Inhibitory Control Demands Research Articles

Explaining dual-action benefits: Inhibitory control and redundancy gains as complementary mechanisms.

Performing two actions at the same time usually results in performance costs. However, recent studies have also reported dual-action benefits: performing only one of two possible actions may necessitate the inhibition of the initially activated, but unwarranted second action, leading to single-action costs. Presumably, two preconditions determine the occurrence and strength of such inhibition-based dual-action benefits: (a) response set reductivity and (b) action prepotency. A nonreductive response set (given when all possible responses have to be kept in working memory) creates inhibitory action control demands in single-, but not in dual-action trials, and the ensuing inhibitory costs are proportional to the level of action prepotency (i.e., an action that is easy to initiate is hard to inhibit). Here, we set out to test this hypothesis by varying representational characteristics in working memory (namely response set reductivity and action prepotency) across four experiments. In Experiments 1 to 3, we compared (a) a randomized mode of trial presentation to (b) intermixed, but predictable fixed sequences of trial types and (c) a completely blocked mode of presentation. As expected, dual-action benefits were strongly present in Experiment 1, significantly reduced in Experiment 2, and absent in Experiment 3. This pattern of results matches our predictions derived from the assumption that differential inhibitory costs in single-action trials are the root cause of dual-action benefits. Crucially, however, the results of Experiment 4 (in which response conditions were only partially blocked) pointed to a secondary source of dual-action benefits that was inseparable from inhibition-based effects in previous experimental designs: semantic redundancy gains. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Effects of Cognitive and Physical Load of Acute Exercise on Inhibitory Control and Prefrontal Cortex Hemodynamics in Children.

Evidence suggests that acute exercise benefits inhibitory control, but it remains unclear how physical and cognitive load influence this ability in preadolescent children, when faced with different types of distractors. We examined their moderating effects along with changes in prefrontal cortex hemodynamics. Using a crossover design, 29 participants completed 10 min of exercise (with an interactive training wall) at 1) low physical and low cognitive load, 2) low physical and high cognitive load, 3) high physical and low cognitive load, and 4) high physical and high cognitive load in a randomized order. Before and after each condition, they performed a Standard and Affective Stroop task. During both tasks, the lateral oxygenation difference in the prefrontal cortex was measured by using functional near-infrared spectroscopy. For the Standard Stroop task, there was no effect of physical and cognitive load on performance. In contrast, exercise with low compared with high cognitive load was associated with a greater reduction of reaction time and increase in accuracy on the Affective Stroop task. This was accompanied by a decrease in lateral oxygenation difference on trials with low inhibitory control demands. Acute exercise with low compared with high cognitive demand benefits the ability to resolve emotional conflict, but the control over inhibition of nonemotional information remains unaffected. This effect of cognitive load is complemented by an increased efficiency of the left prefrontal cortex, when no emotional conflict resolution is required.

An event-related potential study of prepotent motor activity and response inhibition deficits in schizophrenia.

Response inhibition deficits in schizophrenia (SZ) are accompanied by reduced neural activities using event-related potential (ERP) measurements. However, it remains unclear whether the reduction in inhibition-related ERPs in SZ is contingent upon prepotent motor tendencies. This study aimed to examine the relationship between ERP markers of prepotent motor activity (lateralised readiness potential, LRP) and response inhibition (P3) by collecting behavioural and EEG data from healthy control (HC) subjects and SZ patients during a modified Go/No-Go task. A trial-averaged analysis revealed that SZ patients made more commission errors in No-Go trials compared with HC subjects, although there was no significant difference in the inhibition-related P3 effect (i.e. larger P3 amplitudes in No-Go compared with Go trials) between the two groups. Subsequently, No-Go trials were sorted and median-split into bins of stronger and weaker motor tendencies. Both HC and SZ participants made more commission errors when faced with stronger motor tendencies. The LRP-sorted P3 data indicated that HC subjects exhibited larger P3 effects in response to stronger motor tendencies, whereas this trial-by-trial association between P3 and motor tendencies was absent in SZ patients. Furthermore, SZ patients displayed diminished P3 effects in No-Go trials with stronger motor tendencies but not in trials with weaker motor tendencies, relative to HC subjects. Taken together, these findings suggest that SZ patients are unable to dynamically adjust inhibition-related neural activities in response to changing inhibitory control demands and emphasise the importance of considering prepotent motor activity when investigating the neural mechanisms underlying response inhibition deficits in SZ.

Effect of Preadolescents' Obesity on Inhibitory Control During Stop-Signal Task: A Functional EEG Network Study.

Objectives. Until now, limited knowledge remains regarding the association among childhood obesity, cognitive behavior, and brain networks. Utilizing a publicly available dataset, we aimed to investigate the relationships between childhood obesity and functional networks during the stop-signal task. Results. Given the huge conflict-monitoring and inhibitory control demands of the task, both enhanced network connectivity and properties were observed under the "No-go" compared to the "Go" condition for both obese and non-obese preadolescents. Obese preadolescents exhibited significantly increased frontal-parietal, frontal-occipital, and frontal-temporal linkages, as well as heightened network efficiency under both "Go" and "No-go" conditions compared to non-obese counterparts. Additionally, significant correlations were found between network connectivity and properties and preadolescents' body mass index (BMI), with their combination predicting BMI scores successfully. Conclusions. These findings support that childhood obesity is not simply a deviant habit with restricted physical health consequences, but rather associated with the atypical development of frontal-based networks involved in inhibitory control and cognitive performance.

Age-related effects on a novel dual-task Stroop paradigm.

The Stroop task is a traditional measure of cognitive control processes, yet results remain mixed when it comes to assessing age-related differences perhaps in part due to strategies participants use to reduce inhibitory control demands required for success on the task. Thirty-three older adults and 34 younger adults completed a Baseline (traditional, single-task) version of Stroop, followed by two, novel dual-task Stroop variants: Color-Dual (maintain secondary count of prespecified font color regardless the lexical content) and Lexical-Dual (maintain secondary count of prespecified word regardless the font color). With regard to Baseline performance, we predicted an Age x Trial Type interaction in which older adults would be selectively impaired on Incongruent trials compared to younger adults, and this prediction was supported. When we added secondary task demands, we predicted a Trial Type x Dual-Task Type interaction in which performance in the Lexical-Dual condition would be worse than performance in the Color-Dual condition. This prediction was also supported, suggesting that having a secondary task that activated the irrelevant stream of information required more inhibitory control. Finally, we also predicted that Age would interact with Trial Type and Dual-Task Type, which was partially supported in response latencies and more definitively supported in error rates. Overall, our results indicate that Stroop performance is differentially influenced by additional dual-task demands that potentially minimize strategy usage, which has implications for both young and older adult Stroop performance.

Transfer of working memory training to the inhibitory control of auditory distraction

Extended working memory training with the dual n-back task has been shown to improve performance on various untrained cognitive tasks, but previous findings were inconsistent with regard to the extent of such transfer. The dual n-back training task addresses multiple components of working memory as sequential information from two different stimulus modalities needs to be simultaneously encoded, maintained, continuously monitored and updated in working memory while irrelevant information needs to be inhibited. However, it is unclear which executive functions account for the observed transfer effects. In this study, the degree of inhibitory control required during training was manipulated by comparing two versions of the dual n-back task in which participants are asked to either respond or withhold a response on the less frequent trials when an item was identical to an item n trials back. Eight 80-min sessions of training with adaptive versions of both n-back tasks were shown to improve working memory updating. Moreover, in contrast to the standard n-back task, training on the inhibitory n-back task was found to reduce the interference in working memory produced by task-irrelevant speech. This result suggests that enhanced demand for inhibitory control during training enables transfer to the inhibition of distractor interference, whereas the standard n-back task primarily affects working memory updating. The training effects did not transfer to the inhibition of spatially incompatible responses in a Simon task, and it yielded no far transfer effects to untrained executive functions or measures of fluid intelligence.

The role of BMI on cognition following acute physical activity in preadolescent children.

There is an increasing prevalence of physical inactivity during childhood, concurrent with a rise in obesity rates, which is associated with a variety of health problems. However, the extent to which increased body mass index (BMI) influences acute physical activity (PA) benefits on cognition in childhood remains unknown. The aim of this study was to examine whether BMI influences the effects of acute PA on inhibitory control task performance. In a sample of 116 children pooled from four prior studies (ages 8-11; 51 females), demographic measures of age, sex, IQ, socioeconomic status, and aerobic fitness were considered along with BMI. Children participated in a counterbalanced, randomized crossover study, whereby they completed two different interventions; 20 minutes of treadmill walking (60-70% heart rate max) and restful reading (non-exercise control). Following each intervention, children performed a modified flanker task that manipulates inhibitory control demands. Correlations were conducted to determine the influence of demographic variables, fitness, and BMI on inhibitory control following each intervention. Subsequent hierarchical regression analyses were performed with significant demographic factors in the first step, aerobic fitness in the second step when significant, and BMI in the final step. Analyses indicated that children exhibited improved task performance (p's ≤ 0.001) and decreased interference (p=0.04) following the walking intervention compared to the restful reading control condition, indicating greater benefits following acute PA across task condition, with selectively greater benefits for the task condition requiring greater inhibitory control. Regression analyses revealed that greater BMI was related to decreased performance following acute PA (p=0.001); an association not observed following restful reading (p's ≥ 0.11). These results suggest that BMI negatively influences the effect of acute exercise on performance. Confirming previous studies, these findings indicate beneficial effects of acute PA on a flanker task that modulates inhibitory control requirements, but the effects are significantly greater for task conditions requiring greater amounts of inhibitory control. Further, these beneficial effects of PA appear to be blunted in children with higher BMI. These findings suggest that the acute benefits of PA on cognition may not be fully realized in children with higher BMI.

Nicotine dependence (trait) and acute nicotinic stimulation (state) modulate attention but not inhibitory control: converging fMRI evidence from Go-Nogo and Flanker tasks.

Cognitive deficits during nicotine withdrawal may contribute to smoking relapse. However, interacting effects of chronic nicotine dependence and acute nicotine withdrawal on cognitive control are poorly understood. Here we examine the effects of nicotine dependence (trait; smokers (n = 24) vs. non-smoking controls; n = 20) and acute nicotinic stimulation (state; administration of nicotine and varenicline, two FDA-approved smoking cessation aids, during abstinence), on two well-established tests of inhibitory control, the Go-Nogo task and the Flanker task, during fMRI scanning. We compared performance and neural responses between these four pharmacological manipulations in a double-blind, placebo-controlled crossover design. As expected, performance in both tasks was modulated by nicotine dependence, abstinence, and pharmacological manipulation. However, effects were driven entirely by conditions that required less inhibitory control. When demand for inhibitory control was high, abstinent smokers showed no deficits. By contrast, acutely abstinent smokers showed performance deficits in easier conditions and missed more trials. Go-Nogo fMRI results showed decreased inhibition-related neural activity in right anterior insula and right putamen in smokers and decreased dorsal anterior cingulate cortex activity on nicotine across groups. No effects were found on inhibition-related activity during the Flanker task or on error-related activity in either task. Given robust nicotinic effects on physiology and behavioral deficits in attention, we are confident that pharmacological manipulations were effective. Thus findings fit a recent proposal that abstinent smokers show decreased ability to divert cognitive resources at low or intermediate cognitive demand, while performance at high cognitive demand remains relatively unaffected, suggesting a primary attentional deficit during acute abstinence.

Dyscalculia and Typical Math Achievement Are Associated With Individual Differences in Number-Specific Executive Function.

Deficits in numerical magnitude perception characterize the mathematics learning disability developmental dyscalculia (DD), but recent studies suggest the relation stems from inhibitory control demands from incongruent visual cues in the nonsymbolic number comparison task. This study investigated the relation among magnitude perception during differing congruency conditions, executive function, and mathematics achievement measured longitudinally in children (n=448) from ages 4 to 13. This relation was investigated across achievement groups and as it related to mathematics across the full range of achievement. Only performance on incongruent trials related to achievement. Findings indicate that executive function in a numerical context, beyond magnitude perception or executive function in a non-numerical context, relates to DD and mathematics across a wide range of achievement.

The hard work of doing nothing: Accounting for inhibitory costs during multiple action control.

Performing many actions at the same time is usually associated with performance costs. However, recent eye-tracking evidence indicates that under specific conditions, inhibiting a secondary response can be more costly than executing it, resulting in dual-action benefits. Here, we show that performance gains due to the absence of inhibitory control demands in dual-action trials are not limited to saccades as a response modality. In our study, participants had to react to a visually presented directional word by either reading the stimulus aloud (vocal modality), pressing the corresponding arrow key on a keyboard (manual modality), or both. Crucially, manual error rates were significantly lower when participants had to respond with both a button press and naming than when they had to respond with naming only. More specifically, in vocal-only conditions we observed a significant percentage of false-positive manual responses, suggesting difficulties with inhibiting an unwarranted manual action. Thus, our results indicate that difficulties associated with single- (vs. dual-) action control are a stable, domain-general phenomenon that likely arises whenever execution-related demands are accompanied by substantial additional inhibitory control demands.

The acute effects of short bouts of exercise on inhibitory control in adolescents

PurposeThe main objective of the study was to investigate the effect of short bouts of aerobic exercise with various exercise intensities on inhibitory control using a flanker task in adolescents. MethodsThe study used a randomized controlled crossover design with 52 adolescents (mean age 17.7 years). On separate days, participants completed four exercise bouts consisting of three 5-min bouts at either 1) 50%, 2) 65%, or 3) 80% of maximal oxygen uptake reserve (VO2R), 4) one 30-min bout at 65% of VO2R, and 5) a control condition consisting of 30 min of seated rest. Conditions were counterbalanced between participants and completed at ∼4-day intervals. A modified Eriksen flanker task was conducted ∼8 min after each condition. ResultsCompared to the rest Higher response accuracy across stimuli type (i.e., congruent and incongruent) was observed after five minutes of aerobic exercise regardless of exercise intensity, and shorter reaction time (RT) was observed following 80% of VO2R compared to the rest condition and compared to the remaining 5-min conditions. No selective effects on inhibitory control were observed. ConclusionThe results demonstrated that short bouts of aerobic exercise may be a time efficient approach for enhancing general cognitive processes required during performance of tasks that modulate inhibitory control demands.

Time Course of Brain Network Reconfiguration Supporting Inhibitory Control.

Hemodynamic research has recently clarified key nodes and links in brain networks implementing inhibitory control. Although fMRI methods are optimized for identifying the structure of brain networks, the relatively slow temporal course of fMRI limits the ability to characterize network operation. The latter is crucial for developing a mechanistic understanding of how brain networks shift dynamically to support inhibitory control. To address this critical gap, we applied spectrally resolved Granger causality (GC) and random forest machine learning tools to human EEG data in two large samples of adults (test sample n = 96, replication sample n = 237, total N = 333, both sexes) who performed a color-word Stroop task. Time-frequency analysis confirmed that recruitment of inhibitory control accompanied by slower behavioral responses was related to changes in theta and alpha/beta power. GC analyses revealed directionally asymmetric exchanges within frontal and between frontal and parietal brain areas: top-down influence of superior frontal gyrus (SFG) over both dorsal ACC (dACC) and inferior frontal gyrus (IFG), dACC control over middle frontal gyrus (MFG), and frontal-parietal exchanges (IFG, precuneus, MFG). Predictive analytics confirmed a combination of behavioral and brain-derived variables as the best set of predictors of inhibitory control demands, with SFG theta bearing higher classification importance than dACC theta and posterior beta tracking the onset of behavioral response. The present results provide mechanistic insight into the biological implementation of a psychological phenomenon: inhibitory control is implemented by dynamic routing processes during which the target response is upregulated via theta-mediated effective connectivity within key PFC nodes and via beta-mediated motor preparation.SIGNIFICANCE STATEMENT Hemodynamic neuroimaging research has recently clarified regional structures in brain networks supporting inhibitory control. However, due to inherent methodological constraints, much of this research has been unable to characterize the temporal dynamics of such networks (e.g., direction of information flow between nodes). Guided by fMRI research identifying the structure of brain networks supporting inhibitory control, results of EEG source analysis in a test sample (n = 96) and replication sample (n = 237) using effective connectivity and predictive analytics strategies advance a model of inhibitory control by characterizing the precise temporal dynamics by which this network operates and exemplify an approach by which mechanistic models can be developed for other key psychological processes.

Modulation of inhibitory control by prefrontal anodal tDCS: A crossover double-blind sham-controlled fMRI study.

Prefrontal anodal transcranial direct current stimulation (tDCS) has been proposed as a potential approach to improve inhibitory control performance. The functional consequences of tDCS during inhibition tasks remain, however, largely unresolved. We addressed this question by analyzing functional magnetic resonance imaging (fMRI) recorded while participants completed a Go/NoGo task after right-lateralized prefrontal anodal tDCS with a crossover, sham-controlled, double-blind experimental design. We replicated previous evidence for an absence of offline effect of anodal stimulation on Go/NoGo performance. The fMRI results revealed a larger increase in right ventrolateral prefrontal activity for Go than NoGo trials in the anodal than sham condition. This pattern suggests that tDCS-induced increases in cortical excitability have larger effects on fMRI activity in regions with a lower task-related engagement. This was the case for the right prefrontal cortex in the Go condition in our task because while reactive inhibition was not engaged during execution trials, the unpredictability of the demand for inhibitory control still incited an engagement of proactive inhibition. Exploratory analyses further revealed that right prefrontal stimulation interacted with task-related functional demands in the supplementary motor area and the thalamus. Our collective results emphasize the dependency of offline tDCS functional effects on the task-related engagement of the stimulated areas and suggest that this factor might partly account for the discrepancies in the functional effects of tDCS observed in previous studies.

A Large-Scale Reanalysis of Childhood Fitness and Inhibitory Control

The aim of this study was to reanalyze several datasets to investigate the relation of childhood aerobic fitness on cognition via a number of task performance outcomes and the P3 event-related brain potential component during a modified flanker task, which modulates inhibitory control demands. In a sample of 702 preadolescent children (ages 8–11; 342 females), demographic measures of age, sex, IQ, socioeconomic status, and pubertal status were considered along with aerobic fitness (i.e., VO2peak%). Correlational analyses were conducted to determine the influence of the demographic variables and aerobic fitness on inhibitory control outcomes of response accuracy, reaction time (RT), response variability, interference control, cognitive strategies, P3 amplitude, and P3 latency. Subsequent hierarchical regression analyses were performed with significant demographic factors in the first step and aerobic fitness in the final step. Results indicated that after accounting for significant demographic variables specific to each dependent outcome, aerobic fitness was positively related to response accuracy, with no such relations observed for response speed (RT) for congruent and incongruent conditions of the flanker task. However, greater aerobic fitness was associated with less RT variability and lower accuracy interference. In terms of cognitive strategies, greater fitness was also associated with better discrimination accuracy as well as faster and better quality of information uptake. Across a 15-site region of interest around the topographic maximum, findings indicated that aerobic fitness was positively associated with larger P3 amplitude during incongruent trials. No such relation was observed for P3 latency. Relying on a large aggregated dataset, we demonstrated that aerobic fitness may be particularly beneficial to the allocation of attentional resources, as indexed by P3 amplitude as well as response accuracy and intraindividual variability. These findings, while generalized across inhibitory control demands, were especially related to trials that required greater amounts of inhibition. Thus, aerobic fitness may benefit brain and behavioral outcomes during childhood and has public health implications for the role of childhood physical activity on aspects of cognition that underlie scholastic performance and lifelong effective functioning.

Inhibition and behavioral self-regulation: An inextricably linked couple in preschool years

A modified version of the flanker task was used to investigate how children deal with increasing inhibitory control demands. Additional variables such as age, cue salience and behavioral regulation were also considered in the present research. Preschoolers and first graders alike, showed a performance decline once inhibitory control demands increased. When taking behavioral regulation skills into account, an age-related interaction effect was found: Compared to their peers with high behavioral regulation skills, preschoolers with low to moderate behavioral regulation skills showed a weaker performance when faced with increased inhibitory control demands. No such effects were found for first graders. The results suggest that in particular in preschool years inhibition and behavioral regulation are highly intertwined.

Prepotent motor activity and inhibitory control demands in different variants of the go/no-go paradigm.

Inhibitory control enables humans to stop prepotent motor activity, and is commonly studied using go/no-go or stop-signal tasks. In stop-signal tasks, prepotent motor activity is elicited by delaying stop signals relative to go signals. In go/no-go tasks, however, trials include only one signal-go or no-go. Hence, prepotent motor activity has to be ensured differently-for example, by using rare no-go trials and short trial durations. However, a literature survey shows that ∼40% of studies use equiprobable go/no-go trials and ∼20% use long stimulus-stimulus intervals (> 4 s). It is unclear whether such slow-paced, equiprobable go/no-go tasks elicit prepotent motor activity and probe inhibitory control. We recorded EEG during four go/no-go tasks, varying in no-go probability and trial duration. We quantified prepotent motor activity on successfully inhibited no-go trials using the lateralized readiness potential. Only fast-paced go/no-go tasks with rare no-go trials reliably evoked such activity. We then used a stop-signal task and independent component analysis to isolate an established neural signature of inhibitory control, and investigated this signature's activity across the go/no-go tasks. Across tasks, increased prepotent motor activity on individual no-go trials was accompanied by greater frontocentral P3 amplitudes, confirming it as an index of inhibition. Crucially, this inhibition-related activity showed a 75% reduction in slow-paced, equiprobable go/no-go tasks compared to fast-paced, rare no-go versions. Therefore, since many common go/no-go task configurations do not reliably evoke prepotent motor activity, their inhibitory requirements are greatly reduced. This has major implications for the usage of go/no-go tasks in psychological experiments.

Successfully controlling intrusive memories is harder when control must be sustained

ABSTRACTAfter unpleasant events, people often experience intrusive memories that undermine their peace of mind. In response, they often suppress these unwanted memories from awareness. Such efforts may fail, however, when inhibitory control demands are high due to the need to sustain control, or when fatigue compromises inhibitory capacity. Here we examined how sustained inhibitory demand affected intrusive memories in the Think/No-Think paradigm. To isolate intrusions, participants reported, trial-by-trial, whether their preceding attempt to suppress retrieval had triggered retrieval of the memory they intended to suppress. Such counter-intentional retrievals provide a laboratory model of the sort of involuntary retrieval that may underlie intrusive memories. Using this method, we found that longer duration trials increased the probability of an intrusion. Moreover, on later No-Think trials, control over intrusions suddenly declined, with longer trial durations triggering more relapses of items that had been previously been purged. Thus, the challenges of controlling retrieval appear to cause a decline in control over time, due to a change in state, such as fatigue. These findings raise the possibility that characteristics often true of people with psychiatric disorders – such as compromised sleep, and increased demand on control – may contribute to difficulties in suppressing intrusive memories.

Effects of a no-go Task 2 on Task 1 performance in dual - tasking: From benefits to costs

When two tasks are combined in a dual-task experiment, characteristics of Task 2 can influence Task 1 performance, a phenomenon termed the backward crosstalk effect (BCE). Besides instances depending on the (spatial) compatibility of both responses, a particularly interesting example was introduced by Miller (2006): If Task 2 was a no-go task (i.e., one not requiring any action at all), responses were slowed in Task 1. Subsequent work, however, also reported the opposite result-that is, faster Task 1 responses in cases of no-go Task 2 trials. We report three experiments aiming to more precisely identify the conditions under which a no-go Task 2 facilitates or impedes Task 1 performance. The results suggest that an adverse no-go BCE is only observed when the Task 2 response(s) are sufficiently prepared in advance, yielding strong inhibitory control demands for Task 2 that eventually hamper Task 1 processing as well (i.e., inhibitory costs). If this is not the case, encountering a no-go Task 2 trial facilitates Task 1 performance, suggesting that the underlying task representation is reduced to a single - task. These results are discussed in the context of other recent work on BCEs and of recently suggested accounts of the no-go BCE.

Effects of aging on the relationship between cognitive demand and step variability during dual-task walking.

A U-shaped relationship between cognitive demand and gait control may exist in dual-task situations, reflecting opposing effects of external focus of attention and attentional resource competition. The purpose of the study was twofold: to examine whether gait control, as evaluated from step-to-step variability, is related to cognitive task difficulty in a U-shaped manner and to determine whether age modifies this relationship. Young and older adults walked on a treadmill without attentional requirement and while performing a dichotic listening task under three attention conditions: non-forced (NF), forced-right (FR), and forced-left (FL). The conditions increased in their attentional demand and requirement for inhibitory control. Gait control was evaluated by the variability of step parameters related to balance control (step width) and rhythmic stepping pattern (step length and step time). A U-shaped relationship was found for step width variability in both young and older adults and for step time variability in older adults only. Cognitive performance during dual tasking was maintained in both young and older adults. The U-shaped relationship, which presumably results from a trade-off between an external focus of attention and competition for attentional resources, implies that higher-level cognitive processes are involved in walking in young and older adults. Specifically, while these processes are initially involved only in the control of (lateral) balance during gait, they become necessary for the control of (fore-aft) rhythmic stepping pattern in older adults, suggesting that attentional resources turn out to be needed in all facets of walking with aging. Finally, despite the cognitive resources required by walking, both young and older adults spontaneously adopted a "posture second" strategy, prioritizing the cognitive task over the gait task.

DRD2 Schizophrenia-Risk Allele Is Associated With Impaired Striatal Functioning in Unaffected Siblings of Schizophrenia Patients.

A recent Genome-Wide Association Study showed that the rs2514218 single nucleotide polymorphism (SNP) in close proximity to dopamine receptor D2 is strongly associated with schizophrenia. Further, an in silico experiment showed that rs2514218 has a cis expression quantitative trait locus effect in the basal ganglia. To date, however, the functional consequence of this SNP is unknown. Here, we used functional Magnetic resonance imaging to investigate the impact of this risk allele on striatal activation during proactive and reactive response inhibition in 45 unaffected siblings of schizophrenia patients. We included siblings to circumvent the illness specific confounds affecting striatal functioning independent from gene effects. Behavioral analyses revealed no differences between the carriers (n= 21) and noncarriers (n= 24). Risk allele carriers showed a diminished striatal response to increasing proactive inhibitory control demands, whereas overall level of striatal activation in carriers was elevated compared to noncarriers. Finally, risk allele carriers showed a blunted striatal response during successful reactive inhibition compared to the noncarriers. These data are consistent with earlier reports showing similar deficits in schizophrenia patients, and point to a failure to flexibly engage the striatum in response to contextual cues. This is the first study to demonstrate an association between impaired striatal functioning and the rs2514218 polymorphism. We take our findings to indicate that striatal functioning is impaired in carriers of the DRD2 risk allele, likely due to dopamine dysregulation at the DRD2 location.