforts. The aim of this study was to compare response inhibition and interference control between aMCI subtypes using measures of accuracy, mean RT, and RT IIV.

METHOD

We report data from 34 individuals with single-domain aMCI (sdaMCI, 66-86 years), 20 individuals with multiple-domain aMCI (mdaMCI, 68-88 years), and 52 healthy controls (64-88 years) who completed tasks of response inhibition (Go-NoGo) and interference control (Flanker). Group differences in accuracy, mean RT, and RT IIV were examined for both tasks.

RESULTS

Individuals with mdaMCI had higher RT IIV than the other groups on both tasks. In RT IIV, we observed an interference control deficit in mdaMCI and sdaMCI relative to healthy controls, a finding not observed through accuracy or mean RT.

DISCUSSION

RT IIV may detect subtle differences in inhibition deficits between aMCI subtypes that may not be evident with conventional behavioral measures. Findings support the supplementary use of RT IIV when assessing early executive function deficits.

Social isolation during COVID-19 lockdown impairs cognitive function

Studies examining the effect of social isolation on cognitive function typically involve older adults and/or specialist groups (e.g., expeditions). We considered the effects of COVID‐19‐induced social isolation on cognitive function within a representative sample of the general population. We additionally considered how participants ‘shielding’ due to underlying health complications, or living alone, performed. We predicted that performance would be poorest under strictest, most‐isolating conditions. At five timepoints over 13 weeks, participants (N = 342; aged 18–72 years) completed online tasks measuring attention, memory, decision‐making, time‐estimation, and learning. Participants indicated their mood as ‘lockdown’ was eased. Performance typically improved as opportunities for social contact increased. Interactions between participant sub‐groups and timepoint demonstrated that performance was shaped by individuals' social isolation levels. Social isolation is linked to cognitive decline in the absence of ageing covariates. The impact of social isolation on cognitive function should be considered when implementing prolonged pandemic‐related restrictive conditions.

Upper-Extremity Perceptual-Motor Training Improves Whole-Body Reactive Agility Among Elite Athletes With History of Sport-Related Concussion

CONTEXT

Sport-related concussion (SRC) elevates risk for subsequent injury, which may relate to impaired perceptual-motor processes that are potentially modifiable.

OBJECTIVE

To assess a possible upper-extremity (UE) training effect on whole-body (WB) reactive agility performance among elite athletes with history of SRC (HxSRC) and without such history of SRC.

DESIGN

Cohort study.

SETTING

Residential training center.

PARTICIPANTS

Elite athletes (12 males and 8 females), including 10 HxSRC and 10 without such history of SRC.

INTERVENTION

One-minute training sessions completed 2 to 3 times per week over a 3-week period involved verbal identification of center arrow direction for 10 incongruent and 10 congruent flanker test trials with simultaneous reaching responses to deactivate illuminated buttons.

MAIN OUTCOME MEASURES

Pretraining and posttraining assessments of UE and WB reactive responses included flanker test conflict effect (incongruent minus congruent reaction time) and WB lateral average asymmetry derived from reaction time, speed, acceleration, and deceleration in opposite directions. Discrimination was assessed by receiver operating characteristic analysis, and training effect was assessed by repeated-measures analysis of variance.

RESULTS

Pretraining discrimination between HxSRC and without such history of SRC was greatest for conflict effect ≥80 milliseconds and WB lateral average asymmetry ≥18%. Each athlete completed 6 training sessions, which improved UE mean reaction time from 767 to 646 milliseconds (P < .001) and reduced mean conflict effect from 96 to 53 milliseconds (P = .039). A significant group × trial interaction was evident for WB lateral average asymmetry (P = .004), which was reduced from 24.3% to 12.5% among those with HxSRC.

CONCLUSIONS

Suboptimal perceptual-motor performance may represent a subtle long-term effect of concussion that is modifiable through UE training, which appears to improve WB reactive capabilities.

Age-Related Structural and Functional Changes of the Hippocampus and the Relationship with Inhibitory Control

Aging is associated with structural and functional changes in the hippocampus, and hippocampal dysfunction represents a risk marker of Alzheimer’s disease. Previously, we demonstrated age-related changes in reactive and proactive control in the stop signal task, each quantified by the stop signal reaction time (SSRT) and sequential effect computed as the correlation between the estimated stop signal probability and go trial reaction time. Age was positively correlated with the SSRT, but not with the sequential effect. Here, we explored hippocampal gray matter volume (GMV) and activation to response inhibition and to p(Stop) in healthy adults 18 to 72 years of age. The results showed age-related reduction of right anterior hippocampal activation during stop success vs. go trials, and the hippocampal activities correlated negatively with the SSRT. In contrast, the right posterior hippocampus showed higher age-related responses to p(Stop), but the activities did not correlate with the sequential effect. Further, we observed diminished GMVs of the anterior and posterior hippocampus. However, the GMVs were not related to behavioral performance or regional activities. Together, these findings suggest that hippocampal GMVs and regional activities represent distinct neural markers of cognitive aging, and distinguish the roles of the anterior and posterior hippocampus in age-related changes in cognitive control.

Eriksen flanker delta plot shapes depend on the stimulus

Several experimental paradigms are purported to measure response conflict, including the Stroop, Simon, and Eriksen flanker tasks. Although these tasks are often treated as being similar, delta plot analyses of response time distributions have revealed marked differences across them. Several theories have been proposed to explain these differences, however, assessing their veracity is difficult given the numerous differences across tasks. To explore what might cause delta plots to differ in a more controlled manner, here stimulus materials were manipulated across four Eriksen flanker tasks. The results reveal substantially different delta plot shapes for different stimuli: positive-going functions when color or motion served as the target and flankers, and delta plots with negative-going components when stimuli were arrows or orientated gratings. These results cast doubt on the proposal that negative-going delta plots occur only when spatial location serves as the interfering stimulus dimension. Moreover, because targets and flankers were always of the same stimulus type, the results also suggest that differences in materials across the relevant and irrelevant dimensions do not determine delta plot shapes. Instead, we propose that the delta plot shape is determined by several factors, including how early the interfering information is processed in the visual cortex.

Executive functions in the elderly with mild cognitive impairment: a systematic review on motor and cognitive inhibition, conflict control and cognitive flexibility

Background: Mild Cognitive Impairment (MCI) is a syndrome characterised by mild cognitive decline, on one or more domains, but which does not compromise daily functions. Several studies have investigated the relationship between MCI and deficit in executive functions (EFs) but, unlike robust evidence in the mnestic domain, the nature of executive deficits in the MCI population remains uncertain.Objectives: This systematic review aims to evaluate EFs in patients with MCI, considering inhibition (motor and cognitive), conflict control and cognitive flexibility.Method: The databases used for the search were PUBMED, PsycINFO, PsycARTICLES and MEDLINE. Eligibility criteria: use of specific paradigms for EFs assessment ('Wisconsin Card Sorting Test', 'Stroop Task', 'Go/No-Go Task', 'Flanker Task'); age over 65, studies published in English. Exclusion criteria: presence of dementia; psychiatric disorders; stroke; cranial trauma; inclusion of participants with MCI in groups with healthy elderly or those with dementia.Results: Fifty-five studies were selected, namely: Stroop Task (N = 30), WCST (N = 14), Go/No-Go (N = 9), Flanker Task (N = 2). Results have shown in people with MCI deficits in all the EFs considered.Conclusions: The results of this review support the applicability of the four experimental tasks examined for the study of EFs in people with MCI. These paradigms are useful in research, diagnosis and therapeutic purposes, allowing obtaining an articulated EFs profile that can compromise the daily life in elderly. These EFs are not generally evaluated by standard assessment of MCI, but their evaluation can lead to a better knowledge of MCI and help in the diagnosis and treatment.

A measure of the interference effect distribution

We elaborated an index, the Interference Distribution Index, which allows quantifying the relation between response times and the size of the interference effect. This index is associated with an intuitive graphical representation, the Lorenz-interference plot. We show that this index has some convenient properties in terms of sensitivity to changes in the distribution of the interference effect and to aggregation of individual data. Moreover, it turns out that this index is the only one (up to an arbitrary increasing transformation) possessing these properties. The relevance of this index is illustrated through simulations of a cognitive model of interference effects and reanalysis of experimental data.

The Weakened Relationship Between Prestimulus Alpha Oscillations and Response Time in Older Adults With Mild Cognitive Impairment

Background: Prestimulus alpha oscillations associated with preparatory attention have an impact on response time (RT). However, little is known about whether there is a deficit in the relationship between prestimulus alpha oscillations and RT in older adults with mild cognitive impairment (MCI).

Method: We collected electroencephalography (EEG) data from 28 older adults with MCI and 28 demographically matched healthy controls (HCs) when they were performing an Eriksen flanker task. For each participant, single-trial prestimulus alpha power was calculated for combinations of congruency (congruent vs. incongruent) and response speed (fast vs. slow).

Result: Statistical analysis indicated that prestimulus alpha power was significantly lower for fast trials than slow trials in HCs but not in older adults with MCI. The Fisher’s z scores of the within-subject correlation coefficients between single-trial prestimulus alpha power and RT were significantly larger in HCs than in older adults with MCI. In addition, machine learning analyses indicated that prestimulus alpha power and its correlation with RT could serve as features to distinguish older adults with MCI from HCs and to predict performance on some neuropsychological tests.

Conclusion: The reduced correlation between prestimulus alpha activity and RT suggests that older adults with MCI experience impaired preparatory attention.

Sensor-based systems for early detection of dementia (SENDA): a study protocol for a prospective cohort sequential study

Background

Dementia and cognitive decline are serious social and economic burdens. An increase in the population of older people, as well as longer lifespans mean that numbers of dementia cases are exponentially rising. Neuropathological changes associated with dementia are thought to appear before the clinical manifestation of cognitive symptoms, i.e., memory impairments. Further, some older adults (OA) experience cognitive decline before it can be objectively diagnosed. For optimal care of these patients, it is necessary to detect cognitive decline and dementia at an early stage. In this vein, motor, sensory, and neurophysiological declines could be promising factors if found to be present before the onset of cognitive impairment. Hence, the objective of the SENDA study is to develop a multi-dimensional sensor-based instrument that allows early detection of cognitive decline or dementia in OA with the help of cognitive, sensory, motor, and neurophysiological parameters before its clinical manifestation.

Methods/design

In the cohort sequential study, participants are assigned to one of three study groups depending on their cognitive status: 1. cognitively healthy individuals (CHI), 2. subjectively cognitively impaired persons (SCI), or 3. (possible) mildly cognitively impaired persons (pMCI, MCI). All groups take part in the same cognitive (e.g., executive function tests), motor (e.g., gait analyses, balance tests), sensory (e.g., vibration perception threshold test, proprioception tests), and neurophysiological (e.g., electroencephalograms) measurements. Depending on the time at which participants are included into the study, all measurements are repeated up to four times in intervals of 8 months within 3 years to identify associations with cognitive changes over time.

Discussion

This study aims to detect possible motor, sensory, neurophysiological, and cognitive predictors to develop an early screening tool for dementia and its pre-stages in OA. Thus, affected persons could receive optimal health care at an earlier time point to maintain their health resources.

Trial status

The study is ongoing. The recruitment of participants will be continued until May 2020.

Neuropsychological predictors of cognitive deterioration in non-demented individuals

Introduction: Previous studies performed neuropsychological tests in non-demented patients, especially those with mild cognitive impairment (MCI), to predict dementia. Few recent studies reported that subjective cognitive decline (SCD) itself predicts dementia conversion. We evaluated certain characteristics and neuropsychological tests to predict cognitive deterioration in non-demented individuals.Methods: This study included 106 participants with subjective cognitive complaints (SCCs) classified as non-demented (90 MCI and 16 SCD). Data were collected at baseline and follow-up, wherein participants completed a comprehensive neuropsychological assessment to assess their cognitive and daily functions.Results: During the follow-up of all participants, 52 converted to dementia, while 54 did not. There were significant differences in age and education years, as well as language, memory, frontal lobe function, and Barthel's Activities of Daily Living Index between the groups. Correlation analysis showed a significant correlation between the deterioration of the Clinical Dementia Rating scores and baseline language, memory, and frontal lobe function scores.Conclusion(s): SCDs consistently worrying about their SCCs and those identified with SCD by their caregivers were prone to cognitive function deterioration over time. Changes in language, memory, and frontal lobe function in neurocognitive tests were significantly different between the dementia converters and non dementia converters group. Particularly, SCD and MCI individuals with significantly poor initial executive function and memory abilities should be closely monitored for future cognitive decline.

Reduced Capacity of Cognitive Control in Older Adults with Mild Cognitive Impairment

Cognitive control for the coordination of mental operations is essential in normal cognitive functioning of daily life. Although the decline of cognitive control in older adults with mild cognitive impairment (MCI) has been demonstrated, whether this decline is a core deficit in MCI remains unclear. In this study, we employed a perceptual decision-making task to estimate the capacity of cognitive control (CCC) in older adults with MCI (n = 55) and the age-, sex-, and education-matched healthy controls (HC, n = 55) selected based on a commonly used battery of ten neuropsychological tests in five cognitive domains. We found that the CCC was significantly correlated to the neuropsychological measures of the battery. The mean CCC was significantly lower in the MCI group (3.06 bps) than in the HC group (3.59 bps) and significantly lower in the amnestic MCI subgroup (2.90 bps) than in the nonamnestic MCI subgroup (3.22 bps). In detecting and classifying MCI using machine learning, the classifier with the CCC as the input feature outperformed the overall classification with neuropsychological measures in a single cognitive domain. The classification performance was significantly increased when the CCC was included as a feature in addition to measures in a single domain, and the CCC served as a key feature in optimal classifiers with inputs from multiple domains. These results support the hypothesis that the decline in cognitive control is a core deficit in MCI and suggest that the CCC may serve as a key index in the diagnosis of MCI.

Transient and sustained incentive effects on electrophysiological indices of cognitive control in younger and older adults

Preparing for upcoming events, separating task-relevant from task-irrelevant information and efficiently responding to stimuli all require cognitive control. The adaptive recruitment of cognitive control depends on activity in the dopaminergic reward system as well as the frontoparietal control network. In healthy aging, dopaminergic neuromodulation is reduced, resulting in altered incentive-based recruitment of control mechanisms. In the present study, younger adults (18-28 years) and healthy older adults (66-89 years) completed an incentivized flanker task that included gain, loss, and neutral trials. Event-related potentials (ERPs) were recorded at the time of incentive cue and target presentation. We examined the contingent negative variation (CNV), implicated in stimulus anticipation and response preparation, as well as the P3, which is involved in the evaluation of visual stimuli. Both younger and older adults showed transient incentive-based modulation of CNV. Critically, cue-locked and target-locked P3s were influenced by transient and sustained effects of incentives in younger adults, while such modulation was limited to a sustained effect of gain incentives on cue-P3 in older adults. Overall, these findings are in line with an age-related reduction in the flexible recruitment of preparatory and target-related cognitive control processes in the presence of motivational incentives.

Dopamine effects on frontal cortical blood flow and motor inhibition in Parkinson's disease

Parkinson's disease (PD) is characterized by dysfunction in frontal cortical and striatal networks that regulate action control. We investigated the pharmacological effect of dopamine agonist replacement therapy on frontal cortical activity and motor inhibition. Using Arterial Spin Labeling MRI, we examined 26 PD patients in the off- and on-dopamine agonist medication states to assess the effect of dopamine agonists on frontal cortical regional cerebral blood flow. Motor inhibition was measured by the Simon task in both medication states. We applied the dual process activation suppression model to dissociate fast response impulses from motor inhibition of incorrect responses. General linear regression model analyses determined the medication effect on regional cerebral blood flow and motor inhibition, and the relationship between regional cerebral blood flow and motor inhibitory proficiency. We show that dopamine agonist administration increases frontal cerebral blood flow, particularly in the pre-supplementary motor area (pre-SMA) and the dorsolateral prefrontal cortex (DLPFC). Higher regional blood flow in the pre-SMA, DLPFC and motor cortex was associated with better inhibitory control, suggesting that treatments which improve frontal cortical activity could ameliorate motor inhibition deficiency in PD patients.

Impaired conflict monitoring in cognitive decline

Resolving conflicts is an important cognitive ability of executive function, and it may decrease with cognitive decline. The flanker task is a practical test used to assess the ability to suppress responses that are inappropriate in a particular context. The aims of the present study were to investigate conflict monitoring of cognitive control in subjects with different levels of cognitive impairment, and clarify the usefulness of the flanker task in screening cognitive decline. We recruited 50 subjects with mild cognitive impairment (MCI) and 34 patients with Alzheimer's disease (AD), and 44 mentally healthy elderly subjects as a control group. To evaluate cognitive performance, each participant underwent a neuropsychological assessment using the Cognitive Abilities Screening Instrument and a modified flanker task. Compared with the normal controls and those with MCI, the patients with AD had a significantly lower accuracy rate and longer reaction time in both congruent and incongruent trials. The diagnosis of AD predicted significantly poorer performances on the flanker tasks. Furthermore, behavioral data of the patients with AD were significantly correlated with the results of neuropsychological tests. Our results indicated that executive cognitive deficits in conflict monitoring as detected by the flanker task were significantly impaired in the patients with AD. The flanker task could be a quick and easier alternative tool for screening AD among elderly people with suspicious cognitive impairment.

Computerized Cognitive Screen (CoCoSc): A Self-Administered Computerized Test for Screening for Cognitive Impairment in Community Social Centers

BACKGROUND

Computerized cognitive tests may serve as a preliminary, low-cost method to identify individuals with suspected cognitive impairment in the community.

OBJECTIVE

To develop a self-administered computerized test, namely the "Computerized Cognitive Screen (CoCoSc), Hong Kong version", for screening of individuals with cognitive impairment (CI) in community settings.

METHODS

The CoCoSc is a 15-min computerized cognitive screen covering memory, executive functions, orientation, attention and working memory, and prospective memory administered on a touchscreen computer. Individuals with CI and cognitively normal controls were administered the CoCoSc and the Montreal Cognitive Assessment (MoCA). Validity of the CoCoSc was assessed based on the relationship with the MoCA using Pearson correlation. Receiver operating characteristic curve (ROC) was used to examine the ability of the CoCoSc to differentiate CI from controls.

RESULTS

Fifty-nine individuals with CI and 101 controls were recruited. Seventy-five (46.9%) participants had ≤6 years of education. Performance on the CoCoSc differed between normal and CI groups in both low and high education subgroups. Total scores of the CoCoSc and MoCA were significantly correlated (r = 0.71, p < 0.001). The area under ROC was 0.78, p < 0.001 for the CoCoSc total score in differentiating the CI group from the cognitively normal group. A cut-off of ≤30 on the CoCoSc was associated with a sensitivity of 0.78 and specificity of 0.69. The CoCoSc was well accepted by attendees of community social centers.

CONCLUSION

The CoCoSc is a promising computerized cognitive screen for self-administration in community social centers. It is feasible for testing individuals with high or low education levels.

Exposing an "Intangible" Cognitive Skill among Collegiate Football Players: Enhanced Interference Control

American football is played in a chaotic visual environment filled with relevant and distracting information. We investigated the hypothesis that collegiate football players show exceptional skill at shielding their response execution from the interfering effects of distraction (interference control). The performances of 280 football players from National Collegiate Athletic Association Division I football programs were compared to age-matched controls in a variant of the Eriksen flanker task (Eriksen and Eriksen, 1974). This task quantifies the magnitude of interference produced by visual distraction on split-second response execution. Overall, football athletes and age controls showed similar mean reaction times (RTs) and accuracy rates. However, football athletes were more proficient at shielding their response execution speed from the interfering effects of distraction (i.e., smaller flanker effect costs on RT). Offensive and defensive players showed smaller interference costs compared to controls, but defensive players showed the smallest costs. All defensive positions and one offensive position showed statistically smaller interference effects when compared directly to age controls. These data reveal a clear cognitive advantage among football athletes at executing motor responses in the face of distraction, the existence and magnitude of which vary by position. Individual differences in cognitive control may have important implications for both player selection and development to improve interference control capabilities during play.

Effects of age on inhibitory control are affected by task-specific features

Older adults have been argued to have impoverished inhibitory control compared to younger adults. However, these effects of age may depend on processing speed and their manifestation may furthermore depend on the type of inhibitory control task that is used. We present two experiments that examine age effects on inhibition across three tasks: a Simon arrow, static flanker and motion flanker task. The results showed overall slower reaction times (RTs) for older adults on all three tasks. However, effects of age on inhibition costs were only found for the Simon task, but not for the two flanker tasks. The motion flanker task furthermore showed an effect of baseline processing speed on the relation between age and inhibition costs. Older adults with slower baseline responses showed smaller inhibition costs, suggesting they were affected less by the flanker items than faster older adults. These findings suggest that effects of age on inhibition are task dependent and can be modulated by task-specific features such as the type of interference, type of stimuli and processing speed.

An acute bout of aerobic or strength exercise specifically modifies circulating exerkine levels and neurocognitive functions in elderly individuals with mild cognitive impairment

Although exercise is an effective way to decrease the risk of developing Alzheimer's disease, the biological basis for such benefits from the different exercise modes remains elusive. The present study thus aimed (i) to investigate the effects of acute aerobic or resistance exercise on neurocognitive performances and molecular markers when performing a cognitive task involving executive functioning in older adults with amnestic mild cognitive impairment (aMCI), and (ii) to explore relationships of acute exercise-induced neurocognitive changes with changes in circulating levels of neuroprotective growth factors (e.g., BDNF, IGF-1, VEGF, and FGF-2, collectively termed 'exerkines'), elicited by different acute exercise modes. Sixty-six older adults with aMCI were recruited and randomly assigned to an aerobic exercise (AE) group, a resistance exercise (RE) group, or a non-exercise-intervention (control) group. The behavioral [i.e., accuracy rate (AR) and reaction time (RT)] and electrophysiological [i.e., event-related potential (ERP) P3 latency and amplitude collected from the Fz, Cz, and Pz electrodes] indices were simultaneously measured when participants performed a Flanker task at baseline and after either an acute bout of 30 min of moderate-intensity AE, RE or a control period. Blood samples were taken at three time points, one at baseline (T1) and two after an acute exercise intervention (T2 and T3: before and after cognitive task test, respectively). The results showed that the acute AE and RE not only improved behavioral (i.e., RTs) performance but also increased the ERP P3 amplitudes in the older adults with aMCI. Serum FGF-2 levels did not change with acute aerobic or resistance exercise. However, an acute bout of aerobic exercise significantly increased serum levels of BDNF and IGF-1 and tended to increase serum levels of VEGF in elderly aMCI individuals. Acute resistance exercise increased only serum IGF-1 levels. However, the exercise-induced elevated levels of these molecular markers returned almost to baseline levels in T3 (about 20 min after acute exercise). In addition, changes in the levels of neurotrophic and angiogenic factors were not correlated with changes in RTs and P3 amplitudes. The present findings of changes in neuroprotective growth factors and neurocognitive performances through acute AE or RE suggest that molecular and neural prerequisites for exercise-dependent plasticity are preserved in elderly aMCI individuals. However, the distinct pattern of changes in circulating molecular biomarkers induced by two different exercise modes in aMCI elderly individuals and the potentially interactive mechanisms of the effects of BDNF, IGF-1, and VEGF on amyloid-β provide a basis for future long-term exercise intervention to investigate whether AE relative to RE might be more effective in prevention/treatment of an early stage neurodegenerative disease.

Theta and Alpha Alterations in Amnestic Mild Cognitive Impairment in Semantic Go/NoGo Tasks

Growing evidence suggests that cognitive control processes are impaired in amnestic mild cognitive impairment (aMCI); however the nature of these alterations needs further examination. The current study examined differences in electroencephalographic theta and alpha power related to cognitive control processes involving response execution and response inhibition in 22 individuals with aMCI and 22 age-, sex-, and education-matched cognitively normal controls. Two Go/NoGo tasks involving semantic categorization were used. In the basic categorization task, Go/NoGo responses were made based on exemplars of a single car (Go) and a single dog (NoGo). In the superordinate categorization task, responses were made based on multiple exemplars of objects (Go) and animals (NoGo). Behavioral data showed that the aMCI group had more false alarms during the NoGo trials compared to controls. The EEG data revealed between group differences related to response type in theta (4–7 Hz) and low-frequency alpha (8–10 Hz) power. In particular, the aMCI group differed from controls in theta power during the NoGo trials at frontal and parietal electrodes, and in low-frequency alpha power during Go trials at parietal electrodes. These results suggest that alterations in theta power converge with behavioral deterioration in response inhibition, whereas alterations in low-frequency alpha power appear to precede behavioral changes in response execution. Both behavioral and electrophysiological correlates combined provide a more comprehensive characterization of cognitive control deficits in aMCI.

Characterizing cognitive inhibitory deficits in mild cognitive impairment

Individuals with mild cognitive impairment -MCI- show relative weaknesses in executive functioning (EF), as well as poor memory, but the inhibition-related mechanisms behind EF impairment in MCI have not been examined systematically. The aim of the present study was to systematically investigate inhibitory function in individuals with MCI to ascertain whether pathological aging is characterized by deficits in inhibitory processes and whether such impairment is confined to specific inhibition-related mechanisms. Tasks assessing inhibition-related functions - i.e. prepotent response inhibition (measured with the Color Stroop test), response to distracters (assessed using a text with distracters task), and resistance to proactive interference (assessed with a proactive interference task) - were administered to individuals with MCI and to healthy older controls. Individuals with MCI made more intrusion errors in the proactive interference task than controls, while the two groups' performance was comparable in prepotent response inhibition and response to distracters. This pattern of findings suggests that MCI is associated with specific inhibition problems.ty.

Interference Impacts Working Memory in Mild Cognitive Impairment

Mild cognitive impairment (MCI) is considered a transitional stage between healthy aging and dementia, specifically Alzheimer's disease (AD). The most common cognitive impairment of MCI includes episodic memory loss and difficulties in working memory (WM). Interference can deplete WM, and an optimal WM performance requires an effective control of attentional resources between the memoranda and the incoming stimuli. Difficulties in handling interference lead to forgetting. However, the interplay between interference and WM in MCI is not well-understood and needs further investigation. The current study investigated the effect of interference during a WM task in 20 MCIs and 20 healthy elder volunteers. Participants performed a delayed match-to-sample paradigm which consisted in two interference conditions, distraction and interruption, and one control condition without any interference. Results evidenced a disproportionate impact of interference on the WM performance of MCIs, mainly in the presence of interruption. These findings demonstrate that interference, and more precisely interruption, is an important proxy for memory-related deficits in MCI. Thus, the current findings reveal novel evidence regarding the causes of WM forgetting in MCI patients, associated with difficulties in the mechanisms of attentional control.

Interference and conflict monitoring in individuals with amnestic mild cognitive impairment: A structural study of the anterior cingulate cortex

Amnestic mild cognitive impairment (aMCI) is a clinical condition characterized by memory impairment in the absence of any other cognitive impairment and is commonly associated with high conversion to Alzheimer's disease. Recent evidence shows that executive functions and selective attention mechanisms could also be impaired in aMCI. In this study, we investigated performance differences (i.e., reaction times [RTs] and accuracy) between a group of aMCI participants and a group of age-matched healthy individuals on the attentional network task (ANT) focusing on situations with increased interference. In particular, we assessed the relationship between interference and conflict effects and grey matter volumes (GMVs) of the anterior cingulate cortex (ACC)/pre-supplementary motor area in the entire sample because of its crucial role in conflict monitoring. When compared with controls, aMCI participants were less accurate on the ANT, showing increased interference and conflict effects, but no differences in RTs. In addition, aMCI participants exhibited lower GMV in the ACC than controls. While better accuracy for interference and conflict effects was associated with an increase of GMV in the ACC for both groups, RTs from the interference effect were negatively correlated with GMV of the ACC only in aMCI participants. In other words, lower GMV values of the ACC were paralleled with significantly impaired performance in terms of interference resolution. In conclusion, our study suggests the presence of a selective impairment in interference and conflict monitoring in aMCI, which in turn is associated with decreased GMVs in the ACC.

Age differences in reactive strategies and execution time during choice stepping with visual interference

PURPOSE

We aimed to explore the effects of visual interference from a flanker task on a reactive strategy and execution speed of choice stepping among young and older adults.

METHODS

Twenty-two healthy young (21.9 ± 1.4 years) and 21 older participants (72.6 ± 4.9 years) were instructed to execute forward stepping as quickly and accurately as possible on the side indicated by a central arrow (←left vs. right→) of a visual cue during a neutral condition. During a flanker condition, participants were additionally required to ignore flanker arrows on each side of the central arrow (→→→→→ congruent or incongruent →→←→→). Errors in the direction of the initial weight transfer [anticipatory postural adjustment (APA) errors], step execution time, and divided phases (reaction, APA, and swing phases) were measured from the data of vertical force.

RESULTS

Incongruence had larger effects on step execution times and APA phase in older adults than in young adults, while incongruence had smaller effects on reaction phase in older adults than in young adults. Step execution times were prolonged for trials with APA errors relative to trials without those in both groups. Only older adults showed that step execution times during trials with APA errors increased prominently in the incongruent condition as compared to the other conditions.

CONCLUSION

Older adults might have a tendency to make hastier judgments, and might be vulnerable to potential motor program errors caused by an interference effect. Composite measurement of inhibition and stepping in a functional context may increase discriminative ability for age-related deficits in postural control.

Dissociable Effects of Dopamine on the Initial Capture and the Reactive Inhibition of Impulsive Actions in Parkinson's Disease

Dopamine plays a key role in a range of action control processes. Here, we investigate how dopamine depletion caused by Parkinson disease (PD) and how dopamine restoring medication modulate the expression and suppression of unintended action impulses. Fifty-five PD patients and 56 healthy controls (HCs) performed an action control task (Simon task). PD patients completed the task twice, once withdrawn from dopamine medications and once while taking their medications. PD patients experienced similar susceptibility to making fast errors in conflict trials as HCs, but PD patients were less proficient compared with HCs at suppressing incorrect responses. Administration of dopaminergic medications had no effect on impulsive error rates but significantly improved the proficiency of inhibitory control in PD patients. We found no evidence that dopamine precursors and agonists affected action control in PD differently. Additionally, there was no clear evidence that individual differences in baseline action control (off dopamine medications) differentially responded to dopamine medications (i.e., no evidence for an inverted U-shaped performance curve). Together, these results indicate that dopamine depletion and restoration therapies directly modulate the reactive inhibitory control processes engaged to suppress interference from the spontaneously activated response impulses but exert no effect on an individual's susceptibility to act on impulses.

Analysis of Choice Stepping with Visual Interference Can Detect Prolonged Postural Preparation in Older Adults with Mild Cognitive Impairment at High Risk of Falling

BACKGROUND/AIMS

We aimed to clarify postural control deficits in older adults with mild cognitive impairment (MCI) at high risk of falling by addressing the inhibitory process.

METHODS

This study involved 376 community-dwelling older adults with MCI. Participants were instructed to execute forward stepping on the side indicated by the central arrow while ignoring the 2 flanking arrows on each side (→→→→→, congruent, or →→←→→, incongruent). Initial weight transfer direction errors [anticipatory postural adjustment (APA) errors], step execution times, and divided phases (reaction, APA, and swing phases) were measured from vertical force data. Participants were categorized as fallers (n = 37) and non-fallers (n = 339) based on fall experiences in the last 12 months.

RESULTS

There were no differences in the step execution times, swing phases, step error rates, and APA error rates between groups, but fallers had a significantly longer APA phase relative to non-fallers in trials of the incongruent condition with APA errors (p = 0.005). Fallers also had a longer reaction phase in trials with the correct APA, regardless of the condition (p = 0.01).

CONCLUSION

Analyses of choice stepping with visual interference can detect prolonged postural preparation as a specific falling-associated deficit in older adults with MCI.

Neural correlates of attention-executive dysfunction in lewy body dementia and Alzheimer's disease

Attentional and executive dysfunction contribute to cognitive impairment in both Lewy body dementia and Alzheimer's disease. Using functional MRI, we examined the neural correlates of three components of attention (alerting, orienting, and executive/conflict function) in 23 patients with Alzheimer's disease, 32 patients with Lewy body dementia (19 with dementia with Lewy bodies and 13 with Parkinson's disease with dementia), and 23 healthy controls using a modified Attention Network Test. Although the functional MRI demonstrated a similar fronto-parieto-occipital network activation in all groups, Alzheimer's disease and Lewy body dementia patients had greater activation of this network for incongruent and more difficult trials, which were also accompanied by slower reaction times. There was no recruitment of additional brain regions or, conversely, regional deficits in brain activation. The default mode network, however, displayed diverging activity patterns in the dementia groups. The Alzheimer's disease group had limited task related deactivations of the default mode network, whereas patients with Lewy body dementia showed heightened deactivation to all trials, which might be an attempt to allocate neural resources to impaired attentional networks. We posit that, despite a common endpoint of attention-executive disturbances in both dementias, the pathophysiological basis of these is very different between these diseases.