Frontal Beta activity and eyesight


#1

Greetings,

I am new to neurofeedback, I hope this is the right forum to ask this question, my apologies if otherwise. I have yet to buy a more professional setup, I currently am running EEG recordings with a Muse headband, seeing the effects of different brainwave entrainment tracks and other experiments on myself. I lately have noticed the following:

When I look at something left of me, the Beta activity on the left Frontal lobe of my brain becomes higher than the right lobe, and the opposite when i look on the right. Is this something that is known in EEG literature? And if yes, what is the explanation?

I am reading Demos’ book and it says that Beta activity on the left side should typically be higher than on the right side, and the opposite signals possible tendency to anxiety. It doesn’t say anything with regard to eyesight direction though.

Thank you,
Nikos

Correction: Actually it was the TP9 and TP10 sensors (near the ears) where this phenomenon was most visible, not the frontal lobes.


#2

Welcome to the forum @NKon.

One possibility is that you’re seeing an artefact from electrical signals generated by your eye muscles. When activated, muscles give off relatively high-frequency EMG signals which, depending on the software, could be affecting the beta power measurement.

Interference from EOG or electrooculogram voltage could be causing anomalies too, although this probably wouldn’t make it into the beta power measurement.

What software are you using?

Adam


#3

Hi AdamM,

Thank you for the reply. This is using the Muse Monitor android app. This occurs when my eyes stay still, looking left or right of course, could one say that that still the flexed muscles cause artifacts? Moreso, i do not see how the eye muscles looking left or right could affect the 2 sides of the brain differently to such degree, but again I am new to this. Maybe someone could try and see what they get?

Could this be that the right field of vision is processed by the left side of the brain and the opposite?

Regards,
Nikos


#4

Hi NKon,

What you are seeing isn’t “beta” cerebral activity but - as AdamM said - an artifact related to the lateral eye movements.

This is exactly the reason why for ERP/EEG studies we filter the noise produced by the eyes (ICA with ad-hoc low-pass filters).

Remember that cornea is positively while retina is negatively charged.
So, the eye acts like a dipole with a positive pole oriented anteriorly (cornea) and a negative one oriented posteriorly (retina). Eyeball rotating about its axis generates a mid amplitude alternate current which is registered by electrodes near the eyes.

To that, you have to add the noise produced by the muscles of eyes.

During a left movement the positive pole generally moves toward F7 (left prefrontal cortex) and away from F8 (right one) .

Et voilà, this is the origin of your “beta” signal.

Take a look here (a quite old but a good starting point):

Cordially,
Giovanni.