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John P. Phillips

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.

2 papers

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YNICL Journal 2025 Journal Article

A one year longitudinal study of cortical myelination changes following pediatric mild traumatic brain injury

Jessica R. McQuaid
Tracey V. Wick
Josef Ling
Andrew B. Dodd
Divyasree Sasi Kumar
Upasana Nathaniel
Samuel D. Miller
Vadim Zotev

The impact of pediatric mild traumatic brain injury (pmTBI) on cortical (i. e. , grey matter) myelination is not yet understood, especially for interactions with neurodevelopment. The current study examined the impact of pmTBI on cortical myelination relative to healthy controls (HC) by estimating myelin content using the T1w/T2w ratio method. Data were obtained from pmTBI (N = 217) participants at approximately 7 days (Visit 1 [V1]), 4 months (Visit 2 [V2]), and 1 year (Visit 3 [V3]) post-injury, with equivalent sampling points for age and sex-matched HC (N = 180). Clinical results suggested only partial recovery from post-concussive symptoms from V1 to V3, with similar incomplete recovery of sleep, functional outcomes, behavior, and long-term memory. Myelin content increased with chronological age and as a function of individual aging across study visits in a hemisphere specific fashion (left > right), most visibly within the posterior parietal lobe. Myelin content was also greater for females relative to males. There was evidence of both a reduction in myelination within the posterior parietal cortex for the pmTBI group at 4 months post-injury, as well as evidence of increased myelination within the left prefrontal cortex at one-year post-injury. However, neither of these findings survived various sensitivity analyses, suggesting that there were minimal effects of pmTBI on cortical myelin content in general. In summary, although rapid changes in myelin content existed as a function of neurodevelopment, there was little evidence to suggest that pmTBI permanently altered cortical myelin development trajectories.

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YNIMG Journal 2024 Journal Article

Dynamic Functional Connectivity in Pediatric Mild Traumatic Brain Injury

Harm J. van der Horn
Josef M. Ling
Tracey V. Wick
Andrew B. Dodd
Cidney R. Robertson-Benta
Jessica R. McQuaid
Vadim Zotev
Andrei A. Vakhtin

Resting-state fMRI can be used to identify recurrent oscillatory patterns of functional connectivity within the human brain, also known as dynamic brain states. Alterations in dynamic brain states are highly likely to occur following pediatric mild traumatic brain injury (pmTBI) due to the active developmental changes. The current study used resting-state fMRI to investigate dynamic brain states in 200 patients with pmTBI (ages 8-18 years, median = 14 years) at the subacute (∼1-week post-injury) and early chronic (∼ 4 months post-injury) stages, and in 179 age- and sex-matched healthy controls (HC). A k-means clustering analysis was applied to the dominant time-varying phase coherence patterns to obtain dynamic brain states. In addition, correlations between brain signals were computed as measures of static functional connectivity. Dynamic connectivity analyses showed that patients with pmTBI spend less time in a frontotemporal default mode/limbic brain state, with no evidence of change as a function of recovery post-injury. Consistent with models showing traumatic strain convergence in deep grey matter and midline regions, static interhemispheric connectivity was affected between the left and right precuneus and thalamus, and between the right supplementary motor area and contralateral cerebellum. Changes in static or dynamic connectivity were not related to symptom burden or injury severity measures, such as loss of consciousness and post-traumatic amnesia. In aggregate, our study shows that brain dynamics are altered up to 4 months after pmTBI, in brain areas that are known to be vulnerable to TBI. Future longitudinal studies are warranted to examine the significance of our findings in terms of long-term neurodevelopment.

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