Comparison of auditory and visual modalities for EEG-neurofeedback

Neurofeedback (NF) refers to the real-time self-regulation process, during which, using techniques such as electroencephalography (EEG), an individual is presented with a representation of a feature of interest of their own brain activity, so that they can consciously control it. The impact of the sensory modality used as the reinforcement signal representing the extracted features on training effectiveness is yet to be thoroughly assessed and documented. In this thesis, a NF-training system was developed and implemented and a study was conducted to compare the effectiveness of two sensory modalities, visual and auditory, on an EEG-based NF protocol targeting the individual upper-alpha (UA) band and working memory enhancement. Sixteen healthy volunteers were randomly assigned to the Visual or Auditory group, where a radius-varying sphere or a volume-varying sound, respectively, reflected the relative amplitude of UA measured at Cz EEG electrode. Both groups showed significant improvements within training sessions, but no significant improvements regarding working memory. Effects subsequent to NF training were also found beyond the target frequency and scalp location Cz, namely in the lower-alpha and theta bands and in posterior brain regions, respectively. Sample size was small and, thus, further investigation is required to determine if one of the modalities is effectively better. In this work, auditory sensory feedback proved to be as effective as visual, potentiating NF training protocols conducted under mobile conditions, which are possible due to the increasing availability of wireless EEG systems.