Directed Coherency between Optical Imaging Signals from the Cerebellum and Muscle Activity
Summary: Class research project for directed coherence between nueral signals and muscle Activity.
Abstract
Neurological signal analysis is essential to investigate neurological diseases. For the patients suffer from unknown neurological diseases, a lot of researches are progressed. Some of patients has experienced the dysfunction by the episodic abnormal muscle activity, so called dystonia, which means muscle spasm1,3. A cause of dystonia is still controversy, so a meaningful interpretation between the neurological response and the muscle activity has been needed5. One of the approaches for this analysis can be explaining the relationship between Optical images for brain activity and EMG for the muscle. This project measures directed coherency to analyze the interrelationship between Optical image and EMG. Since directed coherency is able to explain the causation as well as the coherence between two signals2, it is an appropriate way to analyze two signals which have different representations of the feature. Laurentiu S. Popaa has recently investigated coherence between Optical image signals and EMG signal acquired from tg mice suffering from dystonia. As a continuing study, this project focuses on finding the causation of them, especially by partial directed coherence, one of the methods using Granger causality. Granger causality is a commonly used way to determine causal influences between signals2. Directed Coherence Analysis between optical images and EMG signal is programmed and investigated in MATLAB, with statistical analysis. This project will contribute to find a causal interrelationship between optical imaging signals from the Cerebellum and EMG resulted from episodic dystonia.
Introduction
The research that episodic dystonia is related with the oscillation of the cerebellum has been investigated. 1 The dystonia is neurological movement disorder in which sustained muscle contractions cause twisting and repetitive movements or abnormal postures4. Primary research clarifies that CACNA1A gene mutations are associated with Episodic ataxia type 2 and dystonia6. Also, it was experimentally identified that this Episodic ataxia type 2 mutations influence on the attacks of dystonia5. Additionally, in regard of the transmission of the neural signals between the muscle and cerebellum, recent study shows that this episodic motor dysfunction has much more intimate relations with abnormal function between the Parallel fiber and Purkinje cell than any other neural activities31. Cav1.2/1.3(L-type) Ca channel is also major factor to explain their transmission. These knowledge infer oscillation in cerebellum may be related to abnormal motor attacks, dystonia1.
Since the reason that above generic mutation results in dystonia is theoretically investigated already, this project just focuses on the interrelationship between cerebellar cortex response and muscle activity resulted from dystonia; Directed Coherency between Optical Imaging Signals from the Cerebellum and Muscle Activity. Optical Imaging signal associates with cerebellar oscillation and EMG signals are recorded on face and hindlimb1.
Optical Images and EMG signal are achieved from awake and anesthetized tg mice(Cacna1atg) on a C57BL/6J background1. To induce dystonia, caffeine is inserted to tg mouse and its cerebellar cortex experiences the oscillations and the dystonias1. The affection of the low frequency oscillation showing on cerebellar cortex is also observed in EMG signals on hindlimb and face muscles. Optical image acquired from a modified Nikon epifluorescence microscope is a flavoprotein autofluo escene image on cerebellar cortex. EMG is recorded on ipsilateral hamstring and/or peri-oral whisker pad muscles with pairs of insulted fine wires1. Optical imaging signals and EMG signal are achieved simultaneously during dystonia activity. While EMG signal is continuously achieved at 6000samples/sec, Optical imaging has 600 sequential frames over 200 msec for each frame1. To measure the coherence between these two signals, EMG signal is down-sampled from 6250Hz to 5Hz1. The coherence
However, the main question of this project is to find the causality between the optical signal on cerebellum and EMG activity. To figure out the causation of these signals, partial directed coherence, known as one of the method of Granger causality2,3, is used. Partial directed coherence can identify the interrelationship between optical signals from the Cerebellum and Muscle Activity including causal influence2,3. This method analyzes signals in frequency domain. This project is helpful to clarify the causal interrelationship between the oscillation on cerebellar cortex and the dystonia in the muscle.
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This work is licensed by Taeho Kim under a Creative Commons Attribution License (CC-BY 2.0).
Last edited by Taeho Kim on Dec 20, 2007 4:54 pm US/Central.