What are the causes of the artefact appearing in the second image (attached) before the mep wave?
Before we didn't encounter such artefact (first image).
Some pitfalls which could be related to the condition:
1. We are not grounding our devices (like TMS, 1902 amplifier or 1401 console).
2. Paste used for emg recording appear to break the signal throughout recording procedures or sometimes we are getting flat line when we attach the electrodes to the subject from the beginning. We tried to use more soluble gel like EEG paste, we achieve some recording but the artefacts appear larger and might even hide the mep.
NB. MEP sometimes get distorted by this initial artefacts which is getting bigger and annoying even if we use the original paste. We have changed our location to another building when the problem appeared. The problem of flat line when attaching the electrodes was already there before our location change, and we used to change couples of electrode until we get some reponse which could be unstable during the recording procedure)
Looking forward to hearing some helpful answers!
Dear Bassam
please check the below steps and provide more details
the amplitude of artefact is constant time by time or it changes?
the time lag between the artefact and stimulus signal is fixed and how much is the time lag?
The artefact looks like a transient voltage which may me as a result of loose connection or semi short circuit. Or if you do not ground all devices or the grounds of the devices are different may result in this artefact.
You should ground all devices and also use the same grounds for all devices in the circuit. Also using faraday cage is a must.
and one more question. Do you use the output of a device as triggering signal for mep recirding? If yes this artefact may be due to non grounding tge devices or different grounding for devices.
- Badges
- Science topic