Oversampling removes only uncorrelated noise. Sampling 200 - 250 times times per second per electrode is enough for basic gamma.
Gamma is problematic to measure because:
* Power of the EEG signal decreases with frequency. Skull and skin muffles gamma frequencies effectively.
* Gamma overlaps perfectly with muscle activity (~20–300 Hz). It's easy to measure muscle artifacts instead of gamma. Meditation relaxes muscles. Unless you are able to recognize and remove these artifacts, you are actually measuring how meditation relaxes muscles.
* Typical research in gamma EEG setting records thousands stimuli-response epochs to find the signal by averaging over these epochs. Biofeedback applications need to get the signal from single epoch. The latter is much harder problem and generally just not done.
If you could drill a hole into the skull and place electrodes inside, things would be much easier.
Gamma is problematic to measure because:
* Power of the EEG signal decreases with frequency. Skull and skin muffles gamma frequencies effectively.
* Gamma overlaps perfectly with muscle activity (~20–300 Hz). It's easy to measure muscle artifacts instead of gamma. Meditation relaxes muscles. Unless you are able to recognize and remove these artifacts, you are actually measuring how meditation relaxes muscles.
* Typical research in gamma EEG setting records thousands stimuli-response epochs to find the signal by averaging over these epochs. Biofeedback applications need to get the signal from single epoch. The latter is much harder problem and generally just not done.
If you could drill a hole into the skull and place electrodes inside, things would be much easier.