Effects of circadian rhythm on brain activity during a dynamic balance task

Shirley Bernal, Christina Vega, Kristin Fyfe, Kara Logan, Nicholas Seim, Yaaqov Libovner, Hazel Cruz, Rachel Lin, Paula Ferreira, Mingyoung Lee, Vincent Powers, Austin Gee
Purpose:

The purpose of this study was to analyze the brain wave PSD of a DBT in the morning versus in the evening using electroencephalography (EEG).

Methods:

Twenty-one healthy graduate students (32±7.9 yrs.) were randomly assigned into groups A and B, corresponding to the time of day for the initial SEBT testing session. Both groups completed two testing sessions: one in the morning and one in the evening. These two sessions were one week apart. EEG recordings took place at baseline and during the balance tests.

Results:

Significant differences in morning versus evening PSD were identified in the forward direction of the SEBT for several brain areas and brain waves but not for posterolateral and posteromedial directions. PSD alpha was significantly increased in the evening at occipital-right parietal regions (p0.05). This result could be related to an increase in inhibitory activities within the motor and parietal cortices to produce finely tuned micromovements required to maintain stability on the left leg during a DBT. PSD beta was also found to be increased in the evening in all brain regions (p0.05). This increase is possibly related to increased motor processing demands in the evening. Gamma waves demonstrated increased activity in the evening as well. Areas with higher gamma activity were found in the left frontal-parietal, right central and occipital regions. Gamma waves increases have been related to active cortical processing and increased balance challenging.

Conclusion(s):

The performance of a dynamic balance test requires increased brain activity in the evening compared to in the morning. Specifically, a significant increase in alpha (possibly due to mental fatigue, or Mu wave activity over the sensorimotor cortex, not calculated) and beta wave activity (possibly due to increased concentration) was observed in the evening compared to morning, particularly in regions associated with sensory integration and motor control. These findings highlight the influence of circadian rhythms on brain function during dynamic balance tasks.

Implications:

Applied to the clinic, when testing a patient’s dynamic balance, a balance assessment tool and subsequent follow-up sessions should all be administered around the same time of day. Administering a dynamic balance assessment tool during an evening session for both baseline and follow-up sessions would consistently measure the patient’s balance ability when cortical dynamic control seems more demanding. This timing would possibly enhance the patient’s safety in the home and community.

Funding acknowledgements:
This study was supported by California States University Northridge, Physical Therapy department.
Keywords:
postural control
dynamic balance
EEG
Primary topic:
Neurology
Did this work require ethics approval?:
Yes
Name the institution and ethics committee that approved your work:
This study was approved by the California States University Committee for the Protection of Human Subjects, Northridge.
Provide the ethics approval number:
IRB Number: IRB-FY22-35.
Has any of this material been/due to be published or presented at another national or international conference prior to the World Physiotherapy Congress 2025?:
No

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