Multiple Types of Movement-Related Information Encoded in Hindlimb/Trunk Cortex in Rats and Potentially Available for Brain–Machine Interface Controls

Abstract

Brain machine interface (BMI) systems hold the potential to return lost functions to patients with motor disorders. Currently most efforts in BMI have concentrated on decoding neural activity from forearm areas of cortex to operate a robotic arm or perform other manipulation tasks. Efforts have neglected the locomotion functions of hindlimb / trunk cortex. However, the role of cortex in hindlimb locomotion of intact rats, which are often model systems for BMI testing, is usually considered to be small. Thus, the quality of representations of locomotion available in this area was uncertain. We designed a new rodent BMI system, and tested decoding of the kinematics of trunk and hindlimbs during locomotion using linear regression. Recordings were made from the motor cortex of the hindlimb / trunk area in rats using arrays of 6 tetrodes (24 channels total). We found that multiple movement related variables could be decoded simultaneously during locomotion, ranging from the proximal robot / pelvis attachment point, and the distal toe position, through hindlimb joint angles and limb endpoint in a polar coordinate system. Remarkably, the best reconstructed motion parameters were the more proximal kinematics, which might relate to global task variables. The pelvis motion was significantly better reconstructed than any other motion features.

Combined motor cortex and spinal cord neuromodulation promotes corticospinal system functional and structural plasticity and motor function after injury

“…Local cortical excitability could reduce the threshold for stimulus-produced network activation. In contrast, a highly-regarded standard for functional/motor behavioral assessments is the correlation between neuronal activity and movement/muscle activity; for example, correlated M1 neuron discharge during a particular motor task or in relation to kinematic or temporal features of movement(Ajemian et al, 2008; Georgopoulos et al, 1982; Song et al, 2009). We used LFP rather than single unit recording because it is well suited to chronic recoding.…”

“…A challenge is to promote functional incorporation of these spared connections into circuitry for motor control, not just to strengthen their connections. For M1, we know the importance of large-scale population coding of movement parameters (Georgopoulos et al, 1982; Song et al, 2009). When the connections of such populations are trimmed to a small number after injury, basic functional coding may not work effectively.…”

“…The correlation coefficient between MEPs during rest and the R-squared values during locomotion was assessed both before and after treatment (iTBS alone, iTBS+c-tsDCS, or control) across each session. The R-squared value is commonly used to evaluate encoding/decoding performance in brain machine interface research and to examine the functional relationship between neural activity (single unit activity or LFP) and behavioral measures (EMG, kinematics and intention) (Flint et al, 2013; Hwang and Andersen, 2013; Song et al, 2009). We tested whether the correlations were significantly different using a bootstrap function (bootstrap, MATLAB R2012).…”

A pelvic implant orthosis in rodents, for spinal cord injury rehabilitation, and for brain machine interface research: Construction, surgical implantation and validation

“…Several of these have been used to good effect by our group. We have tested a pelvis-based brain machine interface system and adaptations using this implant (Song and Giszter, 2011; Song et al, 2009). We have tested robot rehabilitation of complete spinal transected rats using the implant (Udoekwere et al, 2006).…”

“…As part of a system to allow novel robotic-rehabilitation in rats(Udoekwere et al, 2006) and Brain Machine Interface experiments ((Song and Giszter, 2011), (Song et al, 2009)) we have developed a pelvic implantation surgical technique and apparatus that allows direct application of robot generated forces and torques in the pelvic bones. This paper describes the techniques of construction, implantation and validation needed to replicate our methods in other laboratories.…”