No-go activity in the frontal association cortex of human subjects

The effectiveness of high-frequency left DLPFC-rTMS on depression, response inhibition, and cognitive flexibility in female subjects with major depressive disorder

BACKGROUND

The purpose of the present study was to investigate the effect of high-frequency repetitive transcranial magnetic stimulation on depression severity, response inhibition, and cognitive flexibility in subjects with major depressive disorder.

METHODS

Twenty-eight female subjects with major depressive disorder were randomly divided into experimental and control groups. High frequency (20 Hz) rTMS stimulation at 85% of the MT consisted of 25 trains of 5 s duration, a total of 2500 pulses/session or sham stimulation was applied over the left DLPFC for five consecutive days per week, for two weeks. Depression severity, response inhibition, and cognitive flexibility of subjects were assessed by Beck Depression Inventory, Go/NoGo, and Wisconsin sort cards (WCST) tests, respectively, pre- and post-TMS intervention.

RESULTS

rTMS over the left DLPFC significantly decreased the depression severity at the Beck Depression Inventory, enhanced accuracy, and decreased reaction time at the Go/NoGo task. In the Wisconsin Card Sort Test, perseverative and non-perseverative errors and failure to maintain a set index significantly decreased following rTMS treatment.

CONCLUSIONS

Findings indicate that 20-Hz rTMS treatment on the left DLPFC has a positive effect on depression severity, response inhibition, and cognitive flexibility in depressed subjects.

Neuromodulation in Beta-Band Power Between Movement Execution and Inhibition in the Human Hippocampus

INTRODUCTION

The hippocampus is thought to be involved in movement, but its precise role in movement execution and inhibition has not been well studied. Previous work with direct neural recordings has found beta-band (13-30 Hz) modulation in both movement execution and inhibition throughout the motor system, but the role of beta-band modulation in the hippocampus during movement inhibition is not well understood. Here, we perform a Go/No-Go reaching task in ten patients with medically refractory epilepsy to study human hippocampal beta-power changes during movement.

MATERIALS AND METHODS

Ten epilepsy patients (5 female; ages 21-46) were implanted with intracranial depth electrodes for seizure monitoring and localization. Local field potentials were sampled at 2000 Hz during a Go/No-Go movement task. Comparison of beta-band power between Go and No-Go conditions was conducted using Wilcoxon signed-rank hypothesis testing for each patient. Sub-analyses were conducted to assess differences in the anterior vs posterior contacts, ipsilateral vs contralateral contacts, and male vs female beta-power values.

RESULTS

Eight out of ten patients showed significant beta-power decreases during the Go movement response (p < 0.05) compared to baseline. Eight out of ten patients also showed significant beta-power increases in the No-Go condition, occurring in the absence of movement. No significant differences were noted between ipsilateral vs contralateral contacts nor in anterior vs posterior hippocampal contacts. Female participants had a higher task success rate than males and had significantly greater beta-power increases in the No-Go condition (p < 0.001).

CONCLUSION

These findings indicate that increases in hippocampal beta power are associated with movement inhibition. To the best of our knowledge, this study is the first to report this phenomenon in the human hippocampus. The beta band may represent a state-change signal involved in motor processing. Future focus on the beta band in understanding human motor and impulse control will be vital.

Electrophysiological indexes for impaired response inhibition and salience attribution in substance (stimulants and depressants) use disorders: A meta-analysis

The impairment of inhibitory control and reward system is the core feature underlying substance use disorder (SUD). Previous studies suggested that it can be regarded as impaired response inhibition and salience attribution syndrome (iRISA). The neural substrates of the two deficit functions were widely investigated in neuroimaging studies, and the impaired prefrontal cortex, limbic-orbitofrontal network, and fronto-insular-parietal network were observed. Previous Event-related potential (ERP) studies were also conducted to explore EEG indexes related to abnormal brain function. In the current meta-analysis, we aimed to explore the consistency of ERP indexes that can reflect the two aberrant processes: P300/slow potential (SP) for salience attribution and Error-related negativity (ERN)/Nogo-N200/Nogo-P300 for inhibitory control and conflict monitoring. Subgroup analyses for drug type and drug use conditions were also conducted. According to the 60 research studies, we found significantly enhanced drug-cue-induced P300 amplitude and attenuated Nogo-N200 amplitude in SUD individuals relative to Healthy control (HC), which supports the dual model. Moreover, the drug-cue-induced P300 displayed time-dependence recovery, suggesting a potential index for treatment evaluation. In conclusion, drug-cue-induced P300 and Nogo-N200 demonstrated high consistency, and the drug-cue-induced P300 can be used to track the changes of functional recovery for SUD. The integration of the two ERP components could be regarded as a potential biomarker for SUD, which may provide a new insight for clinical treatment and investigation.

Identification of selection and inhibition components in a Go/NoGo task from EEG spectra using a machine learning classifier

INTRODUCTION

Prior Go/NoGo studies have localized specific regions and EEG spectra for which traditional approaches have distinguished between Go and NoGo conditions. A more detailed characterization of the spatial distribution and timing of the synchronization of frequency bands would contribute substantially to the clarification of neural mechanisms that underlie performance of the Go/NoGo task.

METHODS

The present study used a machine learning approach to learn the features that distinguish between ERSPs involved in selection and inhibition in a Go/NoGo task. A single-layer neural network classifier was used to predict task conditions for each subject to characterize ERSPs associated with Go versus NoGo trials.

RESULTS

The final classifier accurately identified individual task conditions at an overall rate of 92%, estimated by fivefold cross-validation. The detailed accounting of EEG time-frequency patterns localized to brain regions (i.e., thalamus, pre-SMA, orbitofrontal cortex, and superior parietal cortex) corroborates and also elaborates upon previous findings from fMRI and EEG studies, and expands the information about EEG power changes in multiple frequency bands (i.e., primarily theta power increase, alpha decreases, and beta increases and decreases) within these regions underlying the selection and inhibition processes engaged in the Go and NoGo trials.

CONCLUSION

This time-frequency-based classifier extends previous spatiotemporal findings and provides information about neural mechanisms underlying selection and inhibition processes engaged in Go and NoGo trials, respectively. This neural network classifier can be used to assess time-frequency patterns from an individual subject and thus may offer insight into therapeutic uses of neuromodulation in neural dysfunction.

Evoked Frontal and Parietal Field Potential Signatures of Target Detection and Response Inhibition in Rats Performing an Equiprobable Auditory Go/No-Go Task

To characterize the rat as a potential model of frontal-parietal auditory processing during sustained attention, target detection, and response inhibition, we recorded field potentials (FPs) at multiple sites in medial-dorsal frontal and posterior parietal cortex simultaneously while rats performed an equiprobable auditory go/no-go discrimination task. Event-related potentials (ERPs) were calculated by averaging tone-triggered FPs across hit, miss, false alarm (FA), and correct rejection (CR) trials separately for each recording session, and five peak amplitudes (termed N1, P2, N2, P3E, and P3L) were extracted from the individual-session ERPs. Comparing peak amplitudes across different trials types indicated a statistically significant amplification of the P2 peak on hit trials that accompanies detection of the target tone prior to the behavioral go response. This result appears analogous to human ERP phenomena during auditory target discrimination. Conversely, the rat P3 responses were not associated with target detection as in the human ERP literature. Likewise, we did not observe the “no-go N2” or “no-go P3” responses reported in the human literature in association with response inhibition, which might reflect differences in task context or a difference in auditory processing between rats and humans. We also present analyses of stimulus-induced spectral power and interarea coherence to characterize oscillatory synchronization which may contribute to ERPs, and discuss possible error-related processing at the N2, P3E, and P3L peaks.

Disentangling specific inhibitory versus general decision-making processes during sleep deprivation using a Go/NoGo ERP paradigm

This study used a Go/NoGo ERP paradigm in which Go and NoGo stimuli occurred rarely and equally often in an attempt to determine if sleep deprivation has a general effect on decision-making or a more specific effect on inhibition. A Go/NoGo task was administered six times to eleven participants during 36 h of sleep deprivation and once again post recovery sleep. In the Go condition, the participant was asked to respond to the rare stimulus. In the separate NoGo condition, the participant was asked to withhold the response to the rare stimulus. ERPs were recorded to the rare stimuli. The NoGo P3 should be attenuated if sleep loss mainly affects inhibitory processes. Both Go and NoGo P3 should be attenuated if sleep loss affects general detection processes. During sleep loss, accuracy decreased for both tasks. RT also gradually increased for the Go task. Performance during the NoGo task was more complex and was better accounted by a speed-accuracy trade-off. Overall, findings indicate that sleep deprivation did not have specific effects on inhibition. However, the amplitude of the Go P3 occurred as early as 12 h after waking and might reflect an effect of task repetition rather than true sleep deprivation. In contrast, the NoGo P3 amplitude was not significantly reduced until after 24 and 36 h of wakefulness, suggesting a true sleep deprivation effect. Both Go and NoGo P3 post recovery sleep did not return to baseline levels, possibly due to residual sleep inertia.

Irritability uniquely predicts prefrontal cortex activation during preschool inhibitory control among all temperament domains: A LASSO approach

Temperament, defined as individual variation in the reactivity and regulation of emotional, motor, and attentional processes, has been shown to influence emotional and cognitive development during the preschool period (ages 4-5). While relationships between temperament and neural activity have been investigated previously, these have typically investigated individual temperament dimensions selected ad hoc. Since significant correlations exist between various temperament dimensions, it remains unclear whether these findings would replicate while analyzing all temperament dimensions simultaneously. Using functional near infrared spectroscopy (fNIRS), 4-5-year-old children (N = 118) were administered a Go/No-Go task to assess prefrontal cortex activation during inhibitory control. The relationship between PFC activation and all 15 temperament domains defined by the Children's Behavior Questionnaire (CBQ) was assessed using automatic feature selection via LASSO regression. Results indicate that only the Anger/Frustration dimension was predictive of activation during the inhibitory control task. These findings support previous work showing relationships between irritability and prefrontal activation during executive function and extend those findings by demonstrating the specificity of the activation-irritability relationship among temperament dimensions.

Hard-wired feed-forward visual mechanisms of the brain compensate for affine variations in object recognition

Humans perform object recognition effortlessly and accurately. However, it is unknown how the visual system copes with variations in objects' appearance and the environmental conditions. Previous studies have suggested that affine variations such as size and position are compensated for in the feed-forward sweep of visual information processing while feedback signals are needed for precise recognition when encountering non-affine variations such as pose and lighting. Yet, no empirical data exist to support this suggestion. We systematically investigated the impact of the above-mentioned affine and non-affine variations on the categorization performance of the feed-forward mechanisms of the human brain. For that purpose, we designed a backward-masking behavioral categorization paradigm as well as a passive viewing EEG recording experiment. On a set of varying stimuli, we found that the feed-forward visual pathways contributed more dominantly to the compensation of variations in size and position compared to lighting and pose. This was reflected in both the amplitude and the latency of the category separability indices obtained from the EEG signals. Using a feed-forward computational model of the ventral visual stream, we also confirmed a more dominant role for the feed-forward visual mechanisms of the brain in the compensation of affine variations. Taken together, our experimental results support the theory that non-affine variations such as pose and lighting may need top-down feedback information from higher areas such as IT and PFC for precise object recognition.

5-HT2A Receptor Binding in the Frontal Cortex of Parkinson's Disease Patients and Alpha-Synuclein Overexpressing Mice: A Postmortem Study

The 5-HT_2A receptor is highly involved in aspects of cognition and executive function and seen to be affected in neurodegenerative diseases like Alzheimer's disease and related to the disease pathology. Even though Parkinson's disease (PD) is primarily a motor disorder, reports of impaired executive function are also steadily being associated with this disease. Not much is known about the pathophysiology behind this. The aim of this study was thereby twofold: (1) to investigate 5-HT_2A receptor binding levels in Parkinson's brains and (2) to investigate whether PD associated pathology, alpha-synuclein (AS) overexpression, could be associated with 5-HT_2A alterations. Binding density for the 5-HT_2A-specific radioligand [³H]-MDL 100.907 was measured in membrane suspensions of frontal cortex tissue from PD patients. Protein levels of AS were further measured using western blotting. Results showed higher AS levels accompanied by increased 5-HT_2A receptor binding in PD brains. In a separate study, we looked for changes in 5-HT_2A receptors in the prefrontal cortex in 52-week-old transgenic mice overexpressing human AS. We performed region-specific 5-HT_2A receptor binding measurements followed by gene expression analysis. The transgenic mice showed lower 5-HT_2A binding in the frontal association cortex that was not accompanied by changes in gene expression levels. This study is one of the first to look at differences in serotonin receptor levels in PD and in relation to AS overexpression.

Mastication accelerates Go/No-go decisional processing: An event-related potential study

OBJECTIVE

The purpose of the present study was to investigate the effect of mastication on Go/No-go decisional processing using event-related potentials (ERPs).

METHOD

Thirteen normal subjects underwent seven sessions of a somatosensory Go/No-go paradigm for approximately 4min; Pre, and Post 1, 2, 3, 4, 5, and 6. The Control condition included the same seven sessions. The RT and standard deviation were recorded, and the peak amplitude and latency of the N140 and P300 components were analyzed.

RESULTS

The RT was significantly shorter in Mastication than in Control at Post 1-3 and 4-6. The peak latency of N140 was earlier in Mastication than in Control at Post 4-6. The latency of N140 was shortened by repeated sessions in Mastication, but not by those in Control. The peak latency of P300 was significantly shorter in Mastication than in Control at Post 4-6. The peak latency of P300 was significantly longer in Control with repeated sessions, but not in Mastication.

CONCLUSIONS

These results suggest that mastication may influence response execution processing in Go trials, as well as response inhibition processing in No-go trials.

SIGNIFICANCE

Mastication accelerated Go/No-go decisional processing in the human brain.

Neural manifestations of implicit self-esteem: an ERP study

Behavioral research has established that humans implicitly tend to hold a positive view toward themselves. In this study, we employed the event-related potential (ERP) technique to explore neural manifestations of positive implicit self-esteem using the Go/Nogo association task (GNAT). Participants generated a response (Go) or withheld a response (Nogo) to self or others words and good or bad attributes. Behavioral data showed that participants responded faster to the self paired with good than the self paired with bad, whereas the opposite proved true for others, reflecting the positive nature of implicit self-esteem. ERP results showed an augmented N200 over the frontal areas in Nogo responses relative to Go responses. Moreover, the positive implicit self-positivity bias delayed the onset time of the N200 wave difference between Nogo and Go trials, suggesting that positive implicit self-esteem is manifested on neural activity about 270 ms after the presentation of self-relevant stimuli. These findings provide neural evidence for the positivity and automaticity of implicit self-esteem.

Somato-motor inhibitory processing in humans: evidence from neurophysiology and neuroimaging

Motor execution processing has been examined using an index of behavioral performance such as reaction times, kinetics, and kinematics. However, difficulties have been associated with the study of motor inhibitory processing because of the absence of actual behavioral performance. Therefore, non-invasive neurophysiological and neuroimaging methods including electroencephalography, magnetoencephalography, transcranial magnetic stimulation, and functional magnetic resonance imaging have been used to investigate neural processes in the central nervous system. We mainly reviewed research on somato-motor inhibitory processing based on data obtained by using these techniques, which can examine 'when', 'where, and 'how' motor inhibition occurs in the brain. Although to date a number of studies have used these techniques separately, few studies have utilized them in a comprehensive manner. In this review, we provide evidence that combining neurophysiological and neuroimaging methods should contribute to our understanding of how executive and inhibitory functions are implemented.

Empirically grounding grounded cognition: the case of color

Grounded cognition theories hold that the neural states involved in experiencing objects play a direct functional role in representing and accessing object knowledge from memory. However, extant data marshaled to support this view are also consistent with an opposing view that perceptuo-motor activations occur only following access to knowledge from amodal memory systems. We provide novel discriminating evidence for the functional involvement of visuo-perceptual states specifically in accessing knowledge about an object's color. We recorded event-related brain potentials (ERPs) while manipulating the visual contrast of monochromatic words ("lime") in a semantic decision task: responses were made for valid colors ("green") and locations ("kitchen") and withheld for invalid colors and locations. Low contrast delayed perceptual processing for both color and location. Critically, low contrast slowed access to color knowledge only. This finding reveals that the visual system plays a functional role in accessing object knowledge and uniquely supports grounded views of cognition.

Inhibitory control gains from higher-order cognitive strategy training

The present study examined the transfer of higher-order cognitive strategy training to inhibitory control. Middle school students enrolled in a comprehension- and reasoning-focused cognitive strategy training program and passive controls participated. The training program taught students a set of steps for inferring essential gist or themes from materials. Both before and after training or a comparable duration in the case of the passive controls, participants completed a semantically cued Go/No-Go task that was designed to assess the effects of depth of semantic processing on response inhibition and components of event-related potentials (ERP) related to response inhibition. Depth of semantic processing was manipulated by varying the level of semantic categorization required for response selection and inhibition. The SMART-trained group showed inhibitory control gains and changes in fronto-central P3 ERP amplitudes on inhibition trials; whereas, the control group did not. The results provide evidence of the transfer of higher-order cognitive strategy training to inhibitory control and modulation of ERPs associated with semantically cued inhibitory control. The findings are discussed in terms of implications for cognitive strategy training, models of cognitive abilities, and education.

Dopamine-agonists and impulsivity in Parkinson's disease: impulsive choices vs. impulsive actions

The control of impulse behavior is a multidimensional concept subdivided into separate subcomponents, which are thought to represent different underlying mechanisms due to either disinhibitory processes or poor decision-making. In patients with Parkinson's disease (PD), dopamine-agonist (DA) therapy has been associated with increased impulsive behavior. However, the relationship among these different components in the disease and the role of DA is not well understood. In this imaging study, we investigated in PD patients the effects of DA medication on patterns of brain activation during tasks testing impulsive choices and actions. Following overnight withdrawal of antiparkinsonian medication, PD patients were studied with a H2 ((15)) O PET before and after administration of DA (1 mg of pramipexole), while they were performing the delay discounting task (DDT) and the GoNoGo Task (GNG). We observed that pramipexole augmented impulsivity during DDT, depending on reward magnitude and activated the medial prefrontal cortex and posterior cingulate cortex and deactivated ventral striatum. In contrast, the effect of pramipexole during the GNG task was not significant on behavioral performance and involved different areas (i.e., lateral prefrontal cortex). A voxel-based correlation analysis revealed a significant negative correlation between the discounting value (k) and the activation of medial prefrontal cortex and posterior cingulate suggesting that more impulsive patients had less activation in those cortical areas. Here we report how these different subcomponents of inhibition/impulsivity are differentially sensitive to DA treatment with pramipexole influencing mainly the neural network underlying impulsive choices but not impulsive action.

The role of response inhibition in temporal preparation: evidence from a go/no-go task

During the foreperiod (FP) of a warned reaction task, participants engage in a process of temporal preparation to speed response to the impending target stimulus. Previous neurophysiological studies have shown that inhibition is applied during FP to prevent premature response. Previous behavioral studies have shown that the duration of FP on both the current and the preceding trial codetermine response time to the target. Integrating these findings, the present study tested the hypothesis that the behavioral effects find their origin in response inhibition on the preceding trial. In two experiments the variable-FP paradigm was combined with a go/no-go task, in which no-go stimuli required explicit response inhibition. The resulting data pattern revealed sequential effects of both FP (long or short) and response requirement (go or no-go), which could be jointly understood as expressions of response inhibition, consistent with the hypothesis.

Alive and grasping: stable and rapid semantic access to an object category but not object graspability

How quickly do different kinds of conceptual knowledge become available following visual word perception? Resolving this question will inform neural and computational theories of visual word recognition and semantic memory use. We measured real-time brain activity using event-related brain potentials (ERPs) during a go/nogo task to determine the upper limit by which category-related knowledge (living/nonliving) and action-related knowledge (graspable/ungraspable) must have been accessed to influence a downstream decision process. We find that decision processes can be influenced by the living/nonliving distinction by 160ms after stimulus onset whereas information about (one-hand) graspability is not available before 300ms. We also provide evidence that rapid access to category-related knowledge occurs for all items, not just a subset of living, nonliving, graspable, or ungraspable ones, and for all participants regardless of their response speed. The latency of the N200 nogo effect by contrast is sensitive to decision speed. We propose a tentative hypothesis of the neural mechanisms underlying semantic access and a subsequent decision process.

Response inhibition in adults and teenagers: spatiotemporal differences in the prefrontal cortex

Inhibition is a core executive function reliant on the frontal lobes that shows protracted maturation through to adulthood. We investigated the spatiotemporal characteristics of response inhibition during a visual go/no-go task in 14 teenagers and 14 adults using magnetoencephalography (MEG) and a contrast between two no-go experimental conditions designed to eliminate a common confound in earlier studies comparing go with no-go trials. Source analyses were performed using an event-related beamformer algorithm with co-registered individual structural MRIs. Performance was controlled to be similar across subjects. Analyses of MEG data revealed bilateral prefrontal activity in the inhibitory condition for both age groups, but with different spatiotemporal patterns: around 300ms after stimulus onset in middle frontal gyri in teenagers vs. around 260ms in inferior frontal gyri in adults. Moreover, the inhibition of a prepotent motor response showed a stronger recruitment of the left hemisphere in teenagers than in adults and of the right hemisphere in adults than in teenagers. These findings provide high-resolution temporal and spatial information regarding response inhibition in adolescents compared to adults, independent of motor components and performance differences.

Response inhibition results in the emotional devaluation of faces: neural correlates as revealed by fMRI

Although it is well established that prior experience with faces determines their subsequent social-emotional evaluation, recent work shows that top-down inhibitory mechanisms, including response inhibition, can lead to social devaluation after even a single, brief exposure. These rapidly induced effects indicate interplay among perceptual, attentional, response-selection and social-emotional networks; yet, the brain mechanisms underlying this are not well understood. This study used functional magnetic resonance imaging (fMRI) to investigate the neural mechanism mediating the relationship between inhibitory control and emotional devaluation. Participants performed two tasks: (i) a Go/No-Go task in response to faces and (ii) a trustworthiness rating task involving the previously seen faces. No-Go faces were rated as significantly less trustworthy than Go faces. By examining brain activations during Task 1, behavioral measures and brain activations obtained in Task 2 could be predicted. Specifically, activity in brain areas during Task 1 associated with (i) executive control and response suppression (i.e. lateral prefrontal cortex) and (ii) affective responses and value representation (i.e. orbitofrontal cortex), systematically covaried with behavioral ratings and amygdala activity obtained during Task 2. The present findings offer insights into the neural mechanisms linking inhibitory processes to affective responses.

Why the white bear is still there: electrophysiological evidence for ironic semantic activation during thought suppression

Much research has focused on the paradoxical effects of thought suppression, leading to the viewpoint that increases in unwanted thoughts are due to an ironic monitoring process that increases the activation of the very thoughts one is trying to rid from consciousness. However, it remains unclear from behavioral findings whether suppressed thoughts become more accessible during the act of suppression. In the current study, event-related potentials were recorded while participants suppressed or expressed thoughts of a focus word during a simple lexical decision task. Modulations in the N400 component reported here demonstrate the paradoxical effects occurring at the semantic level during suppression, as well as some evidence for the rebound effect after suppression periods. Interestingly, semantic activation was greater for focus words during suppression than expression, despite differences in the N1 window suggesting that expression elicited greater perceptual processing than suppression. Results provide electrophysiological evidence for the Ironic Process model and support recent claims of asymmetric network activation during thought suppression.

Executive functioning, irritability, and alcohol-related aggression

The purpose of this investigation was to examine (a) whether irritability mediates the relation between executive functioning (EF) and alcohol-related aggression and (b) whether the alcohol-aggression relation is better explained by the interactive effects of EF and irritability above and beyond the effects of either variable alone. EF was measured using seven well-established neuropsychological tests. Irritability was assessed with the Caprara Irritability Scale. Participants were 313 male and female social drinkers between 21 and 35 years of age. Following the consumption of an alcohol or a placebo beverage, participants were tested on a laboratory aggression task in which electric shocks were given to and received from a fictitious opponent under the guise of a competitive reaction-time task. Aggression was operationalized as the shock intensities administered to the fictitious opponent. Results indicated that irritability successfully mediated the relation between EF and intoxicated aggression for men only. Despite the fact that irritability and EF both independently moderated the alcohol-aggression relation in previous studies, no significant interaction for their combined effect was detected here. The findings are discussed, in part, within a cognitive neoassociationistic framework for aggressive behavior.

The time course of segment and tone encoding in Chinese spoken production: an event-related potential study

The present study investigated the time course of segment and tone encoding in Chinese spoken production with an event-related brain potentials (ERPs) experiment. Native Chinese speakers viewed a series of pictures and made Go/noGo decisions along dimensions of segmental onset or tone information of picture names. Behavioral data and onset latency of the N200 effect indicated that segmental information became available prior to tonal information. Moreover, the results of scalp distributions and onset latency patterns of the N200 effect on segmental and tonal decisions suggest that segmental and metrical encoding is relatively disassociated in Chinese spoken production. Our findings provide additional evidence from Chinese as a kind of non-alphabetic language concerning theories of phonological encoding based on alphabetic languages.

Comparison of smooth pursuit eye movement deficits in multiple system atrophy and Parkinson's disease

Because of the large overlap and quantitative similarity of eye movement alterations in Parkinson's disease (PD) and multiple system atrophy (MSA), a measurement of eye movement is generally not considered helpful for the differential diagnosis. However, in view of the pathophysiological differences between MSA and PD as well as between the cerebellar (MSA-C) and Parkinsonian (MSA-P) subtypes of MSA, we wondered whether a detailed investigation of oculomotor performance would unravel parameters that could help to differentiate between these entities. We recorded eye movements during sinusoidal pursuit tracking by means of video-oculography in 11 cases of MSA-P, 8 cases of MSA-C and 27 cases of PD and compared them to 23 healthy controls (CTL). The gain of the smooth pursuit eye movement (SPEM) component exhibited significant group differences between each of the three subject groups (MSA, PD, controls) but not between MSA-P and MSA-C. The similarity of pursuit impairment in MSA-P and in MSA-C suggests a commencement of cerebellar pathology in MSA-P despite the lack of clinical signs. Otherwise, SPEM gain was of little use for differential diagnosis between MSA and PD because of wide overlap. However, inspection of the saccadic component of pursuit tracking revealed that in MSA saccades typically correct for position errors accumulated during SPEM epochs ("catch-up saccades"), whereas in PD, saccades were often directed toward future target positions ("anticipatory saccades"). The differences in pursuit tracking between PD and MSA were large enough to warrant their use as ancillary diagnostic criteria for the distinction between these disorders.

Left parietal activation related to planning, executing and suppressing praxis hand movements

OBJECTIVE

We sought to investigate the activity of bilateral parietal and premotor areas during a Go/No Go paradigm involving praxis movements of the dominant hand.

METHODS

A sentence was presented which instructed subjects on what movement to make (S1; for example, "Show me how to use a hammer."). After an 8-s delay, "Go" or "No Go" (S2) was presented. If Go, they were instructed to make the movement described in the S1 instruction sentence as quickly as possible, and continuously until the "Rest" cue was presented 3 s later. If No Go, subjects were to simply relax until the next instruction sentence. Event-related potentials (ERP) and event-related desynchronization (ERD) in the beta band (18-22 Hz) were evaluated for three time bins: after S1, after S2, and from -2.5 to -1.5 s before the S2 period.

RESULTS

Bilateral premotor ERP was greater than bilateral parietal ERP after the S2 Go compared with the No Go. Additionally, left premotor ERP was greater than that from the right premotor area. There was predominant left parietal ERD immediately after S1 for both Go and No Go, which was sustained for the duration of the interval between S1 and S2. For both S2 stimuli, predominant left parietal ERD was again seen when compared to that from the left premotor or right parietal area. However, the left parietal ERD was greater for Go than No Go.

CONCLUSION

The results suggest a dominant role in the left parietal cortex for planning, executing, and suppressing praxis movements. The ERP and ERD show different patterns of activation and may reflect distinct neural movement-related activities.

SIGNIFICANCE

The data can guide further studies to determine the neurophysiological changes occurring in apraxia patients and help explain the unique error profiles seen in patients with left parietal damage.

The time course of semantic and orthographic encoding in Chinese word production: an event-related potential study

Previous studies have shown that access to conceptual/semantic information precedes phonological access in alphabetic language production such as English or Dutch. The present study investigated the time course of semantic and orthographic encoding in Chinese (a non-alphabetic language) spoken word production. Participants were shown pictures and carried out a dual-choice go/nogo task based on semantic information and orthographic information. The results of the N200 (related to response inhibition) and LRP (related to response preparation) indicated that semantic access preceded orthographic encoding by 176-202 ms. The different patterns of the two N200 effects suggest that they may tap into different processes. The N200 and LRP analyses also indicate that accessing the orthographic representation in speaking is likely optional and depends on specific task requirement.

Response preparation and inhibition: the role of the cortical sensorimotor beta rhythm

Paradigms requiring either a GO or a NO-GO response are often used to study the neural mechanisms of response inhibition. Here this issue is examined from the perspective of event-related beta (14-30 Hz) oscillatory activity. Two macaque monkeys performed a task that began with a self-initiated lever depression and maintenance (sustained motor output) and required a visual pattern discrimination followed by either a lever release (GO) or continued lever-holding (NO-GO) response. Analyzing simultaneous local field potentials (LFPs) from primary somatosensory, frontal motor, and posterior parietal cortices, we report two results. First, beta oscillation desynchronized shortly after stimulus presentation, the onset of which was approximately the same for both the GO and NO-GO conditions ( approximately 110 ms). Since it is well known that beta desynchronization is a reliable indicator of movement preparation, this result suggests that early motor preparation took place in both conditions. Second, following the GO/NO-GO decision ( approximately 190 ms), beta activity rebounded significantly ( approximately 300 ms) only in the NO-GO condition. Coherence and Granger causality measures revealed that the dynamical organization of the rebounded beta network was similar to that existing during the sustained motor output prior to stimulus onset. This finding suggests that response inhibition led to the restoration of the sensorimotor network to its prestimulus state.

A model of the go/no-go task

In this article, the first explicit, theory-based comparison of 2-choice and go/no-go variants of 3 experimental tasks is presented. Prior research has questioned whether the underlying core-information processing is different for the 2 variants of a task or whether they differ mostly in response demands. The authors examined 4 different diffusion models for the go/no-go variant of each task along with a standard diffusion model for the 2-choice variant (R. Ratcliff, 1978). The 2-choice and the go/no-go models were fit to data from 4 lexical decision experiments, 1 numerosity discrimination experiment, and 1 recognition memory experiment, each with 2-choice and go/no-go variants. The models that assumed an implicit decision criterion for no-go responses produced better fits than models that did not. The best model was one in which only response criteria and the nondecisional components of processing changed between the 2 variants, supporting the view that the core information on which decisions are based is not different between them.

Involvement of the lateral prefrontal cortex in conditional suppression of gaze shift

Conditional execution and suppression of gaze shift are important in everyday life. To examine the possible involvement of the lateral prefrontal cortex (LPFC) in this process, we induced a local and reversible inactivation by injecting muscimol into 66 sites within the LPFC of monkeys and examined muscimol's effect on their performance in an oculomotor Go/No-Go task. This task required a subject to execute (Go) or suppress (No-Go) its gaze toward a target location in response to an instructional visual cue. Local injection of muscimol into 22 regions of the LPFC resulted in significant increases in the number of error saccades toward a few specific target locations during No-Go trials, whereas there were no error saccades in the Go trials. The onset latency of error saccades in No-Go trials was significantly longer than that of correct saccades in Go trials, but their velocity and amplitude were similar to those of correct saccades in Go trials. Go correct saccades appeared intact after the injections. These findings provide evidence that different regions of the LPFC are involved in the conditional suppression of gaze shift toward a few specific target locations, which may occur through a top-down suppressive mechanism.

A model of the go/no-go task

In this article, the first explicit, theory-based comparison of 2-choice and go/no-go variants of 3 experimental tasks is presented. Prior research has questioned whether the underlying core-information processing is different for the 2 variants of a task or whether they differ mostly in response demands. The authors examined 4 different diffusion models for the go/no-go variant of each task along with a standard diffusion model for the 2-choice variant (R. Ratcliff, 1978). The 2-choice and the go/no-go models were fit to data from 4 lexical decision experiments, 1 numerosity discrimination experiment, and 1 recognition memory experiment, each with 2-choice and go/no-go variants. The models that assumed an implicit decision criterion for no-go responses produced better fits than models that did not. The best model was one in which only response criteria and the nondecisional components of processing changed between the 2 variants, supporting the view that the core information on which decisions are based is not different between them.

How response inhibition modulates nociceptive and non-nociceptive somatosensory brain-evoked potentials

OBJECTIVE

To examine and compare the modulation of nociceptive somatosensory laser-evoked potentials (LEPs) and non-nociceptive somatosensory electrically-evoked potentials (SEPs) by brain processes related to response inhibition.

METHODS

A warning auditory tone was followed by either an electrical or a laser stimulus. Subjects performed a Go/Nogo task in which they were instructed to respond to the laser stimulus and refrain from responding to the electrical stimulus in half of the runs. In the other half, they performed the opposite. The paradigm allowed a direct, within-subject comparison of the electrophysiological correlates of brain processes related to the Go/Nogo task in both somatosensory submodalities.

RESULTS

In the Nogo-condition, SEPs displayed an enhanced N120 (early Nogo-response), a reduced vertex P240 and enhanced frontal P3 (late Nogo-responses). In contrast, LEPs only displayed late Nogo-related responses (reduced vertex P350 and enhanced frontal P3).

CONCLUSIONS

The early Nogo-related enhancement of SEPs may reflect brain processes specific to the processing of non-nociceptive somatosensory stimuli. Later components of the Nogo-response may reflect cortical activity common to the processing of both nociceptive and non-nociceptive somatosensory stimuli.

SIGNIFICANCE

Response inhibition significantly modulates both LEPs and SEPs. Part of these activities may be specific of the eliciting stimulus modality.

Validating psychiatric endophenotypes: inhibitory control and attention deficit hyperactivity disorder

ADHD is a heritable condition of childhood for which several risk alleles have been identified. However, observed effect sizes have been small and few replicated polymorphisms have been identified. There are many reasons for the lack of one-to-one correspondence between genotype and phenotype in ADHD. Endophenotypes are non-clinical markers of genetic risk which may facilitate gene discovery in complex disorders like ADHD. The most common endophenotypes under consideration in ADHD are neuropsychological measures of executive function, although a range of psychological, physiological and neuroanatomical endophenotypes have been proposed. If carefully chosen, endophenotypes have the potential to increase the power of genetic research to identify susceptibility genes. If not carefully selected, endophenotypes may generate false negative and false positive results. This paper reviews the theoretical rationale for endophenotypes and proposes a priori criteria by which ADHD endophenotypes should be selected and validated. The literature on motor response inhibition is reviewed to illustrate the validation process which is recommended in the selection of other candidate endophenotypes.

The underlying role of aggressivity in the relation between executive functioning and alcohol consumption

The research literature on the relation between cognitive functioning and alcohol consumption is inconsistent and difficult to interpret. The purpose of this study was to test a causal model that might help reconcile some of these conflicts. The model specifies that aggressivity is an important intermediary mechanism underlying the relation between executive functioning (EF) and alcohol consumption. Participants were 310 (152 men and 158 women) healthy social drinkers between 21 and 35 years of age tested in a laboratory setting. EF was measured with a battery of neuropsychological tests. Aggressivity and alcohol consumption (as well as cigarette and drug use frequency) were measured with self-report and interview formats. Aggressivity played a mechanistic role in the relation between EF and alcohol/drug use for men but not for women. Women evinced some unexpected positive relations between EF and alcohol use. This study serves as a first step in trying to reconcile previous inconsistent findings regarding the relation between cognitive functioning and alcohol use by demonstrating that a better understanding of this relation involves considering aggressivity as an intermediary variable.

The influence of difficult temperament on alcohol-related aggression: better accounted for by executive functioning?

The purpose of this investigation was to test the hypothesis that executive functioning (EF) would mediate the relation between difficult temperament (DT) and intoxicated aggression. Participants were 165 social drinking men and women between the ages of 21-35years old. DT was measured using the Dimension of Temperament Scale - Revised and EF was measured using seven well-established neuropsychological tests. Following consumption of an alcoholic beverage, participants were tested on a laboratory aggression measure in which electric shocks were received from and administered to a fictitious opponent under the guise of a competitive reaction time task. Aggression was operationalized as shock intensities administered to the fictitious opponent under conditions of low and high provocation. Results indicated that EF successfully mediated the relation between DT and intoxicated aggression for men but not for women. These findings are discussed with regard to how they influence current models of aggressive behavior as well as their implications for future violence prevention efforts.

Lexical stress encoding in single word production estimated by event-related brain potentials

An event-related brain potentials (ERPs) experiment was carried out to investigate the time course of lexical stress encoding in language production. Native speakers of Dutch viewed a series of pictures corresponding to bisyllabic names which were either stressed on the first or on the second syllable and made go/no-go decisions on the lexical stress location of those picture names. Behavioral results replicated a pattern that was observed earlier, i.e. faster button-press latencies to initial as compared to final stress targets. The electrophysiological results indicated that participants could make a lexical stress decision significantly earlier when picture names had initial than when they had final stress. Moreover, the present data suggest the time course of lexical stress encoding during single word form formation in language production. When word length is corrected for, the temporal interval for lexical stress encoding specified by the current ERP results falls into the time window previously identified for phonological encoding in language production.

Higher anticipated force required a stronger inhibitory process in go/nogo tasks

OBJECTIVE

We investigated the effect of the inhibitory process with increasing muscle force on event-related potentials (ERPs) and motor evoked potentials (MEPs).

METHODS

The subjects performed a S1-S2 paradigm with go/nogo tasks. S1 was an auditory tone burst, and S2 was an electrical stimulation applied to the second (go stimuli) or fifth digit (nogo stimuli) of the left hand. The recordings were conducted at 3 force levels; 10, 30 and 50% maximal voluntary contraction (MVC). After the presentation of S2, the subjects were instructed to adjust their force level to match the target line with a force trajectory line in only the go trials.

RESULTS

Nogo-N140 was significantly more negative in amplitude than go-N140 in all conditions, and became larger with increasing muscle force. The MEP, which was recorded at 150 ms after S2, became significantly smaller with increasing muscle force in nogo trials, whereas it became larger in go trials.

CONCLUSIONS

Our results indicated that stronger inhibitory cerebral activity was needed for a nogo stimulus, in the case where a stronger response was needed for a go stimulus.

SIGNIFICANCE

The present study showed a significant relationship between cortical inhibitory process and muscle force.

Changing plans: neural correlates of executive control in monkey and human frontal cortex

Changing plans depends on executive control, the orchestration of behavior based on knowledge of both goal and context. Dorsolateral prefrontal (DLPFC) and anterior cingulate (ACC) cortices are clearly involved in these processes. Intracranial recordings in these regions were obtained from a monkey performing an executive control-challenging task that is widely used in clinic and laboratory to assess the integrity of cognitive function, the AX version of the continuous performance task (AX-CPT), and directly compared to scalp-recorded evoked potentials in humans. In this task the subject presses a button when detecting a frequent cue-target probe sequence in a stream of letters presented on a computer screen, and withholds response following incorrect sequences. Thus correct performance requires correct encoding of cue and probe instruction and inhibitory control. Intracranial recordings showed that DLPFC in the monkey was primarily activated by conditions that required inhibition of imminent action, as had been shown in human event-related potential (ERP) recordings. Different subregions of monkey ACC were activated primarily by either initiating or inhibiting action, whereas human ERP had shown ACC activation in both situations. We suggest that simultaneous activation of both types of subregions in conflict conditions may account the ubiquitous ACC activation observed with fMRI and ERP in those conditions.

Juicy fruit and creepy crawlies: an electrophysiological study of the implicit Go/NoGo association task

The Go/NoGo association task (GNAT) has been used in behavioral studies to measure the strength of association between different category groups and two poles of an evaluative dimension. However, reaction time data do not provide information about the neural time course of such associative information. We investigated event-related brain potentials (ERPs) elicited when participants were required to respond (Go) or withhold a response (NoGo) according to task instructions. Task instructions paired words from one of two taxonomic categories (fruit/bugs) with either pole of an evaluative dimension (good/bad). Within a given run, Go responses were assigned to one of the categories and one evaluative dimension. ERPs showed an increased negativity over frontal sites to NoGo as compared to Go responses. Moreover, NoGo minus Go difference waves showed that the N200 effect was delayed in trials within incongruent blocks (e.g., "Press if a bug word or a good word") as compared to trials within congruent blocks (e.g., "Press if a bug word or a bad word"). These results suggest that such associative attitude information is available at a very early stage of processing, less than 250 ms after seeing a fruit or a bug word. This finding is further discussed with respect to alternative explanations of the behavioral effect.

Modulation of early auditory processing by visually based sound prediction

Brain activity was measured by magnetoencephalography (MEG) to investigate whether the early auditory system can detect changes in audio-visual patterns when the visual part is presented earlier. We hypothesized that a template underlying the mismatch field (MMF) phenomenon, which is usually formed by past sound regularities, is also used in visually based sound prediction. Activity similar to the MMF may be elicited by comparing an incoming sound with the template. The stimulus was modeled after a keyboard: an animation in which one of two keys was depressed was accompanied by either a lower or higher tone. Congruent audio-visual pairs were designed to be frequent and incongruent pairs to be infrequent. Subjects were instructed to predict an incoming sound based on key movement in two sets of trials (prediction condition), whereas they were instructed not to do so in the other two sets (non-prediction condition). For each condition, the movement took 50 ms in one set (Delta = 50 ms) and 300 ms in the other (Delta = 300 ms) to reach the bottom, at which time a tone was delivered. As a result, only under the prediction condition with Delta = 300 ms was additional activity for incongruent pairs observed bilaterally in the supratemporal area within 100-200 ms of the auditory stimulus onset; this activity had spatio-temporal properties similar to those of MMF. We concluded that a template is created by the visually based sound prediction only after the visual discriminative and sound prediction processes have already been performed.