Beta and theta oscillations differentially support free versus forced control over multiple-target search

Many important situations require human observers to simultaneously search for more than one object. Despite a long history of research into visual search, the behavioral and neural mechanisms associated with multiple-target search are poorly understood. Here we test the novel theory that the efficiency of looking for multiple targets critically depends on the mode of cognitive control the environment affords to the observer. We used an innovative combination of electroencephalogram (EEG) and eye tracking while participants searched for two targets, within two different contexts: either both targets were present in the search display and observers were free to prioritize either one of them, thus enabling proactive control over selection; or only one of the two targets would be present in each search display, which requires reactive control to reconfigure selection when the wrong target has been prioritized. During proactive control, both univariate and multivariate signals of beta-band (15–35 Hz) power suppression before display onset predicted switches between target selections. This signal originated over midfrontal and sensorimotor regions and has previously been associated with endogenous state changes. In contrast, imposed target selections requiring reactive control elicited prefrontal power enhancements in the delta/theta band (2– 8 Hz), but only after display onset. This signal predicted individual differences in associated oculomotor switch costs, reflecting reactive reconfiguration of target selection. The results provide compelling evidence that multiple target representations are differentially prioritized during visual search, and for the first time reveal distinct neural mechanisms underlying proactive and reactive control over multiple-target search

Early neurophysiological stimulus processing during a performance-monitoring task differentiates women with bipolar disorder from women with ADHD

Adults with attention-deficit/hyperactivity disorder (ADHD) or bipolar disorder (BD) may display similar cognitive impairments and clinical symptoms, which might reflect shared mechanisms. Initial evidence indicates disorder-specific and overlapping neurophysiological alterations using event-related potentials (ERPs) in individuals with BD or ADHD during attentional tasks, but it is unknown whether impairments generalize across other processes and tasks. We conduct the first comparison between women with ADHD (n = 20), women with BD (n = 20) and control women (n = 20) on ERPs from a performance-monitoring flanker task. The BD group showed a significantly attenuated frontal ERP of conflict monitoring (N2) compared to the ADHD group across both low-conflict (congruent) and high-conflict (incongruent) task conditions, and compared to controls in the high-conflict condition. However, when controlling for an earlier attentional ERP (frontal N1), which was significantly reduced in participants with BD compared to participants with ADHD and controls, N2 group differences were no longer significant. These results indicate that ERP differences in conflict monitoring may be attributable to differences in earlier attentional processes. These findings identify neural differences in early attention between BD and ADHD which precede conflict monitoring processes, potentially pointing to distinct neural mechanisms implicated in the two disorders

Decreased Alertness Reconfigures Cognitive Control Networks

Humans' remarkable capacity to flexibly adapt their behavior based on rapid situational changes is termed cognitive control. Intuitively, cognitive control is thought to be affected by the state of alertness; for example, when drowsy, we feel less capable of adequately implementing effortful cognitive tasks. Although scientific investigations have focused on the effects of sleep deprivation and circadian time, little is known about how natural daily fluctuations in alertness in the regular awake state affect cognitive control. Here we combined a conflict task in the auditory domain with EEG neurodynamics to test how neural and behavioral markers of conflict processing are affected by fluctuations in alertness. Using a novel computational method, we segregated alert and drowsy trials from two testing sessions and observed that, although participants (both sexes) were generally sluggish, the typical conflict effect reflected in slower responses to conflicting information compared with nonconflicting information, as well as the moderating effect of previous conflict (conflict adaptation), were still intact. However, the typical neural markers of cognitive control—local midfrontal theta-band power changes—that participants show during full alertness were no longer noticeable when alertness decreased. Instead, when drowsy, we found an increase in long-range information sharing (connectivity) between brain regions in the same frequency band. These results show the resilience of the human cognitive control system when affected by internal fluctuations of alertness and suggest that there are neural compensatory mechanisms at play in response to physiological pressure during diminished alertness

Dissociable mechanisms underlying individual differences in visual working memory capacity

Individuals scoring relatively high on measures of working memory tend to be more proficient at controlling attention to minimize the effect of distracting information. It is currently unknown whether such superior attention control abilities are mediated by stronger suppression of irrelevant information, enhancement of relevant information, or both. Here we used steady-state visual evoked potentials (SSVEPs) with the Eriksen flanker task to track simultaneously the attention to relevant and irrelevant information by tagging target and distractors with different frequencies. This design allowed us to dissociate attentional biasing of perceptual processing (via SSVEPs) and stimulus processing in the frontal cognitive control network (via time–frequency analyses of EEG data). We show that while preparing for the upcoming stimulus, high- and low-WMC individuals use different strategies: High-WMC individuals show attentional suppression of the irrelevant stimuli, whereas low-WMC individuals demonstrate attentional enhancement of the relevant stimuli. Moreover, behavioral performance was predicted by trial-to-trial fluctuations in strength of distractor-suppression for high-WMC participants. We found no evidence for WMC-related differences in cognitive control network functioning, as measured by midfrontal theta-band power. Taken together, these findings suggest that early suppression of irrelevant information is a key underlying neural mechanism by which superior attention control abilities are implemented

Mouse tracking to explore motor inhibition processes in go/no-go and stop signal tasks

Response inhibition relies on both proactive and reactive mechanisms that exert a synergic control on goal-directed actions. It is typically evaluated by the go/no-go (GNG) and the stop signal task (SST) with response recording based on the key-press method. However, the analysis of discrete variables (i.e., present or absent responses) registered by key-press could be insufficient to capture dynamic aspects of inhibitory control. Trying to overcome this limitation, in the present study we used a mouse tracking procedure to characterize movement profiles related to proactive and reactive inhibition. A total of fifty-three participants performed a cued GNG and an SST. The cued GNG mainly involves proactive control whereas the reactive component is mainly engaged in the SST. We evaluated the velocity profile from mouse trajectories both for responses obtained in the Go conditions and for inhibitory failures. Movements were classified as one-shot when no corrections were observed. Multi-peaked velocity profiles were classified as non-one-shot. A higher proportion of one-shot movements was found in the SST compared to the cued GNG when subjects failed to inhibit responses. This result suggests that proactive control may be responsible for unsmooth profiles in inhibition failures, supporting a differentiation between these tasks

Metacognition in decision-making: Exploring age-related changes in confidence

Metacognition is a fundamental human function that supports goal-directed behaviour. By constantly monitoring and evaluating our decisions we are able to detect errors when they occur and adjust the behaviour accordingly. Metacognitive evaluations can be expressed in ratings of decision confidence or error detection reports. Humans are generally capable of forming well-calibrated estimates of their own performance, yet metacognitive abilities have been shown to be specifically affected by healthy ageing. However, the mechanisms underlying this decline remain poorly understood. This thesis aims to investigate the cognitive processes of age-related changes in perceptual metacognitive performance by combining approaches from the fields of error monitoring and decision confidence. For this, we developed a new paradigm for studying the metacognitive evaluation of errors and correct responses that was feasible for adults of all ages. While recording an electroencephalogram (EEG) and response force, a sample of 65 healthy adults from 20 to 76 years made a series of decisions in a modified version of the Flanker task and subsequently indicated how confident they felt about their decision on a four-point scale. Across two studies, conducted in the same large sample, I addressed three specific research questions: first, how is metacognitive performance affected by healthy ageing? Second, what are factors contributing to the observed decline in metacognitive performance? And third, how does an age-related decline in metacognitive performance affect subsequent behaviour? The analysis of behavioural data (Study 1a) showed that metacognitive accuracy declined significantly with older age and that this decline could not be explained by the decline in task performance alone. Independent of age, however, participants adjusted their performance according to their metacognitive evaluation of their previous decision and responded more cautiously after reporting low confidence. The analysis of electrophysiological data (Study 1b) focussed on the modulation of two correlates of error monitoring by confidence and age. The results indicated that the error/correct positivity (Pe/c), a component discussed as a marker of error detection and decision confidence, scaled with reported confidence in errors but did not show the expected modulation by age. The amplitude of the error/correct negativity (Ne/c), a marker of early error monitoring processes, also scaled with reported confidence in errors, but in contrast, was less sensitive to variations in confidence with older age. Finally, Study 2 investigated the effect of age on the relationship between confidence and two response parameters of the initial decision: response time and response force. We replicated a widely reported negative relationship between confidence and response time. Importantly, we showed, for the first time, that confidence was also negatively related to fine-grained changes in peak force, which was intuitively exerted by the participants. Notably, these associations were dependent on the accuracy of the response and changed markedly across age: the relationship between confidence and response time was only found in correct responses and was pronounced with older age, while the relationship between confidence and peak force was only found in errors and only in younger adults. Overall, these findings jointly provide novel insights deepening our understanding of the observed decline in metacognitive performance with older age. A similar modulation of the Pe/c by confidence across the lifespan suggests that the post-decisional process of accumulating evidence about the correctness of a prior decision might generally be intact until old age. Instead, the age-related decline in metacognitive accuracy appears to be related to a multitude of cognitive and neural changes, which might reflect increased noise and hence higher uncertainty in older adults’ computation of confidence. Moreover, I discuss how a metacognitive decline could manifest in real life and how recent findings offer a promising view regarding the effect of training on metacognitive performance

Changing your mind before it is too late: the electrophysiological correlates of online error correction during response selection

Inhibiting actions when they are no longer appropriate is essential for adaptive goal-directed behavior. In this study, we used high-density EEG and a standard flanker task to explore the spatiotemporal dynamics of cognitive control and inhibitory mechanisms aimed to prevent the commission of errors. By recording hand-related electromyographic activity, we could disentangle successful from unsuccessful inhibition attempts. Our results confirm that (a) the latency of the error-related negativity (ERN; or Ne) component is too late to be associated with these online inhibitory mechanisms, and (b) instead, a frontal slow negative component with an earlier time course was associated with the implementation of online inhibition. These findings are consistent with single-cell recordings in monkeys showing that the supplementary motor area provides cognitive control signals to the primary motor cortex to exert online inhibition and in turn rectify the course of erroneous actions

Feedback information transfer in the human brain reflects bistable perception in the absence of report

In the search for the neural basis of conscious experience, perception and the cognitive processes associated with reporting perception are typically confounded as neural activity is recorded while participants explicitly report what they experience. Here, we present a novel way to disentangle perception from report using eye movement analysis techniques based on convolutional neural networks and neurodynamical analyses based on information theory. We use a bistable visual stimulus that instantiates two well-known properties of conscious perception: integration and differentiation. At any given moment, observers either perceive the stimulus as one integrated unitary object or as two differentiated objects that are clearly distinct from each other. Using electroencephalography, we show that measures of integration and differentiation based on information theory closely follow participants' perceptual experience of those contents when switches were reported. We observed increased information integration between anterior to posterior electrodes (front to back) prior to a switch to the integrated percept, and higher information differentiation of anterior signals leading up to reporting the differentiated percept. Crucially, information integration was closely linked to perception and even observed in a no-report condition when perceptual transitions were inferred from eye movements alone. In contrast, the link between neural differentiation and perception was observed solely in the active report condition. Our results, therefore, suggest that perception and the processes associated with report require distinct amounts of anterior-posterior network communication and anterior information differentiation. While front-to-back directed information is associated with changes in the content of perception when viewing bistable visual stimuli, regardless of report, frontal information differentiation was absent in the no-report condition and therefore is not directly linked to perception per se.</p

Frontal theta and posterior alpha in resting EEG: A critical examination of convergent and discriminant validity

Prior research has identified two resting EEG biomarkers with potential for predicting functional outcomes in depression: theta current density in frontal brain regions (especially rostral anterior cingulate cortex) and alpha power over posterior scalp regions. As little is known about the discriminant and convergent validity of these putative biomarkers, a thorough evaluation of these psychometric properties was conducted toward the goal of improving clinical utility of these markers. Resting 71‐channel EEG recorded from 35 healthy adults at two sessions (1‐week retest) were used to systematically compare different quantification techniques for theta and alpha sources at scalp (surface Laplacian or current source density [CSD]) and brain (distributed inverse; exact low resolution electromagnetic tomography [eLORETA]) level. Signal quality was evaluated with signal‐to‐noise ratio, participant‐level spectra, and frequency PCA covariance decomposition. Convergent and discriminant validity were assessed within a multitrait‐multimethod framework. Posterior alpha was reliably identified as two spectral components, each with unique spatial patterns and condition effects (eyes open/closed), high signal quality, and good convergent and discriminant validity. In contrast, frontal theta was characterized by one low‐variance component, low signal quality, lack of a distinct spectral peak, and mixed validity. Correlations between candidate biomarkers suggest that posterior alpha components constitute reliable, convergent, and discriminant biometrics in healthy adults. Component‐based identification of spectral activity (CSD/eLORETA‐fPCA) was superior to fixed, a priori frequency bands. Improved quantification and conceptualization of frontal theta is necessary to determine clinical utility.Magnitude of frontal theta (rostral ACC eLORETA source amplitude) and posterior alpha (spectral components of scalp current source density) at rest have been considered candidate EEG biomarkers of depression outcomes. Given inconsistent findings, we examined the discriminant and convergent validity of these measures in healthy adults. Unlike theta, two distinct alpha components constituted reliable, convergent, and discriminant biometrics. While results have marked implications for clinical utility, we make several recommendations for improving the psychometric properties of resting frontal theta.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/153675/1/psyp13483.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/153675/2/psyp13483_am.pd