Components Of Inhibitory Control Research Articles

Dissociation of prepotent response inhibition and interference control in problematic internet use: evidence from the Go/No-Go and Flanker tasks

BackgroundProblematic Internet Use (PIU), characterized by failures to control the overuse of internet, is associated with a range of functional impairments. However, there is limited research on the specific impact of PIU on inhibitory control functions, particularly in terms of differentiating between prepotent response inhibition and interference control. Therefore, the main objective of this study is to investigate these two components of inhibitory control in individuals with PIU.MethodsThirty participants who met the PIU criteria and 30 control participants were included in the present study. All participants completed the Go/No-Go and Flanker tasks, in which internet-related images and words were used as task stimuli.ResultsIn the Go/No-Go task, all participants exhibited poorer performance in inhibiting internet-related stimuli compared to internet-unrelated stimuli, during the No-Go trials. In the Flanker task, results revealed a three-way interaction of Group, Stimulus type and Congruency. Specifically, in the incongruent condition, participants with PIU exhibited slower responses for internet-unrelated targets compared to internet-related targets, whereas no similar effect was observed among individuals with low internet use.ConclusionsThe findings suggest that difficulties in controlling the interference effect of internet-related information represent a key dysfunction in inhibitory control of PIU.

The (dis)engagement of different components of inhibitory control in trilingual language control.

Despite the worldwide prevalence of multilingualism, the knowledge of the relationship between domain-general cognitive control and multilingual language control remains scant. Here we provide new insights into this issue by examining systematically how different components of inhibitory control (i.e., response inhibition and interference suppression) contribute to language control in multilingual populations with high L2 proficiency. To this end, 65 Tibetan-Chinese-English trilinguals highly proficient in L2 were recruited to complete three tasks: a picture-naming task measuring the performance of online trilingual speech production, and two nonlinguistic tasks, a go/no-go task and a Simon task, as proxies for measuring response inhibition and interference suppression abilities, respectively. Using mixed-effects modeling, we analyzed both the trilingual language switching/nonswitching performances and their correlations with these two components of inhibitory control. Our data revealed unexpected patterns of reversed language dominance effect and (a)symmetries in switch costs. Notably, interaction analysis revealed that while response inhibition was robustly engaged in trilingual language control, interference suppression did not appear to play a role. Taken together, our study suggests that, for trilingual speakers highly proficient in L2, the recruitment of different subprocesses of inhibitory control in lexical access was selective and was constrained to reactive and local-level language control. We conclude by discussing theoretical implications. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Zolpidem Profoundly Augments Spared Tonic GABAAR Signaling in Dentate Granule Cells Ipsilateral to Controlled Cortical Impact Brain Injury in Mice.

Type A GABA receptors (GABAARs) are pentameric combinations of protein subunits that give rise to tonic (ITonicGABA) and phasic (i.e., synaptic; ISynapticGABA) forms of inhibitory GABAAR signaling in the central nervous system. Remodeling and regulation of GABAAR protein subunits are implicated in a wide variety of healthy and injury-dependent states, including epilepsy. The present study undertook a detailed analysis of GABAAR signaling using whole-cell patch clamp recordings from mouse dentate granule cells (DGCs) in coronal slices containing dorsal hippocampus at 1–2 or 8–13 weeks after a focal, controlled cortical impact (CCI) or sham brain injury. Zolpidem, a benzodiazepine-like positive modulator of GABAARs, was used to test for changes in GABAAR signaling of DGCs due to its selectivity for α1 subunit-containing GABAARs. Electric charge transfer and statistical percent change were analyzed in order to directly compare tonic and phasic GABAAR signaling and to account for zolpidem’s ability to modify multiple parameters of GABAAR kinetics. We observed that baseline ITonicGABA is preserved at both time-points tested in DGCs ipsilateral to injury (Ipsi-DGCs) compared to DGCs contralateral to injury (Contra-DGCs) or after sham injury (Sham-DGCs). Interestingly, application of zolpidem resulted in modulation of ITonicGABA across groups, with Ipsi-DGCs exhibiting the greatest responsiveness to zolpidem. We also report that the combination of CCI and acute application of zolpidem profoundly augments the proportion of GABAAR charge transfer mediated by tonic vs. synaptic currents at both time-points tested, whereas gene expression of GABAAR α1, α2, α3, and γ2 subunits is unchanged at 8–13 weeks post-injury. Overall, this work highlights the shift toward elevated influence of tonic inhibition in Ipsi-DGCs, the impact of zolpidem on all components of inhibitory control of DGCs, and the sustained nature of these changes in inhibitory tone after CCI injury.

Validation of a battery of inhibitory control tasks reveals a multifaceted structure in non-human primates.

Inhibitory control, the ability to override an inappropriate prepotent response, is crucial in many aspects of everyday life. However, the various paradigms designed to measure inhibitory control often suffer from a lack of systematic validation and have yielded mixed results. Thus the nature of this ability remains unclear, is it a general construct or a family of distinct sub-components? Therefore, the aim of this study was first to demonstrate the content validity and the temporal repeatability of a battery of inhibitory control tasks. Then we wanted to assess the contextual consistency of performances between these tasks to better understand the structure of inhibitory control. We tested 21 rhesus macaques (Macaca mulatta, 12 males, nine females) in a battery of touchscreen tasks assessing three main components of inhibitory control: inhibition of a distraction (using a Distraction task), inhibition of an impulsive action (using a Go/No-go task) and inhibition of a cognitive set (using a Reversal learning task). All tasks were reliable and effective at measuring the inhibition of a prepotent response. However, while there was consistency of performance between the inhibition of a distraction and the inhibition of an action, representing a response-driven basic form of inhibition, this was not found for the inhibition of a cognitive set. We argue that the inhibition of a cognitive set is a more cognitively demanding form of inhibition. This study gives a new insight in the multifaceted structure of inhibitory control and highlights the importance of a systematic validation of cognitive tasks in animal cognition.

Executive functions in deaf and hearing children: The mediating role of language skills in inhibitory control

This study aimed to analyze one of the critical components of inhibitory control—the ability to suppress interference—in deaf and hearing children and to investigate the mediating role of language skills in this central component of executive functions. To this end, a cross-sectional study was carried out with 40 deaf children with and without cochlear implants (CIs) and 21 hearing children age 7–10 years. The ability to suppress interference was assessed with the children’s version of the Attentional Network Test (child–ANT), and language skills were assessed with a computerized version of the Carolina Picture Vocabulary Test (CPVT), a receptive vocabulary test. As a measure of control of nonverbal cognitive abilities, we used the Test of Nonverbal Intelligence (TONI-2). The results showed that deaf children had lower nonverbal IQ than hearing children. In addition, deaf children, compared with hearing children and regardless of whether they used CIs, showed a lower range of receptive vocabulary and a poorer ability to suppress the interference of distractors in the child–ANT. Linear regression mediation analyses revealed that this more significant interference effect was mediated by receptive vocabulary level and not by hearing deprivation. These results are consistent with the hypothesis that language is one of the critical factors in the development of executive functions.

Heterogeneity of performances in several inhibitory control tasks: male rhesus macaques are more easily distracted than females.

Inhibitory control, the ability to override a dominant response, is crucial in many aspects of everyday life. In animal studies, striking individual variations are often largely ignored and their causes rarely considered. Hence, our aims were to systematically investigate individual variability in inhibitory control, to replicate the most common causes of individual variation (age, sex and rank) and to determine if these factors had a consistent effect on three main components of inhibitory control (inhibition of a distraction, inhibition of an action, inhibition of a cognitive set). We tested 21 rhesus macaques (Macaca mulatta) in a battery of validated touchscreen tasks. We first found individual variations in all inhibitory control performances. We then demonstrated that males had poorer performances to inhibit a distraction and that middle-aged individuals exhibited poorer performance in the inhibition of a cognitive set. Hence, the factors of age and sex were not consistently associated with the main components of inhibitory control, suggesting a multi-faceted structure. The rank of the subjects did not influence any inhibitory control performances. This study adopts a novel approach for animal behaviour studies and gives new insight into the individual variability of inhibitory control which is crucial to understand its evolutionary underpinnings.

The role of prepotent response inhibition and interference control in depression

ABSTRACT Introduction The ability to suppress inappropriate prepotent response and to overcome the interference of irrelevant information are two important components of inhibitory control. Little is known, however, about the relevant contributions in these two components of inhibitory control to depression. The aim of the present study was to assess the prepotent response inhibition and interference control simultaneously in a group of patients diagnosed with major depression disorder (MDD). Methods A clinical group of patients with MDD (n = 41) and a control group of healthy volunteers (n = 39) were recruited and assessed using the stop-signal task and the Flanker task respectively. Results The results showed longer stop-signal reaction time in patients with MDD in the stop-signal task. Regarding the interference control function, the analysis showed the response accuracy under the incongruent condition was significantly lower in patients with MDD than healthy individuals. Conclusions In conclusion, patients with MDD showed impairments both in prepotent response inhibition and interference control. The present findings provide a better understanding of the mechanism of depression-related deficits in inhibition and have great implications for the development of cognitive training programmes to remediate cognitive dysfunction in depression.

Measuring the Impact of Bilingualism on Executive Functioning Via Inhibitory Control Abilities in Autistic Children

One factor that may influence how executive functions develop is exposure to more than one language in childhood. This study explored the impact of bilingualism on inhibitory control in autistic (n = 38) and non-autistic children (n = 51). Bilingualism was measured on a continuum of exposure to investigate the effects of language environment on two facets of inhibitory control. Behavioural control of motor impulses was modulated positively through increased bilingual exposure, irrespective of diagnostic status, but bilingual exposure did not significantly affect inhibition involving visual attention. The results partially support the hypothesis that bilingual exposure differentially affects components of inhibitory control and provides important evidence for families that bilingualism is not detrimental to their development.

Adiposity is related to neuroelectric indices of motor response preparation in preadolescent children

ObjectiveEvent-related brain potentials (ERPs) have been utilized to study the cognitive implications of health-related behaviors, although many questions remain regarding the neural correlates underlying the cognition and adiposity relationship in childhood. Specifically, it is unknown whether excess fat mass is associated with the neural correlates of motor preparation and activation. The present work examined interrelationships between adiposity and ERPs that index inhibition, stimulus evaluation, and motor planning. MethodTo further elucidate the neural components of inhibitory control that are sensitive to adiposity, N2, P3, and response- and stimulus-locked Lateralized Readiness Potential (LRPs) were measured while preadolescent children completed an attentional inhibition task. Whole body percent adiposity was measured via dual-energy x-ray absorptiometry (DXA). ResultsAdiposity was related to the response-locked LRP amplitudes and marginally to P3 amplitude during the incongruent trials, such that participants with less adiposity elicited larger LRP and P3 components. Furthermore, P3 was strongly related to participant reaction times, suggesting that while LRP is strongly associated with adiposity, P3 has a more direct relationship to behavioral task performance. ConclusionsThe results suggest that while different cognitive functions may be affected by health-related characteristics, stimulus evaluation and motor activation may be particularly sensitive to excess adiposity in children. These findings extend previous work implicating adiposity in cognitive health in the pediatric population. Study importance1.What is already known about this subject?a.Excess adiposity is inversely associated with cognitive function in children.b.Adiposity has been associated with several event-related brain potentials, such that smaller P3 components, which index stimulus evaluation, and N2 components, which index attentional inhibition, are related to greater adiposity in children.c.The neural correlates underlying the cognition-adiposity relationship are under specified, and additional ERP components should be studied; one such component is the LRP, which underlies motor planning and activation.2.What does your study add?a.Our results show that adiposity was related to the P3 and the response-locked LRP components such that children with less adiposity showed larger P3 and LRP waveforms.b.These findings suggest that two separable, though related, processes may be affected by adiposity in childhood: One involving the evaluation of a stimulus, represented by the P3, and one involving the activation of motor control, represented by the response-locked LRP.Clinical Registry Number: NCT02630667 at https://clinicaltrials.gov.

Motor Preparation for Action Inhibition: A Review of Single Pulse TMS Studies Using the Go/NoGo Paradigm.

Human behavior must be flexible to respond to environmental and social demands, and to achieve these goals, it requires control. For instance, inhibitory control is used to refrain from executing unwanted or anticipated responses to environmental stimuli. When inhibitory mechanisms are inefficient due to some pathological conditions, such as attention-deficit hyperactivity disorder (ADHD) or pathological gambling, patients show a reduced capability of refraining from executing actions. When planning to execute an action, various inhibitory control mechanisms are activated to prevent the unwanted release of impulses and to ensure that the correct response is produced. A great body of research has used various cognitive tasks to isolate one or more components of inhibitory control (e.g., response selectivity) and to investigate their neuronal underpinnings. However, inter-individual differences in behavior are rarely properly considered, although they often represent a considerable source of noise in the data. In the present review, we will address this issue using the specific case of action inhibition, presenting the results of studies that coupled the so-called Go/NoGo paradigm with non-invasive brain stimulation to directly test the effects of motor inhibition on the excitability of the corticospinal system (CSE). Motor preparation is rarely measured in action inhibition studies, and participants’ compliancy to the task’s requests is often assumed rather than tested. Single pulse transcranial magnetic stimulation (TMS) is a powerful tool to directly measure CSE, whose responsivity depends on both excitatory and inhibitory processes. However, when motor preparation is not measured and the task design does not require participants to prepare responses in advance, fluctuations in CSE levels can be mistaken for active inhibition. One way to isolate motor preparation is to use a carefully designed task that allows to control for excessive variability in the timing of activation of inhibitory control mechanisms. Here, we review single pulse TMS studies that have used variants of the Go/NoGo task to investigate inhibitory control functions in healthy participants. We will identify the specific strategies that likely induced motor preparation in participants, and their results will be compared to current theories of action inhibition.

Activity and Connectivity Differences Underlying Inhibitory Control Across the Adult Life Span.

Inhibitory control requires precise regulation of activity and connectivity within multiple brain networks. Previous studies have typically evaluated age-related changes in regional activity or changes in interregional interactions. Instead, we test the hypothesis that activity and connectivity make distinct, complementary contributions to performance across the life span and the maintenance of successful inhibitory control systems. A representative sample of healthy human adults in a large, population-based life span cohort performed an integrated Stop-Signal (SS)/No-Go task during functional magnetic resonance imaging (n = 119; age range, 18–88 years). Individual differences in inhibitory control were measured in terms of the SS reaction time (SSRT), using the blocked integration method. Linear models and independent components analysis revealed that individual differences in SSRT correlated with both activity and connectivity in a distributed inhibition network, comprising prefrontal, premotor, and motor regions. Importantly, this pattern was moderated by age, such that the association between inhibitory control and connectivity, but not activity, differed with age. Multivariate statistics and out-of-sample validation tests of multifactorial functional organization identified differential roles of activity and connectivity in determining an individual's SSRT across the life span. We propose that age-related differences in adaptive cognitive control are best characterized by the joint consideration of multifocal activity and connectivity within distributed brain networks. These insights may facilitate the development of new strategies to support cognitive ability in old age.SIGNIFICANCE STATEMENT The preservation of cognitive and motor control is crucial for maintaining well being across the life span. We show that such control is determined by both activity and connectivity within distributed brain networks. In a large, population-based cohort, we used a novel whole-brain multivariate approach to estimate the functional components of inhibitory control, in terms of their activity and connectivity. Both activity and connectivity in the inhibition network changed with age. But only the association between performance and connectivity, not activity, differed with age. The results suggest that adaptive control is best characterized by the joint consideration of multifocal activity and connectivity. These insights may facilitate the development of new strategies to maintain cognitive ability across the life span in health and disease.

Food-Related Impulsivity in Obesity and Binge Eating Disorder-A Systematic Update of the Evidence.

The specific eating pattern of Binge Eating Disorder (BED) patients has provoked the assumption that BED might represent a phenotype within the obesity spectrum that is characterized by increased impulsivity. Following the guidelines of the PRISMA statement (preferred reporting items for systematic reviews and meta-analyses), we here provide a systematic update on the evidence on food-related impulsivity in obese individuals, with and without BED, as well as normal-weight individuals. We separately analyzed potential group differences in the impulsivity components of reward sensitivity and rash-spontaneous behavior. Our search resulted in twenty experimental studies with high methodological quality. The synthesis of the latest evidence consolidates conclusions drawn in our initial systematic review that BED represents a distinct phenotype within the obesity spectrum that is characterized by increased impulsivity. Rash-spontaneous behavior in general, and specifically towards food, is increased in BED, while food-specific reward sensitivity is also increased in obese individuals without BED, but potentially to a lesser degree. A major next step for research entails the investigation of sub-domains and temporal components of inhibitory control in BED and obesity. Based on the evidence of impaired inhibitory control in BED, affected patients might profit from interventions that address impulsive behavior.

Assessing Cognitive Performance in Badminton Players: A Reproducibility and Validity Study

Fast reaction and good inhibitory control are associated with elite sports performance. To evaluate the reproducibility and validity of a newly developed Badminton Reaction Inhibition Test (BRIT), fifteen elite (25 ± 4 years) and nine non-elite (24 ± 4 years) Dutch male badminton players participated in the study. The BRIT measured four components: domain-general reaction time, badminton-specific reaction time, domain-general inhibitory control and badminton-specific inhibitory control. Five participants were retested within three weeks on the badminton-specific components. Reproducibility was acceptable for badminton-specific reaction time (ICC = 0.626, CV = 6%) and for badminton-specific inhibitory control (ICC = 0.317, CV = 13%). Good construct validity was shown for badminton-specific reaction time discriminating between elite and non-elite players (F = 6.650, p < 0.05). Elite players did not outscore non-elite players on domain-general reaction time nor on both components of inhibitory control (p > 0.05). Concurrent validity for domain-general reaction time was good, as it was associated with a national ranking for elite (p = 0.70, p < 0.01) and non-elite (p = 0.70, p < 0.05) players. No relationship was found between the national ranking and badminton-specific reaction time, nor both components of inhibitory control (p > 0.05). In conclusion, reproducibility and validity of inhibitory control assessment was not confirmed, however, the BRIT appears a reproducible and valid measure of reaction time in badminton players. Reaction time measured with the BRIT may provide input for training programs aiming to improve badminton players’ performance.

False belief understanding and "cool" inhibitory control in 3-and 4-years-old Italian children.

During preschool years, major developments occur in both executive function and theory of mind (ToM), and several studies have demonstrated a correlation between these processes. Research on the development of inhibitory control (IC) has distinguished between more cognitive, “cool” aspects of self-control, measured by conflict tasks, that require inhibiting an habitual response to generate an arbitrary one, and “hot,” affective aspects, such as affective decision making, measured by delay tasks, that require inhibition of a prepotent response. The aim of this study was to investigate the relations between 3- and 4-year-olds’ performance on a task measuring false belief understanding, the most widely used index of ToM in preschoolers, and three tasks measuring cognitive versus affective aspects of IC. To this end, we tested 101 Italian preschool children in four tasks: (a) the Unexpected Content False Belief task, (b) the Conflict task (a simplified version of the Day–Night Stroop task), (c) the Delay task, and (d) the Delay Choice task. Children’s receptive vocabulary was assessed by the Peabody Picture Vocabulary test. Children’s performance in the False Belief task was significantly related only to performance in the Conflict task, controlling for vocabulary and age. Importantly, children’s performance in the Conflict task did not significantly correlate with their performance in the Delay task or in the Delay Choice task, suggesting that these tasks measure different components of IC. The dissociation between the Conflict and the Delay tasks may indicate that monitoring and regulating a cool process (as flexible categorization) may involve different abilities than monitoring and regulating a hot process (not touching an available and highly attractive stimulus or choosing between a smaller immediate option and a larger delayed one). Moreover, our findings support the view that “cool” aspects of IC and ToM are interrelated, extending to an Italian sample of children previous findings on an association between self-control and ToM.

Comparison of alcohol impairment of behavioral and attentional inhibition

BackgroundDespite the wealth of studies demonstrating the impairing effects of alcohol on behavioral inhibition, less is known regarding effects of the drug on attentional inhibition (i.e., the ability to ignore distracting stimuli in the environment in order to focus attention on relevant information). The current study examined alcohol impairment of both behavioral and attentional inhibition, as well as potential associations between the two mechanisms of inhibitory control. MethodsMen (n=27) and women (n=21) performed a measure of behavioral inhibition (cued go/no-go task) and a measure of attentional inhibition (delayed ocular return task) following three doses of alcohol: 0.65g/kg, 0.45g/kg, and 0.0g/kg (placebo). ResultsAlcohol impaired both behavioral and attentional inhibition relative to placebo; however, correlational analyses revealed no associations between measures of behavioral and attentional inhibition following any dose. Additionally, men committed more inhibitory failures on the behavioral inhibition task, whereas women committed more inhibitory failures on the attentional inhibition task. ConclusionsThese findings suggest that behavioral and attentional inhibition are equally sensitive to the impairing effects of alcohol, yet represent distinct components of inhibitory control. Additionally, the observed gender differences in control of behavior and attention could have important implications regarding negative consequences associated with alcohol-induced disinhibition in men and women.

Efecto del Nivel Socioeconómico en el Control Inhibitorio durante la Edad Preescolar

Recientemente se ha señalado que el nivel socioeconómico (NSE) juega un papel importante en el logro académico y en el funcionamiento de distintos sistemas cognitivos. El lenguaje y las funciones ejecutivas son los procesos donde se encuentran más diferencias significativas en función del NSE, debido a que son funciones que tardan en desarrollarse y por ellos están sujetas a los efectos adversos asociados al NSE. El objetivo de este estudio fue identificar las diferencias en el desempeño en tareas de control inhibitorio entre niños preescolares de NSE alto y bajo. Se evaluó una muestra de 231 niños de 4 a 6 años que cursaban el jardín de Niños. Los resultados muestran que el desempeño en tareas que evalúan la inhibición de respuestas cognitivas y motoras hay un efecto significativo del NSE, los niños de NSE alto obtienen mayores puntajes que los niños de NSE bajo, mientras que en una tarea de demora de gratificación los niños de NSE bajo cometen menos errores. EL NSE es un factor que determina en gran medida el desarrollo de la capacidad de inhibir respuestas dominantes durante la edad preescolar, lo cual es relevante para la autoregulación y facilitación del desarrollo de otras funciones ejecutivas.

C071 Infant vocalizations and prelinguistic behaviours in searching for predictors of language development in deaf infants with cochlear implants

This study aimed to analyze one of the critical components of inhibitory control—the ability to suppress interference—in deaf and hearing children and to investigate the mediating role of language skills in this central component of executive functions. To this end, a cross-sectional study was carried out with 40 deaf children with and without cochlear implants (CIs) and 21 hearing children age 7–10 years. The ability to suppress interference was assessed with the children’s version of the Attentional Network Test (child–ANT), and language skills were assessed with a computerized version of the Carolina Picture Vocabulary Test (CPVT), a receptive vocabulary test. As a measure of control of nonverbal cognitive abilities, we used the Test of Nonverbal Intelligence (TONI-2). The results showed that deaf children had lower nonverbal IQ than hearing children. In addition, deaf children, compared with hearing children and regardless of whether they used CIs, showed a lower range of receptive vocabulary and a poorer ability to suppress the interference of distractors in the child–ANT. Linear regression mediation analyses revealed that this more significant interference effect was mediated by receptive vocabulary level and not by hearing deprivation. These results are consistent with the hypothesis that language is one of the critical factors in the development of executive functions.

Dissociating the components of inhibitory control involved in predisposition to hallucinations

Introduction. We have previously linked hallucinations in schizophrenia and hallucination predisposition to poor intentional inhibition. However, these previous studies have not systematically investigated the separable dimensions of inhibitory control involved, namely, intentional versus unintentional, and inhibition versus resistance to interference. The aim of this study was to clarify the critical component(s) of inhibitory control specifically related to hallucination predisposition. Methods. The Launay-Slade Hallucination Scale–Revised (LSHS-R) was completed by 589 undergraduate students, from which high- (n=28) and low- (n=25) hallucination predisposition groups were drawn. Participants were administered tasks measuring unintentional inhibition (Brown-Peterson variant task) and intentional resistance to interference (directed ignoring [DI] task). Results. The high LSHS-R group showed significant difficulties relative to the low LSHS-R group on the DI task only; although these differences did not remain significant when controlling for anxiety or delusional thinking. Regression analyses showed that anxiety, but not delusional thinking, independently contributed to variance in DI task performance above that accounted for by hallucination predisposition. Conclusions. Intentional rather than unintentional control of intrusive cognitions appears to play an important role in hallucination predisposition. The results indicate that difficulties with the intentional resistance to interference from concurrent external distractors may be a common mechanism underlying positive schizophrenia symptoms and anxiety. However, given previous findings reported by Paulik, Badcock, and Maybery (2007), we propose that hallucination predisposition is also characterised by a difficulty with the active suppression of intrusive cognitions—that is, intentional inhibition—which is not shared with anxiety or delusional symptoms.

Emotional bias and inhibitory control processes in mania and depression

Despite markedly different clinical presentations, few studies have reported differences in neuropsychological functioning between mania and depression. The disinhibited behaviour characteristic of mania and evidence that subgenual prefrontal cortex is differentially activated in mania and depression both suggest that dissociable deficits will emerge on tasks that require inhibitory control and are subserved by ventromedial prefrontal cortex. Manic patients and controls undertook computerized neuropsychological tests of memory and planning ability. In addition, manic and depressed patients were directly compared with controls on a novel affective shifting task that requires inhibitory control over different components of cognitive and emotional processing. Manic patients were impaired on tests of memory and planning. Importantly, affective shifting performance of manic patients differed from that of depressed patients. Manic patients were impaired in their ability to inhibit behavioural responses and focus attention, but depressed patients were impaired in their ability to shift the focus of attention. Depressed patients exhibited an affective bias for negative stimuli, and we believe this to be the first demonstration of an affective bias for positive stimuli in manic patients. Observed impairments on tests of memory and planning suggest a global pathology for mania consistent with previous profiles for this disorder and similar to established profiles for depression. The results on the affective shifting task demonstrate the presence of mood-congruent bias and dissociable components of inhibitory control in mania and depression. Against a background of memory and planning impairments in the two groups, these findings are consistent with a role for the ventromedial prefrontal cortex in mediating mood-cognition relationships.