Helen Huang

How does the brain communicate with muscles during unexpected perturbations, and how does this change with age? We investigated corticomuscular connectivity during perturbed recumbent stepping in young and older adults using high-density EEG and EMG. Young adults demonstrated selective connectivity between error-processing brain regions and specific muscles, with strong involvement of the anterior cingulate cortex. In contrast, older adults showed elevated baseline connectivity and relied on diffuse patterns dominated by motor and posterior parietal cortices, connecting to multiple muscles simultaneously regardless of their biomechanical role. This reveals a strategic reorganization: young adults use dynamic, error-driven control, while older adults employ a stability-focused approach that maintains comparable performance through constitutive hyperconnectivity. These distinct connectivity signatures establish perturbed recumbent stepping as a valuable tool for assessing age-related sensorimotor changes and developing targeted rehabilitation interventions.

Older adults often demonstrate greater co-contraction and motor errors than young adults in response to motor perturbations. We demonstrated that older adults reduced their motor errors more than young adults with brief perturbations during recumbent stepping while maintaining greater muscle co-contraction. In doing so, older adults largely used one muscle pair to drive the stepper, tibialis anterior and soleus, while young adults used all muscles. These two muscles are crucial for maintaining upright balance.

We demonstrate that seated locomotor perturbations produce differential theta-band responses in the anterior cingulate and supplementary motor areas, suggesting that tuning perturbation parameters can potentially modify electrocortical responses.

Download Paper Code and data Abstract Electroencephalography (EEG) and source estimation can be used to identify brain areas activated during a task, which could offer greater insight on cortical dynamics. Source estimation requires knowledge of the locations of the EEG electrodes. This could be provided with a template or obtained by digitizing the EEG electrode locations. Operator skill and inherent uncertainties of a digitizing system likely produce a range of digitization reliabilities, which could affect source estimation and the interpretation of the estimated source locations....

Mismarking fiducial locations can systematically change EEG source locations. We inestigated this effect by systematically moving the fiducial locations to simulate such errors.