Tese de Mestrado Integrado, Engenharia Biomédica e Biofísica (Sinais e Imagens Médicas), 2022, Universidade de Lisboa, Faculdade de CiênciasNeurofeedback (NF) can be defined as a form of biofeedback that trains subjects to have self-control
over brain their functions, by providing real-time feedback of their own cerebral activity. This activity
can be presented in various forms, with auditory and visual feedback being the most common. Recently, NF has been investigated as a potential treatment for various clinical conditions associated with
abnormal brain activity or cognitive capacities. However, the greater research focus is not discussing
how the feedback should be presented. The chosen modality for any NF training system may strongly
influence the training protocol and consequently the outcome of the experiment.
In this thesis, a systematical comparison between two different type of visual modalities (ScreenBased vs. immersive-virtual reality (VR) ) was performed with the goal to evaluate the effectiveness of
each modality on the NF training results. Data from two previous studies, recorded on healthy participants, in protocols that targeted the increase in the upper alpha (UA) band power measured at the EEG
electrode Cz was used. This was then divided into two modality groups: Screen-Based modality group
(N = 8) and the Immersive-VR group (N = 4). An extensive data processing and cleaning protocol was
applied to both groups and the training effectiveness was measured through band power calculation,
the definition of learning ability indexes and the application of statistical tests. Results showed that,
both groups had a generally positive training effect within sessions, however data regarding different
sessions is inconclusive and does not show clear evidence of up-regulation of the target feature. Additionally, when only considering within-session evolution, only the Immersive-VR modality group was
able to maintain an increasing trend in all sessions.
One of the main limitations of this study was the sample size, which was too small to determine
the precise effect of NF training. Future work requires, not only an increase in sample size but also, the
definition and incorporation of learning predictors that allow the pre-selection of subjects before the
training sessions, in order to prevent high number of non-learners
