Estimating the number of principal components via Split-Half Eigenvector Matching (SHEM).

Estimating the number of principal components to retain for dimension reduction is a critical step in many applications of principal component analysis. Common methods may not be optimal, however. The current paper presents an alternative procedure that aims to recover the true number of principal components, in the sense of the number of independent vectors involved in the generation of the data.•Data are split into random halves repeatedly.•For each split, the eigenvectors in one half are compared to those in the other.•The split between high and low similarities is used to estimate the number of principal components. The method is a proof of principle that similarity over split-halves of the data may provide a useful approach to estimating the number of components in dimension reduction, or of similar dimensions in other models.

Cognitive training and remediation interventions for substance use disorders: a Delphi consensus study.

AIMS: Substance use disorders (SUD) are associated with cognitive deficits that are not always addressed in current treatments, and this hampers recovery. Cognitive training and remediation interventions are well suited to fill the gap for managing cognitive deficits in SUD. We aimed to reach consensus on recommendations for developing and applying these interventions. DESIGN, SETTING AND PARTICIPANTS: We used a Delphi approach with two sequential phases: survey development and iterative surveying of experts. This was an on-line study. During survey development, we engaged a group of 15 experts from a working group of the International Society of Addiction Medicine (Steering Committee). During the surveying process, we engaged a larger pool of experts (n = 54) identified via recommendations from the Steering Committee and a systematic review. MEASUREMENTS: Survey with 67 items covering four key areas of intervention development: targets, intervention approaches, active ingredients and modes of delivery. FINDINGS: Across two iterative rounds (98% retention rate), the experts reached a consensus on 50 items including: (i) implicit biases, positive affect, arousal, executive functions and social processing as key targets of interventions; (ii) cognitive bias modification, contingency management, emotion regulation training and cognitive remediation as preferred approaches; (iii) practice, feedback, difficulty-titration, bias modification, goal-setting, strategy learning and meta-awareness as active ingredients; and (iv) both addiction treatment work-force and specialized neuropsychologists facilitating delivery, together with novel digital-based delivery modalities. CONCLUSIONS: Expert recommendations on cognitive training and remediation for substance use disorders highlight the relevance of targeting implicit biases, reward, emotion regulation and higher-order cognitive skills via well-validated intervention approaches qualified with mechanistic techniques and flexible delivery options.

An experimental test of integrating imagery with approach bias modification for alcohol: A cautionary tale.

OBJECTIVES: In terms of dual process models, behaviour can be conceived of as the outcome of an interplay between reflective, top-down and impulsive, bottom-up processes. Behaviour change interventions may benefit from targeting both types of processes in a coherent way. One approach to this, in the context of reducing hazardous drinking, is to combine imagery involving real-life situations involving alcohol with the simple actions involved in Approach Bias Modification (ApBM), a form of Cognitive Bias Modification. DESIGN: We developed and tested a version of this Imagery-enhanced Approach Bias Modification (IApBM) in an experimental design, with two independent factors: imagery versus control and ApBM versus control training components (N = 139). METHODS: An effect of integrating the training factors was hypothesized on the alcohol-approach bias of an alcohol Approach-Avoidance Task. Further exploratory analyses were performed for the bias on alcohol-related Single Attribute Implicit Association Tests and on alcohol-related questionnaires. Finally, the psychometric properties of an imagery interference effect during training were explored. RESULTS: Results showed no benefit of the training and in fact suggested a negative interaction in which combining the training components appeared to block reductions in craving effected by each in isolation. The reliability of the imagery-related interference effect was high and the effect was correlated with alcohol-related scales. CONCLUSIONS: In conclusion, it appears that interference between training components decreases their individual effects when combining imagery and ApBM in the current way. The imagery-related interference effects that could be measured during training conditions may be useful as an implicit measure of automatic processes underlying hazardous drinking.

Effects of tDCS during inhibitory control training on performance and PTSD, aggression and anxiety symptoms: a randomized-controlled trial in a military sample.

BACKGROUND: Post-traumatic stress disorder (PTSD), anxiety, and impulsive aggression are linked to transdiagnostic neurocognitive deficits. This includes impaired inhibitory control over inappropriate responses. Prior studies showed that inhibitory control can be improved by modulating the right inferior frontal gyrus (IFG) with transcranial direct current stimulation (tDCS) in combination with inhibitory control training. However, its clinical potential remains unclear. We therefore aimed to replicate a tDCS-enhanced inhibitory control training in a clinical sample and test whether this reduces stress-related mental health symptoms. METHODS: In a preregistered double-blind randomized-controlled trial, 100 active-duty military personnel and post-active veterans with PTSD, anxiety, or impulsive aggression symptoms underwent a 5-session intervention where a stop-signal response inhibition training was combined with anodal tDCS over the right IFG for 20 min at 1.25 mA. Inhibitory control was evaluated with the emotional go/no-go task and implicit association test. Stress-related symptoms were assessed by self-report at baseline, post-intervention, and after 3-months and 1-year follow-ups. RESULTS: Active relative to sham tDCS neither influenced performance during inhibitory control training nor on assessment tasks, and did also not significantly influence self-reported symptoms of PTSD, anxiety, impulsive aggression, or depression at post-assessment or follow-up. CONCLUSIONS: Our results do not support the idea that anodal tDCS over the right IFG at 1.25 mA enhances response inhibition training in a clinical sample, or that this tDCS-training combination can reduce stress-related symptoms. Applying different tDCS parameters or combining tDCS with more challenging tasks might provide better conditions to modulate cognitive functioning and stress-related symptoms.

Anticipated Attack Slows Responses in a Cued Virtual Attack Emotional Sternberg Task.

Threatening stimuli have varying effects, including reaction time (RT) increase in working memory tasks. This could reflect disruption of working memory or, alternatively, a reversible state of freezing. In the current series of experiments, reversible slowing due to anticipated threat was studied using the cued Virtual Attack Emotional Sternberg Task (cVAEST). In this task visually neutral cues indicate whether a future virtual attack could or could not occur during the maintenance period of a Sternberg task. Three studies (N = 47, 40, and 40, respectively) were performed by healthy adult participants online. The primary hypothesis was that the cVAEST would evoke anticipatory slowing. Further, the studies aimed to explore details of this novel task, in particular the interval between the cue and probe stimuli and the memory set size. In all studies it was found that threat anticipation slowed RTs on the working memory task. Further, Study 1 (memory set size 3) showed a decrease in RT when the attack occurred over all Cue Stimulus Intervals (CSIs). In Study 2 a minimal memory set of one item was used, under which circumstances RTs following attacks were only faster shortly after cue presentation (CSI 200 and 500 ms), when RTs were high for both threat and safe cues. Study 3 replicated results of Study 2 with more fine-grained time intervals. The results confirm that anticipation of attack stimuli can reversibly slow responses on an independent working memory task. The cVAEST may provide a useful method to study such threat-induced response slowing.

Spatial anticipatory attentional bias for threat: Reliable individual differences with RT-based online measurement.

Cues that predict the future location of emotional stimuli may evoke an anticipatory form of automatic attentional bias. The reliability of this bias towards threat is uncertain: experimental design may need to be optimized or individual differences may simply be relatively noisy in the general population. The current study therefore aimed to determine the split-half reliability of the bias, in a design with fewer factors and more trials than in previous work. A sample of 63 participants was used for analysis, who performed the cued Visual Probe Task online, which aims to measure an anticipatory attentional bias. The overall bias towards threat was tested and split-half reliability was calculated over even and odd blocks. Results showed a significant bias towards threat and a reliability of around 0.7. The results support systematic individual differences in anticipatory attentional bias and demonstrate that RT-based bias scores, with online data collection, can be reliable.

An exploration of prospective memory components and subtasks of the Memory for Intentions Test (MIST).

Introduction: Prospective Memory (PM), the ability to execute future intentions, decreases with age and memory-related disorders and may be an early predictor of dementia. The Memory for Intentions Test (MIST) allows the assessment of multiple aspects of PM using a range of subtasks. The current study evaluated and explored a Portuguese version of the MIST and its subtasks.Method: Forty-one patients with Mild Cognitive Impairment (MCI) and forty healthy participants performed the MIST, neuropsychological tests and questionnaires. Analyses were performed testing relationships between MCI and PM components of the MIST, and differences between subtasks of the test were explored.Results: Reliability of the PM component was acceptable within the patient group, but not within the control group. PM components were significantly lower in the MCI patients, but this effect was dependent on subtasks. Groups differed most strongly at shorter intervals. PM scores predicted MCI status. Correlations were found between PM components and cognitive functioning scales.Conclusions: The Portuguese version of the MIST seems suitable for use in clinical practice and research. MCI is differentially related to different PM components and subtasks of the MIST.

Predictive cues and spatial attentional bias for alcohol: Manipulations of cue-outcome mapping.

Previous studies suggest that cues predicting the outcome of attentional shifts provide a measure of anticipatory alcohol-related attentional bias that is correlated with risky drinking and has high reliability. However, this is complicated by potential contributions of visual features of cues to reliability, unrelated to their predictive value. Further, little is known of the sensitivity of the bias to variations in cue-outcome mapping manipulations, limiting our theoretical and methodological knowledge: Does the bias robustly follow varying cue-outcome mappings, or are there automatic cue-related associative processes involved? The current studies aimed to address these issues. Participants performed variations of the cued Visual Probe Task (cVPT) in which cues were non-predictive; in which there were multiple cue pairs, used simultaneously and serially; and in which the cue-outcome mapping was reversed. The major findings were, first, that previously found reliability cannot be attributed to aspects of the cues not related to outcome-prediction; second, that reliability of the bias does not survive deviations from a simple, consistent cue-outcome mapping; third, that all predictive versions of the task showed a bias towards alcohol; fourth, that the bias did not simply follow awareness of the cue-outcome mapping; and finally, that only in the case of simultaneous multiple cue pairs, an association with risky drinking was replicated. The results provide support for the reliability of the anticipatory attentional bias for alcohol, suggest that relatively persistent associative processes underlie the bias in the alcohol context, and provide a foundation for future work using the cVPT.

Threat-induced impulsivity in Go/Nogo tasks: Relationships to task-relevance of emotional stimuli and virtual proximity.

Threatening stimuli are thought to induce impulsive responses, but Emotional Go/Nogo task results are not in line with this. We extend previous research by testing effects of task-relevance of emotional stimuli and virtual proximity. Four studies were performed to test this in healthy college students. When emotional stimuli were task-relevant, threat both increased commission errors and decreased RT, but this was not found when emotional stimuli were task-irrelevant. This was found in both between-subject and within-subject designs. These effects were found using a task version with equal go and nogo rates, but not with 90-10% go-nogo rates. Proximity was found to increase threat-induced speeding, with task-relevant stimuli only, although effects on accuracy were less clear. Threat stimuli can thus induce impulsive responding, but effects depend on features of the task design. The results may be of use in understanding theoretically unexpected results involving threat and impulsivity and designing future studies.

Trial-to-trial carryover effects on spatial attentional bias.

Visual Probe Tasks (VPTs) have been extensively used to measure spatial attentional biases, but as usually analysed, VPTs do not consider trial-to-trial carryover effects of probe location: Does responding to a probe on, e.g., the location of a threat cue affect the bias on the subsequent trial? The aim of the current study was to confirm whether this kind of carryover exists, using a novel task version, the diagonalized VPT, designed to focus on such trial-to-trial interactions. Two versions of the task were performed by a sample of college students. In one version cues were coloured squares; in the other, cues were threat-related and neutral images. Both versions included partially random positive or negative response feedback and varying Cue-Probe Intervals (200 or 600 ms). Carryover effects were found in both versions. Responding to a probe at the location of a cue of a given colour induced an attentional bias on the subsequent trial in the direction of that colour. Responding to a threat-related cue induced an attentional bias towards threat on the subsequent trial. The results provide evidence that trial-to-trial carryover effects on spatial attentional bias indeed exist. A methodological implication is that previous probe location could be considered in analyses or re-analyses of spatial visual attention tasks.

Neural Dynamics of Shooting Decisions and the Switch from Freeze to Fight.

Real-life shooting decisions typically occur under acute threat and require fast switching between vigilant situational assessment and immediate fight-or-flight actions. Recent studies suggested that freezing facilitates action preparation and decision-making but the neurocognitive mechanisms remain unclear. We applied functional magnetic resonance imaging, posturographic and autonomic measurements while participants performed a shooting task under threat of shock. Two independent studies, in unselected civilians (N = 22) and police recruits (N = 54), revealed that preparation for shooting decisions under threat is associated with postural freezing, bradycardia, midbrain activity (including the periaqueductal gray-PAG) and PAG-amygdala connectivity. Crucially, stronger activity in the midbrain/PAG during this preparatory stage of freezing predicted faster subsequent accurate shooting. Finally, the switch from preparation to active shooting was associated with tachycardia, perigenual anterior cingulate cortex (pgACC) activity and pgACC-amygdala connectivity. These findings suggest that threat-anticipatory midbrain activity centred around the PAG supports decision-making by facilitating action preparation and highlight the role of the pgACC when switching from preparation to action. These results translate animal models of the neural switch from freeze-to-action. In addition, they reveal a core neural circuit for shooting performance under threat and provide empirical evidence for the role of defensive reactions such as freezing in subsequent action decision-making.

Predictive Attentional Bias Modification Induces Stimulus-Evoked Attentional Bias for Threat.

Attentional Bias Modification (ABM) aims to modulate attentional biases, but questions remain about its efficacy and there may be new variants yet to explore. The current study tested effects of a novel version of ABM, predictive ABM (predABM), using visually neutral cues predicting the locations of future threatening and neutral stimuli that had a chance of appearing after a delay. Such effects could also help understand anticipatory attentional biases measured using cued Visual Probe Tasks. One hundred and two participants completed the experiment online. We tested whether training Towards Threat versus Away from Threat contingencies on the predABM would cause subsequent attentional biases towards versus away from threat versus neutral stimuli, respectively. Participants were randomly assigned and compared on attentional bias measured via a post-training Dot-Probe task. A significant difference was found between the attentional bias in the Towards Threat versus Away from Threat group. The training contingencies induced effects on bias in the expected direction, although the bias in each group separately did not reach significance. Stronger effects may require multiple training sessions. Nevertheless, the primary test confirmed the hypothesis, showing that the predABM is a potentially interesting variant of ABM. Theoretically, the results show that automatization may involve the process of selecting the outcome of a cognitive response, rather than a simple stimulus-response association. Training based on contingencies involving predicted stimuli affect subsequent attentional measures and could be of interest in future clinical studies.

Anticipatory versus reactive spatial attentional bias to threat.

Dot-probe or visual probe tasks (VPTs) are used extensively to measure attentional biases. A novel variant termed the cued VPT (cVPT) was developed to focus on the anticipatory component of attentional bias. This study aimed to establish an anticipatory attentional bias to threat using the cVPT and compare its split-half reliability with a typical dot-probe task. A total of 120 students performed the cVPT task and dot-probe tasks. Essentially, the cVPT uses cues that predict the location of pictorial threatening stimuli, but on trials on which probe stimuli are presented the pictures do not appear. Hence, actual presentation of emotional stimuli did not affect responses. The reliability of the cVPT was higher at most cue-stimulus intervals and was .56 overall. A clear anticipatory attentional bias was found. In conclusion, the cVPT may be of methodological and theoretical interest. Using visually neutral predictive cues may remove sources of noise that negatively impact reliability. Predictive cues are able to bias response selection, suggesting a role of predicted outcomes in automatic processes.

Effects of threat and sleep deprivation on action tendencies and response inhibition.

The ability to control action is crucial for adaptive responding, but may be compromised in situations involving strong emotions (e.g., threat) or when people are deprived of resources (e.g., sleep). As compromised action control can have large consequences in threatening situations, for example when police officers face a potentially armed suspect, we experimentally investigated how acute threat and partial sleep deprivation affect the ability to control impulsive responses, in 52 healthy young adults performing a simulated shooting task. The results showed that acute threat increased the tendency to act quickly (i.e., reduced response times; b = 9.46, SE = 2.90, 95% CI [3.49, 15.29], p = .001) and impaired response inhibition (i.e., increased stop signal reaction times; b = -4.91, SE = 2.31, 95% CI [-9.47, -0.44], p = .035). In addition, 3 nights of partial sleep deprivation (5 hr [n = 28] vs. 8 hr [n = 24] of sleep), led to a significant decrease in overall response accuracy (b = -0.22, SE = 0.09, 95% CI [-0.40, -0.05], p = .025). Contrary to expectations, our results did not show increased threat sensitivity in sleep-deprived individuals (all p > .13). Nevertheless, they may have important implications for professionals who are required to maintain behavioral control under high levels of threat and who experience disturbed sleep due to for example, shift work, as both factors negatively affected performance. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Using subjective expectations to model the neural underpinnings of proactive inhibition.

Proactive inhibition - the anticipation of having to stop a response - relies on objective information contained in cue-related contingencies in the environment, as well as on the subjective interpretation derived from these cues. To date, most studies of brain areas underlying proactive inhibition have exclusively considered the objective predictive value of environmental cues, by varying the probability of stop-signals. However, by only taking into account the effect of different cues on brain activation, the subjective component of how cues affect behavior is ignored. We used a modified stop-signal response task that includes a measurement for subjective expectation, to investigate the effect of this subjective interpretation. After presenting a cue indicating the probability that a stop-signal will occur, subjects were asked whether they expected a stop-signal to occur. Furthermore, response time was used to retrospectively model brain activation related to stop-expectation. We found more activation during the cue period for 50% stop-signal probability, when contrasting with 0%, in the mid and inferior frontal gyrus, inferior parietal lobe and putamen. When contrasting expected vs. unexpected trials, we found modest effects in the mid frontal gyrus, parietal, and occipital areas. With our third contrast, we modeled brain activation during the cue with trial-by-trial variances in response times. This yielded activation in the putamen, inferior parietal lobe, and mid frontal gyrus. Our study is the first to use the behavioral effects of proactive inhibition to identify the underlying brain regions, by employing an unbiased task-design that temporally separates cue and response.

A Clinical Trial with Combined Transcranial Direct Current Stimulation and Attentional Bias Modification in Alcohol-Dependent Patients.

BACKGROUND: Modifying attentional processes with attentional bias modification (ABM) might be a relevant add-on to treatment in addiction. This study investigated whether influencing cortical plasticity with transcranial direct current stimulation (tDCS) could increase training effects. tDCS could also help alcohol-dependent patients to overcome craving and reduce relapse, independent of training. These approaches were combined to investigate effects in the treatment of alcoholism. METHODS: Ninety-eight patients (analytical sample = 83) were randomly assigned to 4 groups in a 2-by-2 factorial design. Patients received 4 sessions of ABM (control or real training) combined with 2 mA tDCS (active: 20 minutes or sham: 30 seconds) over the left dorsolateral prefrontal cortex. Alcohol bias and craving were assessed, and treatment outcome was measured as relapse after 1 year. RESULTS: Attentional bias scores indicated that during the training only the group with active tDCS and real ABM displayed an overall avoidance bias (p < 0.05). From pre- to postassessment, there were no main or interaction effects of tDCS and ABM on the bias scores, craving, or relapse (p > 0.2). However, effects on relapse after active tDCS were in the expected direction. CONCLUSIONS: There was no evidence of a beneficial effect of tDCS or ABM or the combination. Whether the absence of effect was due to issues with the outcome measurements (e.g., lack of craving, high dropout, and unreliable measurements) or aspects of the intervention should be further investigated.

Training Working Memory in Adolescents Using Serious Game Elements: Pilot Randomized Controlled Trial.

BACKGROUND: Working memory capacity has been found to be impaired in adolescents with various psychological problems, such as addictive behaviors. Training of working memory capacity can lead to significant behavioral improvements, but it is usually long and tedious, taxing participants' motivation to train. OBJECTIVE: This study aimed to evaluate whether adding game elements to the training could help improve adolescents' motivation to train while improving cognition. METHODS: A total of 84 high school students were allocated to a working memory capacity training, a gamified working memory capacity training, or a placebo condition. Working memory capacity, motivation to train, and drinking habits were assessed before and after training. RESULTS: Self-reported evaluations did not show a self-reported preference for the game, but participants in the gamified working memory capacity training condition did train significantly longer. The game successfully increased motivation to train, but this effect faded over time. Working memory capacity increased equally in all conditions but did not lead to significantly lower drinking, which may be due to low drinking levels at baseline. CONCLUSIONS: We recommend that future studies attempt to prolong this motivational effect, as it appeared to fade over time.

Effects of appraisal training on responses to a distressing autobiographical event.

Dysfunctional appraisals are a key factor suggested to be involved in the development and maintenance of PTSD. Research has shown that experimental induction of a positive or negative appraisal style following a laboratory stressor affects analogue posttraumatic stress symptoms. This supports a causal role of appraisal in the development of traumatic stress symptoms and the therapeutic promise of modifying appraisals to reduce PTSD symptoms. The present study aimed to extend previous findings by investigating the effects of experimentally induced appraisals on reactions to a naturally occurring analogue trauma and by examining effects on both explicit and implicit appraisals. Participants who had experienced a distressing life event were asked to imagine themselves in the most distressing moment of that event and then received either a positive or negative Cognitive Bias Modification training targeting appraisals (CBM-App). The CBM-App training induced training-congruent appraisals, but group differences in changes in appraisal over training were only seen for explicit and not implicit appraisals. However, participants trained positively reported less intrusion distress over the subsequent week than those trained negatively, and lower levels of overall posttraumatic stress symptoms. These data support the causal relationship between appraisals and trauma distress, and further illuminate the mechanisms linking the two.

Resting-state functional connectivity in combat veterans suffering from impulsive aggression.

Impulsive aggression is common among military personnel after deployment and may arise because of impaired top-down regulation of the amygdala by prefrontal regions. This study sought to further explore this hypothesis via resting-state functional connectivity analyses in impulsively aggressive combat veterans. Male combat veterans with (n = 28) and without (n = 30) impulsive aggression problems underwent resting-state functional magnetic resonance imaging. Functional connectivity analyses were conducted with the following seed-regions: basolateral amygdala (BLA), centromedial amygdala, anterior cingulate cortex (ACC), and anterior insular cortex (AIC). Regions-of-interest analyses focused on the orbitofrontal cortex and periaqueductal gray, and yielded no significant results. In exploratory cluster analyses, we observed reduced functional connectivity between the (bilateral) BLA and left dorsolateral prefrontal cortex in the impulsive aggression group, relative to combat controls. This finding indicates that combat-related impulsive aggression may be marked by weakened functional connectivity between the amygdala and prefrontal regions, already in the absence of explicit emotional stimuli. Group differences in functional connectivity were also observed between the (bilateral) ACC and left cuneus, which may be related to heightened vigilance to potentially threatening visual cues, as well as between the left AIC and right temporal pole, possibly related to negative memory association in impulsive aggression.