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McLeod, Julianne

University of British Columbia

Background: The human brain functions as a complex network, with dynamic signaling between spatially distinct regions. Even at rest, information is continuously transferred between structurally and functionally linked brain regions. This signaling can be examined through causal connectivity analyses of EEG data, providing valuable insights into the direction of information flow within the brain. Findings of concussion disrupting causal connectivity have been reported, however, existing literature primarily focuses on males and has not been comprehensively examined in females. Additionally, the influence of menstrual cycle hormone fluctuations on female-specific brain connectivity remains largely unexplored. Understanding these hormonal influences is crucial when evaluating causal connectivity changes in females. Objectives: This thesis evaluated whether the strength, pattern, and assortativity of resting-state causal connectivity differed between: (A) female youth athletes with a concussion and those with no reported history of concussion, and (B) females during the early follicular and mid-luteal menstrual cycle phases. Methods: Two independent investigations each involving five minutes of resting-state, eyesclosed EEG data were collected from all participants in each study. Study A included twenty-six female youth with subacute concussion and no reported history of concussion. SCAT5 data were collected from all concussed participants. Study B included fourteen healthy controls during their early follicular and mid-luteal menstrual phase. Saliva samples were collected for hormone analyses. In each study, causal connectivity was calculated from EEG source data. Network topology was evaluated using the degree assortativity coefficient. Results: Study A: Female youth athletes with subacute concussion had a significant increase in connectivity magnitude, posterior-localized strongest connections, and no significant difference in assortativity compared to the control group. Study B: There was no significant difference in connectivity magnitude between early follicular and mid-luteal phases. Females in their midluteal phase (with higher progesterone) had more posterior active connections and significantly higher assortativity. Conclusion: Together, these results offer novel insights into brain plasticity under distinct conditions in females: brain injury and natural hormone fluctuations. Findings emphasize the importance of sex-specific analyses in concussion causal connectivity research and demonstrate that menstrual cycle phase influences information flow within the brain.

Text

2024-08-22

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/89006

Rehabilitation Sciences

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/