(1) This thread is information on the Brainwave Analyzer program, not Bioexplorer or neurofeedback.
(2) Many times scalp muscle tension can appear to be 'gamma' frequencies (40 hz and above), when more likely it is sEMG from the muscles. Also the higher the frequencies, the more difficult it is for those to cross the skull. Try asking your client to relax all face and jaw tension. You can also setup a threshold to detect this fast wave activity and either sound an alert, or inhibit other rewards.