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Andrew A. Nicholson

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9 papers

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YNICL Journal 2026 Journal Article

Bridging the self to the world: resting-state functional connectivity of the temporoparietal junction in post-traumatic stress disorder and its dissociative subtype

Sandhya Narikuzhy
Sherain Harricharan
Daniela Rabellino
Maria Densmore
Jean Théberge
Jonathan Lieberman
Margaret C. McKinnon
Andrew A. Nicholson

BACKGROUND: The temporoparietal junction (TPJ) is a cross-network hub involved in social cognition and attention, processes which are directly impacted by symptoms observed in clinical profiles of post-traumatic stress disorder (PTSD) and its dissociative subtype (PTSD + DS). METHODS: Using SPM12 and CONN, seed-based TPJ resting-state functional connectivity patterns were analyzed in individuals with PTSD (n = 81), PTSD + DS (n = 49), and healthy controls (n = 54) using four seeds [right anterior TPJ (raTPJ), left anterior TPJ (laTPJ), right posterior TPJ (rpTPJ), left posterior TPJ (lpTPJ)]. Post-hoc graph theoretical analyses were performed for raTPJ connectivity in PTSD + DS and healthy controls. RESULTS: As compared to healthy controls, PTSD + DS showed decreased raTPJ functional connectivity with critical anterior frontal lobe nodes involved in the ventral attention and social cognition networks (i.e., left ventrolateral and dorsomedial prefrontal cortices). PTSD showed decreased lpTPJ functional connectivity with the left superior parietal lobule as compared to healthy controls. When comparing PTSD to PTSD + DS, we observed increased bilateral TPJ functional connectivity with the cerebellum. Lastly, compared to healthy controls, both PTSD and PTSD + DS displayed decreased bilateral TPJ functional connectivity with the occipital lobe. Graph theoretical analyses revealed that PTSD + DS showed limited raTPJ involvement and instead more efficient neural communication between occipital lobe and frontal lobe structures as compared to healthy controls, suggesting a possible compensatory neural network in PTSD + DS. CONCLUSIONS: These findings reveal disruptions in TPJ neural circuitry in PTSD and PTSD + DS, which may carry cascading effects on intersecting neural networks involving the TPJ. Implications for psychotherapeutic treatments targeting disembodiment and social cognition are discussed.

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YNICL Journal 2025 Journal Article

Contributions of the default mode and central executive networks during posterior cingulate cortex-targeted fMRI neurofeedback in PTSD

Jonathan M. Lieberman
Ruth A. Lanius
Maria Densmore
Jean Théberge
Daniela Rabellino
Paul A. Frewen
Frank Scharnowski
Rakesh Jetly

INTRODUCTION: Functional magnetic resonance imaging-based neurofeedback (fMRI-NFB) enables individuals to regulate brain activity implicated in psychopathology, including post-traumatic stress disorder (PTSD). While most fMRI-NFB studies in PTSD target the amygdala, which engages the central executive network (CEN) for top-down regulation, the posterior cingulate cortex (PCC), a core node of the default mode network (DMN), has recently emerged as a promising therapeutic target. However, the relative contributions of intra-network DMN mechanisms versus inter-network CEN engagement during PCC downregulation remain unclear. METHODS: We used independent component analysis (ICA) to examine DMN and CEN functional connectivity during PCC-targeted fMRI-NFB in individuals with PTSD (n = 14) and healthy controls (n = 15) while viewing trauma-related/distressing words. Mixed-design repeated measures ANOVAs assessed within- and between-group connectivity changes, and clinical correlations were explored. RESULTS: During PCC downregulation, PTSD participants exhibited greater DMN connectivity than controls with trauma-related regions, including the precentral gyrus and anterior insula, which correlated with PTSD severity and emotion regulation difficulties. Conversely, CEN connectivity decreased in both groups, with PTSD participants showing progressively reduced connectivity across training. Direct comparisons revealed that DMN connectivity exceeded CEN connectivity with several brain regions, particularly among PTSD participants. CONCLUSION: These findings highlight the predominant role of DMN mechanisms in PCC downregulation in PTSD. The reliance on intra-network DMN processes over CEN-driven regulation underscores distinct network dynamics that may be unique to PCC-targeted fMRI-NFB. These neural mechanistic insights may inform targeted fMRI-NFB protocols to recalibrate altered DMN connectivity and enhance emotion regulation in PTSD.

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YNICL Journal 2023 Journal Article

Altered Resting-State functional connectivity in the anterior and posterior hippocampus in Post-traumatic stress disorder: The central role of the anterior hippocampus

Mohammad Chaposhloo
Andrew A. Nicholson
Suzanna Becker
Margaret C. McKinnon
Ruth Lanius
Saurabh Bhaskar Shaw

BACKGROUND: Post-traumatic stress disorder can be viewed as a memory disorder, with trauma-related flashbacks being a core symptom. Given the central role of the hippocampus in autobiographical memory, surprisingly, there is mixed evidence concerning altered hippocampal functional connectivity in PTSD. We shed light on this discrepancy by considering the distinct roles of the anterior versus posterior hippocampus and examine how this distinction may map onto whole-brain resting-state functional connectivity patterns among those with and without PTSD. METHODS: We first assessed whole-brain between-group differences in the functional connectivity profiles of the anterior and posterior hippocampus within a publicly available data set of resting-state fMRI data from 31 male Vietnam war veterans diagnosed with PTSD (mean age = 67.6 years, sd = 2.3) and 29 age-matched combat-exposed male controls (age = 69.1 years, sd = 3.5). Next, the connectivity patterns of each subject within the PTSD group were correlated with their PTSD symptom scores. Finally, the between-group differences in whole-brain functional connectivity profiles discovered for the anterior and posterior hippocampal seeds were used to prescribe post-hoc ROIs, which were then used to perform ROI-to-ROI functional connectivity and graph-theoretic analyses. RESULTS: The PTSD group showed increased functional connectivity of the anterior hippocampus with affective brain regions (anterior/posterior insula, orbitofrontal cortex, temporal pole) and decreased functional connectivity of the anterior/posterior hippocampus with regions involved in processing bodily self-consciousness (supramarginal gyrus). Notably, decreased anterior hippocampus connectivity with the posterior cingulate cortex/precuneus was associated with increased PTSD symptom severity. The left anterior hippocampus also emerged as a central locus of abnormal functional connectivity, with graph-theoretic measures suggestive of a more central hub-like role for this region in those with PTSD compared to trauma-exposed controls. CONCLUSIONS: Our results highlight that the anterior hippocampus plays a critical role in the neurocircuitry underlying PTSD and underscore the importance of the differential roles of hippocampal sub-regions in serving as biomarkers of PTSD. Future studies should investigate whether the differential patterns of functional connectivity stemming from hippocampal sub-regions is observed in PTSD populations other than older war veterans.

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YNICL Journal 2023 Journal Article

Increased top-down control of emotions during symptom provocation working memory tasks following a RCT of alpha-down neurofeedback in PTSD

Saurabh Bhaskar Shaw
Andrew A. Nicholson
Tomas Ros
Sherain Harricharan
Braeden Terpou
Maria Densmore
Jean Theberge
Paul Frewen

BACKGROUND: Posttraumatic stress disorder (PTSD) has been found to be associated with emotion under-modulation from the prefrontal cortex and a breakdown of the top-down control of cognition and emotion. Novel adjunct therapies such as neurofeedback (NFB) have been shown to normalize aberrant neural circuits that underlie PTSD psychopathology at rest. However, little evidence exists for NFB-linked neural improvements under emotionally relevant cognitive load. The current study sought to address this gap by examining the effects of alpha-down NFB in the context of an emotional n-back task. METHODS: We conducted a 20-week double-blind randomized, sham-controlled trial of alpha-down NFB and collected neuroimaging data before and after the NFB protocol. Participants performed an emotional 1-back and 2-back working memory task, with interleaved trauma-neutral and trauma-relevant cues in the fMRI scanner. Data from 35 participants with a primary diagnosis of PTSD were analyzed in this study (n = 18 in the experimental group undergoing alpha-down NFB, n = 17 in the sham-control group). RESULTS: Firstly, within-group analyses showed clinically significant reductions in PTSD symptom severity scores at the post-intervention timepoint and 3-month follow-up for the experimental group, and not for the sham-control group. The neuroimaging analyses revealed that alpha-down NFB enhanced engagement of top-down cognitive and emotional control centers, such as the dorsolateral prefrontal cortex (dlPFC), and improved integration of the anterior and posterior parts of the default mode network (DMN). Finally, our results also indicate that increased alpha-down NFB performance correlated with increased activity in brain regions involved in top-down control and bodily consciousness/embodied processing of self (TPJ and posterior insula). CONCLUSION: This is the first study to provide mechanistic insights into how NFB may normalize dysfunctional brain activity and connectivity in PTSD under cognitive load with simultaneous symptom provocation, adding to a growing body of evidence supporting the therapeutic neuromodulatory effects of NFB. This preliminary study highlights the benefits of alpha-down NFB training as an adjunctive therapy for PTSD and warrants further investigation into its therapeutic effects on cognitive and emotion control in those with PTSD.

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YNIMG Journal 2021 Journal Article

Predictors of real-time fMRI neurofeedback performance and improvement – A machine learning mega-analysis

Amelie Haugg
Fabian M. Renz
Andrew A. Nicholson
Cindy Lor
Sebastian J. Götzendorfer
Ronald Sladky
Stavros Skouras
Amalia McDonald

Real-time fMRI neurofeedback is an increasingly popular neuroimaging technique that allows an individual to gain control over his/her own brain signals, which can lead to improvements in behavior in healthy participants as well as to improvements of clinical symptoms in patient populations. However, a considerably large ratio of participants undergoing neurofeedback training do not learn to control their own brain signals and, consequently, do not benefit from neurofeedback interventions, which limits clinical efficacy of neurofeedback interventions. As neurofeedback success varies between studies and participants, it is important to identify factors that might influence neurofeedback success. Here, for the first time, we employed a big data machine learning approach to investigate the influence of 20 different design-specific (e.g. activity vs. connectivity feedback), region of interest-specific (e.g. cortical vs. subcortical) and subject-specific factors (e.g. age) on neurofeedback performance and improvement in 608 participants from 28 independent experiments. With a classification accuracy of 60% (considerably different from chance level), we identified two factors that significantly influenced neurofeedback performance: Both the inclusion of a pre-training no-feedback run before neurofeedback training and neurofeedback training of patients as compared to healthy participants were associated with better neurofeedback performance. The positive effect of pre-training no-feedback runs on neurofeedback performance might be due to the familiarization of participants with the neurofeedback setup and the mental imagery task before neurofeedback training runs. Better performance of patients as compared to healthy participants might be driven by higher motivation of patients, higher ranges for the regulation of dysfunctional brain signals, or a more extensive piloting of clinical experimental paradigms. Due to the large heterogeneity of our dataset, these findings likely generalize across neurofeedback studies, thus providing guidance for designing more efficient neurofeedback studies specifically for improving clinical neurofeedback-based interventions. To facilitate the development of data-driven recommendations for specific design details and subpopulations the field would benefit from stronger engagement in open science research practices and data sharing.

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YNICL Journal 2020 Journal Article

A randomized, controlled trial of alpha-rhythm EEG neurofeedback in posttraumatic stress disorder: A preliminary investigation showing evidence of decreased PTSD symptoms and restored default mode and salience network connectivity using fMRI

Andrew A. Nicholson
Tomas Ros
Maria Densmore
Paul A. Frewen
Richard W.J. Neufeld
Jean Théberge
Rakesh Jetly
Ruth A. Lanius

OBJECTIVE: The default-mode network (DMN) and salience network (SN) have been shown to display altered connectivity in posttraumatic stress disorder (PTSD). Restoring aberrant connectivity within these networks with electroencephalogram neurofeedback (EEG-NFB) has been shown previously to be associated with acute decreases in symptoms. Here, we conducted a double-blind, sham-controlled randomized trial of alpha-rhythm EEG-NFB in participants with PTSD (n = 36) over 20-weeks. Our aim was to provide mechanistic evidence underlying clinical improvements by examining changes in network connectivity via fMRI. METHODS: We randomly assigned participants with a primary diagnosis of PTSD to either the experimental group (n = 18) or sham-control group (n = 18). We collected resting-state fMRI scans pre- and post-NFB intervention, for both the experimental and sham-control PTSD groups. We further compared baseline brain connectivity measures pre-NFB to age-matched healthy controls (n = 36). RESULTS: With regard to the primary outcome measure of PTSD severity, we found a significant main effect of time in the absence of a group × time interaction. Nevertheless, we found significantly decreased PTSD severity scores in the experimental NFB group only, when comparing post-NFB (dz = 0.71) and 3-month follow-up scores (dz = 0.77) to baseline measures. Interestingly, we found evidence to suggest a shift towards normalization of DMN and SN connectivity post-NFB in the experimental group only. Both decreases in PTSD severity and NFB performance were correlated to DMN and SN connectivity post-NFB in the experimental group. Critically, remission rates of PTSD were significant higher in the experimental group (61.1%) as compared to the sham-control group (33.3%). CONCLUSION: The current study shows mechanistic evidence for therapeutic changes in DMN and SN connectivity that are known to be associated with PTSD psychopathology with no patient dropouts. This preliminary investigation merits further research to demonstrate fully the clinical efficacy of EEG-NFB as an adjunctive therapy for PTSD.

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YNICL Journal 2020 Journal Article

Classifying heterogeneous presentations of PTSD via the default mode, central executive, and salience networks with machine learning

Andrew A. Nicholson
Sherain Harricharan
Maria Densmore
Richard W.J. Neufeld
Tomas Ros
Margaret C. McKinnon
Paul A. Frewen
Jean Théberge

Intrinsic connectivity networks (ICNs), including the default mode network (DMN), the central executive network (CEN), and the salience network (SN) have been shown to be aberrant in patients with posttraumatic stress disorder (PTSD). The purpose of the current study was to a) compare ICN functional connectivity between PTSD, dissociative subtype PTSD (PTSD+DS) and healthy individuals; and b) to examine the use of multivariate machine learning algorithms in classifying PTSD, PTSD+DS, and healthy individuals based on ICN functional activation. Our neuroimaging dataset consisted of resting-state fMRI scans from 186 participants [PTSD (n = 81); PTSD + DS (n = 49); and healthy controls (n = 56)]. We performed group-level independent component analyses to evaluate functional connectivity differences within each ICN. Multiclass Gaussian Process Classification algorithms within PRoNTo software were then used to predict the diagnosis of PTSD, PTSD+DS, and healthy individuals based on ICN functional activation. When comparing the functional connectivity of ICNs between PTSD, PTSD+DS and healthy controls, we found differential patterns of connectivity to brain regions involved in emotion regulation, in addition to limbic structures and areas involved in self-referential processing, interoception, bodily self-consciousness, and depersonalization/derealization. Machine learning algorithms were able to predict with high accuracy the classification of PTSD, PTSD+DS, and healthy individuals based on ICN functional activation. Our results suggest that alterations within intrinsic connectivity networks may underlie unique psychopathology and symptom presentation among PTSD subtypes. Furthermore, the current findings substantiate the use of machine learning algorithms for classifying subtypes of PTSD illness based on ICNs.

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YNICL Journal 2020 Journal Article

The hijacked self: Disrupted functional connectivity between the periaqueductal gray and the default mode network in posttraumatic stress disorder using dynamic causal modeling

Braeden A. Terpou
Maria Densmore
Jean Théberge
Paul Frewen
Margaret C. McKinnon
Andrew A. Nicholson
Ruth A. Lanius

Self-related processes define assorted self-relevant or social-cognitive functions that allow us to gather insight and to draw inferences related to our own mental conditions. Self-related processes are mediated by the default mode network (DMN), which, critically, shows altered functionality in individuals with posttraumatic stress disorder (PTSD). In PTSD, the midbrain periaqueductal gray (PAG) demonstrates stronger functional connectivity with the DMN [i.e., precuneus (PCN), medial prefrontal cortex (mPFC)] as compared to healthy individuals during subliminal, trauma-related stimulus processing. Here, we analyzed the directed functional connectivity between the PAG and the PCN, as well as between the PAG and the mPFC to more explicitly characterize the functional connectivity we have observed previously on the corresponding sample and paradigm. We evaluated three models varying with regard to context-dependent modulatory directions (i.e., bi-directional, bottom-up, top-down) among individuals with PTSD (n = 26) and healthy participants (n = 20), where Bayesian model selection was used to identify the most optimal model for each group. We then compared the effective connectivity strength for each parameter across the models and between our groups using Bayesian model averaging. Bi-directional models were found to be favoured across both groups. In PTSD, we revealed the PAG to show stronger excitatory effective connectivity to the PCN, as well as to the mPFC as compared to controls. In PTSD, we further demonstrated that PAG-mediated effective connectivity to the PCN, as well as to the mPFC were modulated more strongly during subliminal, trauma-related stimulus conditions as compared to controls. Clinical disturbances towards self-related processes are reported widely by participants with PTSD during trauma-related stimulus processing, where altered functional connectivity directed by the PAG to the DMN may elucidate experiential links between self- and trauma-related processing in traumatized individuals.

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YNICL Journal 2016 Journal Article

Alpha oscillation neurofeedback modulates amygdala complex connectivity and arousal in posttraumatic stress disorder

Andrew A. Nicholson
Tomas Ros
Paul A. Frewen
Maria Densmore
Jean Théberge
Rosemarie C. Kluetsch
Rakesh Jetly
Ruth A. Lanius

OBJECTIVE: Electroencephalogram (EEG) neurofeedback aimed at reducing the amplitude of the alpha-rhythm has been shown to alter neural networks associated with posttraumatic stress disorder (PTSD), leading to symptom alleviation. Critically, the amygdala is thought to be one of the central brain regions mediating PTSD symptoms. In the current study, we compare directly patterns of amygdala complex connectivity using fMRI, before and after EEG neurofeedback, in order to observe subcortical mechanisms associated with behavioural and alpha oscillatory changes among patients. METHOD: We examined basolateral (BLA), centromedial (CMA), and superficial (SFA) amygdala complex resting-state functional connectivity using a seed-based approach via SPM Anatomy Toolbox. Amygdala complex connectivity was measured in twenty-one individuals with PTSD, before and after a 30-minute session of EEG neurofeedback targeting alpha desynchronization. RESULTS: EEG neurofeedback was associated with a shift in amygdala complex connectivity from areas implicated in defensive, emotional, and fear processing/memory retrieval (left BLA and left SFA to the periaqueductal gray, and left SFA to the left hippocampus) to prefrontal areas implicated in emotion regulation/modulation (right CMA to the medial prefrontal cortex). This shift in amygdala complex connectivity was associated with reduced arousal, greater resting alpha synchronization, and was negatively correlated to PTSD symptom severity. CONCLUSION: These findings have significant implications for developing targeted non-invasive treatment interventions for PTSD patients that utilize alpha oscillatory neurofeedback, showing evidence of neuronal reconfiguration between areas highly implicated in the disorder, in addition to acute symptom alleviation.

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