Alec Titan
Muscle artifacts, or myogenic potentials, are signals detected by EEGs that arise from muscle activity rather than cerebral activity. They are characterised by surges in high-frequency activity and are commonly caused by the frontalis and temporalis muscles, such as when a patient clenches their jaw. They can also be caused by the orbicularis muscles, as well as chewing and tongue movements. The amplitude of the noise caused by muscle artifacts depends on the force of contraction and the type of muscle.
| Characteristics | Values |
|---|---|
| Definition | Muscle artifacts are undesired signals that can introduce changes in the measurements and affect the signal of interest. |
| Cause | Myogenic potentials are the most common artifacts. Frontalis and temporalis muscles (e.g. clenching of jaw muscles) are common causes. |
| Identification | Muscle artifacts are characterised by surges in high-frequency activity and are easily identified due to their outlying high values relative to the local background activity. |
| Detection | A simple algorithm compares high-frequency activity in each 4-second epoch with the activity level in a local 3-minute window. |
| Detection Range | Between 15 and 32 Hz, muscle artifacts made up a substantial part (20-70%) of all-night EEG power density. |
| Removal | Numerous techniques have been proposed to remove EMG artifacts, including filtering, linear regression, blind source separation, source decomposition, neural networks, and wavelet-based techniques. |
Explore related products
What You'll Learn
- Muscle artifacts are characterised by surges in high-frequency activity
- They are caused by muscle movements, especially in the frontal or lateral temporal regions
- They can be caused by chewing, tongue movements, or respiration
- They can be identified by their outlying high values relative to the local background activity
- They can be removed from EEG signals using a multi-stage denoising method
Muscle artifacts are characterised by surges in high-frequency activity
EEG, or electroencephalogram, is a method of recording cerebral activity. However, it can also record electrical activities that arise from sites other than the brain, which are termed "artifacts". Artifacts can be further divided into physiologic and extraphysiologic artifacts. While physiologic artifacts are generated from the patient, they arise from sources other than the brain (i.e. the body). Extraphysiologic artifacts, on the other hand, arise from outside the body, such as from equipment or the environment.
Myogenic potentials are the most common artifacts. Frontalis and temporalis muscles (e.g. clenching of jaw muscles) are common causes. The potentials generated in the muscles are generally of shorter duration than those generated in the brain and can be easily identified based on duration, morphology, and rate of firing (i.e. frequency). Particular patterns of electromyogram (EMG) artifacts can occur in some movement disorders. For example, hemifacial spasm, a disorder that can produce repetitive muscle artifacts.
The amplitude of the noise caused by muscle artifacts depends on the force of contraction and the type of muscle. Examples of movements that can produce artifacts include chewing, tongue movements, or respiration. Removing muscle artifacts from an EEG can be challenging as it is difficult to isolate the muscle activity from a single-channel measurement. However, there are multiple approaches to limit the influence of muscle artifacts on EEG signals, such as filtering, linear regression, blind source separation, source decomposition, and neural networks.
The Cardiac Muscle Mystery: Single or Multi-Nucleated?
You may want to see also
Explore related products
They are caused by muscle movements, especially in the frontal or lateral temporal regions
Muscle artifacts, or myogenic artifacts, are caused by muscle movements, especially in the frontal or lateral temporal regions. They are characterised by surges in high-frequency activity and can be identified by their outlying high values relative to the local background activity. Myogenic potentials are the most common type of artifact. They are generated in the muscles and are typically shorter in duration than those generated in the brain. They are identified by their duration, morphology, and rate of firing (frequency).
The frontalis and temporalis muscles are common sources of myogenic artifacts, which can be caused by movements such as chewing or clenching the jaw. Chewing artifacts, for example, are caused by the temporalis muscle and are marked by sudden, intermittent bursts of fast activity. Similarly, tongue movements, or hypoglossal artifacts, can also cause muscle artifacts. These artifacts are characterised by diffuse slow activity and are often accompanied by chewing artifacts.
Eye movements, such as blinking and lateral eye movements, are another common source of muscle artifacts. Blinking creates a large positive deflection in frontal electrodes due to the upward movement of the eyeballs during a blink, known as Bell's Phenomenon. Lateral eye movements appear as positive and negative frontal deflections on the side to which the patient looks. These eye movements can be mistaken for electrode pops, so it is important to distinguish between the two.
Muscle artifacts can also be caused by disorders such as hemifacial spasm and the photomyoclonic response, which occurs during intermittent photic stimulation. These contractions occur in the frontalis and orbicularis muscles and are typically located frontally.
The detection and removal of muscle artifacts are important to ensure accurate interpretations of EEG data. Various techniques have been proposed to address this issue, including filtering, linear regression, blind source separation, source decomposition, neural networks, and wavelet-based techniques.
Hand Muscles: What Are They and Where?
You may want to see also
Explore related products
They can be caused by chewing, tongue movements, or respiration
Muscle artifacts are undesired signals that can interfere with EEG readings. They are caused by muscle activity, which can contaminate EEG recordings. EEGs are designed to record cerebral activity, but they also pick up electrical activity from sites other than the brain. Physiological artifacts are generated by the patient but arise from sources other than the brain, whereas extra-physiological artifacts arise from outside the body, such as from equipment or the environment.
Muscle artifacts are characterised by surges in high-frequency activity and are easily identified by their outlying high values relative to the local background activity. They are most commonly found in the frontal or lateral temporal regions due to the frontalis and temporalis muscles. The amplitude of the noise is dependent on the force of contraction and the type of muscle.
Chewing, tongue movements, and respiration can all cause muscle artifacts. Chewing artifacts are caused by the temporalis muscle and are marked by sudden onset, intermittent bursts of fast activity. Tongue movements, or hypoglossal artifacts, are seen as diffuse slow, synchronised activity. They arise from the mechanical movement of the tongue itself. Tongue and chewing artifacts often occur together, especially during eating.
There are several methods to limit the influence of muscle artifacts on EEG signals, such as filtering, linear regression, blind source separation, source decomposition, and neural networks.
Massaging Your Plantaris Muscle: Techniques for Relief
You may want to see also
Explore related products
They can be identified by their outlying high values relative to the local background activity
Muscle artifacts, also known as myogenic artifacts, are characterised by surges in high-frequency activity. They can be readily identified by their outlying high values relative to the local background activity.
Muscle artifacts are caused by muscle movements, particularly those of the frontalis and temporalis muscles, such as clenching the jaw or chewing. They are most commonly found in the frontal or lateral temporal regions and are usually most prominent when the patient is awake.
In EEG recordings, muscle artifacts can contaminate the signal and lead to incorrect interpretations. They are identified by their high-frequency activity, often with low amplitude, overlying the normal cerebral rhythms. A simple algorithm can be used to detect muscle artifacts by comparing the high-frequency activity in each 4-second epoch with the activity level in a local 3-minute window.
The elimination of muscle artifacts is important for interpreting quantitative EEG data and distinguishing between cortical and myogenic activity. Various techniques have been proposed to remove these artifacts, including filtering, linear regression, blind source separation, source decomposition, and neural networks, and wavelet-based techniques.
Shin Anatomy: Is It A Muscle Or Not?
You may want to see also
Explore related products
They can be removed from EEG signals using a multi-stage denoising method
Muscle artifacts, or myogenic potentials, are electrical activities recorded by EEG that arise from sites other than the brain, such as the body or muscles. They are characterised by very fast activity that often overlays normal cerebral rhythms and is usually more prominent frontally.
EEG signals may be contaminated by muscle artifacts, which can lead to misinterpretations in medical diagnoses. To address this, a multi-stage denoising method has been proposed, which combines wavelet packet decomposition (WPD) with a modified non-local means (NLM) algorithm. This method is capable of correcting EMG artifacts from multi-channel EEG signals, ensuring that the significant features of the EEG signals are preserved while noises are removed.
Firstly, the artifact EEG signal is identified through a pre-trained classifier. Next, the identified EEG signal is decomposed into wavelet coefficients and corrected through a modified NLM filter. Finally, the artifact-free EEG is reconstructed from the corrected wavelet coefficients through inverse WPD. This method is fully automatic and can be implemented in online applications, making it a valuable tool for removing muscle artifacts from EEG signals.
There are also other methods for removing muscle artifacts from EEG signals, such as the use of hybrid methods like VMD-CCA, EEMD-ICA, and EEMD-CCA, which combine various techniques to improve denoising effects. Additionally, blind source separation (BSS) techniques, such as independent component analysis (ICA) and canonical correlation analysis (CCA), can be used to extract and isolate components from EEG for artifact identification and removal. These techniques offer various advantages, such as shorter computational times and improved performance in muscle artifact suppression.
Understanding Muscle Enzymes: What Do They Mean?
You may want to see also
Frequently asked questions
Muscle artifacts, or myogenic potentials, are signals that are recorded by EEGs that arise from sources other than the brain, such as muscle activity.
Muscle artifacts occur when electrical activity from muscle tissue on the skull intermingles with cortical EEG signals.
Chewing, tongue movements, and respiration can all produce muscle artifacts.
Muscle artifacts can contaminate EEG recordings and lead to a wrong interpretation of the data, which can have implications for medical diagnoses.
There are several techniques to address muscle artifacts, including filtering, linear regression, blind source separation, source decomposition, neural networks, and wavelet-based techniques.
