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Tom A. Schweizer

Possible papers associated with this exact author name in Arrow. This page groups case-insensitive exact name matches and is not a full identity disambiguation profile.

5 papers

1 author row

YNICL Journal 2025 Journal Article

Multi-voxel pattern analysis for characterizing functional connectivity and neurocognitive function in major depression: A CAN-BIND-1 report

Alice Rueda
Ilya Demchenko
Vanessa K. Tassone
Fatemeh Gholamali Nezhad
Vanessa Peters
Nathan W. Churchill
Benicio N. Frey
Stefanie Hassel

BACKGROUND: Major depressive disorder (MDD) affects not only mood but also neurocognitive function. In this study, we used whole-brain functional connectivity multi-voxel pattern analysis (fc-MVPA) to examine the relationship between resting-state functional connectivity (rsFC) and neurocognitive function in individuals with MDD compared to healthy controls (HC). METHODS: Baseline functional magnetic resonance imaging (fMRI) scans from the CAN-BIND-1 dataset were analyzed using a data-driven whole-brain fc-MVPA approach in 147 individuals with MDD and 98 HC. All participants completed the Computerized Neurocognitive Assessment Vital Signs (CNS-VS) battery outside the scanner, and correlations between rsFC differences and CNS-VS domain scores were explored. RESULTS: The fc-MVPA reduced the dimensionality of fMRI data at both individual and group levels, identifying six clusters with altered rsFC in MDD relative to HC: left cerebellar crus I, right precuneus, left superior lateral occipital cortex, right ventral caudate, left superior parietal lobule, and left dorsal anterior cingulate cortex. Using these clusters as seeds, post-hoc analyses identified 24 patterns of altered rsFC in MDD involving the default mode, central executive, visual recognition, salience, and sensorimotor networks. Five of these patterns showed significant correlations with CNS-VS domain scores for composite memory, neurocognition index, processing speed, executive function, and simple attention in HC, but these associations were absent in individuals with MDD. CONCLUSIONS: Our findings highlight that MDD is associated with disrupted rsFC across networks relevant to neurocognitive function. The data-driven nature of the fc-MVPA identified the left cerebellar crus I as the most significant region of aberrant rsFC.

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YNICL Journal 2020 Journal Article

Neurometabolites and sport-related concussion: From acute injury to one year after medical clearance

Nathan W. Churchill
Michael G. Hutchison
Simon J. Graham
Tom A. Schweizer

Sport-related concussion is associated with acute disturbances in neurometabolic function, with effects that may last weeks to months after injury. However, is presently unknown whether these disturbances resolve at medical clearance to return to play (RTP) or continue to evolve over longer time intervals. Moreover, little is known about how these neurometabolic changes correlate with other measures of brain physiology. In this study, these gaps were addressed by evaluating ninety-nine (99) university-level athletes, including 33 with sport-related concussion and 66 without recent injury, using multi-parameter magnetic resonance imaging (MRI), which included single-voxel spectroscopy (SVS), diffusion tensor imaging (DTI) and resting-state functional MRI (fMRI). The concussed athletes were scanned at the acute phase of injury (27/33 imaged), medical clearance to RTP (25/33 imaged), one month post-RTP (25/33 imaged) and one year post-RTP (13/33 imaged). We measured longitudinal changes in N-acetyl aspartate (NAA) and myo-inositol (Ins), over the course of concussion recovery. Concussed athletes showed no significant abnormalities or longitudinal change in NAA values, whereas Ins was significantly elevated at RTP and one month later. Interestingly, Ins response was attenuated by a prior history of concussion. Subsequent analyses identified significant associations between Ins values, DTI measures of white matter microstructure and fMRI measures of functional connectivity. These associations varied over the course of concussion recovery, suggesting that elevated Ins values at RTP and beyond reflect distinct changes in brain physiology, compared to acute injury. These findings provide novel information about neurometabolic recovery after a sport-related concussion, with evidence of disturbances that persist beyond medical clearance to RTP.

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YNICL Journal 2018 Journal Article

Connectomic markers of symptom severity in sport-related concussion: Whole-brain analysis of resting-state fMRI

Nathan W. Churchill
Michael G. Hutchison
Simon J. Graham
Tom A. Schweizer

Concussion is associated with significant adverse effects within the first week post-injury, including physical complaints and altered cognition, sleep and mood. It is currently unknown whether these subjective disturbances have reliable functional brain correlates. Resting-state functional magnetic resonance imaging (rs-fMRI) has been used to measure functional connectivity of individuals after traumatic brain injury, but less is known about the relationship between functional connectivity and symptom assessments after a sport concussion. In this study, rs-fMRI was used to evaluate whole-brain functional connectivity for seventy (70) university-level athletes, including 35 with acute concussion and 35 healthy matched controls. Univariate analyses showed that greater symptom severity was mainly associated with lower pairwise connectivity in frontal, temporal and insular regions, along with higher connectivity in a sparser set of cerebellar regions. A novel multivariate approach also extracted two components that showed reliable covariation with symptom severity: (1) a network of frontal, temporal and insular regions where connectivity was negatively correlated with symptom severity (replicating the univariate findings); and (2) a network with anti-correlated elements of the default-mode network and sensorimotor system, where connectivity was positively correlated with symptom severity. These findings support the presence of connectomic signatures of symptom complaints following a sport-related concussion, including both increased and decreased functional connectivity within distinct functional brain networks.

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YNICL Journal 2017 Journal Article

Symptom correlates of cerebral blood flow following acute concussion

Nathan W. Churchill
Michael G. Hutchison
Simon J. Graham
Tom A. Schweizer

Concussion is associated with significant symptoms within hours to days post-injury, including disturbances in physical function, cognition, sleep and emotion. However, little is known about how subjective impairments correlate with objective measures of cerebrovascular function following brain injury. This study examined the relationship between symptoms and cerebral blood flow (CBF) in individuals following sport-related concussion. Seventy university level athletes had CBF measured using Arterial Spin Labelling (ASL), including 35 with acute concussion and 35 matched controls and their symptoms were assessed using the Sport Concussion Assessment Tool 3 (SCAT3). For concussed athletes, greater total symptom severity was associated with elevated posterior cortical CBF, although mean CBF was not significantly different from matched controls (p =0. 46). Examining symptom clusters, athletes reporting greater cognitive symptoms also had lower frontal and subcortical CBF, relative to athletes with greater somatic symptoms. The “cognitive” and “somatic” subgroups also exhibited significant differences in CBF relative to controls (p ≤0. 026). This study demonstrates objective CBF correlates of symptoms in recently concussed athletes and shows that specific symptom clusters may have distinct patterns of altered CBF, significantly extending our understanding of the neurobiology of concussion and traumatic brain injury.

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YNICL Journal 2017 Journal Article

The first week after concussion: Blood flow, brain function and white matter microstructure

Nathan W. Churchill
Michael G. Hutchison
Doug Richards
General Leung
Simon J. Graham
Tom A. Schweizer

Concussion is a major health concern, associated with short-term deficits in physical function, emotion and cognition, along with negative long-term health outcomes. However, we remain in the early stages of characterizing MRI markers of concussion, particularly during the first week post-injury when symptoms are most severe. In this study, 52 varsity athletes were scanned using Magnetic Resonance Imaging (MRI), including 26 athletes with acute concussion (scanned 1-7 days post-injury) and 26 matched control athletes. A comprehensive set of functional and structural MRI measures were analyzed, including cerebral blood flow (CBF) and global functional connectivity (Gconn) of grey matter, along with fractional anisotropy (FA) and mean diffusivity (MD) of white matter. An analysis comparing acutely concussed athletes and controls showed limited evidence for reliable mean effects of acute concussion, with only MD showing spatially extensive differences between groups. We subsequently demonstrated that the number of days post-injury explained a significant proportion of inter-subject variability in MRI markers of acutely concussed athletes. Athletes scanned at early acute injury (1-3 days) had elevated CBF and Gconn and reduced FA, but those scanned at late acute injury (5-7 days) had the opposite response. In contrast, MD showed a more complex, spatially-dependent relationship with days post-injury. These novel findings highlight the variability of MRI markers during the acute phase of concussion and the critical importance of considering the acute injury time interval, which has significant implications for studies relating acute MRI data to concussion outcomes.

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