Alpha and beta/low-gamma frequency bands may have distinct neural origin and function during post-stroke walking

Area of Science:

• Neuroscience
• Biomechanics
• Rehabilitation Science

Background:

• Plantarflexor muscles are crucial for propulsion during walking.
• Corticospinal and corticoreticulospinal tracts provide descending drive to plantarflexors with potential frequency-specificity.
• Stroke can differentially affect these tracts, impairing post-stroke walking function.

Purpose of the Study:

• To investigate frequency-specificity of descending drives in plantarflexors during post-stroke walking.
• To examine the relationship between intermuscular coherence (IMC) and walking parameters (speed, propulsive impulse).
• To explore potential alterations in corticospinal and corticoreticulospinal tract function after stroke.

Main Methods:

• Surface electromyography (sEMG) of soleus (SOL), lateral gastrocnemius (LG), and medial gastrocnemius (MG) during treadmill walking in 14 chronic stroke individuals.
• Calculation of intermuscular coherences (IMCs) in alpha, beta, and low-gamma bands between plantarflexor muscles.
• Measurement of ground reaction forces (GRF) to determine propulsive impulse at self-selected and fast walking speeds (SSWS and FWS).

Main Results:

• Degraded beta (LG-MG at SSWS) and low-gamma (SOL-LG at FWS) IMCs were observed on the paretic side.
• Only alpha IMCs showed a statistically significant difference from random coherence within the limb.
• Alpha LG-MG IMC positively correlated with propulsive impulse in the paretic limb during SSWS.

Conclusions:

• Alpha and beta/low-gamma frequency bands may reflect distinct functional roles related to descending drive specificity.
• The persistent alpha band coherence and its link to propulsive impulse suggest altered corticoreticulospinal tract function post-stroke.
• Findings indicate the presence of frequency-specific descending drives to plantarflexors in individuals with chronic stroke.