Attention training improves aberrant neural dynamics during working memory processing in veterans with PTSD

Glycemic control level alters working memory neural dynamics in adults with type 2 diabetes

Poor glycemic control in type 2 diabetes has been associated with accentuated age-related cognitive decline, although the underlying neural mechanisms are not well understood. The current study sought to identify the impact of glycemic control on the neural dynamics serving working memory in adults with type 2 diabetes. Participants (n = 34, ages = 55-73) performed a working memory task while undergoing MEG. Significant neural responses were examined relative to poorer (A1c > 7.0%) or tighter glycemic control (A1c < 7.0%). Those with poorer glycemic control showed diminished responses within left temporal and prefrontal regions during encoding and showed diminished responses within right occipital cortex during maintenance but showed an enhanced activity in the left temporal, occipital, and cerebellar regions during maintenance. Notably, left temporal activity in encoding and left lateral occipital activity in maintenance significantly predicted performance on the task such that diminished temporal activity led to longer reaction times, which were driven by the poorer glycemic control group. Greater lateral occipital activity during maintenance was associated with both lower accuracy and longer reaction times across all participants. These findings suggest that glycemic control has a robust impact on the neural dynamics serving working memory, with distinct effects by subprocess (e.g. encoding vs. maintenance) and direct effects on behavior.

Posttraumatic stress, visual working memory, and visual imagery in military personnel

Posttraumatic stress disorder (PTSD) is characterized by disruptions to cognitive functioning. Two studies were conducted to examine the relevance of military-related PTSD to two cognitive functions - visual working memory and visual imagery. Participants were military personnel who reported their PTSD diagnosis history and completed a self-administered screening tool for PTSD, the PTSD Checklist - Military Version. In Study 1, 138 personnel also completed a memory span task and a 2-back task using colored words in which Stroop interference was introduced via the semantic content of the words. In Study 2, a separate group of 211 personnel completed measures of perceived imagery vividness and spontaneous use of visual imagery. Interference effects on working memory in PTSD-diagnosed military personnel were not replicated. However, ANCOVA and structural equation modelling revealed that PTSD-intrusions were associated with poorer working memory whereas PTSD-arousal was associated with spontaneous use of visual imagery. We interpret these results as evidence that intrusive flashbacks disrupt working memory performance not by limiting memory capacity nor by interfering directly with memory functions such as inhibition, but by adding internal noise in the form of task-irrelevant memories and emotions. Visual imagery appears to be unrelated to these flashbacks but with arousal symptoms of PTSD, perhaps in the form of flashforwards about feared/anticipated threats.

Male and female impairments in odor span are observed in a rat model of PTSD

Posttraumatic stress disorder (PTSD) is associated with neural and behavioral alterations in response to trauma exposure, including working memory impairments. Rodent models of PTSD have not fully investigated chronic or reactive working memory deficits, despite clinical relevance. The present study uses footshock to induce a posttraumatic stress state in male and female rats and evaluates the effect of footshock and trauma-paired odor cues on working memory performance in the odor span task. Results demonstrate the emergence of chronic deficits in working memory among animals exposed to footshock by 3 wk after traumatic stress. The presentation of a trauma-paired odor cue was associated with further decrement in working memory performance for male animals. Furthermore, anxiety-like behaviors associated with the PTSD-like phenotype could predict the degree of working memory impairment in response to the trauma-paired odor cue. This study enhances validation of an existing rodent model of PTSD through replication of the clinical observations of working memory deficits associated with PTSD and provides novel insight into effects in female rodents. This will facilitate work to probe underlying mechanistic dysregulation of working memory following footshock trauma exposure and future development of novel treatment strategies.

Comparing resting-state connectivity of working memory networks in U.S. Service members with mild traumatic brain injury and posttraumatic stress disorder

Mild traumatic brain injury (mTBI) and posttraumatic stress disorder (PTSD) are prevalent among military populations, and both have been associated with working memory (WM) impairments. Previous resting-state functional connectivity (rsFC) research conducted separately in PTSD and mTBI populations suggests that there may be similar and distinct abnormalities in WM-related networks. However, no studies have compared rsFC of WM brain regions in participants with mTBI versus PTSD. We used resting-state fMRI to investigate rsFC of WM networks in U.S. Service Members (n = 127; ages 18-59) with mTBI only (n = 46), PTSD only (n = 24), and an orthopedically injured (OI) control group (n = 57). We conducted voxelwise rsFC analyses with WM brain regions to test for differences in WM network connectivity in mTBI versus PTSD. Results revealed reduced rsFC between ventrolateral prefrontal cortex (vlPFC), lateral premotor cortex, and dorsolateral prefrontal cortex (dlPFC) WM regions and brain regions in the dorsal attention and somatomotor networks in both mTBI and PTSD groups versus controls. When compared to those with mTBI, individuals with PTSD had lower rsFC between both the lateral premotor WM seed region and middle occipital gyrus as well as between the dlPFC WM seed region and paracentral lobule. Interestingly, only vlPFC connectivity was significantly associated with WM performance across the samples. In conclusion, we found primarily overlapping patterns of reduced rsFC in WM brain regions in both mTBI and PTSD groups. Our finding of decreased vlPFC connectivity associated with WM is consistent with previous clinical and neuroimaging studies. Overall, these results provide support for shared neural substrates of WM in individuals with either mTBI or PTSD.

Executive functioning deficits exacerbate posttraumatic stress symptoms: A longitudinal mediation model

Executive functioning (EF) consists of a set of related, but distinct, higher-level cognitive abilities that are used to organize and integrate lower-level processes in the service of engaging in goal-direct behavior. Evidence suggests that deficits in EF are a vulnerability factor for the development of posttraumatic stress (PTS) symptoms. Less understood, however, is the role that EF plays in symptom maintenance and exacerbation following trauma exposure. As such, the primary purpose of the present study was to determine whether EF deficits exacerbate PTS symptoms over the course of one year. A secondary aim of this study was to use a cross-lagged design to determine the directional relations among EF deficits and PTS. Trauma-exposed adults (N = 98) completed a clinical interview and self-report measures at an initial assessment session (Time 1 [T1]). Participants also completed self-report measures at 6- (Time 2 [T2]; n = 92) and 12-month (Time 3 [T3]; n = 91) follow-up sessions. As predicted, EF deficits at T2 mediated the relationship between PTS symptoms from T1 to T3, thus suggesting that EF deficits exacerbate PTS symptoms following trauma exposure. Results from a cross-lagged path analysis from T2 to T3 suggest that deficits in EF exert a stronger influence on the maintenance of PTS symptoms than vice versa. These results have implications for (a) identifying individuals that are at elevated risk for developing PTS symptoms, (b) developing precision medicine-based approaches for alleviating PTS symptoms, and (c) improving well-established PTSD treatments for those with relative deficits in EF.

Longitudinal changes in the neural oscillatory dynamics underlying abstract reasoning in children and adolescents

Fluid reasoning is the ability to problem solve in the absence of prior knowledge and is commonly conceptualized as “non-verbal” intelligence. Importantly, fluid reasoning abilities rapidly develop throughout childhood and adolescence. Although numerous studies have characterized the neural underpinnings of fluid reasoning in adults, there is a paucity of research detailing the developmental trajectory of this neural processing. Herein, we examine longitudinal changes in the neural oscillatory dynamics underlying fluid intelligence in a sample of typically developing youths. A total of 34 participants age 10 to 16 years-old completed an abstract reasoning task during magnetoencephalography (MEG) on two occasions set one year apart. We found robust longitudinal optimization in theta, beta, and gamma oscillatory activity across years of the study across a distributed network commonly implicated in fluid reasoning abilities. More specifically, activity tended to decrease longitudinally in additional, compensatory areas such as the right lateral prefrontal cortex and increase in areas commonly utilized in mature adult samples (e.g., left frontal and parietal cortices). Importantly, shifts in neural activity were associated with improvements in task performance from one year to the next. Overall, the data suggest a longitudinal shift in performance that is accompanied by a reconfiguration of the functional oscillatory dynamics serving fluid reasoning during this important period of development.

Trauma moderates the development of the oscillatory dynamics serving working memory in a sex-specific manner

Working memory, the ability to hold items in memory stores for further manipulation, is a higher order cognitive process that supports many aspects of daily life. Childhood trauma has been associated with altered cognitive development including particular deficits in verbal working memory (VWM), but the neural underpinnings remain poorly understood. Magnetoencephalography (MEG) studies of VWM have reliably shown decreased alpha activity in left-lateralized language regions during encoding, and increased alpha activity in parieto-occipital cortices during the maintenance phase. In this study, we examined whether childhood trauma affects behavioral performance and the oscillatory dynamics serving VWM using MEG in a cohort of 9- to 15-year-old youth. All participants completed a modified version of the UCLA Trauma History Profile and then performed a VWM task during MEG. Our findings indicated a sex-by-age-by-trauma three-way interaction, whereby younger females experiencing higher levels of trauma had the lowest d' accuracy scores and the strongest positive correlations with age (i.e. older performed better). Likewise, females with higher levels of childhood trauma exhibited altered age-related alpha changes during the maintenance phase within the right temporal and parietal cortices. These findings suggest that trauma exposure may alter the developmental trajectory of neural oscillations serving VWM processing in a sex-specific way.

Multielectrode Transcranial Electrical Stimulation of the Left and Right Prefrontal Cortices Differentially Impacts Verbal Working Memory Neural Circuitry

Recent studies have examined the effects of conventional transcranial direct current stimulation (tDCS) on working memory (WM) performance, but this method has relatively low spatial precision and generally involves a reference electrode that complicates interpretation. Herein, we report a repeated-measures crossover study of 25 healthy adults who underwent multielectrode tDCS of the left dorsolateral prefrontal cortex (DLPFC), right DLPFC, or sham in 3 separate visits. Shortly after each stimulation session, participants performed a verbal WM (VWM) task during magnetoencephalography, and the resulting data were examined in the time-frequency domain and imaged using a beamformer. We found that after left DLPFC stimulation, participants exhibited stronger responses across a network of left-lateralized cortical areas, including the supramarginal gyrus, prefrontal cortex, inferior frontal gyrus, and cuneus, as well as the right hemispheric homologues of these regions. Importantly, these effects were specific to the alpha-band, which has been previously implicated in VWM processing. Although stimulation condition did not significantly affect performance, stepwise regression revealed a relationship between reaction time and response amplitude in the left precuneus and supramarginal gyrus. These findings suggest that multielectrode tDCS targeting the left DLPFC affects the neural dynamics underlying offline VWM processing, including utilization of a more extensive bilateral cortical network.

Circuit-Based Biomarkers for Mood and Anxiety Disorders

Mood and anxiety disorders are complex heterogeneous syndromes that manifest in dysfunctions across multiple brain regions, cell types, and circuits. Biomarkers using brain-wide activity patterns in humans have proven useful in distinguishing between disorder subtypes and identifying effective treatments. In order to improve biomarker identification, it is crucial to understand the basic circuitry underpinning brain-wide activity patterns. Leveraging a large repertoire of techniques, animal studies have examined roles of specific cell types and circuits in driving maladaptive behavior. Recent advances in multiregion recording techniques, data-driven analysis approaches, and machine-learning-based behavioral analysis tools can further push the boundary of animal studies and bridge the gap with human studies, to assess how brain-wide activity patterns encode and drive emotional behavior. Together, these efforts will allow identifying more precise biomarkers to enhance diagnosis and treatment.

Numerical working memory alters alpha-beta oscillations and connectivity in the parietal cortices

Although the neural bases of numerical processing and memory have been extensively studied, much remains to be elucidated concerning the spectral and temporal dynamics surrounding these important cognitive processes. To further this understanding, we employed a novel numerical working memory paradigm in 28 young, healthy adults who underwent magnetoencephalography (MEG). The resulting data were examined in the time-frequency domain prior to image reconstruction using a beamformer. Whole-brain, spectrally-constrained coherence was also employed to determine network connectivity. In response to the numerical task, participants exhibited robust alpha/beta oscillations in the bilateral parietal cortices. Whole-brain statistical comparisons examining the effect of numerical manipulation during memory-item maintenance revealed a difference centered in the right superior parietal cortex, such that oscillatory responses during numerical manipulation were significantly stronger than when no manipulation was necessary. Additionally, there was significantly reduced cortico-cortical coherence between the right and left superior parietal regions during the manipulation compared to the maintenance trials, indicating that these regions were functioning more independently when the numerical information had to be actively processed. In sum, these results support previous studies that have implicated the importance of parietal regions in numerical processing, but also provide new knowledge on the spectral, temporal, and network dynamics that serve this critical cognitive function during active working memory maintenance.

Rethinking post-traumatic stress disorder - A predictive processing perspective

Predictive processing has become a popular framework in neuroscience and computational psychiatry, where it has provided a new understanding of various mental disorders. Here, we apply the predictive processing account to post-traumatic stress disorder (PTSD). We argue that the experience of a traumatic event in Bayesian terms can be understood as a perceptual hypothesis that is subsequently given a very high a-priori likelihood due to its (life-) threatening significance; thus, this hypothesis is re-selected although it does not fit the actual sensory input. Based on this account, we re-conceptualise the symptom clusters of PTSD through the lens of a predictive processing model. We particularly focus on re-experiencing symptoms as the hallmark symptoms of PTSD, and discuss the occurrence of flashbacks in terms of perceptual and interoceptive inference. This account provides not only a new understanding of the clinical profile of PTSD, but also a unifying framework for the corresponding pathologies at the neurobiological level. Finally, we derive directions for future research and discuss implications for psychological and pharmacological interventions.

New perspectives on the neurobiology of PTSD: High-resolution imaging of neural circuit (dys)function with magnetoencephalography

Introduction: Combat-related posttraumatic stress disorder (PTSD) is increasingly conceptualized in psychiatry as a disorder of dysfunctional neural circuits. Advances in neuroimaging have enabled the study of those networks non-invasively. PTSD is currently assessed using subjective self-reporting to inform crucial decisions, such as fitness to deploy, but objective markers would aid in diagnosis and return-to-deployment decisions. Methods: Magnetoencephalography (MEG) allows investigation of neural circuit function via imaging of brain waves (known as neural oscillations) that index information processing in the brain and would prove a reliable, objective, biomarker. These measures of brain function establish how regions communicate to form brain circuits that support thinking and behaviour. Results: Studies into intrinsic brain function, both during rest and when engaged in a task designed to tap into cognitive dysfunction, have found these neurobiological mechanisms are disrupted in PTSD and are a reliable objective marker of illness. We now know that these alterations in brain function are directly related to core symptoms of PTSD and comorbid cognitive-behavioural challenges. Discussion: Continued characterization of neural function using MEG and related methods will advance understanding of the neurobiology underlying PTSD; allow for the identification of biomarkers that, coupled with machine learning, will aid in diagnoses; provide individualized therapeutic targets for neurostimulation; predict treatment outcomes; and track disorder remission in military personnel and Veterans who are disproportionately affected by this devastating illness.

The Predictive Processing Model of EMDR

Eye Movement Desensitization and Reprocessing Therapy (EMDR) is an effective treatment for Post-traumatic Stress Disorder (PTSD). The Adaptive Information Processing Model (AIP) guides the development and practice of EMDR. The AIP postulates inadequately processed memory as the foundation of PTSD pathology. Predictive Processing postulates that the primary function of the brain is prediction that serves to anticipate the next moment of experience in order to resist the dissipative force of entropy thus facilitating continued survival. Memory is the primary substrate of prediction, and is optimized by an ongoing process of precision weighted prediction error minimization that refines prediction by updating the memories on which it is based. The Predictive Processing model of EMDR postulates that EMDR facilitates the predictive processing of traumatic memory by overcoming the bias against exploration and evidence accumulation. The EMDR protocol brings the traumatic memory into an active state of re-experiencing. Defensive responding and/or low sensory precision preclude evidence accumulation to test the predictions of the traumatic memory in the present. Sets of therapist guided eye movements repeatedly challenge the bias against evidence accumulation and compel sensory sampling of the benign present. Eye movements reset the theta rhythm organizing the flow of information through the brain, facilitating the deployment of both overt and covert attention, and the mnemonic search for associations. Sampling of sensation does not support the predictions of the traumatic memory resulting in prediction error that the brain then attempts to minimize. The net result is a restoration of the integrity of the rhythmic deployment of attention, a recalibration of sensory precision, and the updating (reconsolidation) of the traumatic memory. Thus one prediction of the model is a decrease in Attention Bias Variability, a core dysfunction in PTSD, following successful treatment with EMDR.

Aberrant regional homogeneity in post-traumatic stress disorder after traffic accident: A resting-state functional MRI study

OBJECTIVES

The present study explored the changes in spontaneous regional activity in post-traumatic stress disorder (PTSD) patients, who experienced severe traffic accidents.

METHODS

20 drug-naive PTSD patients and 18 healthy control subjects were imaged using resting-state functional magnetic resonance imaging (rs-fMRI) and analyzed by the algorithm of regional homogeneity (ReHo).

RESULTS

Compared to the healthy control group, the PTSD group showed decreased ReHo values in the right angular gyrus. In addition, a negative correlation was found between the activity level of the angular gyrus and the CAPS score.

CONCLUSION

The dysfunctions were found in the memory- and emotion-related areas, suggested a possible mechanism of memory dysregulation that might be related to the intrusive memory symptoms of PTSD. These results provided imaging evidence that might provide an in-depth understanding of the intrinsic functional architecture of PTSD.

Aberrant brain dynamics in neuroHIV: Evidence from magnetoencephalographic (MEG) imaging

Magnetoencephalography (MEG) is a noninvasive, silent, and totally passive neurophysiological imaging method with excellent temporal resolution (~1ms) and good spatial precision (~3-5mm). While MEG studies of neuroHIV remain relatively rare, the number of studies per year has sharply increased recently and this trend will likely continue into the foreseeable future. The current in-depth review focuses on the studies that have been conducted to date, which include investigations of somatosensory and visual modalities, resting-state, as well as motor control and higher-level functions such as working memory and visual attention. The review begins with an introduction to the principles and methods of MEG, and then transitions to a review of each of the empirical studies that have been conducted to date, separated by sensory modality for the basic studies and cognitive domain for the higher-level investigations. As such, this review attempts to be exhaustive in its coverage of empirical MEG studies of neuroHIV. Across studies major themes emerge including aberrant neural oscillatory activity in HIV-infected adults, both in primary sensory regions of the brain and higher-order executive regions. Many studies have also connected the amplitude of neural oscillations to behavioral and/or neuropsychological function in the study population, making a vital connection to performance and improving the veracity of the findings. One conspicuous emerging area is the use of MEG to distinguish cognitively-impaired from unimpaired HIV-infected adults, with major success reported and future studies sure to come. The review concludes with a summary of findings and suggested focus areas for future studies.

Treatment of military-related post-traumatic stress disorder: challenges, innovations, and the way forward

Post-traumatic stress disorder (PTSD) is one of the common mental disorders in military and veteran populations. Considerable research and clinical opinion has been focused on understanding the relationship between PTSD and military service and the implications for prevention, treatment, and management. This paper examines factors associated with the development of PTSD in this population, considers issues relating to engagement in treatment, and discusses the empirical support for best practice evidence-based treatment. The paper goes on to explore the challenges in those areas, with particular reference to treatment engagement and barriers to care, as well as treatment non-response. The final section addresses innovative solutions to these challenges through improvements in agreed terminology and definitions, strategies to increase engagement, early identification approaches, understanding predictors of treatment outcome, and innovations in treatment. Treatment innovations include enhancing existing treatments, emerging non-trauma-focused interventions, novel pharmacotherapy, personalized medicine approaches, advancing functional outcomes, family intervention and support, and attention to physical health.

Load modulates the alpha and beta oscillatory dynamics serving verbal working memory

A network of predominantly left-lateralized brain regions has been linked to verbal working memory (VWM) performance. However, the impact of memory load on the oscillatory dynamics serving VWM is far less understood. To further investigate this, we had 26 healthy adults perform a high-load (6 letter) and low-load (4 letter) variant of a VWM task while undergoing magnetoencephalography (MEG). MEG data were evaluated in the time-frequency domain and significant oscillatory responses spanning the encoding and maintenance phases were reconstructed using a beamformer. To determine the impact of load on the neural dynamics, the resulting images were examined using paired-samples t-tests and virtual sensor analyses. Our results indicated stronger increases in frontal theta activity in the high- relative to low-load condition during early encoding. Stronger decreases in alpha/beta activity were also observed during encoding in bilateral posterior cortices during the high-load condition, and the strength of these load effects increased as encoding progressed. During maintenance, stronger decreases in alpha activity in the left inferior frontal gyrus, middle temporal gyrus, supramarginal gyrus, and inferior parietal cortices were detected during high- relative to low-load performance, with the strength of these load effects remaining largely static throughout maintenance. Finally, stronger increases in occipital alpha activity were observed during maintenance in the high-load condition, and the strength of these effects grew stronger with time during the first half of maintenance, before dissipating during the latter half of maintenance. Notably, this was the first study to utilize a whole-brain approach to statistically evaluate the temporal dynamics of load-related oscillatory differences during encoding and maintenance processes, and our results highlight the importance of spatial, temporal, and spectral specificity in this regard.

Altered Brain Dynamics in Patients With Type 1 Diabetes During Working Memory Processing

It is now generally accepted that diabetes increases the risk for cognitive impairment, but the precise mechanisms are poorly understood. A critical problem in linking diabetes to cognitive impairment is that patients often have multiple comorbidities (e.g., obesity, hypertension) that have been independently linked to cognitive deficits. In the study reported here we focused on young adults with and without type 1 diabetes who were virtually free of such comorbidities. The two groups were matched on major health and demographic factors, and all participants completed a verbal working memory task during magnetoencephalographic brain imaging. We hypothesized that patients would have altered neural dynamics in verbal working memory processing and that these differences would directly relate to clinical disease measures. Accordingly, we found that patients had significantly stronger neural responses in the superior parietal cortices during memory encoding and significantly weaker activity in parietal-occipital regions during maintenance compared with control subjects. Moreover, disease duration and glycemic control were both significantly correlated with neural responses in various brain regions. In conclusion, young healthy adults with type 1 diabetes already have aberrant neural processing relative to their peers without diabetes, using compensatory responses to perform the task, and glucose management and duration may play a central role.

Attention training modulates resting-state neurophysiological abnormalities in posttraumatic stress disorder

Recent research indicates the relative benefits of computerized attention control treatment (ACT) and attention bias modification treatment (ABMT) for posttraumatic stress disorder (PTSD); however, neural changes underlying these therapeutic effects remain unknown. This study examines how these two types of attention training modulate neurological dysfunction in veterans with PTSD. A community sample of 46 combat veterans with PTSD participated in a randomized double-blinded clinical trial of ACT versus ABMT and 32 of those veterans also agreed to undergo resting-state magnetoencephalography (MEG) recordings. Twenty-four veterans completed psychological and MEG assessments at pre- and post-training to evaluate treatment effects. MEG data were imaged using an advanced Bayesian reconstruction method and examined using statistical parametric mapping. In this report, we focus on the neural correlates and the differential treatment effects observed using MEG; the results of the full clinical trial have been described elsewhere. Our results indicated that ACT modulated occipital and ABMT modulated medial temporal activity more strongly than the comparative treatment. PTSD symptoms decreased significantly from pre- to post-test. These initial neurophysiological outcome data suggest that ACT modulates visual pathways, while ABMT modulates threat-processing regions, but that both are associated with normalizing aberrant neural activity in veterans with PTSD.

Veterans with post-traumatic stress disorder exhibit altered emotional processing and attentional control during an emotional Stroop task

BACKGROUND

Post-traumatic stress disorder (PTSD) is often associated with attention allocation and emotional regulation difficulties, but the brain dynamics underlying these deficits are unknown. The emotional Stroop task (EST) is an ideal means to monitor these difficulties, because participants are asked to attend to non-emotional aspects of the stimuli. In this study, we used magnetoencephalography (MEG) and the EST to monitor attention allocation and emotional regulation during the processing of emotionally charged stimuli in combat veterans with and without PTSD.

METHOD

A total of 31 veterans with PTSD and 20 without PTSD performed the EST during MEG. Three categories of stimuli were used, including combat-related, generally threatening and neutral words. MEG data were imaged in the time-frequency domain and the network dynamics were probed for differences in processing threatening and non-threatening words.

RESULTS

Behaviorally, veterans with PTSD were significantly slower in responding to combat-related relative to neutral and generally threatening words. Veterans without PTSD exhibited no significant differences in responding to the three different word types. Neurophysiologically, we found a significant three-way interaction between group, word type and time period across multiple brain regions. Follow-up testing indicated stronger theta-frequency (4-8 Hz) responses in the right ventral prefrontal (0.4-0.8 s) and superior temporal cortices (0.6-0.8 s) of veterans without PTSD compared with those with PTSD during the processing of combat-related words.

CONCLUSIONS

Our data indicated that veterans with PTSD exhibited deficits in attention allocation and emotional regulation when processing trauma cues, while those without PTSD were able to regulate emotion by directing attention away from threat.

Aberrant Neuronal Dynamics during Working Memory Operations in the Aging HIV-Infected Brain

Impairments in working memory are among the most prevalent features of HIV-associated neurocognitive disorders (HAND), yet their origins are unknown, with some studies arguing that encoding operations are disturbed and others supporting deficits in memory maintenance. The current investigation directly addresses this issue by using a dynamic mapping approach to identify when and where processing in working memory circuits degrades. HIV-infected older adults and a demographically-matched group of uninfected controls performed a verbal working memory task during magnetoencephalography (MEG). Significant oscillatory neural responses were imaged using a beamforming approach to illuminate the spatiotemporal dynamics of neuronal activity. HIV-infected patients were significantly less accurate on the working memory task and their neuronal dynamics indicated that encoding operations were preserved, while memory maintenance processes were abnormal. Specifically, no group differences were detected during the encoding period, yet dysfunction in occipital, fronto-temporal, hippocampal, and cerebellar cortices emerged during memory maintenance. In addition, task performance in the controls covaried with occipital alpha synchronization and activity in right prefrontal cortices. In conclusion, working memory impairments are common and significantly impact the daily functioning and independence of HIV-infected patients. These impairments likely reflect deficits in the maintenance of memory representations, not failures to adequately encode stimuli.