ABSTRACT
Advanced Parkinson's disease (PD) is characterized by an excessive oscillatory beta band activity in the subthalamic nucleus (STN). Deep brain stimulation (DBS) of STN alleviates motor symptoms in PD and suppresses the STN beta band activity. The effect of DBS on cortical sensorimotor activity is more ambiguous; both increases and decreases of beta band activity have been reported. Non-invasive studies with simultaneous DBS are problematic due to DBS-induced artifacts. We recorded magnetoencephalography (MEG) from 16 advanced PD patients with and without STN DBS during rest and wrist extension. The strong magnetic artifacts related to stimulation were removed by temporal signal space separation. MEG oscillatory activity at 5-25â¯Hz was suppressed during DBS in a widespread frontoparietal region, including the sensorimotor cortex identified by the cortico-muscular coherence. The strength of suppression did not correlate with clinical improvement. Our results indicate that alpha and beta band oscillations are suppressed at the frontoparietal cortex by STN DBS in PD.
Subject(s)
Alpha Rhythm/physiology , Beta Rhythm/physiology , Deep Brain Stimulation/methods , Magnetoencephalography/methods , Parkinson Disease/physiopathology , Sensorimotor Cortex/physiology , Adult , Aged , Female , Humans , Male , Middle Aged , Parkinson Disease/surgery , Subthalamic Nucleus/physiology , Subthalamic Nucleus/surgeryABSTRACT
Corticokinematic coherence (CKC), i.e., coherence calculated between MEG and an accelerometer signal, recording movement kinematics, can be used for functional mapping of the sensorimotor cortex. Cortical sources of CKC, induced by both voluntary and passive movements, localize at the proximity of sensorimotor cortex. We tested the CKC during a static muscle contraction to compare it with simultaneously measured cortico-muscular coherence (CMC) estimated between MEG and surface EMG to study the role of postural tremor in CMC in ten healthy volunteers. CKC was detectable also during this static task. CKC and CMC spectra had similar power distributions, and sources of CMC and CKC colocalized at the cortex in close proximity of the central sulcus. During the static hold task, the accelerometer signal originates from the postural tremor. The similarities between CMC and CKC indicate that postural tremor is related to CMC in healthy subjects.
Subject(s)
Cerebral Cortex/physiopathology , Movement , Muscle Contraction , Muscle, Skeletal/physiopathology , Posture , Tremor/physiopathology , Adult , Brain Mapping , Electromyography , Female , Humans , Magnetoencephalography , Male , Middle Aged , Wrist/physiopathology , Young AdultABSTRACT
OBJECTIVE: Cortico-muscular coherence (CMC) is thought to reflect the interplay between cortex and muscle in motor coordination. In Parkinson's disease (PD) patients, levodopa has been shown to enhance CMC. This study examined whether subthalamic nucleus (STN) deep brain stimulation (DBS) affects the CMC in advanced PD. METHODS: Magnetoencephalography (MEG) and electromyography (EMG) measurements were done simultaneously both with DBS on and off to determine the CMC during wrist extension. The spatiotemporal signal space separation (tSSS) was used for artifact suppression. RESULTS: CMC peaks between 13 and 25 Hz were found in 15 out of 19 patients. The effect of DBS on CMC was variable. Moreover, the correlation between CMC and motor performance was inconsistent; stronger CMC did not necessarily indicate better function albeit tremor and rigidity may diminish the CMC. Patients having CMC between 13 and 25 Hz had the best motor scores at the group level. CONCLUSIONS: DBS modifies the CMC in advanced PD with large interindividual variability. SIGNIFICANCE: DBS does not systematically modify CMC amplitude in advanced PD. The results suggest that some components of the CMC may be related to the therapeutic effects of DBS.
