Effect of Neurofeedback on Brain Activation: Inhibitory Control
While neurofeedback has been consistently found to be an effective treatment for ADHD, most studies have measured this solely through behavioural outcomes, and thus the mechanisms driving this effect are not well-understood. In 2018, Baumeister and colleagues aimed to identify the impact of neurofeedback on the brain, especially in regions known to have specific functions related to cognition. Of primary interest were regions within the fronto-striatal dopaminergic network which regulate inhibitory control. This refers to the ability to ignore stimuli that are irrelevant to completing current tasks, and is often impaired among individuals with ADHD. Previous neuroimaging studies have shown that activation in these regions is correlated with successful inhibition, and that these regions are hypoactive in ADHD populations.
To test the effects of neurofeedback on this network, Baumeister and colleagues recruited children with ADHD and randomly assigned them to receive either 20 sessions of neurofeedback, or 20 sessions of another form of biofeedback (EMG rather than EEG, to record muscular rather than neural activity) as the control group. Importantly, neither children nor their parents were informed about the type of training they were receiving, so that expectations of the efficacy of their treatments would not substantially influence their results. All children also performed a classic inhibitory control task before and after their treatment block, while undergoing fMRI to monitor changes in activity across the brain during the task.
Corroborating previous data, children who received neurofeedback were rated as having fewer or less severe ADHD symptoms afterwards by their parents, while this benefit was not achieved among the children receiving biofeedback. More notably, only the children who received neurofeedback exhibited increased activation of the brain regions associated with inhibitory control* when successfully performing the inhibitory control task after their treatment block compared to before. Hence, neurofeedback was able to encourage the firing of neurons in relevant brain regions that were previously hypoactive. By relating the effect of neurofeedback on the frontal-striatal network to its function of inhibitory control, Baumeister and colleagues not only demonstrated that neurofeedback creates observable changes in brain functioning, but also provided an explanation for how neurofeedback mitigates ADHD symptoms.
*dorsolateral prefrontal cortex, caudate nucleus, middle cingulate cortex
Baumeister, S., Wolf, I., Holz, N., Boecker-Schlier, R., Adamo, N., Holtmann, M., Ruf, M., Banaschewski, T., Hohmann, S., & Brandeis, D. (2018). Brain Activation in ADHD: A Matter of Learning? Neuroscience. 378, 89-99. doi: 10.1016/j.neuroscience.2016.09.025