Cortical representation of rhythmic foot movements.
ABSTRACT The cortex is involved in rhythmic hand movements. The cortical contribution to rhythmic motor patterns of the feet, however, has never been evaluated in humans. In this study we investigated EEG activity related to rhythmic stepping and tapping movements in 10 healthy subjects. Subjects performed self-paced fast bilateral anti-phase, in-phase and unilateral rhythmic foot movements as well as an isometric cocontraction of the calf muscles, while being seated as relaxed as possible. Surface EMG from the anterior tibial muscles was recorded in parallel with a 64 channel EEG. Power spectra, corticomuscular coherence and corticomuscular delay were calculated. All subjects showed corticomuscular coherence at the stepping frequencies in the central midline region that extended further to the frontal mesial area. The magnitude and the topography of this coherence were equal for the right and left anterior tibial muscle and all movement conditions. During cocontraction there was coherence in the 15-30 Hz range which was refined to the central midline area. EEG-EMG delays were significant in 9 subjects with values between 14 and 26 ms, EMG-EEG feedback was only found in 6 subjects with delays between 25 and 40 ms. We conclude that rhythmic motor patterns of the feet are represented in the cortex, transmitted to the muscles with delays compatible with fast corticospinal transmission and fed back to the cortex. A similar cortical contribution may be important also for gait control in humans.
Conference Proceeding: An analysis of EEG signals during voluntary rhythmic foot movements[show abstract] [hide abstract]
ABSTRACT: Human locomotion is based on complex interactions of several cortical and subcortical structures. Over the years, the main underlying mechanisms have been partially unveiled thanks to standard functional neuroimaging techniques as well as electroencephalography (EEG). However, a complete picture is still lacking to date, due to particularly challenging experimental difficulties arising on top of the inherent complexity of the involved mechanisms. In this context, the aim of this study was to investigate the EEG dynamics associated to the production of voluntary rhythmic foot movements only. We used an experimental protocol limiting drastically the presence of movement artifacts in the EEG signals compared to real walk on a treadmill. A time-frequency analysis was performed, based on a time-warping method allowing an ensemble averaging of the data of 3 subjects. Characteristic alternation of power increases and decreases in the alpha, beta and gamma bands during the movement cycle is demonstrated as well as the emergence of two different neural coordination schemes related to in-phase and anti-phase foot movements.Neural Engineering (NER), 2011 5th International IEEE/EMBS Conference on; 01/2011