Oscillatory Control over Representational States in Working Memory

In the visual world, attention is guided by perceptual goals activated in visual working memory (VWM). However, planning multiple-task sequences also requires VWM to store representations for future goals. These future goals need to be prevented from interfering with the current perceptual task. Recent findings have implicated neural oscillations as a control mechanism serving the implementation and switching of different states of prioritization of VWM representations. We review recent evidence that posterior alpha-band oscillations underlie the flexible activation and deactivation of VWM representations and that frontal delta-to-theta-band oscillations play a role in the executive control of this process. That is, frontal delta-to-theta appears to orchestrate posterior alpha through long-range oscillatory networks to flexibly set up and change VWM states during multitask sequences

Mobile EEG reveals functionally dissociable dynamic processes supporting real-world ambulatory obstacle avoidance : evidence for early proactive control

This work is supported by a scholarship from the University of Stirling and a reseach grant from SINAPSE (Scottish Imaging Network: A Platform for Scientific excellence). GL is supported by the Wellcome Trust [209209/Z/17/Z].The ability to safely negotiate the world on foot takes humans years to develop, reflecting the huge cognitive demands associated with real‐time planning and control of walking. Despite the importance of walking, methodological limitations mean that surprisingly little is known about the neural and cognitive processes that support ambulatory motor control. Here, we report mobile EEG data recorded from thirty‐two healthy young adults during real‐world ambulatory obstacle avoidance. Participants walked along a path while stepping over expected and unexpected obstacles projected on the floor, allowing us to capture the dynamic oscillatory response to changes in environmental demands. Compared to obstacle‐free walking, time‐frequency analysis of the EEG data revealed clear frontal theta and centro‐parietal beta power neural markers of proactive and reactive forms of movement control (occurring before and after crossing an obstacle). Critically, the temporal profile of changes in frontal theta allowed us to arbitrate between early selection and late adaptation mechanisms of proactive control. Our data show that motor plans are updated as soon as an upcoming obstacle appears, rather than when the obstacle is reached. In addition, regardless of whether motor plans required updating, a clear beta rebound was present after obstacles were crossed, reflecting the resetting of the motor system. Overall, mobile EEG recorded during real‐world walking provides novel insight into the cognitive and neural basis of dynamic motor control in humans, suggesting new routes to the monitoring and rehabilitation of motor disorders such as dyspraxia and Parkinson’s disease.Publisher PDFPeer reviewe

Context-oriented performance biases in cognitive control

Cognitive control, the ability to guide goal-directed behavior, is comprised of a variety of cognitive components functioning in a dynamic balance. Control adjustments are commonly cast as temporally local adaptations reflecting recently encountered task conflict; however, global control processes representing broad task expectancies are relatively unexplored. In an electroencephalographic (EEG) study of a prepotent response inhibition task, we tested whether the congruency effect, where performance tends to be worse for trials involving controlled processes, would be impacted by the overall task context as defined by trial-type proportions. As the proportion of high-control trials increased, we observed that accuracy improved in a more demanding, high-control condition while worsening in the less demanding, low-control condition. More interestingly, this tradeoff resulted in a reversed congruency effect in accuracy for task contexts dominated by high control trials. Furthermore, delay period EEG spectral power in the alpha-frequency band (i.e., 9-13 Hz)—a putative inhibitory mechanism (Klimesch, 2012)—was found to modulate with the task. A significant trial condition by task context interaction revealed a positive monotonic association between accuracy and induced alpha synchrony in low control task contexts with a negative monotonic association in the high control context. Our behavioral results are consistent with cognitive control adjustments occurring through an ‘adaptation-by-binding’ which posits that the continuous arousal resulting from a high conflict context strengthens active task and sensory representations even if disadvantageous to automatic processes (Verguts & Notebaert, 2009). Further, ongoing synchronous cortical alpha-band oscillations could serve as a potential neural mechanism by which this binding effect is achieved

Striatal GABA-MRS predicts response inhibition performance and its cortical electrophysiological correlates

Response inhibition processes are important for performance monitoring and are mediated via a network constituted by different cortical areas and basal ganglia nuclei. At the basal ganglia level, striatal GABAergic medium spiny neurons are known to be important for response selection, but the importance of the striatal GABAergic system for response inhibition processes remains elusive. Using a novel combination of behavior al, EEG and magnetic resonance spectroscopy (MRS) data, we examine the relevance of the striatal GABAergic system for response inhibition processes. The study shows that striatal GABA levels modulate the efficacy of response inhibition processes. Higher striatal GABA levels were related to better response inhibition performance. We show that striatal GABA modulate specific subprocesses of response inhibition related to pre-motor inhibitory processes through the modulation of neuronal synchronization processes. To our knowledge, this is the first study providing direct evidence for the relevance of the striatal GABAergic system for response inhibition functions and their cortical electrophysiological correlates in humans

Should I stay or should I go? How local-global implicit temporal expectancy shapes proactive motor control: An hdEEG study

In this study, we investigated the effect of global temporal prediction on the brain capability to implicitly adjust proactive motor control. We used the Dynamic Temporal Prediction (DTP), in which local and global predictions of an imperative stimulus were manipulated by using different stimulus-onset asynchronies (SOAs), presented with several distribution probabilities. At a behavioural level, the results show a performance adjustment (reaction time decrease) depending on the implicit use of global prediction. At a neurophysiological level, three separate computational steps underlying motor control were investigated. First, the expectancy implementation was associated with global probability-dependent contingent negative variation (CNV) modulation supported by the recruitment of a frontoparietal network involving the anterior cingulate, the left intraparietal sulcus, the occipital, and the premotor areas. Second, the response implementation was modulated by the global prediction fostering stimulus processing (P3 increase) at the motor response level, as suggested by both oscillatory (beta desynchronization), as well as source analysis (frontal cortical network). Third, the expectancy violation lead to a negativity increase (omission-detection potential) time locked to the global rule violation and additionally, to delta and theta power increase interpreted as inhibitory control and rule violation detection, respectively. The expectancy violation further engaged a left lateralized network including the temporal parietal junction (TPJ) and the motor cortex, suggesting involvement of attentional reorienting and a motor adjustment. Finally, these findings provide new insights on the neurocognitive mechanisms underlying proactive motor control, suggesting an overlapping between implicit and explicit processes

EEG, MEG and neuromodulatory approaches to explore cognition: Current status and future directions

Neural oscillations and their association with brain states and cognitive functions have been object of extensive investigation over the last decades. Several electroencephalography (EEG) and magnetoencephalography (MEG) analysis approaches have been explored and oscillatory properties have been identified, in parallel with the technical and computational advancement. This review provides an up-to-date account of how EEG/MEG oscillations have contributed to the understanding of cognition. Methodological challenges, recent developments and translational potential, along with future research avenues, are discussed. Keywords: Cognition; Electrophysiology; Event-related-potentials; Neural oscillations; Neural synchronisation; Neuromodulatio

Boosting Generalization in Bio-Signal Classification by Learning the Phase-Amplitude Coupling

Various hand-crafted features representations of bio-signals rely primarily on the amplitude or power of the signal in specific frequency bands. The phase component is often discarded as it is more sample specific, and thus more sensitive to noise, than the amplitude. However, in general, the phase component also carries information relevant to the underlying biological processes. In fact, in this paper we show the benefits of learning the coupling of both phase and amplitude components of a bio-signal. We do so by introducing a novel self-supervised learning task, which we call Phase-Swap, that detects if bio-signals have been obtained by merging the amplitude and phase from different sources. We show in our evaluation that neural networks trained on this task generalize better across subjects and recording sessions than their fully supervised counterpart.Comment: Accepted at GCPR 202

Fronto-parietal network oscillations reveal relationship between working memory capacity and cognitive control

Executive-attention theory proposes a close relationship between working memory capacity (WMC) and cognitive control abilities. However, conflicting results are documented in the literature, with some studies reporting that individual variations in WMC predict differences in cognitive control and trial-to-trial control adjustments (operationalized as the size of the congruency effect and congruency sequence effects, respectively), while others report no WMC-related differences. We hypothesized that brain network dynamics might be a more sensitive measure of WMC-related differences in cognitive control abilities. Thus, in the present study, we measured human EEG during the Simon task to characterize WMC-related differences in the neural dynamics of conflict processing and adaptation to conflict. Although high- and low-WMC individuals did not differ behaviorally, there were substantial WMC-related differences in theta (4-8 Hz) and delta (1-3 Hz) connectivity in fronto-parietal networks. Group differences in local theta and delta power were relatively less pronounced. These results suggest that the relationship between WMC and cognitive control abilities is more strongly reflected in large-scale oscillatory network dynamics than in spatially localized activity or in behavioral task performance

ELECTROPHYSIOLOGICAL MECHANISMS FOR PREPARING CONTROL IN TIME

Cognitive control is critical in guiding goal-directed behavior, preparing neural resources and adapting processing to promote optimal action in a given environment. According to the Dual Mechanisms of Control theory (Braver, 2012), control can be dichotomized into proactive and reactive modes of control, utilized reciprocally in ahead-of-time preparation versus last-minute, stimulus-evoked reaction. Although a substantial body of work has tested differences between proactive control and reactive control, the underlying assumption of proactive control as a unitary process has not been systematically investigated. Very little is known as to how or when proactive control is initiated, sustained, or implemented. As time is an integral building block of perception, cognition, and action (Buhusi & Meck, 2005), one should expect temporal information to be integrated into proactive control. Cognitive control is costly (Shenhav, Botvinick, & Cohen, 2013), and a temporally-guided modulation of control may offer substantial cost savings. By measuring proactive control on a sub-second time-scale, we can begin to gauge whether dissociable sub-types of proactive control are utilized demanding on temporal demands. Moreover, by comparing proactive control processes across different temporal demands, we can parse out when different aspects of control are computed and implemented. Through a meta-analytic review and three empirical experiments, this dissertation provides insight into how timing dynamics may influence the computation, maintenance, and instantiation of proactive cognitive control. First, a meta-analysis on the cued control literature reveals that seemingly trivial experimental parameters shape the use of proactive versus reactive control. Two EEG studies then demonstrate how modulating timing dynamics influences prefrontal mechanisms for preparatory cognitive control. In a final EEG study, we compare the mechanisms utilized to retain control goals versus visuo-spatial working memory items. Overall, this dissertation elucidates several novel electrophysiological mechanisms by which timing information is implemented in the computation and retention of cognitive control rules. Further, we provide evidence that individual differences in impulsivity and working memory shape distinct aspects of preparation. The findings reported here make clear that timing information is critical in guiding proactive control processes, and support a fundamental reconsideration of proactive control based on temporal dynamics

Attentional Control Processing in Working Memory: Effects of Aging and Bilingualism

Selective attention is required for working memory and is theorized to underlie the process of selecting between two active languages in bilinguals. Studies of working memory performance and bilingualism have produced divergent results and neural investigations are still in the early stages. The purpose of the current series of studies using older and younger bilingual and monolingual adults was to examine working memory processing by manipulating attentional control demands and task domain. It was hypothesized that bilinguals in both age groups will outperform monolinguals when verbal demands are low and when attentional control demands are high. Study 1 included behavioural tasks that varied by domain and attentional control. Study 2 addressed these factors by examining the neural correlates of maintenance and updating using ERPs. A third analytic approach using partial least squares (PLS) analysis was performed on the recognition data from Study 2 to assess contrasting group patterns of amplitude and signal variability using multiscale entropy (MSE). Bilingual performance was poorer than monolingual when the task involved verbal production, but bilinguals outperformed monolinguals when the task involved nonverbal interference resolution. P3 amplitude was largely impacted by attentional demands and aging, whereas language group differences were limited. Extensive language and age group differences emerged once whole brain neural patterns were examined. Bilingual older adults displayed a neural signature similar to younger adults for both amplitude and MSE measures. Older adult monolinguals did not show these patterns and required additional frontal resources for the difficult spatial update condition. Younger bilinguals showed long-range, frontal-parietal MSE patterns for updating in working memory. These results are consistent with the interpretation of brain functional reorganization for bilingual working memory processing and may represent adaptations to a top-down attentional control mechanism