Examining the Interactions Between Expectations and tDCS Effects on Motor and Cognitive Performance

Background: Despite a growing literature and commercial market, the effectiveness of transcranial direct current stimulation (tDCS) remains questionable. Notably, studies rarely examine factors such as expectations of outcomes, which may influence tDCS response through placebo-like effects. Here we sought to determine whether expectations could influence the behavioral outcomes of a tDCS intervention.Methods: Through an initial study and self-replication, we recruited 121 naïve young adults 18–34 years of age (M = 21.14, SD = 3.58; 88 women). We evaluated expectations of tDCS and of motor and cognitive performance at three times: (i) at baseline; (ii) after being primed to have High or Low expectations of outcomes; and (iii) after a single session of sham-controlled anodal tDCS over the left or right motor cortex. Before and after stimulation, participants performed the Grooved Pegboard Test and a choice reaction time task as measures of motor dexterity, response time, and response inhibition.Results: Repeated measures ANOVA revealed that participants had varying, largely uncertain, expectations regarding tDCS effectiveness at baseline. Expectation ratings significantly increased or decreased in response to High or Low priming, respectively, and decreased following the intervention. Response times and accuracy on motor and cognitive measures were largely unaffected by expectation or stimulation conditions. Overall, our analysis revealed no effect attributable to baseline expectations, belief of group assignment, or experimental condition on behavioral outcomes. Subjective experience did not differ based on expectation or stimulation condition.Conclusions: Our results suggest no clear effects of tDCS or of expectations on our performance measures, highlighting the need for further investigations of such stimulation methods

Personal semantics: Is it distinct from episodic and semantic memory? An electrophysiological study of memory for autobiographical facts and repeated events in honor of Shlomo Bentin

Declarative memory is thought to consist of two independent systems: episodic and semantic. Episodic memory represents personal and contextually unique events, while semantic memory represents culturally-shared, acontextual factual knowledge. Personal semantics refers to aspects of declarative memory that appear to fall somewhere in between the extremes of episodic and semantic. Examples include autobiographical knowledge and memories of repeated personal events. These two aspects of personal semantics have been studied little and rarely compared to both semantic and episodic memory. We recorded the event-related potentials (ERPs) of 27 healthy participants while they verified the veracity of sentences probing four types of questions: general (i.e., semantic) facts, autobiographical facts, repeated events, and unique (i.e., episodic) events. Behavioral results showed equivalent reaction times in all 4 conditions. True sentences were verified faster than false sentences, except for unique events for which no significant difference was observed. Electrophysiological results showed that the N400 (which is classically associated with retrieval from semantic memory) was maximal for general facts and the LPC (which is classically associated with retrieval from episodic memory) was maximal for unique events. For both ERP components, the two personal semantic conditions (i.e., autobiographical facts and repeated events) systematically differed from semantic memory. In addition, N400 amplitudes also differentiated autobiographical facts from unique events. Autobiographical facts and repeated events did not differ significantly from each other but their corresponding scalp distributions differed from those associated with general facts. Our results suggest that the neural correlates of personal semantics can be distinguished from those of semantic and episodic memory, and may provide clues as to how unique events are transformed to semantic memory

Computerized attention training for childhood behavior disorders: a non-pharmaceutical treatment approach

Cognitive training paradigms constitute a budding field in both research and the commercial market. Engulfed in hype, computerized training programs are particularly enticing in the "Informatics Era" and have fostered the development of increasingly complex programs aiming to improve cognitive function. With the promise of enhancing skills such as attention and memory, cognitive training programs appeal particularly to atypically developing individuals as a non-pharmaceutical alternative to treatment. Such claims have led both professionals and laypersons to question the effectiveness of commercially-available products. In our critical review, we investigate the potential benefits of various cognitive training paradigms and evaluate the evidence supporting or discounting popular programs in specific populations. This investigation reveals that, while certain forms of training demonstrate benefits for improving certain cognitive skills, many programs require more rigorous scientific evaluation to validate their claims. Our experimental piece studies the effectiveness of an adaptation on one scientifically-validated form of cognitive training: computerized attention training. We seek to determine the clinical effectiveness of this type of program in children with common impulse-control disorders, including attention deficit hyperactivity disorder, oppositional defiance disorder, and conduct disorder. Findings from this study suggest that, while subjective ratings of behavior may improve as a result of training, children may require prolonged training periods to benefit on objective ratings of attention and intelligence. Future studies remain to elucidate the effectiveness and sustainability of such training programs when administered over longer periods, as well as more subtle changes detected through neuroimaging.L'entrainement cognitif de l'attention est un domaine qui prend de plus en plus d'ampleur à la fois dans le monde de la recherche et dans le marché commercial. Couverts de publicité, des programmes informatiques d'entrainement mettent sur pieds des logiciels de plus en plus complexes ayant pour cible le développement des fonctions cognitives. Promettant d'améliorer des aptitudes telles que la capacité mnémonique ou l'attention, ces programmes d'entrainement cognitif sont particulièrement attirants pour des individus atteints de problèmes développementaux puisqu'ils semblent offrir une alternative aux traitements pharmaceutiques. Ces promesses ont cependant conduit les professionnels de la santé, ainsi que le public, à s'interroger sur l'efficacité réelle des produits disponibles sur le marché. Dans notre revue critique, nous tentons de saisir les bienfaits que divers programmes d'entrainement cognitif peuvent apporter, et nous évaluons les preuves en faveur ou en défaveur des programmes d'entrainement cognitif disponibles sur le marché. Nos recherches indiquent que, bien que certains types d'entrainement soient source de bienfaits cognitifs, plusieurs programmes promettent des effets qui ne sont pas soutenus par des preuves scientifiques suffisantes. Dans notre projet de recherche, nous étudions l'efficacité d'une adaptation d'un programme d'entrainement cognitif ayant été validé scientifiquement : l'entrainement de l'attention par programme informatisé. Nous tentons de déterminer l'efficacité clinique de ce type d'intervention chez les jeunes enfants atteints de troubles d'habitudes et d'impulsions, entre autre chez les enfants atteints du trouble de déficit de l'attention avec hyperactivité, du trouble oppositionnel avec provocation ou du trouble des conduites. Les résultats de notre étude révèlent que, bien que l'évaluation subjective du comportement de l'enfant semble s'améliorer suite à l'entrainement de l'attention, il est possible que les enfants aient besoin de séances d'entrainement prolongées afin de démontrer des bienfaits pouvant être mesurés objectivement, tels qu'une augmentation de l'intelligence ou de l'attention. Les études à venir devront évaluer l'efficacité et la stabilité à long terme des effets de ces programmes et enquêter la possibilité qu'un entrainement soutenu provoque des changements plus précis pouvant éventuellement être détectés par des techniques d'imagerie cérébrale

Postural responses to multidirectional perturbations to the hand during stance

Humans are easily able to maintain their balance while applying force with their hands to move or stabilize objects. Based on Newton\u27s laws, the applied force must be counteracted by ground reaction force (GRF) to maintain balance. However, because the GRF is partitioned between the two legs there is no unique solution. Furthermore, central nervous system (CNS) can employ an infinite number of muscle activation patterns to achieve ground reaction force (GRF) vectors needed to satisfy both the task-level goal and balance. This study examines the postural response when hand position must remain stable as an external force is applied in different directions during normal stance. We investigated whether the CNS uses an invariant strategy to compensate for forces acting in different directions

Visual Event-Related Potentials in Mild Cognitive Impairment and Alzheimer's Disease: A Literature Review

BACKGROUND: Cognitive deficits are correlated with increasing age and become more pronounced for people with mild cognitive impairment (MCI) and dementia caused by Alzheimer's disease (AD). Conventional methods to diagnose cognitive decline (i.e., neuropsychological testing and clinical judgment) can lead to false positives. Tools such as electroencephalography (EEG) offer more refined, objective measures that index electrophysiological changes associated with healthy aging, MCI, and AD. OBJECTIVE: We sought to review the EEG literature to determine whether visual event-related potentials (ERPs) can distinguish between healthy aging, MCI, and AD. METHOD: We searched Medline and PyscInfo for articles published between January 2005 and April 2018. Articles were considered for review if they included participants aged 60+ who were healthy older adults or people with MCI and AD, and examined at least one visually elicited ERP component. RESULTS: Our search revealed 880 records, of which 34 satisfied the inclusion criteria. All studies compared cognitive function between at least two of the three groups (healthy older adults, MCI, and AD). The most consistent finding