LFP Power Spectra in Rat Primary Motor Cortex: The Effect of Locomotion Speed

Background and Aim: Restoring the movement ability in people with walking disabilities (due to amputation, spinal cord injury, etc.) is one of the significant concerns that is not yet resolved. One solution to this problem is using the signals of the motor cortex to extract movement-related information for controlling external devices. To this end, we first need to know what types of information (high level/low level) about walking can be decoded from brain signals. The speed of locomotion is a very important high-level information about walking, which has been ignored in previous studies. Here, we investigated the information about the speed of locomotion available via Local Field Potentials (LFPS) recorded from the primary motor cortex of rats. Methods In this study, a low noise rat-treadmill was used to make subjects walk with three desired constant speeds. The subjects (two female hooded rats weighing ۲۵۰-۲۶۰ gr) were trained to walk smoothly on the treadmill. A ۴-channel microwire array was implanted into the hindlimb area of the primary motor cortex of each subject. After the recovery period, subjects walked on the treadmill on the speeds of ۱۲, ۱۵ and ۲۰ m/min, and their brain signals were recorded simultaneously. The power spectral density of the LFP signals in different locomotion speeds was calculated using the Welch method and the band power of ۶ different frequency bands (۰-α(۵-۱۵ Hz), β(۱۵-۳۰ Hz), γ۱ (۳۰-۵۰ Hz), γ۲ (۵۰-۱۰۰ Hz), ɣ۳ (۱۰۰-۲۰۰), broad high frequency band (۲۰۰-۴۰۰ Hz)) was extracted for each speed. Results: The purpose of this study is to investigate the existence of any informative covariate for the locomotion speed in recorded LFP signals from rats' primary motor cortex. Conclusion Our preliminary results show considerable correlations between the power of LFP signals in γ۱ and ɣ۳ bands and the locomotion speed. These preliminary results indicate the presence of locomotion speed covariate in LFP signals recorded from the primary motor cortex.

Keywords:

Walking speed , motor cortex , local field potential , rat , PSD