| Human brain cortex can be divided into different regions according to their function. Brain regions with the same duty have close functional relationship, though they separate with each other in structural space. When the brain is in a state without the intervention of the outside world (i.e., resting state), spontaneous activity signals produced by a specific brain region is not in disorder, the low frequency (0.01 Hz-0.08 Hz) fluctuations (LFFs) of blood-oxygenation-level-dependent (BOLD) signals are time coherent. Resting-state functional Connectivity method is to investigate the phase consistency of the LFFs of time series from resting state, which are considered to reflect the spontaneous activities of neuronal. Meanwhile, it is well known that resting-state functional MRI (Rs-fMRI) is more suitable for the brain research of stroke patients with movement disorders, due to its simple and easy data acquisition process.Motor imagery can be defined as an internal psychological simulation process, without motor output. As an important part of motor preparation, it shares similar neurological basis with motor movement. So lesions on execution and preparation path of motor will also lead to damage of motor imagery. The currently available fMRI studies mainly focus on motor execution damage and its relevant brain reorganization after stroke, however, the dysfunction of motor imagery related to stroke has not yet been studied. In this research, a seed-based functional connectivity analysis was used to mainly investigate motor imagery functional connectivity dysfunction induced by stroke, which included two parts:one is to investigate normal motor imagery-related functional connectivity in a group of healthy subjects, and another is to investigate motor imagery-related cortex functional connectivity damage in a subcortical stroke patients.Part I:Resting state functional connectivity analysis on motor imagery network of normal subjects. Objective:To explore the characteristics of motor imagery network connectivity at resting state, and uncover the different responsibility of inferior parietal lobe (IPL) and supplementary motor area (SMA) in the process of motor imagery. Materials and Method:The resting state fMRI data of 20 healthy adults were collected and analyzed the functional connectivity of the left IPL and left SMA in which both were confirmed to be activated during task-designed fMRI of motor imagery. Results:brain areas having remarkable functional connectivity with the left IPL included itself, right IPL, Pre-supplementary motor area, caudal part of cingulate gyrus, pre-motor cortex, inferior frontal lobe, temporal lobe, cerebellum and thalamus, while brain areas having remarkable functional connectivity with the left SMA included itself, right SMA, precentral gyrus and postcentral gyrus, superior and inferior parietal lobe, caudal part of cingulate gyrus, inferior frontal lobe. Conclusion:This shows that brain areas responsible for motor imagery don’t exist independently, but have tight functional connectivity with each other at the resting state of brain. IPL is mainly responsible for motor information coding and motor execution controlling, while SMA is closely related to both motor preparation and execution.Part II:The subcortical stroke:Its effect on motor imagery-related cortex functional connectivity. Background and Objective:It is difficult to investigate motor imagery ability using task-based fMRI due to the concealed nature of motor imagery process. The aim of this study is to do a tentative exploration in the motor imagery disfunction of stroke by using resting-state functional MRI connectivity analysis approach. Materials and Methods:24 patients with subcortical stroke in the left motor pathway and displayed only motor deficits were performed resting-state functional MRI examination. Resting-state functional connectivity of the ipsilesional inferior parietal lobe (IPL) was assessed and compared with that of healthy subjects. Results:Compared with heath controls, stroke patients showed significant reduced connectivity in motor imagery related brain areas. The decreased connectivity with the ipsilesional IPL were mainly located in the contralesional cerebral hemisphere, including inferior parietal lobe, supplementary area, Pre-motor cortex, opercular part of inferior frontal gyrus, and middle occipital gyrus, while in the ipsilesional cerebral hemisphere, only involving supplementary area and Pre-motor cortex. Instead, functional connectivity with the ipsilesional inferior frontal gyrus opercular part and both sides of cerebellum were increased in stroke patients. Conclusions:Motor imagery impairment in stroke was visualized by resting-state fMRI functional connectivity analysis. This research provides a new effective way to investigate motor imagery impairment induced by stroke and the neural mechanism of motor imagery therapy. |
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