Cerebral cortical dynamics during visuomotor transformation: adaptation to a cognitive-motor executive challenge

EEG was employed during cognitive-motor adaptation to a visuomotor transformation that required inhibition of an established motor plan. Performance was positively related to frontal alpha and theta power during both planning and execution of reaching movements to visual targets. EEG changes suggest initial involvement of frontal executive functioning to suppress established visuomotor mappings followed by progressive idling (i.e., alpha synchrony). Also, progressive idling of the temporal and parietal sites over the trials was observed, suggesting a decreasing role of working memory and encoding of the new visuomotor map, respectively. The regional changes in the cortical dynamics translated into the quality of motor behavior. This study expands our understanding of the role of frontal executive processes beyond the cognitive domain to the cognitive-motor domain.     

Effects of Task Difficulty on Regional Cerebral Blood Flow: Relationships with Anxiety and Performance

Associations have been described between task difficulty and autonomic arousal. This study addresses task difficulty effects on regional cerebral blood flow (rCBF), a measure of cortical activity. Earlier work suggested that in contrast to a positive association between anxiety and autonomic arousal, there is a curvilinear, inverted-U relationship between anxiety and cortical activity. A sample of 26 normal volunteers (14 men, 12 women) was administered the 133-Xenon inhalation technique for measuring rCBF. Measurements were taken under three conditions: Resting baseline, and Easy and Hard verbal analogy tasks. Subjects were grouped into three anxiety levels on the basis of their average score on a self-report measure. The rCBF was higher during task performance than at rest, but did not differ between the two difficulty conditions. There were Task × Hemisphere interactions showing the expected asymmetry of activation, with higher left hemispheric increase for the verbal task. Anxiety had an inverted-U relationship with both performance and rCBF, which were themselves positively related. These results with measures of central nervous system activity differ from those reported for autonomic responses. They indicate that anxiety effects on cortical activity may mediate the relation between anxiety and performance.     

Circadian rhythms in cognitive performance: methodological constraints, protocols, theoretical underpinnings

The investigation of time-of-day effects on cognitive performance began in the early days of psychophysiological performance assessments. Since then, standardised, highly controlled protocols (constant routine and forced desynchrony) and a standard performance task (psychomotor vigilance task) have been developed to quantify sleep-wake homeostatic and internal circadian time-dependent effects on human cognitive performance. However, performance assessment in this field depends on a plethora of factors. The roles of task difficulty, task duration and complexity, the performance measure per se, practice effects, inter-individual differences, and ageing are all relevant aspects. Therefore, well-defined theoretical approaches and standard procedures are needed for tasks pinpointing higher cortical functions along with more information about time-dependent changes in the neural basis of task performance. This promises a fascinating challenge for future research on sleep-wake related and circadian aspects of different cognitive domains.     

Investigation of brain dynamics in Parkinson's disease by methods derived from nonlinear dynamics

EEGs were recorded from patients in early stages of Parkinson's disease (17 patients, 9 females) and healthy controls (12 subjects, 8 females) during rest and during execution/imagining of a complex motor task. The prediction that Parkinson's disease patients compared to controls would show more complex brain dynamics during performance of a complex motor task and imagination of the movements was confirmed by methods derived from nonlinear dynamics. In the resting state, analysis of correlation dimension of EEG time series revealed only slight topographical differences between the groups. During performance of a complex motor task, however, data from Parkinson's disease patients showed higher dimensionality than data from controls, indicating more complex EEG time series. The same difference was found when subjects did not perform any motor movements but imagined the complex movements they had just performed. The data are consistent with the hypothesis that the disturbances in Parkinson's disease result in the recruitment of superfluous cortical networks due to failed inhibition of alternative motor programs in the striatum and thus increase the complexity of cortical representation in motor conditions.     

The effects of a recency task on the left and right hand tapping performance

The intrahemispheric overflow hypothesis was examined by the cognitive-motor interference method. Subjects were 12 right handed male adults. As the concurrent cognitive task the present study employed Milner's recent-memory (verbal and nonverbal) task which was assumed by the author to be related to the frontal lobe function. The motor task was a single finger repetitive tapping, which control is thought to involve the motor area in the anterior regions of the hemispheres. In verbal material, general interference occurred during both encoding and decoding periods. In nonverbal material, however, recency task interfered with the left hand during decoding period only when the load effect was maximum. The result indicated that even if there were no functional overlap, interference could occur by neural overflow.     

Cerebral cortical dynamics and the quality of motor behavior during social evaluative challenge

To determine the influence of arousal on cerebral cortical dynamics and motor behavior, 58 channels of EEG were recorded in 13 college‐age men (n=6) and women during an aiming task performed alone and in a social evaluation condition. Moderate arousal, as measured by heart rate, skin conductance, and self‐reported mood, was induced during the social evaluation. In accord with the Yerkes–Dodson Hypothesis, which posits optimal performance during moderate arousal, improved performance (i.e., quality of the aiming trajectories) was observed. During social evaluation, changes in electroencephalogram dynamics included decreased coherence between the motor planning (Fz) and right temporal region (T4), increased coherence in the sensorimotor networks subserving the task, and increased local processing (gamma, 30–44 Hz) in the temporal regions. The results imply that moderate arousal promotes specific alterations in cortical dynamics that facilitate motor performance.     

Influence of cognitive-motor expertise on brain dynamics of anticipatory-based outcome processing

Motor experience plays an important role in the ability to anticipate action outcomes, but little is known about the brain processes through which it modulates the preparation for unexpected events. To address this issue, EEG was employed while table tennis players and novices observed videos of serves in order to predict the expected ball direction based on the kinematics of a model’s movement. Furthermore, we manipulated the congruency between the model’s body kinematics and the subsequent ball trajectory while assessing the cerebral cortical activity of novices and experts to understand how experts respond to unexpected outcomes. Experts were more accurate in predicting the ball trajectories than novices and were further differentiated from novices in the cortical dynamics just prior to ball contact and during the period of observation of the ball trajectories. Consistent with the predicted response-outcome model, experts exhibited elevated theta oscillations during the incongruent relative to the congruent trajectories, while no such differences were observed in the novices. Source estimation for theta activity revealed stronger activation in the middle frontal gyrus for the experts in response to the incongruent trajectories. Collectively, the observed differences in cortical dynamics between the groups suggest that motor experience promotes central neural system adaptations that facilitate preparation for anticipated outcomes and contributes to adaptive cognitive-motor responses in the face of uncertainty.     

Phasic T-Wave Amplitude and Heart Rate Changes as Indices of Mental Effort and Task Incentive

The sensitivities of T-wave amplitude (TWA) and heart rate (HR) to manipulations of the mental effort (ME) and incentive associated with performance of the backward digit span task were investigated. The experimental task was so chosen because it could be administered without requiring subjects to speak during its performance, thus minimizing the intrusion of respiratory and motor artifacts. The ME required during task performance was manipulated by varying the number of digits presented, creating Hard and Easy trials. The incentive for subjects to perform well was varied by the threat of the delivery of a noxious noise stimulus, which was ostensibly contingent upon adequate performance on some (Test) but not other (Practice) trials. TWA attenuation and HR acceleration were greater on the Hard as compared to the Easy Trials, and on the Test as compared to the Practice trials. No interactions between the ME and Incentive factors emerged for either cardiac variable. These results suggest that the effort and the incentive of subjects during mental work may be indexed reliably by phasic changes in TWA and HR. The conjoint use of these two cardiac measures may also elucidate the involvement of the two autonomic branches during task performance.     

Intelligence related differences in EEG-bandpower

Several studies on the relationship between event-related desynchronization/synchronization (ERD/ERS) and cognitive performance revealed contradictory results particularly for the alpha band. Studies from our laboratory have shown that good performers show a larger upper alpha ERD (interpreted in terms of larger cortical activation) than bad performers. In contrast, other researchers found evidence for the neural efficiency hypothesis, which states that more intelligent subjects exhibit a smaller extent of cortical activation, which is assumed to be reflected by a smaller upper alpha ERD. Here we address the question whether these divergent results may be due to differences in general task difficulty. Using a modified version of the RAVEN, individually divided into easy and difficult tasks, a group of average and a group of highly intelligent subjects (IQ- and IQ+) have been investigated. While in the theta frequency IQ+ subjects generally exhibited a significantly stronger activation, we found a significant interaction of task difficulty and IQ group in the upper alpha band, indicating both, a weaker activation for the high IQ group during the easy tasks, and a significant increase from easy to difficult tasks for IQ+ only.     

Temporal evolution of oscillatory activity predicts performance in a choice-reaction time reaching task

In this study, we characterized the patterns and timing of cortical activation of visually guided movements in a task with critical temporal demands. In particular, we investigated the neural correlates of motor planning and on-line adjustments of reaching movements in a choice-reaction time task. High-density electroencephalography (EEG, 256 electrodes) was recorded in 13 subjects performing reaching movements. The topography of the movement-related spectral perturbation was established across five 250-ms temporal windows (from prestimulus to postmovement) and five frequency bands (from theta to beta). Nine regions of interest were then identified on the scalp, and their activity was correlated with specific behavioral outcomes reflecting motor planning and on-line adjustments. Phase coherence analysis was performed between selected sites. We found that motor planning and on-line adjustments share similar topography in a fronto-parietal network, involving mostly low frequency bands. In addition, activities in the high and low frequency ranges have differential function in the modulation of attention with the former reflecting the prestimulus, top-down processes needed to promote timely responses, and the latter the planning and control of sensory-motor processes.     

An animal model for delirium.

This study describes an animal model for delirium comparing rats treated with either saline or atropine. The model was defined by recordings of cortical EEGs, maze performance, and behavioral observations. EEG slowing and increased amplitude, difficulty with attention and memory, sleep-wake cycle reversal, and changes in behavior (lack of focused direction, irritability, fluctuating levels of activity, excessive random sniffing) appeared consistent with signs and symptoms seen in human delirium. EEG abnormalities in atropine-treated rats returned to normal before cognitive deficits did. Motor activity monitoring did not reveal diminished motor activity as a confounding variable in maze performance.     

Phasic increases in cortical beta activity are associated with alterations in sensory processing in the human

Oscillatory activity in the beta (β)-frequency band (13–35 Hz) can be recorded over the sensorimotor cortex in humans. It is coherent with electromyographic activity (EMG) during tonic contraction, but whether the cortical β-oscillations are primarily motor or sensorimotor in function remains unclear. We tested the hypothesis that cortical β-activity is associated with an up-regulation of sensory inputs that may be relevant to the organization of the motor response. We recorded cortical somatosensory potentials (SEPs) elicited by electrical stimuli to the median nerve at the wrist triggered by increases of electroencephalographic (EEG) β-activity in the contralateral fronto-central EEG and compared these to SEPs presented at random intervals. The involvement of motor cortex in the triggering EEG activity was confirmed by a simultaneous elevation of cortico-spinal synchrony in the β-band. The negative cortical evoked potential peaking at 20 ms and the positive evoked potential peaking at 30 ms after median nerve shocks were increased in size when elicited after phasic increases in β-activity. The functional coupling of sensory and motor cortices in the β-band was confirmed in recordings of electrocorticographic activity in two patients with chronic pain syndromes, suggesting a means by which β-activity may simultaneously influence cortical sensory processing, motor output and promote sensory-motor interaction. An erratum to this article can be found at     

Detecting deteriorated vigilance using percentage of eyelid closure time during behavioral maintenance of wakefulness tests

The present study tested the hypothesis of an additive interaction between intrinsic, extraneous and germane cognitive load, by manipulating factors of mental workload assumed to have a specific effect on either type of cognitive load. The study of cognitive load factors and their interaction is essential if we are to improve workers' wellbeing and safety at work. High cognitive load requires the individual to allocate extra resources to entering information. It is thought that this demand for extra resources may reduce processing efficiency and performance. The present study tested the effects of three factors thought to act on either cognitive load type, i.e. task difficulty, time pressure and alertness in a working memory task. Results revealed additive effects of task difficulty and time pressure, and a modulation by alertness on behavioral, subjective and psychophysiological workload measures. Mental overload can be the result of a combination of task-related components, but its occurrence may also depend on subject-related characteristics, including alertness. Solutions designed to reduce incidents and accidents at work should consider work organization in addition to task constraints in so far that both these factors may interfere with mental workload.     

Proposal for using time estimation training for the treatment of Parkinson’s disease

Studies have shown an association between time perception and the basal ganglia and cortical areas, suggesting a role for these regions in the perception of seconds, minutes, and hours. We present the hypothesis that time estimation training tasks may change the modulatory activity of dopamine in the basal ganglia and the cortical areas related to temporal perception. Through this mechanism, the estimated training time interval can promote a compensatory effect on motor and cognitive performance via a dynamic neural adaptation process. We believe that the training will develop a competition between neural pathways involved in the process of time perception, positively affecting the brain pathways related to Parkinson’s disease, and thereby minimizing the cognitive and motor deficits caused by the disease.     

Combined assessment of attentional reserve and cognitive‐motor effort under various levels of challenge with a dry EEG system

A novel ERP approach was proposed to index variations in mental workload, particularly in attentional reserve, which is complementary to EEG spectral content thought to reflect mental effort. To our knowledge, no study has assessed mental effort and attentional reserve simultaneously in EEG gel‐based and, importantly, dry systems, which are particularly well suited for real‐world settings. Therefore, by systematically considering ERP, EEG spectral, and importantly the combination of both, this study examined if a small set of dry EEG electrodes could detect changes in both spectral and ERP metrics to assess the mental workload under various challenges with a similar fidelity to their gel‐based counterparts in a laboratory setting. By employing both EEG gel‐based and dry systems, the ERP and spectral markers were computed while participants executed a visuomotor task under three levels of challenge. For both EEG systems, more challenging levels of difficulty were associated with concomitant changes in ERP amplitude, and spectral power reflected a reduction of the attentional reserve and an increase in cognitive‐motor effort, respectively. Those variations in attentional reserve and cognitive‐motor effort collectively indexed mental workload with nearly identical fidelity for both gel‐based and dry EEG systems. These findings promise to assess the mental workload in situations where the use of dry EEG systems could be advantageously employed to examine human cognitive‐motor performance.     

Brain electrical activity signatures during performance of the Multisource Interference Task

The Multisource Interference Task (MSIT) was developed to test cognitive control in normal and pathological conditions and has become a reliable tool for exploring the integrity of cingulo‐frontal‐parietal cognitive/attentional networks in fMRI studies. Analysis of EEG recordings made during performance of the MSIT may provide additional information about the temporal dynamics of cognitive control. However, this has not yet been investigated in depth. In this study, we analyzed the ERPs and carried out time‐frequency decomposition of EEG recorded during control and interference conditions of the MSIT. The N2 ERP component and midfrontal theta power (both considered neural signatures of conflict processing) were significantly larger in interference than in control trials. Theta also showed higher phase synchronization between midfrontal and right frontolateral scalp locations in the interference condition, supporting the view that this frequency band entrains additional brain resources when a need for greater control arises. In interference trials, we also observed longer P3 latency, larger P3 amplitude, and greater reduction of posterior alpha (modulations related to allocation of attentional resources), in addition to a greater reduction of central beta power (related to motor preparation). In conclusion, the MSIT reliably modulated brain electrical activity related to cognitive control and attention. The EEG indices obtained during the performance of this task may be useful for exploring the functioning of cognitive/attentional networks in healthy and clinical populations.     

Greater childhood cardiorespiratory fitness is associated with better top-down cognitive control: A midfrontal theta oscillation study

The aim of the current study was to examine the association between cardiorespiratory fitness and electroencephalogram-based neural oscillations, using midfrontal theta, during an inhibitory control task in children. One-hundred seventy-one school-aged children (mean age = 8.9 ± 0.6 years; 46% girls) were recruited. Cardiorespiratory fitness was assessed by a test of maximal oxygen consumption (VO_2peak) while inhibitory control performance was measured via a modified flanker task with an electroencephalogram. Behavioral findings demonstrated that higher cardiorespiratory fitness was associated with higher response accuracy regardless of task difficulty as well as lower response variability during trials with lower cognitive demand. Neuroelectric outcomes revealed that higher cardiorespiratory fitness was correlated with smaller modulation of theta (4–7 Hz) oscillatory power regardless of task difficulty. Collectively, the current findings indicate that higher cardiorespiratory fitness is associated with better performance on a task that modulates inhibitory control, signified by higher, and more stable, task performance. More importantly, higher childhood cardiorespiratory fitness is associated with better top-down control and cortical communication, as reflected by midfrontal theta. Such findings support the critical role of cardiorespiratory fitness in brain health during childhood.     

Effects of Coping on Blood Pressure Responses to Threat of Aversive Stimulation

The purpose of this study was to examine effects on systolic and diastolic blood pressure due to availability and difficulty of control over anticipated aversive auditory stimulation. In a 2 × 2 factorial design, 44 subjects were presented either of two instructional sets regarding control: a) that exposure to the aversive stimulus would be contingent on the subject's performance at a cognitive task (Control), or b) that the stimulus would occur at random during the task period (No Control). The experimental task consisted of problems in concept formation and was presented to Control and No Control subjects at either of two levels of difficulty (Difficult or Easy); task success was manipulated by the experimenter to assure equivalent performance across groups. Results indicated that within the Task Difficult condition, Control subjects evidenced greater systolic blood pressure elevations than subjects in the No Control group, whereas Control and No Control subjects in the Task Easy condition showed no reliable differences. Diastolic blood pressure did not vary by control or task difficulty. It was concluded that the availability of control responses may induce greater arousal in situations involving threat of aversive stimulation, but that this effect obtains only when subjects experience some degree of difficulty employing available coping strategies.     

Extracting Information from Cortical Connectivity Patterns Estimated from High Resolution EEG Recordings: A Theoretical Graph Approach

Over the last 20 years, a body of techniques known as high resolution EEG has allowed precise estimation of cortical activity from non-invasive EEG measurements. The availability of cortical waveforms from non-invasive EEG recordings allows to have not only the level of activation within a single region of interest (ROI) during a particular task, but also to estimate the causal relationships among activities of several cortical regions. However, interpreting resulting connectivity patterns is still an open issue, due to the difficulty to provide an objective measure of their properties across different subjects or groups. A novel approach addressed to solve this difficulty consists in manipulating these functional brain networks as graph objects for which a large body of indexes and tools are available in literature and already tested for complex networks at different levels of scale (Social, WorldWideWeb and Proteomics). In the present work, we would like to show the suitability of such approach, showing results obtained comparing separately two groups of subjects during the same motor task and two different motor tasks performed by the same group. In the first experiment two groups of subjects (healthy and spinal cord injured patients) were compared when they moved and attempted to move simultaneously their right foot and lips, respectively. The contrast between the foot–lips movement and the simple foot movement was addressed in the second experiment for the population of the healthy subjects. For both the experiments, the main question is whether the “architecture” of the functional connectivity networks obtained could show properties that are different in the two groups or in the two tasks. All the functional connectivity networks gathered in the two experiments showed ordered properties and significant differences from “random” networks having the same characteristic sizes. The proposed approach, based on the use of indexes derived from graph theory, can apply to cerebral connectivity patterns estimated not only from the EEG signals but also from different brain imaging methods.