T M Srihari Mukesh et al 2006 Physiol. Meas. 27 61 doi:10.1088/0967-3334/27/1/006
T M Srihari Mukesh, V Jaganathan and M Ramasubba Reddy
Show affiliationsThe objective is to increase the number of selections in brain computer interfaces (BCI) by recording and analyzing the steady state visual evoked potential response to dual stimulation. A BCI translates the VEP signals into user commands. The frequency band from which stimulation frequency can be selected is limited for SSVEP. This paper discusses a method to increase the number of commands by using a suitable combination of frequencies for stimulation. A biopotential amplifier based on the driven right leg circuit (DRL) is used to record 60 s epochs of the SSVEP (Oz-A1) on 15 subjects using simultaneous overlapped stimulation (6, 7, 12, 13 and 14 Hzs and corresponding half frequencies). The power spectrum of each recording is obtained by frequency domain averaging of 400 ms SSVEPs and the spectral peaks were normalized. The spectral peaks of the combination frequencies of stimulation are predominant compared to individual stimulating frequencies. This method increases the number of selections by using a limited number of stimulating frequencies in BCI. For example, six selections are possible by generating only three frequencies.
42.66.Ew Physiology of eye; optic-nerve structure and function
87.19.R- Mechanical and electrical properties of tissues and organs
Instrumentation and measurement
Issue 1 (January 2006)
Received 12 August 2005, accepted for publication 7 November 2005
Published 1 December 2005
T M Srihari Mukesh et al 2006 Physiol. Meas. 27 61
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