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The Effect of Feedback Signal Presentation Latency on the Effectiveness of Training in Neurofeedback Paradigm

Student: Anastasiia Belinskaia

Supervisor: Alexey Ossadtchi

Faculty: Institute for Cognitive Neuroscience

Educational Programme: Cognitive Sciences and Technologies: From Neuron to Cognition (Master)

Year of Graduation: 2019

Neurofeedback (NFB) is a real-time paradigm, where subjects attempt to self-regulate their brain activity. Although the first NFB experiments date back nearly six decades ago, it is still controversial whether NFB is an efficient method for tuning the brain processing in desired ways. Our poor understanding of what would be optimal NFB settings is the major hindrance to the progress of the NFB-based approaches. Among various NFB paradigm characteristics, feedback latency is a key parameter that is thought to have profound effects on training efficiency. To investigate the effect of feedback latency we trained 4 groups of subjects with 3 different artificially imposed feedback signal latency values and mock feedback group to upregulate their occipital alpha-rhythm power. All 3 feedback groups demonstrated a steady and significant growth of P4-alpha band power as compared to the mock group. More detailed analysis of neurofeedback induced changes revealed that in the zero-additional latency group significant differences occurred only in the rate of alpha-spindles occurrence leaving average alpha bursts duration and their amplitude intact. 500 ms of additional latency caused further morphological changes in alpha bursts duration and amplitude of alpha bursts. Moreover, we demonstrated that the ratio of alpha rhythm power observed during the eyes-open resting state block immediately preceding training to that during the first training block serves as a predictor of NFB training efficiency and prediction accuracy is highest in the zero-additional latency group. We conclude that feedback delay even when varied within the range of large values typical to commercial NFB systems causes differential effects on the morphology of occipital alpha rhythm. Therefore, the delay is to be considered as an additional parameter of NFB intervention and NFB equipment manufactures should include the possibility for physicians to adjust feedback latency depending on the particular case.

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