Researchers* report that participants’ sleep and declarative memory improved after they received 10 sessions of human sensorimotor rhythm (SMR) neurofeedback in a randomized parallel group design. SMR is an EEG frequency band from 12-15 Hz that is associated with an alert, attentive state coupled with calm or silent motor activities. The cat who remains completely still, yet focused the moment before he nabs a mouse makes for a good analogy. The researchers created an ingenious study design to overcome a common criticism of neurofeedback research where both groups (experimental and control groups) do not receive exact same conditions (except for the actual treatment). This study design is described in more detail below.
The overall study design is complex. Please review the original article for a complete description. Primary outcome measures included pre/post naps, sleep onset latency times, sleep diaries, mood measures, declarative memory tasks, and polygraphic sleep recordings with sleep spindle analysis. 13 male and 14 female healthy subjects (mean age = 23.63; SD=2.69) were randomly assigned to receive SMR neurofeedback (experimental group) or randomized frequency neurofeedback (control group). The use of the randomized frequency neurofeedback is a brilliant way to ensure equal treatment of groups. Basically, persons in the control group are exposed to the exact same conditions as the experimental group except that the control group are reinforced with a different EEG frequency band (except 12-15 Hz, of course) at each session. I assume that subjects were blinded to condition, and it is unclear whether researchers were blinded to participant condition. Ten neurofeedback sessions were administered over 10 days (1/day) with a total session time of 1 hour. The neurofeedback protocol called for eight 3 minute blocks with each block containing a 3-second baseline (to calculate participant specific SMR amplitudes) followed by audio and visual reinforcement when SMR amplitudes exceeded threshold for 250ms (milliseconds) or longer.
The researchers report that participants benefited from SMR neurofeedback on number of sleep and memory related improvements. Specifically, participants in the experimental group exhibited significantly increased SMR amplitudes (demonstrates that conditioned learning occurred), enhanced sleep spindles, decreased sleep latency onset time, and improved memory after learning exercises at post-assessment. These are very impressive results, especially in light of the fairly low number of neurofeedback sessions (10). I wonder what additional improvements would be realized after 20-30 sessions?
The authors point out that while this experimental paradigm needs be investigated with an insomniac population, their findings combined with previous research strongly suggests that neurofeedback should be considered as a possible alternative treatment for primary insomnia. An additional question raised is whether increased SMR amplitudes per se accounted for the memory improvements or if they were due to heightened attention and/or relaxation. In fact, SMR training is commonly used for the treatment of Attention Deficit/Hyperactivity Disorder (ADHD) so these factors are certainly possible explanations for the improved memory recall.
I personally want to commend Hoedlmoser and colleagues for their notable creativity in this excellent neurofeedback design. Additional quality neurofeedback research is desperately needed that includes larger group sizes and randomized double blinded designs. I hope that the current study serves to inspire other neurofeedback researchers to refuse to accept sub-par study designs and to improve the credibility of their research through clever experimental paradigms.
*Hoedlmoser, K., Pecherstorfer, T., Gruber, G., Anderer, P., Doppelmayr, M., Klimesch, W., & Schabus, M. (2008). Instrumental conditioning of human sensorimotor rhythm (12-15 Hz) and its impact on sleep as well as declarative learning. Sleep, 31(10), 1401-1408.