User:129.174.252.6/I.T. Discussion 5

== Combining the massive steps taken to secure an understanding of the human biological function and the progress made to diagram the brains activity, we reach a pinnacle in human ingenuity. A climax of intuition and hundreds of years of progress has left us able to read the thoughts of the disabled, predict thought patterns, and produce reliable psychological tests. This invention is called the P300 speller. The P300 speller is a type of BCI( Brain Computer Interface). Brain-Computer Interfaces work so well because they can interpret the multitudes of electrical signals our brains give off. Neurons are separate nerve cells that are connected through a network of axons and dendrites. Every thought, every action, every memory requires the neurons to work. That work is sent by small electrical signal from neuron to neuron and these are the signals scientists can detect. The simplest method of interpretation is an electroencephalograph because it is non-intrusive yet it is the easiest to distort due to the skull’s interference. Higher yielding signals come from implanting electrodes into the grey matter, beneath the skull, or on the brains surface. Issues arise in this method as well due to the fact that it requires invasive surgery and the resulting scar-tissue can block signals. “Regardless of the location of the electrodes, the basic mechanism is the same: The electrodes measure minute differences in the voltage between neurons. The signal is then amplified and filtered. In current BCI systems, it is then interpreted by a computer program, although you might be familiar with older analogue encephalographs, which displayed the signals via pens that automatically wrote out the patterns on a continuous sheet of paper.” (Grabianowski, 2007). However, in the case of a sensory BCI, the progress is in reverse order. Converted signals from computers are amplified to trigger neurons. These signals are directed into the designated area of the brain and begin to activate neurons. Once the neurons fire the projected visual image is conversed into the subject’s mind. The P300 Speller is a two part device. The first part being a fitted cap that has electrodes embedded into it. This cap it attached to an amplifier which is then connected to a computer holding the proper software (BCI2000). The second part is the computer system and the paradigm of letters. The letters are arranged in a 6x6 matrix from which the person chooses the letters in proper sequence in order to spell. The rows and columns flash is rapid succession to evoke a response. Each choice comes from a specific P300 ERP which is classified to determine if the signal corresponded to a positive or negative choice. From this, the data is recorded and then displayed to show the patients thoughts. The software used for analysis of the matrices is called MATLAB (Matrix Laboratory). Once originally just for the purpose of numerical computation, it is used in most fields of science for calculation. Different tests are run on separate patients to observe variances in brain-wave activity and stimulus-response times. ==