SMR neurofeedback training for cognitive enhancement: the mediating effect of SMR baseline levels

In this study, 24 adults without any psychological or neurological disorders participated either in 10 neurofeedback training sessions to increase the amplitude of a frequency band between 12 and 15 Hz (sensorimotor rhythm - SMR) or in ten mock neurofeedback sessions. Pre and post training measures of memory and executive functions were completed, along with quantitative electroencephalography (QEEG) measurements in order to detect changes after the training course. Furthermore, measures of SMR amplitude were taken within and across sessions to determine whether self-regulation of SMR had been achieved. The data analysis performed shows no significant differences in cognitive performance between the group who underwent neurofeedback training and the group who underwent mock neurofeedback training. The groups did not show electrophysiological changes after the training. Additionally, no significant changes in SMR amplitude or percent time above threshold across or within the 10 sessions were found in the experimental group. Moreover, the data showed a tendency, which indicates that the higher the baseline amplitude and absolute power of SMR the less time was spent above threshold during the training and the less increase in SMR amplitude between baseline and training periods. The findings obtained indicate that neurofeedback training did not affect memory, executive functions or the QEEG. The absence of significant changes in SMR amplitude across sessions might reflect failure in learning the neurofeedback task and may account for the lack of cognitive improvement and QEEG changes. The fact that the ability to self-regulate SMR might be dependent on baseline amplitude has important implications in setting thresholds. Setting thresholds according to baseline levels might increase the difficulty in maintaining SMR above threshold when the baseline is higher. Future research should also address whether baseline amplitude has a predictive value in determining successful self-regulation of brain activity.