Brain Computer Interfaces Part 2

(Note this is part 2 of a 2 part series of posts on BCIs)

The alternative method is the non-invasive BCI.  Typically this is a tight fitting cap enhanced with a multitude of sensors. Donning a cap is preferable to surgery in terms of risks and upgradability, however it is also burdened with disadvantages. A non-invasive BCI can only detect neural activity near the surface of the cortex close to the skull. Signals in deeper areas are more difficult to distinguish. This is also a one-way communication. Signals come out of the brain to the computer but the computer is not able to send anything back.

The greater issue with both types of BCI is the narrow bandwidth they provide. Either type of BCI has a maximum bandwidth of less than 0.5 bits per second. Compared other forms of computer input this is relatively slow. For example using a mouse or joystick the rate is around 11 bit/s and auditorily received spoken English is approximately 38 bit/s. Reading is notable in that it has a relatively high maximum rate of around 42 bit/s.[i]

The fact that reading has such a relatively high bit rate should not be surprising considering the human visual processing system has a bandwidth astronomically larger than any of these channels. The retina can process more than 1010 bit/s.[ii] After the initial retinal processing the optic nerve is capable of carrying around 3 x 106 bit/s. Since the visual processing system is able to handle one million times more information than current BCI technology it seems an intriguing potential alternative path into the mind.

[i] Kacprzyk, Janusz, and Witold Pedrycz. Springer Handbook of Computational Intelligence (Dordrecht: Springer, 2015), 760.

[ii] Anderson, Charles H. Van Essen, David C. and Olshausen, Bruno A., “Directed visual attention and the dynamic control of information flow,” Neurobiology of Attention, eds. Laurent Itti, Geraint Rees & John K. Tsotsos (Burlington, MA: Elsevier, 2005) 12.

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