Fang et al. (2009)

Functional corticomuscular connection during reaching is weakened following stroke.

Yin Fang, Janis J Daly, Jiayang Sun, Ken Hvorat, Eric Fredrickson, Svetlana Pundik, Vinod Sahgal, and Guang H Yue.

OBJECTIVE:To investigate the functional connection between motor cortex and muscles, we measured electroencephalogram-electromyogram (EEG-EMG) coherence of stroke patients and controls.

METHODS:Eight healthy controls and 21 patients with shoulder and elbow coordination deficits were enrolled. All subjects performed a reaching task involving shoulder flexion and elbow extension. EMG of the anterior deltoid (AD) and brachii muscles (BB, TB) and 64-channel scalp EEG were recorded during the task. Time-frequency coherence was calculated using the bivariate autoregressive model.

RESULTS:Stroke patients had significantly lower corticomuscular coherence compared with healthy controls for the AD and BB muscles at both the beta (20-30 Hz) and lower gamma (30-40 Hz) bands during the movement. BH procedure (FDR) identified a reduced corticomuscular coherence for stroke patients in 11 of 15 scalp area-muscle combinations. There was no statistically significant difference between stroke patients and control subjects according to coherence in other frequency bands.

CONCLUSION:Poorly recovered stroke survivors with persistent upper-limb motor deficits exhibited significantly lower gamma-band corticomuscular coherence in performing a reaching task.

SIGNIFICANCE:The study suggests poor brain-muscle communication or poor integration of the EEG and EMG signals in higher frequency band during reaching task may reflect an underlying mechanism producing movement deficits post-stroke.

Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology, 2009 vol. 120 (5) pp. 994-1002

Prasad & Sahin (2006)

Extraction of motor activity from the cervical spinal cord of behaving rats.

Abhishek Prasad and Mesut Sahin.

Injury at the cervical region of the spinal cord results in the loss of the skeletal muscle control from below the shoulders and hence causes quadriplegia. The brain-computer interface technique is one way of generating a substitute for the lost command signals in these severely paralyzed individuals using the neural signals from the brain. In this study, we are investigating the feasibility of an alternative method where the volitional signals are extracted from the cervical spinal cord above the point of injury. A microelectrode array assembly was implanted chronically at the C5-C6 level of the spinal cord in rats. Neural recordings were made during the face cleaning behavior with forelimbs as this task involves cyclic forelimb movements and does not require any training. The correlation between the volitional motor signals and the elbow movements was studied. Linear regression technique was used to reconstruct the arm movement from the rectified-integrated version of the principal neural components. The results of this study demonstrate the feasibility of extracting the motor signals from the cervical spinal cord and using them for reconstruction of the elbow movements.

J Neural Eng, 2006 vol. 3 (4) pp. 287-292