Abstract
Electroencephalography (EEG) is a staple of non-invasive neuroscience research that has been ubiquitously applied to the study of the visual system. Owing to the fact that EEG measures electrical-potential differences between distal locations on the scalp, the EEG signal is highly vulnerable to electrical artifacts. One approach for addressing this has been implemented through the development of tri-polar concentric ring electrodes (tCREs). tCREs measure potential differences across three circular conductive surfaces that together span up to no more that 10mm in diameter. These electrodes provide a neural correlate (tripolar-electroencephalography or tEEG) that is robust to far-field electrical artifacts. Here we assessed the suitability of tCREs and tEEG for the study of the visual evoked potential (VEP). We measured responses to visual stimuli commonly used in clinical and basic EEG settings using tCREs positioned at six posterior scalp locations. The tCREs were also used to simultaneously produce an emulated standard EEG signal (eEEG) allowing for the direct comparison of the tEEG. In 10 subjects, we compared pattern reversal VEPs measured in response to large (1º) and small (0.25º) checkerboards reversing polarity at 2hz, across seven fixation locations including central full-field stimulation. In all cases the tCREs were able to measure a high SNR pattern reversing VEP that showed comparable morphology to the classic pattern reversal VEP (i.e. N70, P100). We note subtle differences between the tEEG and eEEG waveforms including latency shifts in the N70 and P100 suggesting the tCREs measure common, yet not identical neural sources. We also had participants clench their jaws or chew rhythmically to produce large muscle artifacts. The tEEG VEP was much more robust in response to this behavior than the eEEG. Conclusion: tCREs and tEEG is a very promising alternative to classic EEG and is very well suited to the study of the visual system.