A Critical View of Neurofeedback Experimental Designs : Sham and Control as Necessary Conditions

C l i n M e d International Library Citation: Aliño M, Gadea M, Espert R (2016) A Critical View of Neurofeedback Experimental Designs: Sham and Control as Necessary Conditions. Int J Neurol Neurother 3:041 Received: January 29, 2016: Accepted: February 25, 2016: Published: February 27, 2016 Copyright: © 2016 Aliño M, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. ISSN: 2378-3001 Volume 3 | Issue 1 Aliño et al. Int J Neurol Neurother 2016, 3:041


Introduction
Neurofeedback (NF) emerged to employ neural feedback via EEG as an evolution of biofeedback in the 1960 [1,2].Specifically, NF entails to learn to self-control the brain activity according to operant principles through a visual, auditory or even tactile representation of participant's brain activity as a feedback [3], with the aim of improving mental states, whether or not in clinical conditions [4].
To this day, specialized clinics and private institutions are offering variations on EEG-NF for the treatment of different disorders.These interventions have been largely dismissed in many studies as being placebo-driven [2], mostly due to a lack of well-controlled experimental designs.Briefly, a veritable feedback (experimental group) implies a feedback from the region or frequency of interest derived directly from the participant's brain activity.Alternatively, a sham feedback (control group) consists of a feedback not derived from the participant's brain activity but obtained from a previous trial with a different participant; another type of sham feedback is that in fact derived from the participant's brain, but not from the region or frequency of interest [2].A critical point here is that most studies do not include a control group not exposed to NF, so the importance of the simple exposure to the technique without receiving real feedback cannot be tested.

Current Practice and Factors Associated with NF Training
Some defenders of NF argue that nonspecific factors alone cannot account for clinical improvement because changes are observable via objective measurements, including EEG [5] and resting state fMRI [6,7].However, how can researchers or clinicians assure that the effect is due to the administration of neurofeedback if a proper experimental design is not available to evidence so?Few, if any, studies rule out the influence of other parameters.These can be intrinsic to feedback training, such as price (it costs money), length (requires many sessions), involves medical-like instrumentation and carries the appeal of brain science [8]; or are associated to individual factors that will be discussed shortly.Given the whole range of parameters and factors that might impact NF results, it is surprising objectives of the study, a control group or a sham group where participants do not receive an intervention could have ethical connotations.Also, researchers sometimes see a saving of time in using only a sham feedback group, especially pertinent when more than one protocol or group is under study [13].However, as we mentioned before, this decision might impact on outcome assessments negatively or not having methodologically enough power to control for practice effects, especially when cognitive testing is used in a pre-post design with NF as an intervention [13].
In summary, our claim is that the experimental designs that lack a no-feedback or sham-feedback controls cannot dissociate whether the change in measures relies on feedback or on factors such as mental strategies and the attention and motivation that comes through participation in NF experiments, or on factors intrinsic to NF itself.Thus, well-controlled designs are desperately needed in this field to tease apart the benefits of NF and its new modalities.determine the result, the rationale to include a sham and a control conditions appears.

Current Practice with Real Feedback and Placebo on a Subject Receiving NF Training
During a session where a real feedback is given (experimental condition), the perception of control is usually experienced as contingent with the feedback received and results should evidence significant outcomes in the appropriate direction of the study.However, the difficulty comes when the feedback received by the participant is not real (sham condition).As far as we know, a realistic but fake feedback has been used in many studies (around 60-70% of the literature) as the standard control group [2].Participants are instructed to try to get control over the feedback on the screen in the same way as in a real training session with NF [3].In this situation, is it the same when the feedback received is your real own brain activity or someone else's?First of all, participants sometimes acknowledge their lack of control over the brain activity and the inexistence of contingency of reward.In these cases, the limitation of a sham condition appears which is risking the motivation of participants.As Gruzelier affirms [13], by using the inactive no-training control, researchers may cause a loss of interest in participants, who would desist in the task at hand (lack of motivation) or even experience feelings of frustration.An alternative has been suggested to avoid this limitation of a simple sham condition.Providing, at least, a second sham control group with feedback from a different area of their brain or different frequency of their brain activity could help equalize the belief that they are receiving veritable feedback from the region of interest [2].However, it is not enough to train a different brain signal to build a control group.This alternative brain signal has to be functionally and neuroanatomically as independent as possible from the signals being assessed in any given study.But, certainly, participants do not always realize what they are experiencing is not a real feedback of their own brain activity and, thus, deep relaxation is inevitable in a majority of participants [13].Indeed, in some studies, participants experienced the same level of relaxation as the experimental group despite non contingency of reward and without the significant enhancement or reduction of specific ratios trained [14].As a result, what researchers might obtain is a placebo phenomenon where even though the participant did not receive a real feedback and, therefore, did not execute real NF training, experiments a fake feeling of control and a certain state of relaxation.

Suggestions for an Optimized Experimental Design
Therefore, an optimization of the designs applied to the modern study of NF is in demand to study and tease apart all factors impacting the results of this technique.We think that this improvement would start with the consideration of three additional groups: two sham groups (one where another area or frequency of the brain activity is trained and another where a fake feedback is administered) and a control group (non intervention).Specifically, a non intervention group with no feedback at all is a necessary condition to determine the importance of the exposure to NF consciously.There are only few studies, around 10% of the literature, where this type of group has been included in the design and it certainly marks a difference [15,16].Also, within the ADHD and NF field, Gonzalez-Castro, Cueli, Rodriguez, Garcia and Alvarez [17] included a control group that was not trained in NF and did not receive pharmacological support either.The working hypothesis in these cases is that, although all treated groups (experimental and sham groups) will improve in the variables assessed, the control group will remain unaffected.Also, we can find in the literature studies where other treatments (mindfulness, relaxation therapy, etc.) are used as control groups, which is another valid experimental design to test the effectiveness of NF although the development of this issue is not the aim of the present short note.
Anyway, no approach is free from some limitation.To a certain degree and depending on the sample, the circumstances or the