The effect of multiple sub-concussive blows on brain structural and functional integrity: combined virtual reality and neuroimaging study

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To determine the differential sensitivity of subjects, with and without prior history of concussion, towards multiple sub-concussive impacts. We hypothesised that previous concussions may increase the athletes' vulnerability to repetitive blows leading to brain metabolic, structural and/or functional compromised integrity.


A set of Virtual Reality (VR) tests and MRI scans (fMRI, DTI, MRS) before and within 3 h after a competition was implemented. The number and type of sub-concussive blows was documented via observational charts incorporated with reconstruction of impacts captured on video.


Subjects were recruited from Penn State collegiate football and rugby teams.


12 football and rugby players (with n=6 and without n=6 history of concussion) often experiencing multiple blows during practices and games were recruited for this study.

Outcome Measures

Spatial working memory, balance, and speed of information processing were assessed by VR testing using Head Mounted Display. Brain metabolic profile (MRS NAA/Cho; NAA/CR of the corpus callosum), functional connectivity (DMN during rs-fMRI) and white matter tracks integrity (DTI, FA) were the primary neuroimaging measures.


We observed decreased interhemispheric functional connectivity (rs-fMRI, left-right hippocampus; r=0.82/0.55), reduced FA (DTI in Genu, 0.7/0.4), and reduced NAA/Cho ratio (MRS measures) at frontal (2.21/1.72) ROI after the competition only in subjects with prior history of concussion. These subjects also experienced deficient balance and spatial memory problems assessed by VR.


This study provides a solid foundation to begin improving the current understanding of the neural substrate(s) differential response(s) to sub-concussive blows occurring in athletics.

Competing interests


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