Enhanced reactive inhibition in adolescents with non-suicidal self-injury disorder.

AIM: To investigate whether the core of the pathophysiology underlying non-suicidal self-injury (NSSI) relates to poor impulse control due to impaired motor inhibition (i.e. the ability to inhibit a preplanned motor response). METHOD: We conducted a case-control study to compare the proficiency of two domains of motor inhibition, that is, reactive and proactive inhibition, by giving the reaching arm version of the stop-signal task and a go-only task to 28 drug-naive adolescents with NSSI disorder (NSSID) (mean age [SD] 15 years 8 months [1 year 4 months]; three males and 25 females) and 28 typically developing adolescents (mean age 15 years 8 months [1 year 5 months]; three males and 25 females). RESULTS: Reactive inhibition, as determined by the duration of the stop-signal reaction time, was enhanced in adolescents with NSSID compared to typically developing controls (194.2 [22.5 ms] vs 217.5 [17.3 ms], p < 0.001). By contrast, proactive inhibition was similar in both groups. Lastly, the level of impulsivity, assessed using the Barratt Impulsiveness Scale Version 11, did not differ between typically developing adolescents and adolescents with NSSID. However, adolescents with NSSID were more impulsive than controls in a subscale of the UPPS-P Impulsive Behavior Scale. INTERPRETATION: NSSID is not driven by heightened motor impulsivity. Instead, adolescents with NSSID exhibited greater proficiency in reactive inhibition, a proxy for motor impulsivity. We suggest that the enhancement of reactive inhibition strengthens action control, allowing adolescents to suppress their self-protection instinct and perform NSSI behaviours.

The Cerebellum in Drug-naive Children with Tourette Syndrome and Obsessive-Compulsive Disorder.

Tourette syndrome (TS) and obsessive-compulsive disorder (OCD) are two neurodevelopmental disorders characterized by repetitive behaviors. Our recent study in drug-naive children with TS and OCD provided evidence of cerebellar involvement in both disorders. In addition, cerebellar functional connectivity (FC) was similar in TS patients without comorbidities (TSpure) and TS patients with OCD comorbidity (TS + OCD), but differed in pure OCD patients. To investigate in detail the cerebellar involvement in the pathophysiology of TS and OCD, we explored cerebellar structural and functional abnormalities in drug-naive children with TSpure, TS + OCD, and OCD and assessed possible correlations with severity scores. We examined 53 drug-naive children, classified as TSpure (n = 16), TS + OCD (n = 14), OCD (n = 11), or controls (n = 12). All subjects underwent a multimodal 3T magnetic resonance imaging examination. Cerebellar lobular volumes and quantitative diffusion tensor imaging parameters of cerebellar peduncles were used as measures of structural integrity. The dentate nucleus was selected as a region of interest to examine cerebello-cerebral functional connectivity alterations. Structural analysis revealed that both TSpure and TS + OCD patients had higher fractional anisotropy in cerebellar peduncles than controls. Conversely, OCD patients were characterized by lower fractional anisotropy than both controls and TSpure and TS + OCD patients. Lastly, cerebellar functional connectivity analysis revealed significant alterations in the cerebello-thalamo-cortical circuit in TSpure, TS + OCD, and OCD patients. Early cerebellar structural and functional changes in drug-naive pediatric TSpure, TS + OCD, and OCD patients support a primary role of the cerebellum in the pathophysiology of these disorders.

Inhibitory control and impulsive responses in neurodevelopmental disorders.

The impairment of inhibitory control is often assumed to be the core deficit of several neurodevelopmental disorders characterized by poor impulse control. However, could the same deficit explain different clinical phenotypes? Evidence from behavioural studies is very mixed. This is partly because inhibition is a highly complex executive function. Thus, the different types of tasks that generically tap into inhibitory control are likely to provide different outcomes. Additionally, sample inhomogeneity in terms of age, comorbidity, and medical treatment are confounding factors. Therefore, to make a reliable assessment of the deficit of inhibitory control in a given disorder, the same task and samples with similar characteristics must be employed. This article reviews and discusses studies on five neurodevelopmental disorders with impaired impulse control where these criteria have been used: Tourette syndrome; obsessive-compulsive disorder; attention-deficit/hyperactivity disorder; primary motor stereotypies; and autism spectrum disorder. Overall, they suggest that the mechanisms underlying the inability to control urges are extremely heterogeneous and cannot be ascribed to a general impairment of inhibition. These findings do not support the hypothesis that inhibitory deficits represent a transdiagnostic feature of neurodevelopmental disorders with poor impulse control. WHAT THIS PAPER ADDS: The mechanisms underlying the inability to control urges in neurodevelopmental disorders are heterogeneous. Inhibition impairments cannot generally explain all neurodevelopmental disorders characterized by poor urge control.

Early-stage Parkinson's patients show selective impairment in reactive but not proactive inhibition.

BACKGROUND: It is well known that a deficit in inhibitory control is a hallmark of Parkinson's disease (PD). However, inhibition is not a unitary construct, and it is unclear whether patients in the early stage of the disease (Hoehn and Yahr stage 1) exhibit a deficit in outright stopping (reactive inhibition), a deficit in the ability to shape their response strategies according to the context (proactive inhibition), or both. OBJECTIVE: We assessed whether PD patients at Hoehn and Yahr stage 1 show a global or selective impairment in inhibitory control. As it has been suggested that inhibition relies upon a right-lateralized pathway, we tested whether left-dominant PD patients suffered from a more severe deficit in this executive function than right-dominant PD patients. METHODS: Via a reaching stop-signal task, we assessed both proactive and reactive inhibition in 17 left-dominant PD and 17 right-dominant PD patients and in 24 age-matched participants. RESULTS: We found that reactive inhibition was more impaired in PD patients than in healthy participants. However, proactive inhibition was not affected. Furthermore, we found no differences between left-dominant PD and right-dominant PD patients. CONCLUSIONS: For the first time, we found evidence for a deficit of reactive inhibition in the early-stage PD patients in the absence of evidence for deficits in proactive inhibition. These findings have clinical relevance as they provide critical insights on the time course of the disease. In addition, we confirmed, on a population of PD patients at Hoehn and Yahr stage 1, previous results showing that the onset of the disease does not affect inhibition. © 2019 International Parkinson and Movement Disorder Society.

Inhibition is impaired in children with obsessive-compulsive symptoms but not in those with tics.

BACKGROUND: Impaired inhibitory control is thought to be a core deficit in psychiatric disorders where patients exhibit problems with controlling urges. These problems include the urge to perform movements typical of Tourette syndrome and the urge to execute compulsive actions typical of obsessive-compulsive disorder. However, the picture emerging from studies that address this issue is controversial. Furthermore, most studies have only focused on reactive control (the ability of subjects to react to a stop signal), but not on proactive control (the ability of patients to shape their response strategies in anticipation of known task demands). OBJECTIVES: We assessed reactive and proactive inhibitory control in drug naïve children/adolescents affected by Tourette syndrome, obsessive-compulsive disorder, and in those in which the 2 disorders co-occur. METHODS: Reaching version of the stop signal task and of a simple reaction time task were given to 37 unmedicated patients (mean age ± SD, 11.0 ± 2.3) and to 37 healthy age- and gender-matched controls (mean age ± SD, 10.8 ± 1.6). RESULTS: Both reactive and proactive inhibition scaled with the severity of obsessive-compulsive symptoms, but not with those of tic symptoms (ie, inhibitory control in uncomplicated Tourette patients was comparable with that of healthy controls). CONCLUSIONS: We suggest that the cognitive mechanisms underlying tics and compulsions controls are likely to be different. Possibly the preserved ability to suppress actions in uncomplicated Tourette patients allows them to experience a greater feeling of self-control, and this fact might play a key role in evolution of the disorder beyond adolescence. © 2018 International Parkinson and Movement Disorder Society.

Interfacing to the brain's motor decisions.

It has been long known that neural activity, recorded with electrophysiological methods, contains rich information about a subject's motor intentions, sensory experiences, allocation of attention, action planning, and even abstract thoughts. All these functions have been the subject of neurophysiological investigations, with the goal of understanding how neuronal activity represents behavioral parameters, sensory inputs, and cognitive functions. The field of brain-machine interfaces (BMIs) strives for a somewhat different goal: it endeavors to extract information from neural modulations to create a communication link between the brain and external devices. Although many remarkable successes have been already achieved in the BMI field, questions remain regarding the possibility of decoding high-order neural representations, such as decision making. Could BMIs be employed to decode the neural representations of decisions underlying goal-directed actions? In this review we lay out a framework that describes the computations underlying goal-directed actions as a multistep process performed by multiple cortical and subcortical areas. We then discuss how BMIs could connect to different decision-making steps and decode the neural processing ongoing before movements are initiated. Such decision-making BMIs could operate as a system with prediction that offers many advantages, such as shorter reaction time, better error processing, and improved unsupervised learning. To present the current state of the art, we review several recent BMIs incorporating decision-making components.

Heterogeneous attractor cell assemblies for motor planning in premotor cortex.

Cognitive functions like motor planning rely on the concerted activity of multiple neuronal assemblies underlying still elusive computational strategies. During reaching tasks, we observed stereotyped sudden transitions (STs) between low and high multiunit activity of monkey dorsal premotor cortex (PMd) predicting forthcoming actions on a single-trial basis. Occurrence of STs was observed even when movement was delayed or successfully canceled after a stop signal, excluding a mere substrate of the motor execution. An attractor model accounts for upward STs and high-frequency modulations of field potentials, indicative of local synaptic reverberation. We found in vivo compelling evidence that motor plans in PMd emerge from the coactivation of such attractor modules, heterogeneous in the strength of local synaptic self-excitation. Modules with strong coupling early reacted with variable times to weak inputs, priming a chain reaction of both upward and downward STs in other modules. Such web of "flip-flops" rapidly converged to a stereotyped distributed representation of the motor program, as prescribed by the long-standing theory of associative networks.

Effects of probability bias in response readiness and response inhibition on reaching movements.

It is solidly established that unequal stimulus frequencies lead to faster responses to the more likely stimulus; however, the effect of this probability bias on response inhibition is still debated. To tackle this issue, we administered two versions of the stop-signal task to 18 right-handed healthy subjects. In one version, we manipulated the frequency of right and left targets appearance when subjects were required to produce speeded responses (no-stop trials) with the right arm, whereas stop signals occurred with equal frequencies after right or left targets (no-stop signal bias). In the other version, we manipulated the frequency of appearance of stop signals after right or left targets, whereas no-stop trials toward right or left targets had the same frequency (stop-signal bias). Surprisingly, we found a very modest, if any, increase in response readiness toward the more frequent stimulus. However, the no-stop signal bias had an effect on the speed of inhibitory control, as subjects were always faster to suppress a movement toward the side where targets were less likely to occur. Differently, the stop-signal bias had a much more powerful effect. In fact, subjects were faster to withhold movements toward the side where targets were more frequent, while they exhibited longer reaction times for reaches toward the more likely targets. Overall, these results suggest that action preparation and action inhibition are independent competing processes, but subjects tend to place automatically greater importance on the stop task.

Investigating the impact of surgical masks on behavioral reactions to facial emotions in the COVID-19 era.

Introduction: The widespread use of surgical masks during the COVID-19 pandemic has posed challenges in interpreting facial emotions. As the mouth is known to play a crucial role in decoding emotional expressions, its covering is likely to affect this process. Recent evidence suggests that facial expressions impact behavioral responses only when their emotional content is relevant to subjects' goals. Thus, this study investigates whether and how masked emotional faces alter such a phenomenon. Methods: Forty participants completed two reaching versions of the Go/No-go task in a counterbalanced fashion. In the Emotional Discrimination Task (EDT), participants were required to respond to angry, fearful, or happy expressions by performing a reaching movement and withholding it when a neutral face was presented. In the Gender Discrimination Task (GDT), the same images were shown, but participants had to respond according to the poser's gender. The face stimuli were presented in two conditions: covered by a surgical mask (masked) or without any covering (unmasked). Results: Consistent with previous studies, valence influenced behavioral control in the EDT but not in the GDT. Nevertheless, responses to facial emotions in the EDT exhibited significant differences between unmasked and masked conditions. In the former, angry expressions led to a slowdown in participants' responses. Conversely, in the masked condition, behavioral reactions were impacted by fearful and, to a greater extent, by happy expressions. Responses to fearful faces were slower, and those to happy faces exhibited increased variability in the masked condition compared to the unmasked condition. Furthermore, response accuracy to masked happy faces dramatically declined compared to the unmasked condition and other masked emotions. Discussion: In sum, our findings indicate that surgical masks disrupt reactions to emotional expressions, leading people to react less accurately and with heightened variability to happy expressions, provided that the emotional dimension is relevant to people's goals.

The role of task relevance in saccadic responses to facial expressions.

Recent research on healthy individuals suggests that the valence of emotional stimuli influences behavioral reactions only when relevant to ongoing tasks, as they impact reaching arm movements and gait only when the emotional content cued the responses. However, it has been suggested that emotional expressions elicit automatic gaze shifting, indicating that oculomotor behavior might differ from that of the upper and lower limbs. To investigate, 40 participants underwent two Go/No-go tasks, an emotion discrimination task (EDT) and a gender discrimination task (GDT). In the EDT, participants had to perform a saccade to a peripheral target upon the presentation of angry or happy faces and refrain from moving with neutral ones. In the GDT, the same images were shown, but participants responded based on the posers' gender. Participants displayed two behavioral strategies: a single saccade to the target (92.7%) or two saccades (7.3%), with the first directed at a task-salient feature, that is, the mouth in the EDT and the nose-eyes regions in the GDT. In both cases, the valence of facial expression impacted the saccades only when relevant to the response. Such evidence indicates the same principles govern the interplay between emotional stimuli and motor reactions despite the effectors employed.

Context matters: task relevance shapes neural responses to emotional facial expressions.

Recent research shows that emotional facial expressions impact behavioral responses only when their valence is relevant to the task. Under such conditions, threatening faces delay attentional disengagement, resulting in slower reaction times and increased omission errors compared to happy faces. To investigate the neural underpinnings of this phenomenon, we used functional magnetic resonance imaging to record the brain activity of 23 healthy participants while they completed two versions of the go/no-go task. In the emotion task (ET), participants responded to emotional expressions (fearful or happy faces) and refrained from responding to neutral faces. In the gender task (GT), the same images were displayed, but participants had to respond based on the posers' gender. Our results confirmed previous behavioral findings and revealed a network of brain regions (including the angular gyrus, the ventral precuneus, the left posterior cingulate cortex, the right anterior superior frontal gyrus, and two face-responsive regions) displaying distinct activation patterns for the same facial emotional expressions in the ET compared to the GT. We propose that this network integrates internal representations of task rules with sensory characteristics of facial expressions to evaluate emotional stimuli and exert top-down control, guiding goal-directed actions according to the context.

Effects of dopaminergic treatment on inhibitory control differ across Hoehn and Yahr stages of Parkinson's disease.

Motor inhibitory control, a core component of cognitive control, is impaired in Parkinson's disease, dramatically impacting patients' abilities to implement goal-oriented adaptive strategies. A progressive loss of the midbrain's dopamine neurons characterizes Parkinson's disease and causes motor features responsive to dopaminergic treatments. Although such treatments restore motor symptoms, their impact on response inhibition is controversial. Most studies failed to show any effect of dopaminergic medicaments, although three studies found that these drugs selectively improved inhibitory control in early-stage patients. Importantly, all previous studies assessed only one domain of motor inhibition, i.e. reactive inhibition (the ability to react to a stop signal). The other domain, i.e. proactive inhibition (the ability to modulate reactive inhibition pre-emptively according to the current context), was utterly neglected. To re-examine this issue, we recruited cognitively unimpaired Parkinson's patients under dopaminergic treatment in the early (Hoehn and Yahr, 1-1.5, n = 20), intermediate (Hoehn and Yahr 2, n = 20), and moderate/advanced (Hoehn and Yahr, 2.5-3, n = 20) stages of the disease. Using a cross-sectional study design, we compared their performance on a simple reaction-time task and a stop-signal task randomly performed twice on dopaminergic medication (ON) and after medication withdrawal (OFF). Normative data were collected on 30 healthy controls. Results suggest that medication effects are stage-dependent. In Hoehn and Yahr 1-1.5 patients, drugs selectively impair reactive inhibition, leaving proactive inhibition unaffected. In the ON state, Hoehn and Yahr two patients experienced impaired proactive inhibition, whereas reactive inhibition is no longer affected, as it deteriorates even during the OFF state. By contrast, Hoehn and Yahr 2.5-3 patients exhibited less efficient reactive and proactive inhibition in the OFF state, and medication slightly improved proactive inhibition. This evidence aligns with the dopamine overdose hypothesis, indicating that drug administration may overdose intact dopamine circuitry in the earliest stages, impairing associated cognitive functions. In later stages, the progressive degeneration of dopaminergic neurons prevents the overdose and can exert some beneficial effects. Thus, our findings suggest that inhibitory control assessment might help tailor pharmacological therapy across the disease stage to enhance Parkinson's disease patients' quality of life by minimizing the hampering of inhibitory control and maximizing the reduction of motor symptoms.

Beyond Reactive Inhibition: Unpacking the Multifaceted Nature of Motor Inhibition.

Inhibition is a pillar of cognitive control, i [...].

Unveiling the influence of task-relevance of emotional faces on behavioral reactions in a multi-face context using a novel Flanker-Go/No-go task.

Recent research indicates that emotional faces affect motor control only when task-relevant. However, these studies utilized a single-face presentation, which does not accurately mirror real-life situations wherein we frequently engage with multiple individuals simultaneously. To overcome this limitation, we gave 40 participants two versions of a novel Flanker-Go/No-go task, where we presented three-face stimuli with a central target and two task-irrelevant flankers that could be congruent or incongruent with the target for valence and gender. In the Emotional Discrimination Task (EDT), participants had to respond to fearful or happy targets and refrain from moving with neutral ones. In the Gender Discrimination Task (GDT), the same images were shown, but participants had to respond according to the target's gender. In line with previous studies, we found an effect of valence only in EDT, where fearful targets increased reaction times and omission error rates compared to happy faces. Notably, the flanker effect, i.e., slower and less accurate responses in incongruent than congruent conditions, was not found. This likely stems from the higher perceptual complexity of faces than that of stimuli traditionally used in the Eriksen Flanker task (letters or signs), leading to a capacity limit in face feature processing.

Angry and happy expressions affect forward gait initiation only when task relevant.

Whole-body movements represent an ecologically valid model for assessing the effect of emotional stimuli valence on approach/avoidance reactions as they entail a change of the physical distance between such stimuli and the self. However, research in this field has provided inconsistent results as the task relevance of the emotional content of the stimuli was not properly controlled, and very often, it is impossible to dissociate the effect of arousal from that of valence. To overcome these limitations, we studied the effect of facial emotional expressions (anger and happiness) on forward gait initiation using an experimental paradigm that allows us to compare the impact of the stimuli emotional content when they are task relevant and when they are not. We found that angry and happy expressions altered forward gait initiation parameters differently only when relevant for ongoing goals. In particular, both the reaction times and the percentages of omission errors increased when the go signal was an angry face compared to when the go signal was a happy face. These results indicate that forward step movements share the same features as reaching arm movements regarding emotional stimuli, that is, facial emotions do not automatically influence behavioral responses. Instead, their effects depend critically on their conscious appraisal. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Happy facial expressions impair inhibitory control with respect to fearful facial expressions but only when task-relevant.

The ability to generate appropriate responses, especially in social contexts, requires integrating emotional information with ongoing cognitive processes. In particular, inhibitory control plays a crucial role in social interactions, preventing the execution of impulsive and inappropriate actions. In this study, we focused on the impact of facial emotional expressions on inhibition. Research in this field has provided highly mixed results. In our view, a crucial factor explaining such inconsistencies is the task-relevance of the emotional content of the stimuli. To clarify this issue, we gave two versions of a Go/No-go task to healthy participants. In the emotional version, participants had to withhold a reaching movement at the presentation of emotional facial expressions (fearful or happy) and move when neutral faces were shown. The same pictures were displayed in the other version, but participants had to act according to the actor's gender, ignoring the emotional valence of the faces. We found that happy expressions impaired inhibitory control with respect to fearful expressions, but only when they were relevant to the participants' goal. We interpret these results as suggesting that facial emotions do not influence behavioral responses automatically. They would instead do so only when they are intrinsically germane for ongoing goals. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Emotional body postures affect inhibitory control only when task-relevant.

A classical theoretical frame to interpret motor reactions to emotional stimuli is that such stimuli, particularly those threat-related, are processed preferentially, i.e., they are capable of capturing and grabbing attention automatically. Research has recently challenged this view, showing that the task relevance of emotional stimuli is crucial to having a reliable behavioral effect. Such evidence indicated that emotional facial expressions do not automatically influence motor responses in healthy young adults, but they do so only when intrinsically pertinent to the ongoing subject's goals. Given the theoretical relevance of these findings, it is essential to assess their generalizability to different, socially relevant emotional stimuli such as emotional body postures. To address this issue, we compared the performance of 36 right-handed participants in two different versions of a Go/No-go task. In the Emotional Discrimination task, participants were required to withhold their responses at the display of emotional body postures (fearful or happy) and to move at the presentation of neutral postures. Differently, in the control task, the same images were shown, but participants had to respond according to the color of the actor/actress' t-shirt, disregarding the emotional content. Results showed that participants made more commission errors (instances in which they moved even though the No-go signal was presented) for happy than fearful body postures in the Emotional Discrimination task. However, this difference disappeared in the control task. Such evidence indicates that, like facial emotion, emotional body expressions do not influence motor control automatically, but only when they are task-relevant.

White matter alterations in drug-naïve children with Tourette syndrome and obsessive-compulsive disorder.

Tourette syndrome (TS) and early-onset obsessive-compulsive disorder (OCD) are frequently associated and conceptualized as distinct phenotypes of a common disease spectrum. However, the nature of their relationship is still largely unknown on a pathophysiological level. In this study, early structural white matter (WM) changes investigated through diffusion tensor imaging (DTI) were compared across four groups of drug-naïve children: TS-pure (n = 16), TS+OCD (n = 14), OCD (n = 10), and 11 age-matched controls. We analyzed five WM tracts of interest, i.e., cortico-spinal tract (CST), anterior thalamic radiations (ATR), inferior longitudinal fasciculus (ILF), corpus callosum (CC), and cingulum and evaluated correlations of DTI changes to symptom severity. Compared to controls, TS-pure and TS+OCD showed a comparable pattern of increased fractional anisotropy (FA) in CST, ATR, ILF and CC, with FA changes displaying negative correlation to tic severity. Conversely, in OCD, FA decreased in all WM tracts (except for the cingulum) compared to controls and negatively correlated to symptoms. We demonstrate different early WM microstructural alterations in children with TS-pure/TS+OCD as opposed to OCD. Our findings support the conceptualization of TS+OCD as a subtype of TS while suggesting that OCD is characterized by independent pathophysiological mechanisms affecting WM development.

Neurons in area V4 of the macaque translate attended visual features into behaviorally relevant categories.

Neural processing at most stages of the primate visual system is modulated by selective attention, such that behaviorally relevant information is emphasized at the expenses of irrelevant, potentially distracting information. The form of attention best understood at the cellular level is when stimuli at a given location in the visual field must be selected (space-based attention). In contrast, fewer single-unit recording studies have so far explored the cellular mechanisms of attention operating on individual stimulus features, specifically when one feature (e.g., color) of an object must guide behavioral responses while a second feature (e.g., shape) of the same object is potentially interfering and therefore must be ignored. Here we show that activity of neurons in macaque area V4 can underlie the selection of elemental object features and their "translation" into a categorical format that can directly contribute to the control of the animal's behavior.