Artifact Reduction

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Tips to minimize artifact

From the beginning of the assessment let the client  know their head must be facing straight and not tilted to the side or not down with their chin dropped to their chest.  Arms and legs should be uncrossed and shoulders dropped, feet still and on the ground The jaw must be slightly open and forehead relaxed and they must minimize blink as much as possible.

 Have the client watch the activity for a minute so they can see what their movement looks like in the EEG. You can start the recording and ask them to watch the EEG tracing and then blink and show them what blink looks like, then clench their teeth, then wiggle their forehead, wiggle their tongue, swallow etc.  Once you all know what the movement looks like in the EEG you will know how to recognize activity that is not EEG and the client will know how they are expected to sit, as still as possible Ask them to see what they can do to make the activity drop completely down without any spiking.  This can be helpful for you both of you to know  what sitting “very still” looks like

If you see spikes in the EEG graphs (muscle or eye blink) during the recordings stop the recording and coach the client to sit still with jaw slightly open and keeping very still, minimizing movement before you start a new recording again.

To help prevent blink during the eyes open minutes find a pretty or colorful object or picture to place in front of the client for them to focus on. For excessive eye blink you can offer some eye drops before the recordings since dry eyes can cause one to blink more.  Make sure there is no fan or draft blowing on the clients face or body.  Ask them to remove eye contacts if they are wearing them.  

If there is a lot of eye flutter during eyes closed ask the client to place their fingers on top of their eye lids to stop the flutter.  Have them be aware of not creating tension with their arms or shoulders as they place their fingers on their eye lids.

Removing earrings from the lobes minimizes artifact from metals touching each other. 

To minimize 50/60HZ electrical interference: try pushing the clients chair further away from the computer desk, place the Q-wiz on their lap, make sure there are no electrical power strips or electrical outlets near the client, turn off printers or other equipment that might be on near the client.  Try unplugging the computer and running on battery for the assessment. In extreme cases try using Nu-Prep scrubbing gel (tube that came with your electrode kit) to rub on the ear lobes before putting the ear clips back on.