Neurofeedback and BCI are two methods that analyze the EEG signal in real-time and use the results of the real-tiem analysis to provide some kind of feedback to the participant. The two methods are closely related in terms of the mechanisms used but can have quite different goals.
Brain-computer interface (BCI) is generally conceived as the use of EEG signals to provide a communication channel between the brain and the computer or some other device. Imagine controlling a computer cursor or turning on and off devices in the home by thinking rather than moving a mouse or pressing a button. These are examples of fast BCI control, in which immediate results are needed. Now, imagine a scenario in which a computer game consol;e automatically selects the type of game or adjusts the level of difficulty based on the player's brain-state, inferred from the EEG signal. This might be thought of as slow BCI control, since the effect of the control is a change that evolves over a longer period of time and it may rely on analysis of a larger sample (longer epoch) of EEG.
Neurofeedback is like BCI in that it involves continuous analysis of EEG signals (and potentially other physiological signals as well) in real-time and continuous feedback to the participant based on the results of the analysis. The main goal of neurofeedback is to help the participant learn to control the generators of the targeted brain signals for therapeutic benefit, to enhance performance on a task or some other related goal. Neurofeedback is often implemented in ways that relate most closely to the slow BCI control above, although a wide variety of methods exist and some may look more like fast BCI control.
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