Report On Brain Computer Interface: Checkerboard Paradigm

The purpose of electroencephalographic brain-computer interface or BCI is to provide a non-muscular means of communication to the people suffering from amyotrophic lateral sclerosis (ALS) or other neuromuscular disorders. The paper will focus on the performance of the checkerboard paradigm or CBP over the row/column paradigm or RCP. The tests regarding RCP have been done in order to achieve effective communication that is ideal for in-home use. There are many electrode montages, matrix size and stimulus properties in the RCP that helps to achieve the desired outcomes. Researchers have tried to introduce different modification in RCP such as different luminance and chromatic phase patterns, but none of such modifications improves the performance of P300-based BSI. In addition there are some errors in the RCB process that causes slow communication, frustration and reduces the resource of attention. Such errors mainly occur due to the greatest frequency at the same row or column of the adjacent to the attended item. Due to such incident the flashes of non-target row and columns attracts the attention of the participant and causes error in the response of P300. Another error is related to the double flashes caused by the rapid rate of intensification of the target row or column. Despite of such errors the users also want a BCI that is easy to use and has speed and accuracy. In order to achieve the expected outcomes the alternative of RCB has been introduced that is known as checkerboard paradigm or CBP that contains 8 x 9 matrix for 72 items. In the CBP the virtual rows flash first and then the virtual columns flash thus it successfully overcomes the issue of double flash. Another fact is that in the CBP the time between the successive flashes has been increased that has helped to increase the amplitude of P300 response thus increased the accuracy and speed of the BCI. In order to ensure the supreme performance of the CBP, 18 adults that are native to the use of BCI and 3 people with ALS were recruited to the participant pool. All of them have used both the RCP and the CBP alternatively and have provided their consent regarding the performance of the both BCI. The result of the experiment has shown that accuracy regarding the bit rate and time was higher in the CBP as compare to RCP. It was identified that the error in the CBP is less as it reduces the selection of number of items that are adjacent to the target item that indicates the improvement in the performance. The result from the people with ALS has indicated that the accuracy rate in CBP is 89% and it has provided best option for the communication (Townsend et al. 2010).

Fig. 5 of the paper has provided the target response and non-target response at 8-Hz oscillation at a frequency of stimulus presentation for both the CBP and RCP in the four electrode location. The result has shown that the apparent oscillation was less for the RCP as compare to the CBP and amplitude for non-target response has shown that the time difference between the flashes is high in case of CBP. Thus, it can be concluded from the result that, the CBP has reduced the error rate by increasing the time difference and the accuracy is higher in the CBP than RCP (Townsend et al. 2010). The introduction of CBP has achieved the desired outcomes in an effective manner.

Reference:

Townsend, G., LaPallo, B.K., Boulay, C.B., Krusienski, D.J., Frye, G.E., Hauser, C., Schwartz, N.E., Vaughan, T.M., Wolpaw, J.R. and Sellers, E.W., 2010. A novel P300-based brain–computer interface stimulus presentation paradigm: moving beyond rows and columns. Clinical Neurophysiology, 121(7), pp.1109-1120.