RAW TOO HIGH & Artifact Suppression

The RAW TOO HIGH/adjust artifact threshold message can show up when the raw signal is exceeding the thresholds of the raw trace. 'Artifact' is what EEGer uses to describe raw signal from the amplifier which is outside of the signal expected for normal brain waves. Artifact can be thought of as background interference or something 'getting in the way' of the connection. Causes of artifact may be as simple as the client moving around, but it could also indicate a problem with the electrode or connection to the user's scalp.

EEGer has an artifact suppression system to filter out signal which is not EEG data. This is done in an effort to prevent training to signal which is not coming from the client's brain.

Verifying the Connections

The most common cause of RAW TOO HIGH is simply a poor connection to the client's scalp, or an electrode being unsecured from the amplifier.

1. Verify that all electrodes are fully inserted into the amplifier's jacks.
2. Ensure that the electrode sites have been properly cleaned and prepped. Using an appropriate amount of conductive paste is important to ensure the electrodes are well-seated on the head.
3. Make sure your client is relaxed and not moving. Clenching the jaw or facial muscles can cause artifact to be picked up by the electrodes. Make sure the electrode leads are not laying on the client, as they may be bumped and cause artifact issues.
4. If using an amplifier such as the Alpha or J&J Model of amplifiers, you can check impedance by pressing CTRL+F7 on your keyboard. A value under 20 is expected. Higher numbers may indicate improper placement or that the electrode has a bad connection to the client's scalp. If you're noticing values of 50 for all signals/references, that may indicate a problem with the ground electrode.

Bad Ground Electrode

When checking impedance, if all electrodes are reporting impedance of 40-50, it may indicate a bad ground electrode.

1. Squeeze the ground electrode while viewing the impedance screen. If you see all the values drop down considerably, or to normal levels, it may indicate the ground electrode is not sufficiently connected or that it is faulty. Ensure that the ground electrode is properly applied to the client.
2. If this does not resolve the issue, swap the ground electrode for one of the electrodes you are using as a reference electrode. If you are noticing good impedance after doing this, your original ground electrode may be faulty.

Bad Electrode

If you are confident that the placements are alright and that you do not have a bad connection, you may be suffering from a faulty electrode.

1. If you are seeing an impedance of 40-50 with a particular electrode, that may indicate a poor connection or a faulty electrode. Ensure the electrode is properly connected to the client's scalp and check if the impedance readings return to expected values.
2. If you have additional electrodes available, try swapping out the electrode reporting high impedance and see if this resolves the issue.

Electrical & Signal Interference

Mobile devices, such as cell phones, pagers, and smartwatches, can cause interference that is picked up by the amplifier. This can contribute to artifact, as well as nearby electrical devices such as telephones, lighting fixtures, and computers using wi-fi.

1. Eliminate devices from the area you are doing neurofeedback that may be communicating over the internet, bluetooth, or radio. If you are unsure about a device, relocate it while doing neurofeedback and see if this reduces your artifact value.
2. Dim or turn off the lights. Florescent lights can create a significant amount of interference. If you do neurofeedback in the same location and you have not noticed the issue before, it is unlikely to be a fixed item in the room.
3. If you have a desktop telephone, try disconnecting or moving the phone when doing neurofeedback.