When the ignored gets bound: sequential effects in the flanker task

Recent research on attentional control processes in the Eriksen flanker task has focused on the so-called congruency sequence effect a.k.a. the Gratton effect, which is the observation of a smaller flanker interference effect after incongruent than after congruent trials. There is growing support for the view that in this paradigm, the congruency sequence effect is due to repetition of the target or response across trials. Here, results from two experiments are presented that separate the contributions of target, flanker, and response repetition. The results suggest that neither response repetition alone nor conflict is necessary to produce the effect. Instead, the data reveal that only flanker repetition is sufficient to produce congruency sequence effects. In other words, information that is associated with a response irrespective whether it is relevant for the current trial is bound to response representations. An account is presented in which the fleeting event files are the activated part of the task set in which flankers, targets, and response representations are associatively linked and updated through conflict-modulated reinforcement learning

Short-term memory as a working memory control process

Aben et al. (2012) take issue with the unthoughtful use of the terms “working memory” (WM) and “short-term memory” (STM) in the cognitive and neuroscientific literature. Whereas I agree that neuroscientists using the term WM to refer to sustained neural activation and cognitive psychologists using the terms interchangeably reflects that the field has lost control over its own dictionary, the recommendations to develop more tasks does not seem to get to the heart of the matter. Here, I argue in favor of a theoretical approach to the constructs of WM and STM, as the terms have become as impure as the tasks that purport to measure the constructs

Computational investigations of cognitive impairment in Huntington's Disease

Book synopsis: Huntington's Disease is one of the well-studied neurodegenerative conditions, a quite devastating and currently incurable one. It is a brain disorder that causes certain types of neurons to become damaged, causing various parts of the brain to deteriorate and lose their function. This results in uncontrolled movements, loss of intellectual capabilities and behavioural disturbances. Since the identification of the causative mutation, there have been many significant developments in understanding the cellular and molecular perturbations. This book, "Huntington's Disease - Core Concepts and Current Advances", was prepared to serve as a source of up-to-date information on a wide range of issues involved in Huntington's Disease. It will help the clinicians, health care providers, researchers, graduate students and life science readers to increase their understanding of the clinical correlates, genetic aspects, neuropathological findings, cellular and molecular events and potential therapeutic interventions involved in HD. The book not only serves reviewed fundamental information on the disease but also presents original research in several disciplines, which collectively provide comprehensive description of the key issues in the area

A computational approach to developing cost-efficient adaptive-threshold algorithms for EEG neuro feedback

In electroencephalography (EEG) neurofeedback protocols, trainees receive feedback about the spectral power of the target brain wave oscillation and are tasked to increase or decrease this feedback signal compared to a predetermined threshold. In a recent computational analysis of a neurofeedback protocol it was shown that the placement of the threshold has a major impact on the learning rate and that placed too low or too high leads to no learning or even unlearning, respectively. However, the optimal threshold placement is not known in real-life scenarios. Here, these analyses were extended to assess whether an adaptive-mean threshold procedure could lead to faster learning curves. The results indicate that such a procedure is indeed superior to a fixed-mean procedure and that the distribution of asymptotic EEG power values converges to that obtained with the optimal-threshold procedure. Surprisingly, the adaptive-mean procedure leads to thresholds that are higher than the optimal one, which is explained through the increase in threshold lagging behind the increase in the likelihood of activation of the target neurons. To date, no computational model was used to compute the cost-efficiency of EEG neurofeedback procedures. The current simulation (within the specific reinforcement schedule) demonstrated a 35% reduction in training time, which could translate into sizeable financial savings. This study demonstrates the utility of computational methods in neurofeedback research and opens up further developments that tackle specific neurofeedback protocols to assess their real-life cost- efficiency

Semantic similarity dissociates shortfrom long-term recency effects: testing a neurocomputational model of list memory

The finding that recency effects can occur not only in immediate free recall (i.e., short-term recency) but also in the continuous-distractor task (i.e., long-term recency) has led many theorists to reject the distinction between short- and long-term memory stores. Recently, we have argued that long-term recency effects do not undermine the concept of a short-term store, and we have presented a neurocomputational model that accounts for both short- and long-term recency and for a series of dissociations between these two effects. Here, we present a new dissociation between short- and long-term recency based on semantic similarity, which is predicted by our model. This dissociation is due to the mutual support between associated items in the short-term store, which takes place in immediate free recall and delayed free recall but not in continuous-distractor free recall

Mechanisms of neurofeedback: a computation-theoretic approach

Neurofeedback training is a form of brain training in which information about a neural measure is fed back to the trainee who is instructed to increase or decrease the value of that particular measure. This paper focuses on electroencephalography (EEG) neurofeedback in which the neural measures of interest are the brain oscillations. To date, the neural mechanisms that underlie successful neurofeedback training are still unexplained. Such an understanding would benefit researchers, funding agencies, clinicians, regulatory bodies, and insurance firms. Based on recent empirical work, an emerging theory couched firmly within computational neuroscience is proposed that advocates a critical role of the striatum in modulating EEG frequencies. The theory is implemented as a computer simulation of peak alpha upregulation, but in principle any frequency band at one or more electrode sites could be addressed. The simulation successfully learns to increase its peak alpha frequency and demonstrates the influence of threshold setting – the threshold that determines whether positive or negative feedback is provided. Analyses of the model suggest that neurofeedback can be likened to a search process that uses importance sampling to estimate the posterior probability distribution over striatal representational space, with each representation being associated with a distribution of values of the target EEG band. The model provides an important proof of concept to address pertinent methodological questions about how to understand and improve EEG neurofeedback success

An Analysis of the Working Memory Capacity Paradox

Abstract In the literature on working memory (WM), a paradox exists according to which very similar memory tasks provide support for very different estimates of working memory capacity. The current paper analyses the conflicting estimates of a capacity of 4+/-1 with a capacity of 1. To this end a dynamic process model of short-term recognition is used to generate data to which exponential speed-accuracy trade-off functions are fitted. The results show that even though the process model has a capacity larger than one, the exponential SAT functions indicate a one-chunk hypothesis. Further nested modeling reveals, counter to the dominant belief, that retrieval rate is insensitive to differences in WM capacity. The resolution of the WM capacity paradox lies in the choice of dependent measure

Increased physical fitness is associated with higher executive functioning in people with dementia

Physical fitness (PF) has been associated with improved cognition in older age, but less is known about its effects on different cognitive domains in individuals diagnosed with dementia. We explored the associations between PF and cognitive performance in 40 healthy elderly and 30 individuals with dementia. Participants completed a battery of standardized cognitive tests (Mini-Mental State Exam, Verbal Fluency, Prospective and Retrospective Memory Questionnaire, Clock Drawing, and California Verbal Learning Test) and were classified into high versus low levels of PF based on their score on the Physical Fitness Questionnaire. Analyses took into account age, gender, education, occupation, head injury, Internet use, brain training, and past levels of exercise and revealed overall benefits of PF, in particular for the people with dementia. Discriminant analysis showed high accuracy of reclassification, with most errors being due to the misclassification of dementia cases as healthy when they had high PF. The first discriminant function accounted for 83% of the variance. Using individual estimates of this function, which reflected global cognitive performance, confirmed the beneficial role of PF in dementia, even when taking into account age, past level of exercise, and the number of years since the dementia diagnosis. Finally, univariate analyses confirmed the differential sensitivity of the cognitive tests, with MMSE and clock drawing showing reliable interaction effects. This work shows that PF is associated with a reduced level of cognitive deterioration expected with dementia, especially in executive functioning and provides empirical support for the cognitive benefits of interventions promoting PF for individuals with dementia

Differential effects of angry faces on working memory updating in younger and older adults

Research suggests that cognition-emotion interactions change with age. Here, younger and older adults completed a 2-back task, and the effects of negative stimuli were analyzed as a function of their status in the n-back sequence. Older adults were found to benefit more from angry than from neutral probes relative to younger adults. However, they were slower when lures were angry and less accurate when lures and probes had the same emotion. The results suggest that recollection of the n-back sequence was reduced in older adults, making them more susceptible to the facilitating and impairing effects of negative emotion