The theta paradox-delayed reduction of frontal midline theta following downregulation neurofeedback training

Phasic increase of frontal midline theta (Fm theta) power has been described as a key indicator of cognitive processing, while relatively lower task-related Fm theta power is associated with reduced cognitive strain, reflecting less intensive cognitive processing. In a previous investigation, reduced task-related Fm theta power in relation to higher expertise, as well as higher setting anticipation performance in the domain of volleyball was identified. In the present study a single-session sham-controlled neurofeedback training (NFT) intervention was conducted to investigate the feasibility of Fm theta downregulation for the improvement of volleyball setting anticipation. A total of 24 volleyball novices was allocated to "Real" (n = 12) and "Sham" (n = 12) Fm theta downregulation NFT groups. Event-related de-/synchronization (ERD/S) of Fm theta during the NFT intervention, as well as pre-/post-NFT setting anticipation task performance and corresponding Fm theta ERD/S were analyzed. Additionally, resting EEG power directly before and after the experiment was examined. Incongruous with our expectations, the Real NFT group showed a tendency toward stronger event-related Fm theta synchronization compared with the Sham group during NFT. Anticipation task performance did not change significantly from before to after NFT in both groups, yet a significantly stronger event-related desynchronization of Fm theta was observed in the Real NFT group, during the post-NFT anticipation task measurement. A post-NFT rebound of Fm theta power could be responsible for this result. With our findings we provide further evidence for the existence of an apparent paradox of Fm theta downregulation, in which cognitive control mechanisms, associated with oscillatory Fm theta activity, appear to hinder explicit downregulation of Fm theta power through classical neurofeedback learning mechanisms.