Executive functioning in posttraumatic stress disorder: Understanding how inhibition, switching, and test modality affect reaction times.

OBJECTIVE: Posttraumatic stress disorder (PTSD) has been linked to deficits in executive functioning, but the literature suggests these associations are inconsistent. Results vary depending on the task used, test modality, and the specific subdomain being measured, such as inhibitory control (interference resolution, response inhibition) or set shifting (task switching, rule switching). Notably, deficits are more consistently observed in computerized tasks that measure precise reaction times (RTs) than in classic paper-and-pencil measures, but few studies have parsed specific executive functioning deficits in PTSD using detailed analyses of RT data. METHOD: The present study used a cued-switching Stroop Task to examine both interference resolution and task switching in 28 veterans with PTSD and 28 age-matched controls. Each trial required attending to a randomly presented cue and responding to the specified target while ignoring irrelevant or opposing information. Analyses of RT distributions estimated both Gaussian (normal) and ex-Gaussian (exponential) parameters. RESULTS: Veterans with PTSD had slower and more variable RTs than the controls on trials that required ignoring conflicting information (interference resolution, d' = .68). These effects were confined to the normal distribution, not to excessively slow responses (as estimated by ex-Gaussian parameters). Veterans with PTSD also showed modestly slower RTs on trials that required switching between cues, but Bayesian evidence for this was weak, and measures by ex-Gaussian parameters were not significant. CONCLUSIONS: These results highlight the importance of examining executive functioning in PTSD with a more nuanced approach, as clarity around these deficits may have important implications for future intervention and rehabilitation strategies. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

The Association Between Loneliness and Maladaptive Moods and Beliefs: A Pilot Study in U.S. Veterans.

INTRODUCTION: Loneliness is a powerful predictor of several medical and psychiatric conditions that are highly prevalent in Veterans, including depression and PTSD. Despite this, few studies have examined loneliness in Veterans or how best to intervene upon Veteran loneliness. Additional empirical research is needed in these areas in order to define clear intervention targets and improve Veteran care. MATERIALS AND METHODS: In this pilot study, we used 62 Veterans' self-reported loneliness and symptoms of post-traumatic stress to examine whether specific symptom clusters of post-traumatic stress were associated with greater loneliness. Post-traumatic stress was measured using the PTSD Checklist for DSM-5, and responses were further parsed into four symptom clusters: intrusions, avoidance, negative alterations in mood and cognition (excluding the social withdrawal item), and alterations in arousal and reactivity. RESULTS: Results revealed that only the negative alterations in mood and cognition symptom cluster was associated with increased Veteran loneliness, even after adjusting for sociodemographic factors, social isolation, and symptoms of depression. These analyses were also repeated using a subset of our sample (n = 29) who completed repeated measures of the PTSD Checklist. Results again revealed that the same symptom cluster predicted Veteran loneliness over 1 year later. CONCLUSIONS: This pilot study demonstrates the value of a publicly available PTSD measure for identifying lonely Veterans and highlights how reducing negative alterations in mood and cognition may serve as a potentially critical target for future Veteran loneliness interventions.

Stress Inoculation Training (SIT-NORCAL), Part 1: The Development and Preliminary Evaluation of a Psychological Performance Training Protocol.

BACKGROUND: Stress inoculation training (SIT) interventions have demonstrated promise within military contexts for human performance enhancement and psychological health applications. However, lack of manualized guidance on core content selection, delivery, and measurement processes has limited their use. PURPOSE: The purpose of this study was to develop and evaluate a comprehensive SIT intervention protocol to enhance the performance and health of military personnel engaged in special warfare and first-response activities. METHODS: Multidisciplinary teams of subject matter experts (n = 19) were consulted in protocol generation. The performance improvement/human performance technology (HPT) model was used in the selection, refinement, and measurement of core skills. The protocol was trialed and refined (44 cohorts, n = =300; 2013-2020) to generate the results. RESULTS: Four primary aims were achieved: (1) The generation of a flexible, evidence-based/evidence-driven psychological performance and health sustainment hybrid, SIT-NORCAL. (2) Manualized content and process guidance. (3) The creation of multimedia materials using evidence-based methodologies. (4) The design of initial measurement systems. Preliminary quality improvement analysis demonstrated positive results using standard-of-care and performance enhancement assessments. CONCLUSION: Hybridized human performance and psychological health sustainment protocols represent a paradigm shift in the delivery of psychological performance training with the potential to overcome barriers to success in traditional care. Further study is needed to determine the effectiveness and reach of SIT-NORCAL.

Stress Inoculation Training (SIT-NORCAL), Part 2: A Pilot Study Among Explosive Ordnance Disposal Special Warfare Enablers.

BACKGROUND: Despite being a well-supported strategy, Stress Inoculation Training (SIT) has not been fully incorporated in the advancement of human performance among most military personnel. The RAND Study recommendations for maximizing SIT's potential within high-risk/ high-intensity occupational groups were used in designing the Core Training protocol targeting psychological performance, SIT-NORCAL (Part 1). PURPOSE: The current project (Part 2) sought to further develop the protocol as a health and human performance hybrid through quality improvement analysis of the content, process, and measurement elements for use in the human performance context. METHODS: Evidence-based/evidence-driven methodologies were used in collaborative design tailored to the unique needs of special warfare enablers specializing in Explosive Ordnance Disposal (n = 17). The resultant three-phase training was conducted with a novice group (n = 10) using standardized measurements of collaboration, human performance, and adaptive capabilities on identified training targets. RESULTS: Process elements demonstrated high feasibility, resulting in high collaboration and trainee satisfaction. Significant improvements in psychological performance targets were observed pre- to post-training, and during an Adaptive Environmental Simulation designed by unit members. Two weeks post-training, unit members (n = 5) responded to an actual crash of an F-16 aircraft; measurements indicated maintenance of skill set from training to real-world events. CONCLUSION: Deployment of the elements in the SIT-NORCAL protocol demonstrated early feasibility and positive training impact on occupationally relevant skills that carried over into real-world events.

The Specificity of Inhibitory Control Deficits in Post-Traumatic Stress Disorder: A Dissociation Between the Speed and Reliability of Stopping.

Inhibitory control over thoughts, emotions, and actions is challenging for people with Post-Traumatic Stress Disorder (PTSD). Whether specific aspects of inhibitory control are differentially affected in PTSD remains an open question. Here we examined performance on two popular response inhibition tasks in 28 combat Veterans with PTSD and 27 control Veterans. We used a Hybrid variant that intermixed 75% Go trials, 12.5% NoGo trials, and 12.5% Stop trials. Parameters from an ex-Gaussian race model (Matzke et al., 2017) provided estimates of stopping speed (µ Stop) and stopping variability (τ Stop). Participants with PTSD had higher error rates on NoGo trials, replicating previous results. The estimated probability of "trigger failures" (failures to launch inhibitory control) on Stop trials was also higher in PTSD patients, suggesting that sustained attention was a common deficit in the two tasks. Stopping variability was also increased in participants with PTSD, which supports a difficulty with maintaining task goals. Conversely, stopping speed did not differ between patients and controls, suggesting that core inhibitory processes were intact. These results demonstrate a dissociation between the speed and reliability of motor response inhibition in PTSD, and suggest that top-down inhibitory control was deployed less consistently in participants with PTSD.

Stress inoculation training outcomes among veterans with PTSD and TBI.

OBJECTIVE: Stress inoculation training (SIT) is a cognitive-behavioral treatment that has demonstrated potential as a nontrauma based intervention for veterans with posttraumatic stress disorder (PTSD). The purpose of this study was to explore the efficacy of a novel 3-phase group formulation of SIT applied to a naturalistic population of veterans with PTSD and traumatic brain injury (TBI). The goals were to reduce symptoms of PTSD and depression, improve perceived functioning, and increase treatment initiation among veterans who were reticent to initiate established evidence-based and trauma-focused therapies. METHOD: A program development and evaluation archival analysis of 65 veterans engaged in SIT over an 18-month period at an outpatient VA PTSD clinic was conducted. Participants completed baseline self-report measures of PTSD and depression symptoms, substance use, and perceived performance. RESULTS: Paired samples t tests were used to evaluate pre- to posttreatment gains and demonstrated significant reductions in PTSD (PTSD Checklist, d = 0.66) and depression symptoms (Beck Depression Inventory, d = 0.67), increases in aspects of perceived stress tolerance and performance in multiple life domains, as well as improvements in both social and occupational functioning (Situational Adaptation to Stress Scale, d = 1.26). Eighty-eight percent of the intent-to-treat sample followed through with the recommended follow-up treatment. CONCLUSIONS: The results of this study provide preliminary support for the use of this SIT protocol in reducing symptoms of PTSD and depression, improving performance, and increasing rates of treatment initiation in evidence-based and trauma-focused treatments. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Angry and Fearful Face Conflict Effects in Post-traumatic Stress Disorder.

In the presence of threatening stimuli, post-traumatic stress disorder (PTSD) can manifest as hypervigilance for threat and disrupted attentional control. PTSD patients have shown exaggerated interference effects on tasks using trauma-related or threat stimuli. In studies of PTSD, faces with negative expressions are often used as threat stimuli, yet angry and fearful facial expressions may elicit different responses. The modified Eriksen flanker task, or the emotional face flanker, has been used to examine response interference. We compared 23 PTSD patients and 23 military controls on an emotional face flanker task using angry, fearful and neutral expressions. Participants identified the emotion of a central target face flanked by faces with either congruent or incongruent emotions. As expected, both groups showed slower reaction times (RTs) and decreased accuracy on emotional target faces, relative to neutral. Unexpectedly, both groups showed nearly identical interference effects on fearful and neutral target trials. However, post hoc testing suggested that PTSD patients showed faster RTs than controls on congruent angry faces (target and flanker faces both angry) relative to incongruent, although this finding should be interpreted with caution. This possible RT facilitation effect with angry, but not fearful faces, also correlated positively with self-report measures of PTSD symptoms. These results suggest that PTSD patients may be more vigilant for, or primed to respond to, the appearance of angry faces, relative to fearful, but further study is needed.

Enhanced Attentional Bias Variability in Post-Traumatic Stress Disorder and its Relationship to More General Impairments in Cognitive Control.

Hypervigilance towards threat is one of the defining features of post-traumatic stress disorder (PTSD). This symptom predicts that individuals with PTSD will be biased to attend to potential dangers in the environment. However, cognitive tasks designed to assess visual-spatial attentional biases have shown mixed results. A newer proposal suggests that attentional bias is not a static phenomenon, but rather is characterized by fluctuations towards and away from threat. Here, we tested 28 combat Veterans with PTSD and 28 control Veterans on a dot probe task with negative-neutral word pairs. Combat-related words and generically negative words were presented in separate blocks. Replicating previous results, neither group showed a bias to attend towards or away from threat, but PTSD patients showed greater attentional bias variability (ABV), which correlated with symptom severity. However, the cognitive processes indexed by ABV are unclear. The present results indicated that ABV was strongly correlated with standard deviation at the reaction time (RT) level and with excessively long RTs (ex-Gaussian tau) related to cognitive failures. These findings suggest an overall increase in response variability unrelated to threat-related biases in spatial attention, and support a disruption in more general cognitive control processes in PTSD.

Dissociation between working memory performance and proactive interference control in post-traumatic stress disorder.

Deficits in working memory (WM) and cognitive control processes have been reported in post-traumatic stress disorder (PTSD), in addition to clinical symptoms such as hypervigilance, re-experiencing, and avoidance of trauma reminders. Given the uncontrollable nature of intrusive memories, an important question is whether PTSD is associated with altered control of interference in WM. Some studies also suggest that episodic memory shows a material-specific dissociation in PTSD, with greater impairments in verbal memory and relative sparing of nonverbal memory. It is unclear whether this dissociation applies to WM, as no studies have used identical task parameters across material. Here we tested 29 combat Veterans with PTSD and 29 age-matched control Veterans on a recent probes WM task with words and visual patterns in separate blocks. Participants studied four-item sets, followed by a probe stimulus that had been presented in the previous set (recent probe) or not (nonrecent probe). Participants with PTSD made more errors than controls, and this decrement was similar for verbal and visual stimuli. Proactive interference from items recently presented, but no longer relevant, was not significantly different in the PTSD group and showed no relationship to re-experiencing symptom severity. These results demonstrate that PTSD is not reliably associated with increased intrusions of irrelevant representations into WM when non-emotional stimuli are used. Future studies that use trauma-related material may provide insight into the flashbacks and intrusive thoughts that plague those with PTSD.

Intact error monitoring in combat Veterans with post-traumatic stress disorder.

The error-related negativity (ERN) is a neuroelectric signature of performance monitoring during speeded response time tasks. Previous studies indicate that individuals with anxiety disorders show ERN enhancements that correlate with the degree of clinical symptomology. Less is known about the error monitoring system in post-traumatic stress disorder (PTSD). PTSD is characterized by impairments in the regulation of fear and other emotional responses, as well as deficits in maintaining cognitive control. Here, combat Veterans with PTSD were compared to control Veterans in two different versions of the flanker task (n=13 or 14 per group). Replicating and extending previous findings, PTSD patients showed an intact ERN in both experiments. In addition, task performance and error compensation behavior were intact. Finally, ERN amplitude showed no relationship with self-reported PTSD, depression, or post-concussive symptoms. These results suggest that error monitoring represents a relative strength in PTSD that can dissociate from cognitive control functions that are impaired, such as response inhibition and sustained attention. A healthy awareness of errors in external actions could be leveraged to improve interoceptive awareness of emotional state. The results could have positive implications for PTSD treatments that rely on self-monitoring abilities, such as neurofeedback and mindfulness training.

Lesions to Lateral Prefrontal Cortex Impair Lexical Interference Control in Word Production.

Speaking is an action that requires control, for example, to prevent interference from distracting or competing information present in the speaker's environment. Control over task performance is thought to depend on the lateral prefrontal cortex (PFC). However, the neuroimaging literature does not show a consistent relation between left PFC and interference control in word production. Here, we examined the role of left PFC in interference control in word production by testing six patients with lesions to left PFC (centered around the ventrolateral PFC) on a control-demanding task. Patients and age-matched controls named pictures presented along with distractor words, inducing within-trial interference effects. We varied the degree of competing information from distractors to increase the need for interference control. Distractors were semantically related, phonologically related, unrelated to the picture name, or neutral (XXX). Both groups showed lexical interference (slower responses with unrelated than neutral distractors), reflecting naming difficulty in the presence of competing linguistic information. Relative to controls, all six left PFC patients had larger lexical interference effects. By contrast, patients did not show a consistent semantic interference effect (reflecting difficulty in selecting amongst semantic competitors) whereas the controls did. This suggests different control mechanisms may be engaged in semantic compared to lexical interference resolution in this paradigm. Finally, phonological facilitation (faster responses with phonological than unrelated distractors) was larger in patients than in controls. These findings suggest that the lateral PFC is a necessary structure in providing control over lexical interference in word production, possibly through an early attentional blocking mechanism. By contrast, the left PFC does not seem critical in semantic interference resolution in the picture-word interference paradigm.

Material-specific interference control is dissociable and lateralized in human prefrontal cortex.

The prefrontal cortex (PFC) plays a key role in the ability to pursue a particular goal in the face of competing alternatives, an ability that is fundamental to higher-order human behavior. Whether this region contributes to cognitive control through material-general mechanisms, or through hemispheric specialization of component abilities, remains unclear. Here we show that left or right ventrolateral PFC damage in humans leads to doubly dissociable deficits in two classic tests of interference control. Patients with damage centered on left ventrolateral prefrontal cortex had exaggerated interference effects in the color-word Stroop, but not the Eriksen flanker task, whereas patients with damage affecting right ventrolateral prefrontal cortex showed the opposite pattern. Thus, effective interference resolution requires either right or left lateral PFC, depending on the nature of the task. This finding supports a lateralized, material-specific account of cognitive control in humans.

Posttraumatic stress disorder is associated with limited executive resources in a working memory task.

Patients with posttraumatic stress disorder (PTSD) can show declines in working memory. A dual-task design was used to determine whether these impairments are linked to executive control limitations. Participants performed a Sternberg memory task with either one or four letters. In the dual-task condition, the maintenance period was filled with an arrow flanker task. PTSD patients were less accurate on the working memory task than were controls, especially in the dual-task condition. In the single-task condition, both groups showed similar patterns of brain potentials from 300 to 500 ms when discriminating old and new probes. However, when taxed with an additional task, the event-related potentials (ERPs) of the PTSD group no longer differentiated old and new probes. In contrast, interference resolution processes in both the single- and dual-task conditions of the flanker task were intact. The lack of differentiation in the ERPs reflects impaired working memory performance under more difficult, dual-task conditions. Exacerbated difficulty in performing a working memory task with concurrent task demands suggests a specific limitation in executive control resources in PTSD.

Increased response variability as a marker of executive dysfunction in veterans with post-traumatic stress disorder.

The stability of cognitive control processes over time can be indexed by trial-to-trial variability in reaction time (RT). Greater RT variability has been interpreted as an indicator of executive dysfunction, inhibitory inefficiency, and excessive mental noise. Previous studies have demonstrated that combat veterans with post-traumatic stress disorder (PTSD) show substantial impairments in inhibitory control, but no studies have examined response variability in this population. In the current experiment, RT variability in the Go/NoGo response inhibition task was assessed for 45 veterans with PTSD and 34 control veterans using the intra-individual coefficient of variation (ICV) and ex-Gaussian analysis of RT distributions. Despite having mean RTs that were indistinguishable from controls, the PTSD patients had significantly greater RT variability as measured by ICV. More variable RTs were in turn associated with a greater number of false alarm errors in the patients, suggesting that less consistent performers were less successful at inhibiting inappropriate responses. RT variability was also highly correlated with self-reported symptoms of PTSD, depression, and attentional impulsiveness. Furthermore, response variability predicted diagnosis even when controlling for PTSD symptom severity. In turn, PTSD severity was correlated with self-rated attentional impulsiveness. Deficits in the top-down cognitive control processes that cause greater response variability might contribute to the maintenance of PTSD symptomology. Thus, the distractibility issues that cause more variable reaction times might also result in greater distress related to the trauma.

Attentional bias for trauma-related words: exaggerated emotional Stroop effect in Afghanistan and Iraq war veterans with PTSD.

BACKGROUND: Post-traumatic stress disorder (PTSD) involves debilitating symptoms that can disrupt cognitive functioning. The emotional Stroop has been commonly used to examine the impact of PTSD on attentional control, but no published study has yet used it with Afghanistan and Iraq war veterans, and only one previous study has compared groups on habituation to trauma-related words. METHODS: We administered the emotional Stroop, the Beck Depression Inventory (BDI), and the PTSD Checklist (PCL) to 30 veterans with PTSD, 30 military controls, and 30 civilian controls. Stroop word types included Combat, Matched-neutral, Neutral, Positive and Negative. RESULTS: Compared to controls, veterans with PTSD were disproportionately slower in responding to Combat words. They were also slower and less accurate overall, did not show interference on Negative or Positive words relative to Neutral, and showed a trend for delayed but successful habituation to Combat words. Higher PCL and BDI scores also correlated with larger interference effects. CONCLUSIONS: Because of its specificity in detecting attentional biases to trauma-related words, the emotional Stroop task may serve as a useful pre- and post task with intervention studies of PTSD patients.

Impaired response inhibition in veterans with post-traumatic stress disorder and mild traumatic brain injury.

Combat veterans with post-traumatic stress disorder (PTSD) can show impairments in executive control and increases in impulsivity. The current study examined the effects of PTSD on motor response inhibition, a key cognitive control function. A Go/NoGo task was administered to veterans with a diagnosis of PTSD based on semi-structured clinical interview using DSM-IV criteria (n = 40) and age-matched control veterans (n = 33). Participants also completed questionnaires to assess self-reported levels of PTSD and depressive symptoms. Performance measures from the patients (error rates and reaction times) were compared to those from controls. PTSD patients showed a significant deficit in response inhibition, committing more errors on NoGo trials than controls. Higher levels of PTSD and depressive symptoms were associated with higher error rates. Of the three symptom clusters, re-experiencing was the strongest predictor of performance. Because the co-morbidity of mild traumatic brain injury (mTBI) and PTSD was high in this population, secondary analyses compared veterans with PTSD+mTBI (n = 30) to veterans with PTSD only (n = 10). Although preliminary, results indicated the two patient groups did not differ on any measure (p > .88). Since cognitive impairments could hinder the effectiveness of standard PTSD therapies, incorporating treatments that strengthen executive functions might be considered in the future. (JINS, 2012, 18, 1-10).

Effects of working memory load on visual selective attention: behavioral and electrophysiological evidence.

Working memory and attention interact in a way that enables us to focus on relevant items and maintain current goals. The influence of working memory on attention has been noted in several studies using dual task designs. Multitasking increases the demands on working memory and reduces the amount of resources available for cognitive control functions such as resolving stimulus conflict. However, few studies have investigated the temporal activation of the cortex while multitasking. The present study addresses the extent to which working memory load influences early (P1) and late (P300) attention-sensitive event-related potential components using a dual task paradigm. Participants performed an arrow flanker task alone (single task condition) or concurrently with a Sternberg memory task (dual task condition). In the flanker task, participants responded to the direction of a central arrow surrounded by congruent or incongruent arrows. In the dual task condition, participants were presented with a Sternberg task that consisted of either four or seven consonants to remember prior to a short block of flanker trials. Participants were slower and less accurate on incongruent versus congruent trials. Furthermore, accuracy on incongruent trials was reduced in both dual task conditions. Likewise, P300 amplitude to incongruent flanker stimuli decreased when working memory load increased. These findings suggest that interference from incongruent flankers was more difficult to suppress when working memory was taxed. In addition, P1 amplitude was diminished on all flanker trials in the dual task condition. This result indicates that top-down attentional control over early visual processing is diminished by increasing demands on working memory. Both the behavioral and electrophysiological results suggest that working memory is critical in maintaining attentional focus and resolving conflict.

Are the neural correlates of stopping and not going identical? Quantitative meta-analysis of two response inhibition tasks.

Neuroimaging studies have utilized two primary tasks to assess motor response inhibition, a major form of inhibitory control: the Go/NoGo (GNG) task and the Stop-Signal Task (SST). It is unclear, however, whether these two tasks engage identical neural systems. This question is critical because assumptions that both tasks are measuring the same cognitive construct have theoretical and practical implications. Many papers have focused on a right hemisphere dominance for response inhibition, with the inferior frontal gyrus (IFG) and the middle frontal gyrus (MFG) receiving the bulk of attention. Others have emphasized the role of the pre-supplementary motor area (pre-SMA). The current study performed separate quantitative meta-analyses using the Activation Likelihood Estimate (ALE) method to uncover the common and distinctive clusters of activity in GNG and SST. Major common clusters of activation were located in the right anterior insula and the pre-SMA. Insular activation was right hemisphere dominant in GNG but more bilaterally distributed in SST. Differences between the tasks were observed in two major cognitive control networks: (1) the fronto-parietal network that mediates adaptive online control, and (2) the cingulo-opercular network implicated in maintaining task set (Dosenbach et al., 2007) and responding to salient stimuli (Seeley et al., 2007). GNG engaged the fronto-parietal control network to a greater extent than SST, with prominent foci located in the right MFG and right inferior parietal lobule. Conversely, SST engaged the cingulo-opercular control network to a greater extent, with more pronounced activations in the left anterior insula and bilateral thalamus. The present results reveal the anterior insula's importance in response inhibition tasks and confirm the role of the pre-SMA. Furthermore, GNG and SST tasks are not completely identical measures of response inhibition, as they engage overlapping but distinct neural circuits.

The role of Broca's area in regular past-tense morphology: an event-related potential study.

It has been suggested that damage to anterior regions of the left hemisphere results in a dissociation in the perception and lexical activation of past-tense forms. Specifically, in a lexical-decision task in which past-tense primes immediately precede present-tense targets, such patients demonstrate significant priming for irregular verbs (spoke-speak), but, unlike control participants, fail to do so for regular verbs (looked-look). Here, this behavioral dissociation was first confirmed in a group of eleven patients with damage to the pars opercularis (BA 44) and pars triangularis (BA 45) of the left inferior frontal gyrus (i.e., Broca's area). Two conditions containing word-onset orthographic-phonological overlap (bead-bee, barge-bar) demonstrated that the disrupted regular-verb priming was accompanied by, and covaried with, disrupted ortho-phonological priming, regardless of whether prime stimuli contained the regular inflectional rhyme pattern. Further, the dissociation between impaired regular-verb and preserved irregular-verb priming was shown to be continuous rather than categorical; priming for weak-irregular verbs (spent-spend) was intermediate in size between that of regular verbs and strong verbs. Such continuous dissociations grounded in ortho-phonological relationships between present- and past-tense forms are predicted by single-system, connectionist approaches to inflectional morphology and not predicted by current dual-system, rule-based models. Event-related potential data demonstrated that N400 priming effects were intact for both regular and irregular verbs, suggesting that the absence of significant regular-verb priming in the response time data did not result from a disruption of lexical access, and may have stemmed instead from post-lexical events such as covert articulation, segmentation strategies, and/or cognitive control.