Electroencephalography of response inhibition tasks: Functional networks and cognitive contributions

Brain electrical source imaging in manic and depressive episodes of bipolar disorder

OBJECTIVE

Bipolar disorder (BD) electroencephalographic (EEG) studies have reported varying results. The present study compared EEG in BD during manic and depressive episodes, using brain electrical source imaging [standardized low-resolution electromagnetic tomography (sLORETA)] to assess the cortical spatial distribution of the sources of EEG oscillation frequencies.

METHODS

Two independent datasets (a total of 95 patients with bipolar I disorder, of whom 59 were female) were analyzed. Dataset #1 comprised 14 patients in a manic as well as a depressive episode. Dataset #2 comprised 26 patients in a manic episode and 55 patients in a depressive episode. From the head surface-recorded EEG, sLORETA cortical activity was computed in eight EEG frequency bands, and compared between mood states in both datasets. The results from the two datasets were combined using conjunction analysis.

RESULTS

Conjunction analysis yielded significant differences between mood states: In manic compared to depressive states, patients had lesser theta frequency band activity (right-hemispheric lateral lower prefrontal and anterior temporal, mainly Brodmann areas 13, 38, and 47), and greater beta-2 and beta-3 frequency band activity (extended bilateral prefrontal-to-parietal, mainly Brodmann area 6, and the cingulate).

CONCLUSIONS

The spatial organization of the brain's electrical oscillations differed in patients with BD between manic and depressive mood states. The brain areas implementing the main functions that show opposing abnormalities during manic and depressive episodes were affected by unduly increased or decreased activity (beta or theta). The discussion considers that facilitating (beta) or inhibiting (theta) electrical activity can in either case result in behavioral facilitation or inhibition, depending on the function of the brain area.

Combat veterans with comorbid PTSD and mild TBI exhibit a greater inhibitory processing ERP from the dorsal anterior cingulate cortex

Posttraumatic stress disorder (PTSD) is common among combat personnel with mild traumatic brain injury (mTBI). While patients with either PTSD or mTBI share abnormal activation of multiple frontal brain areas, anterior cingulate cortex (ACC) activity during inhibitory processing may be particularly affected by PTSD. To further test this hypothesis, we recorded electroencephalography from 32 combat veterans with mTBI-17 of whom were also comorbid for PTSD (mTBI+PTSD) and 15 without PTSD (mTBI-only). Subjects performed the Stop Task, a validated inhibitory control task requiring inhibition of initiated motor responses. We observed a larger inhibitory processing eventrelated potential (ERP) in veterans with mTBI+PTSD, including greater N200 negativity. Furthermore, greater N200 negativity correlated with greater PTSD severity. This correlation was most dependent on contributions from the dorsal ACC. Support vector machine analysis demonstrated that N200 and P300 amplitudes objectively classified veterans into mTBI-only or mTBI+PTSD groups with 79.4% accuracy. Our results support a model where, in combat veterans with mTBI, larger ERPs from cingulate areas are associated with greater PTSD severity and likely related to difficulty controlling ongoing brain processes, including trauma-related thoughts and feelings.

It's not too late: the onset of the frontocentral P3 indexes successful response inhibition in the stop-signal paradigm

The frontocentral P3 event-related potential has been proposed as a neural marker of response inhibition. However, this association is disputed: some argue that P3 latency is too late relative to the timing of action stopping (stop-signal reaction time; SSRT) to index response inhibition. We tested whether P3 onset latency is a marker of response inhibition, and whether it coincides with the timing predicted by neurocomputational models. We measured EEG in 62 participants during the stop-signal task, and used independent component analysis and permutation statistics to measure the P3 onset in each participant. We show that P3 onset latency is shorter when stopping is successful, that it is highly correlated with SSRT, and that it coincides with the purported timing of the inhibition process (towards the end of SSRT). These results demonstrate the utility of P3 onset latency as a noninvasive, temporally precise neural marker of the response inhibition process.

Inhibitory motor control based on complex stopping goals relies on the same brain network as simple stopping

Much research has modeled action-stopping using the stop-signal task (SST), in which an impending response has to be stopped when an explicit stop-signal occurs. A limitation of the SST is that real-world action-stopping rarely involves explicit stop-signals. Instead, the stopping-system engages when environmental features match more complex stopping goals. For example, when stepping into the street, one monitors path, velocity, size, and types of objects and only stops if there is a vehicle approaching. Here, we developed a task in which participants compared the visual features of a multidimensional go-stimulus to a complex stopping-template, and stopped their go-response if all features matched the template. We used independent component analysis of EEG data to show that the same motor inhibition brain network that explains action-stopping in the SST also implements motor inhibition in the complex-stopping task. Furthermore, we found that partial feature overlap between go-stimulus and stopping-template led to motor slowing, which also corresponded with greater stopping-network activity. This shows that the same brain system for action-stopping to explicit stop-signals is recruited to slow or stop behavior when stimuli match a complex stopping goal. The results imply a generalizability of the brain's network for simple action-stopping to more ecologically valid scenarios.

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.

Alcohol abuse and ERP components in Go/No-go tasks using alcohol-related stimuli: impact of alcohol avoidance

Alcohol addictive behaviors are associated with a combination of deficits in executive functions, such as a weak response inhibition, and potent automatic appetitive responses to alcohol-related cues. The aim of the present study was to investigate behavioral responses and event-related potentials (ERPs) associated with specific response inhibition for alcohol-related cues. Thirty participants (15 heavy drinkers and 15 light drinkers) took part in the study. Response inhibition was assessed by a classical letter Go/No-go task and by a modified alcohol Go/No-go task. Participants were also classified as high and low alcohol avoiders. Results showed that heavy drinkers made more false alarms in the letter Go/No-go task. In the alcohol Go/No-go task, an absence of N200 amplitude anteriorization was found in heavy drinkers as compared to light drinkers. Participants with a high level of alcohol avoidance exhibited more false alarms, and higher N200 amplitude for the No-go trials as compared to the Go trials for alcohol-related cues. Higher P300 amplitude was observed in low alcohol avoiders for No-go as compared to Go trials. Therefore, a context involving alcohol-related cues disturbed inhibition capacities of high alcohol avoiders. These results suggest that the level of alcohol avoidance must be taken into account in studies investigating alcohol-related cognitive biases.

Increased impulsivity in response to food cues after sleep loss in healthy young men

OBJECTIVE

To investigate whether acute total sleep deprivation (TSD) leads to decreased cognitive control when food cues are presented during a task requiring active attention, by assessing the ability to cognitively inhibit prepotent responses.

METHODS

Fourteen males participated in the study on two separate occasions in a randomized, crossover within-subject design: one night of TSD versus normal sleep (8.5 hours). Following each nighttime intervention, hunger ratings and morning fasting plasma glucose concentrations were assessed before performing a go/no-go task.

RESULTS

Following TSD, participants made significantly more commission errors when they were presented "no-go" food words in the go/no-go task, as compared with their performance following sleep (+56%; P<0.05). In contrast, response time and omission errors to "go" non-food words did not differ between the conditions. Self-reported hunger after TSD was increased without changes in fasting plasma glucose. The increase in hunger did not correlate with the TSD-induced commission errors.

CONCLUSIONS

Our results suggest that TSD impairs cognitive control also in response to food stimuli in healthy young men. Whether such loss of inhibition or impulsiveness is food cue-specific as seen in obesity-thus providing a mechanism through which sleep disturbances may promote obesity development-warrants further investigation.

The dorsal medial frontal cortex mediates automatic motor inhibition in uncertain contexts: evidence from combined fMRI and EEG studies

Response inhibition is commonly thought to rely on voluntary, reactive, selective, and relatively slow prefrontal mechanisms. In contrast, we suggest here that response inhibition is achieved automatically, nonselectively, within very short delays in uncertain environments. We modified a classical go/nogo protocol to probe context-dependent inhibitory mechanisms. Because no single neuroimaging method can definitely disentangle neural excitation and inhibition, we combined fMRI and EEG recordings in healthy humans. Any stimulus (go or nogo) presented in an uncertain context requiring action restraint was found to evoke activity changes in the supplementary motor complex (SMC) with respect to a control condition in which no response inhibition was required. These changes included: (1) An increase in event-related BOLD activity, (2) an attenuation of the early (170 ms) event related potential generated by a single, consistent source isolated by advanced blind source separation, and (3) an increase in the evoked-EEG Alpha power of this source. Considered together, these results suggest that the BOLD signal evoked by any stimulus in the SMC when the situation is unpredictable can be driven by automatic, nonselective, context-dependent inhibitory activities. This finding reveals the paradoxical mechanisms by which voluntary control of action may be achieved. The ability to provide controlled responses in unpredictable environments would require setting-up the automatic self-inhibitory circuitry within the SMC. Conversely, enabling automatic behavior when the environment becomes predictable would require top-down control to deactivate anticipatorily and temporarily the inhibitory set.

Response inhibition and interference control in obsessive-compulsive spectrum disorders

Over the past 20 years, motor response inhibition and interference control have received considerable scientific effort and attention, due to their important role in behavior and the development of neuropsychiatric disorders. Results of neuroimaging studies indicate that motor response inhibition and interference control are dependent on cortical–striatal–thalamic–cortical (CSTC) circuits. Structural and functional abnormalities within the CSTC circuits have been reported for many neuropsychiatric disorders, including obsessive–compulsive disorder (OCD) and related disorders, such as attention-deficit hyperactivity disorder, Tourette’s syndrome, and trichotillomania. These disorders also share impairments in motor response inhibition and interference control, which may underlie some of their behavioral and cognitive symptoms. Results of task-related neuroimaging studies on inhibitory functions in these disorders show that impaired task performance is related to altered recruitment of the CSTC circuits. Previous research has shown that inhibitory performance is dependent upon dopamine, noradrenaline, and serotonin signaling, neurotransmitters that have been implicated in the pathophysiology of these disorders. In this narrative review, we discuss the common and disorder-specific pathophysiological mechanisms of inhibition-related dysfunction in OCD and related disorders.

Benign hereditary chorea as an experimental model to investigate the role of medium spiny neurons for response adaptation

Processing errors is a major requirement for behavioral adaptation. While it has been assumed that the basal ganglia play an important role in initiating these processes, the role of the striatal microstructure for these processes remains to be uncovered. Previous studies in basal ganglia diseases could not elucidate the relevance of the striatal medium spiny neuron (MSN) microstructure unambiguously because structural alterations occur together with alterations in various neurotransmitter systems. We present and examine a possible model that allows the examination of MSN dysfunction unbiased by other modulations, i.e. a case of 'benign hereditary chorea' (BHC) in comparison to healthy controls. We apply event-related potentials (ERPs) to uncover the underlying neurophysiological mechanisms underlying post-error behavioral adaptation. The BHC patient revealed a smaller error-related negativity (ERN) together with almost absent behavioral adaptation after an error and generally more error-prone behavior. Performance monitoring processes unrelated to errors, as well as response inhibition processes, were not affected in the BHC patient. The results suggest that the striatal MSN microstructural integrity is more important for error-related behavioral adaptation than for other response monitoring processes unrelated to errors.

Stimulus-response mappings shape inhibition processes: a combined EEG-fMRI study of contextual stopping

Humans are rarely faced with one simple task, but are typically confronted with complex stimulus constellations and varying stimulus-relevance in a given situation. Through modifying the prototypical stop-signal task and by combined recording and analysis of electroencephalography (EEG) and functional magnetic resonance imaging (fMRI), we studied the effects of stimulus relevance for the generation of a response or its inhibition. Stimulus response mappings were modified by contextual cues, indicating which of two different stimuli following a go stimulus was relevant for stopping. Overall, response inhibition, that is comparing successful stopping to a stop-signal against go-signal related processes, was associated with increased activity in right inferior and left midfrontal regions, as well as increased EEG delta and theta power; however, stimulus-response conditions in which the most infrequent stop-signal was relevant for inhibition, were associated with decreased activity in regions typically involved in response inhibition, as well as decreased activity in the delta and theta bands as compared to conditions wherein the relevant stop-signal frequency was higher. Behaviorally, this (aforementioned) condition, which demanded inhibition only from the most infrequent stimulus, was also associated with reduced reaction times and lower error rates. This pattern of results does not align with typical stimulus frequency-driven findings and suggests interplay between task relevance and stimulus frequency of the stop-signal. Moreover, with a multimodal EEG-fMRI analysis, we demonstrated significant parameterization for response inhibition with delta, theta and beta time-frequency values, which may be interpreted as reflecting conflict monitoring, evaluative and/or motor processes as suggested by previous work (Huster et al., 2013; Aron, 2011). Further multimodal results suggest a possible neurophysiological and behavioral benefit under conditions whereby the most infrequent stimulus demanded inhibition, indicating that the frequency of the stop-signal interacts with the current stimulus-response contingency. These results demonstrate that response inhibition is prone to influence from other cognitive functions, making it difficult to dissociate real inhibitory capabilities from the influence of moderating mechanisms.

Aging and motor inhibition: a converging perspective provided by brain stimulation and imaging approaches

The ability to inhibit actions, one of the hallmarks of human motor control, appears to decline with advancing age. Evidence for a link between changes in inhibitory functions and poor motor performance in healthy older adults has recently become available with transcranial magnetic stimulation (TMS). Overall, these studies indicate that the capacity to modulate intracortical (ICI) and interhemispheric (IHI) inhibition is preserved in high-performing older individuals. In contrast, older individuals exhibiting motor slowing and a declined ability to coordinate movement appear to show a reduced capability to modulate GABA-mediated inhibitory processes. As a decline in the integrity of the GABA-ergic inhibitory processes may emerge due to age-related loss of white and gray matter, a promising direction for future research would be to correlate individual differences in structural and/or functional integrity of principal brain networks with observed changes in inhibitory processes within cortico-cortical, interhemispheric, and/or corticospinal pathways. Finally, we underscore the possible links between reduced inhibitory functions and age-related changes in brain activation patterns.

Temporal constraints of behavioral inhibition: relevance of inter-stimulus interval in a Go-Nogo task

The capacity to inhibit prepotent and automatic responses is crucial for proper cognitive and social development, and inhibitory impairments have been considered to be key for some neuropsychiatric conditions. One of the most used paradigms to analyze inhibitory processes is the Go-Nogo task (GNG). This task has been widely used in psychophysical and cognitive EEG studies, and more recently in paradigms using fMRI. However, a technical limitation is that the time resolution of fMRI is poorer than that of the EEG technique. In order to compensate for these temporal constraints, it has become common practice in the fMRI field to use longer inter-stimulus intervals (ISI) than those used in EEG protocols. Despite the noticeable temporal differences between these two techniques, it is currently assumed that both approaches assess similar inhibitory processes. We performed an EEG study using a GNG task with both short ISI (fast-condition, FC, as in EEG protocols) and long ISI (slow-condition, SC, as in fMRI protocols). We found that in the FC there was a stronger Nogo-N2 effect than in the SC. Moreover, in the FC, but not in the SC, the number of preceding Go trials correlated positively with the Nogo-P3 amplitude and with the Go trial reaction time; and negatively with commission errors. In addition, we found significant topographical differences for the Go-P3 elicited in FC and SC, which is interpreted in terms of different neurotransmitter dynamics. Taken together, our results provide evidence that frequency of stimulus presentation in the GNG task strongly modulates the behavioral response and the evoked EEG activity. Therefore, it is likely that short-ISI EEG protocols and long-ISI fMRI protocols do not assess equivalent inhibitory processes.

Impact of orbitofrontal lesions on electrophysiological signals in a stop signal task

Behavioral inhibition and performance monitoring are critical cognitive functions supported by distributed neural networks including the pFC. We examined neurophysiological correlates of motor response inhibition and action monitoring in patients with focal orbitofrontal (OFC) lesions (n = 12) after resection of a primary intracranial tumor or contusion because of traumatic brain injury. Healthy participants served as controls (n = 14). Participants performed a visual stop signal task. We analyzed behavioral performance as well as event-related brain potentials and oscillations. Inhibition difficulty was adjusted individually to yield an equal amount of successful inhibitions across participants. RTs of patients and controls did not differ significantly in go trials or in failed stop trials, and no differences were observed in estimated stop signal RT. However, electrophysiological response patterns during task performance distinguished the groups. Patients with OFC lesions had enhanced P3 amplitudes to congruent condition go signals and to stop signals. In stop trials, patients had attenuated N2 and error-related negativity, but enhanced error positivity. Patients also showed enhanced and prolonged post-error beta band increases for stop errors. This effect was particularly evident in patients whose lesion extended to the subgenual cingulate cortex. In summary, although response inhibition was not impaired, the diminished stop N2 and ERN support a critical role of the OFC in action monitoring. Moreover, the increased stop P3, error positivity, and post-error beta response indicate that OFC injury affected action outcome evaluation and support the notion that the OFC is relevant for the processing of abstract reinforcers such as performing correctly in the task.

Neurocognitive, psychological and behavioral correlates of binge drinking and use of alcohol with caffeinated beverages in college-aged adults

BACKGROUND

We examined event-related potential (ERP), behavioral and psychological correlates of binge drinking and the use of alcohol mixed with caffeinated beverages (AmCBs) in college-aged (18-26 years) adults.

OBJECTIVE

Our objective was to delineate the neurocognitive correlates of different patterns of risky alcohol use in this population.

METHODS

We collected ERP data while an initial sample of 60 participants completed visual oddball and go/no-go tasks. We also collected self-report data measuring levels of sensation seeking, impulsivity, and drinking-induced disinhibition. In our primary analyses between binge drinker (N = 17) and comparison participants (N = 29), we used analysis of covariance (ANCOVA) to control for monthly marijuana usage and excluded participants who reported using other illicit drugs. As separate, exploratory analyses, we compared participants who reported using AmCBs (n = 14) and those who did not (n = 46), co-varying for monthly marijuana and recreational drug use.

RESULTS

We found that binge drinkers and AmCB users reported significantly higher levels of sensation seeking and drinking-induced disinhibition. In addition, we found that binge drinkers exhibited greater P3a/b amplitudes in the oddball task. In contrast, AmCB users exhibited significantly attenuated P3a amplitudes to distracter stimuli in the oddball task. However, we found no statistically significant differences in the amplitudes of P2(00) or N2(00) components between binge drinkers and comparison participants or between AmCB users and nonusers.

CONCLUSIONS

Overall, these data suggest that binge drinking and AmCB use are associated with P3 alterations, but the specific effects may differ for individuals with different patterns of risky alcohol use.

Unexpected events induce motor slowing via a brain mechanism for action-stopping with global suppressive effects

When an unexpected event occurs in everyday life (e.g., a car honking), one experiences a slowing down of ongoing action (e.g., of walking into the street). Motor slowing following unexpected events is a ubiquitous phenomenon, both in laboratory experiments as well as such everyday situations, yet the underlying mechanism is unknown. We hypothesized that unexpected events recruit the same inhibition network in the brain as does complete cancellation of an action (i.e., action-stopping). Using electroencephalography and independent component analysis in humans, we show that a brain signature of successful outright action-stopping also exhibits activity following unexpected events, and more so in blocks with greater motor slowing. Further, using transcranial magnetic stimulation to measure corticospinal excitability, we show that an unexpected event has a global motor suppressive effect, just like outright action-stopping. Thus, unexpected events recruit a common mechanism with outright action-stopping, moreover with global suppressive effects. These findings imply that we can now leverage the considerable extant knowledge of the neural architecture and functional properties of the stopping system to better understand the processing of unexpected events, including perhaps how they induce distraction via global suppression.

Cortical surface alignment in multi-subject spatiotemporal independent EEG source imaging

Brain responses to stimulus presentations may vary widely across subjects in both time course and spatial origins. Multi-subject EEG source imaging studies that apply Independent Component Analysis (ICA) to data concatenated across subjects have overlooked the fact that projections to the scalp sensors from functionally equivalent cortical sources vary from subject to subject. This study demonstrates an approach to spatiotemporal independent component decomposition and alignment that spatially co-registers the MR-derived cortical topographies of individual subjects to a well-defined, shared spherical topology (Fischl et al., 1999). Its efficacy for identifying functionally equivalent EEG sources in multi-subject analysis is demonstrated by analyzing EEG and behavioral data from a stop-signal paradigm using two source-imaging approaches, both based on individual subject independent source decompositions. The first, two-stage approach uses temporal infomax ICA to separate each subject's data into temporally independent components (ICs), then estimates the source density distribution of each IC process from its scalp map and clusters similar sources across subjects (Makeig et al., 2002). The second approach, Electromagnetic Spatiotemporal Independent Component Analysis (EMSICA), combines ICA decomposition and source current density estimation of the artifact-rejected data into a single spatiotemporal ICA decomposition for each subject (Tsai et al., 2006), concurrently identifying both the spatial source distribution of each cortical source and its event-related dynamics. Applied to the stop-signal task data, both approaches gave IC clusters that separately accounted for EEG processes expected in stop-signal tasks, including pre/postcentral mu rhythms, anterior-cingulate theta rhythm, and right-inferior frontal responses, the EMSICA clusters exhibiting more tightly correlated source areas and time-frequency features.

Developmental change in EEG theta activity in the medial prefrontal cortex during response control

Cognitive control functions continue to improve from infancy until early adulthood, allowing flexible adaptation to a complex environment. However, it remains controversial how this development in cognitive capabilities is mediated by changes in cortical activity: both age-related increases and decreases of mediofrontal neural activity have been observed and interpreted as neural underpinnings of this functional development. To better understand this developmental process, we examined EEG theta activity in the mediofrontal region using a Go/No-go response control task. We found that both pre-stimulus baseline theta-power and theta-power during the response control task, without baseline-correction, decreased with age. Conversely, when task-related theta-power was baseline corrected (using a ratio method), it exhibited a positive developmental trajectory. The age-related theta-power increase was source-localized to the anterior cingulate cortex. This increase in theta activity also partially mediated age-related improvements in response control and was greatest in a condition that demanded greater effort. Theta activity in older children also showed greater temporal reliability across trials as measured by inter-trial phase-coherence. Interestingly, directly subtracting baseline activity from task-related activity did not yield significant developmental effects, which highlights the necessity of separating and contrasting the pre-stimulus baseline with task-related processing in the understanding of neurodevelopmental changes.

Beta oscillatory responses in healthy subjects and subjects with mild cognitive impairment

The aim of the present study was to investigate the role of beta oscillatory responses upon cognitive load in healthy subjects and in subjects with mild cognitive impairment (MCI). The role of beta oscillations upon cognitive stimulation is least studied in comparison to other frequency bands. The study included 17 consecutive patients with MCI (mean age = 70.8 ± 5.6 years) according to Petersen's criteria, and 17 age- and education-matched normal elderly controls (mean age = 68.5 ± 5.5 years). The experiments used a visual oddball paradigm. EEG was recorded at 30 cortical locations. EEG-evoked power, inter-trial phase synchronization, and event-related beta responses filtered in 15-20 Hz were obtained in response to target and non-target stimuli for both groups of subjects. In healthy subjects, EEG-evoked beta power, inter-trial phase synchronization of beta responses and event-related filtered beta responses were significantly higher in responses to target than non-target stimuli (p < 0.05). In MCI patients, there were no differences in evoked beta power between target and non-target stimuli. Furthermore, upon presentation of visual oddball paradigm, occipital electrodes depict higher beta response in comparison to other electrode sites. The increased beta response upon presentation of target stimuli in healthy subjects implies that beta oscillations could shift the system to an attention state, and had important function in cognitive activity. This may, in future, open the way to consider beta activity as an important operator in brain cognitive processes.

EEG signatures associated with stopping are sensitive to preparation

Preparing to stop may "prime" the neural mechanism for stopping and alter brain activity at the time of stopping. Much electroencephalography (EEG) research has studied the N2/P3 complex over frontocentral electrodes during outright stopping. Here, we used differential reward of the stop and go processes in a stop signal task to study the sensitivity of these EEG components to preparation. We found that (a) stopping was faster when it was rewarded; (b) the P3 amplitude was larger for successful versus failed stopping, and this difference was greater when stopping was rewarded over going; (c) the N2 component was observed only on failed stop trials; and (d) there was greater EEG coherence between frontocentral and occipitoparietal electrodes at 12 Hz during the initiation of a go response when stopping was rewarded over going. We propose that frontocentral cortical mechanisms active before and at the time of stopping are sensitive to preparation.

Eye blink correction: a test on the preservation of common ERP components using a regression based technique

Eye blinks are a pervasive problem in electroencephalography research as they contaminate the brain signal. This paper tests the merits of a software tool employing the regression-based Gratton method that claims to remove the detrimental effects of the eye blink and leaves the activity of the brain. The efficacy of the correction tool was tested on five common stimulus-locked Event Related Potential (ERP) components used in a standard Go/Nogo task. Results suggested that the ‘corrected’ data could be predicted from data containing no eye blinks, suggesting the tool does not distort the data to great extent. This effect was found significant for all components, except for the P3. The conclusion is that this tool distorts the data at acceptable levels, yet caution should be taken when interpreting later components, like the P3.

Variations in midcingulate morphology are related to ERP indices of cognitive control

The midcingulate cortex (MCC; often somewhat imprecisely referred to as dorsal or cognitive part of the anterior cingulate cortex or dACC) is a core region contributing to cognitive control. Neuroanatomical deviations in the midcingulate region have been observed in a variety of mental disorders. Even in healthy subjects a high degree of morphological variability is seen, for example concerning the degree of anterior midcingulate fissurization. To investigate the relationship between anterior midcingulate morphology and function, individuals with a leftward midcingulate folding asymmetry (LEFT) were compared to individuals showing a lower degree of fissurization or a rightward asymmetric folding (REST). Data from two experiments, a masked Stroop paradigm and a combined go/no-go and stop-signal task, are reported. With the masked Stroop task, LEFT subjects revealed a better processing of incongruent Stroop stimuli when compared to REST subjects. This was reflected in both augmented N400 responses as well as significantly higher accuracy scores. In addition, similar effects were found with event-related potentials from the combined go/no-go and stop-signal task. Here, the N200 but not the P300, which have been associated with conflict-related and evaluative processing stages, respectively, was found to be significantly increased with LEFT subjects. The results of this study foster an association of midcingulate fissurization with differences in behavior and neurophysiological functioning related to cognitive control.