The role of inhibitory processes in the relationship between subsyndromal PTSD symptoms and aggressive behaviour

The issue of aggressive behaviours among military populations is important for a number of reasons, including the potential associated occupational, social and functional impacts. Controlled aggressive behaviour is an adaptive requirement of some military roles, however, this aggression can become maladaptive when uncontrolled, or contextually inappropriate. Elevated aggression among deployed veterans has been identified in a number of studies, although the reasons for it are not well understood. Deployed populations have elevated levels of stress and trauma exposure, have higher rates of childhood and other lifetime trauma exposures and have a heightened risk for subsyndromal or full PTSD. Both trauma exposure and PTSD have been found to be associated with executive function deficits, and increased anger and aggressive behaviours. The purpose of this paper was to explore the contribution of both early PTSD symptoms and cognitive disinhibition in predicting increased aggressive behaviour following deployment in a healthy active serving cohort. After controlling for pre-deployment PTSD symptoms and cognitive function, there were significant main effects of both PTSD symptoms and cognitive function on increased aggression at post-deployment. Furthermore, the positive association between PTSD symptoms and post-deployment aggression was moderated by response inhibition deficits in the domains of false positive errors as well as faster reaction times. Subsidiary analyses showed that the effects of increased reaction time in particular increased the likelihood of PTSD symptoms being coupled with increased aggression. These findings highlight the potential effects of repeated occupational stress exposure and point to possible cognitive adaptations and long-term risk for disorder.

Response inhibition in problematic social network sites use: an ERP study

Given the current literature debate on whether or not Problematic Social Network Sites Use (PSNSU) can be considered a behavioral addiction, the present study was designed to test whether, similarly to addictive behaviors, PSNSU is characterized by a deficit in inhibitory control in emotional and addiction-related contexts. Twenty-two problematic Facebook users and 23 nonproblematic users were recruited based on their score on the Problematic Facebook Use Scale. The event-related potentials were recorded during an emotional Go/Nogo Task, including Facebook-related, unpleasant, pleasant, and neutral pictures. The amplitudes of the Nogo-N2 and the Nogo-P3 were computed as measures of the detection of response conflict and response inhibition, respectively. Reaction times and accuracy also were measured. The results showed that problematic users were less accurate on both Go and Nogo trials than nonproblematic users, irrespective of picture content. For problematic users only, the Nogo-P3 amplitude was lower to Facebook-related, pleasant, and neutral than to unpleasant stimuli, suggesting less efficient inhibition with natural and Facebook-related rewards. Of note, all participants were slower to respond to Facebook-related and pleasant Go trials compared with unpleasant and neutral pictures. Consistently, the Nogo-N2 amplitude was larger to Facebook-related than all other picture contents in both groups. Overall, the findings suggest that PSNSU is associated with reduced inhibitory control. These results should be considered in the debate about the neural correlates of PSNSU, suggesting more similarities than differences between PSNSU and addictive behaviors.

Perceptual Inhibition Is Not a Specific Component of the Sensory Integration Process Necessary for a Rapid Voluntary Step Initiation in Healthy Older Adults

OBJECTIVES

We investigated whether performing step initiation during a proprioceptive perturbation would require greater perceptual or motor inhibitory control in older adults.

METHOD

Fifty-two healthy adults (young: n = 26, mean age 22.5 years vs. older: n = 26, mean age 70.1 years) performed a stepping reaction time task, with different inhibition requirements (i.e., perceptual vs. motor inhibitory conflict), with two proprioceptive configurations: with and without application of Achilles tendon vibrations.

RESULTS

Beyond a systematically greater stepping reaction time in older adults (p < .01), no difference was found between the perceptual versus motor inhibitory conflict resolution, regardless of age and proprioceptive configuration. Furthermore, slower reaction time was observed for young participants in the presence of Achilles tendon vibrations unlike older adults, who showed the same reactive stepping performance with or without vibrations (p < .05).

DISCUSSION

These findings show that perceptual inhibition cannot be considered as specifically involved in the central processing of proprioceptive signals, at least not in active older adults. Rather than motor system malfunctioning or a reduced amount of proprioceptive afference, we propose that cortical-proprioceptive processing in older adults remains as effective as in young adults, regardless of the high attentional requirements for step responses.

Negation markers inhibit motor routines during typing of manual action verbs

We explored whether negation markers recruit inhibitory mechanisms during keyboard-based action-verb typing. In each trial, participants read two sentences: the first featured a context (There is a contract) and the second ended with a relevant verb which had to be immediately typed. Crucially, the verb could describe manual actions, non-manual actions or non-motor processes, with either affirmative (You do sign it) or negative (You don't sign it) polarity. We assessed the impact of verb type and polarity on two typing dimensions: motor programming (lapse between target onset and first keystroke) and motor execution (lapse between first and last keystroke). Negation yielded no effect on motor planning, but it selectively delayed typing execution for manual-action verbs, irrespective of the subjects' typing skills. This suggests that processing negations during comprehension of manual-action sentences recruits inhibitory mechanisms acting on same-effector movements. Our novel finding extends embodied models of language and effector-specific motor-language integration.

Examination of reactive motor responses to Achilles tendon vibrations during an inhibitory stepping reaction time task

Inhibition is known to influence balance, step initiation and gait control. A specific subcomponent of inhibition, the perceptual inhibition process, has been suggested to be specifically involved in the integration of proprioceptive information that is necessary for efficient postural responses. This study aimed to investigate the inhibition requirements of planning and executing a choice step initiation task in young adults following experimental perturbation of proprioceptive information using Achilles tendon vibrations. We developed an inhibitory stepping reaction time task in which participants had to step in response to visual arrows that manipulated specific perceptual or motor inhibition according to two proprioceptive configurations: without or with application of vibrations. Performance of twenty-eight participants (mean age 21 years) showed that Achilles tendon vibrations induced an increase in attentional demands (higher reaction time and longer motor responses). Further, this increase in attentional demands did not affect specifically the different inhibitory processes tested in this reactive stepping task. It suggests that attentional demands associated with the vibratory perturbation to postural control do not lead to a shift from automatic to more attentional inhibition processes, at least in young adults.

The availability of attentional resources modulates the inhibitory strength related to weakly activated priming

The current study investigated the role of attention in inhibitory processes (the inhibitory processes described in the current study refer only to those associated with masked or flanked priming) using a mixed paradigm involving the negative compatibility effect (NCE) and object-based attention. Accumulating evidence suggests that attention can be spread more easily within the same object, which increases the availability of attentional resources, than across different objects. Accordingly, we manipulated distractor location (with primes presented in the same object versus presented in different objects) together with prime/target compatibility (compatible versus incompatible) and prime-distractor stimulus onset asynchrony (SOA, 23 ms vs 70 ms). The aim was to investigate whether inhibitory processes related to weakly activated priming, which have been previously assumed to be automatic, depend on the availability of attentional resources. The results of Experiment 1 showed a significant NCE for the 70-ms SOA when the prime and distractor were presented in the same object (greater attentional resource availability); however, reversed NCEs were obtained for all other conditions. Experiment 2 was designed to disentangle whether the results of Experiment 1 were affected by the prime position, and the results indicated that the prime position did not modulate the NCE in Experiment 1. Together, these results are consistent with the claim that the availability of attentional resources modulates the inhibitory strength related to weakly activated priming. Specifically, if attentional resources are assigned to the distractor when it is presented in the same object as the prime, the strength of the inhibition elicited by the distractor may increase and reverse the activation elicited by the prime, which could lead to a significant NCE.

Inhibition deficit in OCD patients

BACKGROUND AND OBJECTIVES

Patients with obsessive-compulsive disorders (OCD) suffer from intrusive thoughts, which are assumed to be due to diminished inhibitory processes. The spatial cueing task indicates that a deficit in the inhibition of return (IOR) can be used as a marker for inhibitory deficits.

METHOD

The present study served to replicate previous findings with this task in OCD patients and, additionally, to control for the effects of the probability of valid cues. A supplementary experiment with phobic patients served to test the specificity of these effects. The task was performed in two versions: with equal and with unequal probability of valid and invalid cues.

RESULTS

No IOR was observed in the task with unequal probability of valid and invalid cues. An IOR did occur in the task with equal probability, but it was not generally diminished in OCD patients, but depended on the visual hemifield of the stimulus. IOR in patients with specific phobias was not affected.

LIMITATIONS

The negative result may be due to the relative small sample size.

CONCLUSIONS

The results do not support the notion of generally diminished inhibitory process in OCD patients, but only lateralized effects. They further indicate that a reliable IOR is only visible in a spatial cueing task with equal probability of valid and invalid cues.

The intentionality bias in schizophrenia

The tendency to over-interpret events of daily life as resulting from voluntary or intentional actions is one of the key aspects of schizophrenia with persecutory delusions. Here, we ask whether this characteristic may emerge from the abnormal activity of a basic cognitive process found in healthy adults and children: the intentionality bias, which refers to the implicit and automatic inclination to interpret human actions as intentional (Rosset, 2008, Cognition 108, 771-780). In our experiment, patients with schizophrenia and healthy controls were shown sentences describing human actions in various linguistic contexts, and were asked to indicate whether the action was intentional or not. The results indicated that people with schizophrenia exhibited a striking bias to over attribute intentionality regardless of linguistic context, contrary to healthy controls who did not exhibit such a general intentionality bias. Moreover, this study provides some insight into the cognitive mechanisms underlying this bias: an inability to inhibit the automatic attribution of intentionality.

Inhibitory processes in visual perception: a bilingual advantage

Bilingual inhibitory control advantages are well established. An open question is whether inhibitory superiority also extends to visual perceptual phenomena that involve inhibitory processes. This research used ambiguous figures to assess inhibitory bilingual superiority in 3-, 4-, and 5-year-old mono- and bilingual children (N=141). Findings show that bilinguals across all ages are superior in inhibiting a prevalent interpretation of an ambiguous figure to perceive the alternative interpretation. In contrast, mono- and bilinguals revealed no differences in understanding that an ambiguous figure can have two distinct referents. Together, these results suggest that early bilingual inhibitory control superiority is also evident in visual perception. Bilinguals' conceptual understanding of figure ambiguity is comparable to that of their monolingual peers.