Abstract:Many different factors can temporarily or permanently impair movement and impairs cortical organization, e.g. hand immobilization. Such changes have been widely studied using electroencephalography. Within this context, we have investigated the immobilization effects through the theta band coherence analysis, in order to find out whether the immobilization period causes any changes in the inter and intra-hemispheric coherence within the cerebral cortex, as well as to observe whether the theta band provides any… Show more
“…However, in this case, the frequency contributing to the PAC signal was in the beta range, whereas in our case, it was in the theta/delta range. Even though the beta band is considered very important for the motor function in PD, connections to the motor function could also be established for the theta/delta band ( Brauns et al, 2014 ; Hamel-Thibault et al, 2018 ; van der Cruijsen et al, 2021 ). Since cortical network formation in PD also occurs in the theta/delta band ( Sharma et al, 2021 ), this work further highlights that when looking at PAC in PD, broadband oscillatory activity, i.e., not only beta, should be considered.…”
IntroductionParkinson’s disease (PD) is a neurodegenerative disorder affecting the whole brain, leading to several motor and non-motor symptoms. In the past, it has been shown that PD alters resting state networks (RSN) in the brain. These networks are usually derived from fMRI BOLD signals. This study investigated RSN changes in PD patients based on maximum phase-amplitude coupling (PAC) throughout the cortex. We also tested the hypothesis that levodopa medication shifts network activity back toward a healthy state.MethodsWe recorded 23 PD patients and 24 healthy age-matched participants for 30 min at rest with magnetoencephalography (MEG). PD patients were measured once in the dopaminergic medication ON and once in the medication OFF state. A T1-MRI brain scan was acquired from each participant for source reconstruction. After correcting the data for artifacts and performing source reconstruction using a linearly constrained minimum variance beamformer, we extracted visual, sensorimotor (SMN), and frontal RSNs based on PAC.ResultsWe found significant changes in all networks between healthy participants and PD patients in the medication OFF state. Levodopa had a significant effect on the SMN but not on the other networks. There was no significant change in the optimal PAC coupling frequencies between healthy participants and PD patients.DiscussionOur results suggest that RSNs, based on PAC in different parts of the cortex, are altered in PD patients. Furthermore, levodopa significantly affects the SMN, reflecting the clinical alleviation of motor symptoms and leading to a network normalization compared to healthy controls.
“…However, in this case, the frequency contributing to the PAC signal was in the beta range, whereas in our case, it was in the theta/delta range. Even though the beta band is considered very important for the motor function in PD, connections to the motor function could also be established for the theta/delta band ( Brauns et al, 2014 ; Hamel-Thibault et al, 2018 ; van der Cruijsen et al, 2021 ). Since cortical network formation in PD also occurs in the theta/delta band ( Sharma et al, 2021 ), this work further highlights that when looking at PAC in PD, broadband oscillatory activity, i.e., not only beta, should be considered.…”
IntroductionParkinson’s disease (PD) is a neurodegenerative disorder affecting the whole brain, leading to several motor and non-motor symptoms. In the past, it has been shown that PD alters resting state networks (RSN) in the brain. These networks are usually derived from fMRI BOLD signals. This study investigated RSN changes in PD patients based on maximum phase-amplitude coupling (PAC) throughout the cortex. We also tested the hypothesis that levodopa medication shifts network activity back toward a healthy state.MethodsWe recorded 23 PD patients and 24 healthy age-matched participants for 30 min at rest with magnetoencephalography (MEG). PD patients were measured once in the dopaminergic medication ON and once in the medication OFF state. A T1-MRI brain scan was acquired from each participant for source reconstruction. After correcting the data for artifacts and performing source reconstruction using a linearly constrained minimum variance beamformer, we extracted visual, sensorimotor (SMN), and frontal RSNs based on PAC.ResultsWe found significant changes in all networks between healthy participants and PD patients in the medication OFF state. Levodopa had a significant effect on the SMN but not on the other networks. There was no significant change in the optimal PAC coupling frequencies between healthy participants and PD patients.DiscussionOur results suggest that RSNs, based on PAC in different parts of the cortex, are altered in PD patients. Furthermore, levodopa significantly affects the SMN, reflecting the clinical alleviation of motor symptoms and leading to a network normalization compared to healthy controls.
“…S4a), which is usually related to sensorimotor integration processes [98,99]. Overall, bilateral cerebellar involvement in fronto-parietal executive function control loops is well established [100] and bilateral cerebello-thalamic projections have been also recently confirmed in humans [101].…”
Section: Contribution Of Interhemispheric Connectivitymentioning
Although cerebellar-cortical interactions have been studied extensively in animal models and humans using modern neuroimaging techniques, the effects of cerebellar stroke and focal lesions on cerebral cortical processing remain unknown. In the present study, we analyzed the large-scale functional connectivity at the cortical level by combining high-density electroencephalography (EEG) and source imaging techniques to evaluate and quantify the compensatory reorganization of brain networks after cerebellar damage. The experimental protocol comprised a repetitive finger extension task by 10 patients with unilateral focal cerebellar lesions and 10 matched healthy controls. A graph theoretical approach was used to investigate the functional reorganization of cortical networks. Our patients, compared with controls, exhibited significant differences at global and local topological level of their brain networks. An abnormal rise in small-world network efficiency was observed in the gamma band (30-40 Hz) during execution of the task, paralleled by increased long-range connectivity between cortical hemispheres. Our findings show that a pervasive reorganization of the brain network is associated with cerebellar focal damage and support the idea that the cerebellum boosts or refines cortical functions. Clinically, these results suggest that cortical changes after cerebellar damage are achieved through an increase in the interactions between remote cortical areas and that rehabilitation should aim to reshape functional activation patterns. Future studies should determine whether these hypotheses are limited to motor tasks or if they also apply to cerebro-cerebellar dysfunction in general.
“…Increase in theta power is mainly linked to memory functions and hippocampal activity [26,27]. However, theta oscillations have also been associated with sensorimotor integration arising from the hippocampal formation [28] and can be modulated after a motor task [29]. In this context, the reduced muscle hypertonia observed in responders together with increased theta activity in the frontocentral regions could result from a normalization of brain activity or reduced cortical maladaptive plasticity, leading to spasticity.…”
Background: Spasticity management in severely brain-injured patients with disorders of consciousness (DOC) is a major challenge because it leads to complications and severe pain that can seriously affect quality of life. Objectives: We aimed to determine the feasibility of using transcranial direct current stimulations (tDCS) to reduce spasticity in chronic patients with DOC. Methods: We enrolled 14 patients in this double-blind, sham-controlled randomized crossover pilot study. Two cathodes were placed over the left and right primary motor cortex and 2 anodes over the left and right prefrontal cortex. Hypertonia of the upper limbs and level of consciousness were assessed by the Modified Ashworth Scale (MAS) and the Coma Recovery Scale-Revised (CRS-R). Resting state electroencephalography was also performed. Results: At the group level, spasticity was reduced in only finger flexors. Four responders (29%) showed reduced hypertonicity in at least 2 joints after active but not sham stimulation. We found no behavioural changes by the CRS-R total score. At the group level, connectivity values in beta2 were higher with active versus sham stimulation. Relative power in the theta band and connectivity in the beta band were higher for responders than non-responders after the active stimulation. Conclusion: This pilot study highlights the potential benefit of using tDCS for reducing upper-limb hypertonia in patients with chronic DOC. Large-sample clinical trials are need to optimize and validate the technique.
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