Spindle-like patterns in EEG under normal conditions

edited March 2017 in Ganglion

Hello, after a long run of the Ganglion, I have a strange repetitive spindle-like pattern
in my EEG (under normal conditions). It is not related to blinks. For instance I tried three below.

image


The pattern that I get
is shown here at channel 3. I tried doing two blinks also:

image


The pattern appeared
in another channel later:



image

And eventually at all
channels:

image


It also coexists with
alpha activity (eyes closed):

image

Could I please ask for
your help?

Thank you

Best wishes

Elisabeth

(PS: I am in Europe and I use the 50Hz notch)

Comments

  • biomurphbiomurph Brooklyn, NY
    It does look like the noise spikes that your seeing are around the 50Hz band. I can see that the filter is trying it's best to attenuate the spike, but it's not able to overcome it.
    I think you might be experiencing some very large environmental noise. What is your environment like where you are using the Ganglion?

    Can you move to a different location where there is very little or no 50Hz sources and try again there?
  • Hello @biomurph,
    Thank you for your response. My environment consisted of the following electric appliances and elements: 10-inch laptop, 3 halogen lamps on the wall, one small refrigerator and a cable TV-WiFi box. (Electrode 3 would be closest to the box). I was surprised that the problem occurred after a long run. For instance, in the first image, the 50 Hz signal is almost fully attenuated. Actually, I had also tested switching off the mains power in the apartment (the light from the laptop screen sufficed) and I had obtained the following result. So theoretically that would be a possibility. (I understand that some people also use Faraday cages.)

    image

    Best wishes

    Elisabeth
  • Elisabeth,

    Is there any chance that you had a cell phone turned on nearby when you were making these recordings? The triplet especially in the top graph looks a bit like the signal that leaks into our student neurophysiology amplifiers when a cell phone communicates with the local tower. If you or someone else does have a cell phone in the vicinity, try putting them in airplane mode and see if that helps at all.
  • Hello @pwilliams,

    Thank you for your comment. My cell phone was at a distance of 1.5m/5ft in my bag and its status was the same during the whole recording - actually I don't know if it did an app update but it did not for instance play a video. I had been to a demonstration of the National Agency of Frequencies (in France) where they showed us with their instruments how the cell phone signal was increasing when a YouTube video was played. They also explained to us that when we are in the countryside the cell phone has to try harder to communicate with the cell tower and this is why the battery is running low more quickly.

    Thank you again for your comment, I take note of your advice.

    Best wishes

    Elisabeth
  • I think that this might be a good guess, then. We see the signals even when the cell phones are not obviously active. The only way to disable this is to either turn the cell phone off or to stop its cellular signal (by, e.g., putting it in "airplane mode"). I think that cell phones periodically send something like a brief "Hi, I'm here!" sort of signal to local cell towers, and that's what we pick up. That could be what you're seeing too.
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