Brainloop

8. Direct Brain–Computer Communication
	8.5. Visual target stimulus modifying the EEG

From experiments with EEG-based cursor movement, we have evidence that already 500 ms after the visual target appearance a target-specific response is found in recordings from electrode positions overlaying the hand area.
It is demonstrated that visual input associated with recognition of objects results in an increased excitability of motor cortex neurons. An example of a spatially filtered time series from one subject is displayed in the picture below.

It can be seen that:

	1) The response is found as early as 250 ms after cue onset.
	2) The responses are different depending on the visual cue.

It is important to note that only observations of a specific visual cue stimulus might selectively activate the right or left primary sensorimotor cortex some 100 ms after stimulus onset.
This finding, that two different visual targets can result in two distinguishable spatiotemporal EEG patterns as early as 250 ms after stimulus-onset, is of special importance in BCI research and opens new ways to install a fast communication channel between brain and computer.

Picture: Examples of spatially filtered time series for one subject from filters calculated for the time window 3.5–4.5 s. From top to bottom: time series from left (upper panels) and right (lower panels) imagination obtained with “left filter” and “right filter.” Y -scale in arbitrary units, X-scale time in seconds. Visual cue presentation is marked by “gray” (modified from).

8. Direct Brain–Computer Communication
	8.1. A short overview of EEG-based BCI systems 8.2. Neurophysiological considerations   8.2.1. Dynamics of Brain Oscillations 8.2.2. Motor Imagery 8.3. Components of graz BCI   8.3.1. Parameter Estimation and Classification   8.3.1.1. Band Power Estimates 8.3.1.2. Adaptive Autoregressive Model 8.3.1.3. Common Spatial Patterns 8.3.1.4. Hidden Markov Model 8.3.2. Hardware–Software Requirements
	8.4. Man–Machine Learning Dilemma (MMLD)
	8.5. Visual target stimulus modifying the EEG

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Source: Motor Imagery and Direct Brain–Computer Communication, Gert Pfurtscheller and Christa Neuper