This document describes a study that used a visual-auditory oddball paradigm to elicit P300 event-related potentials for use in a brain-computer interface. The study presented participants with a matrix of characters that would intensify in groups of four along with an associated sound. P300 signals were recorded from a 40-channel EEG system in response to target versus standard stimuli. Results showed the anticipated P300 component peaking at 350ms for target stimuli and an absence of a distinct peak for standard stimuli. Scalp topographies revealed high voltage activity originating from posterior electrodes 350ms after target onset, consistent with P300 morphology. The study concluded the paradigm successfully elicited P300 signals but did not test real-time capability,

1. Towards an improved visual-auditory oddball paradigm for a P300-
based, non-invasive, Brain-Computer Interface
2. Methods
Visual-Auditory Oddball Paradigm:
Matrix populated with characters that intensify
in random groups of four. One of eight auditory
sound associated with two different groups of
characters, will also play simultaneous to the
character intensification. Participant responded
by attending to the desired character during in-
tensification and auditory playback.
P300 event-related potentials (ERPs)
 Collected on Neuroscan 40-channel EEG
system.
 P300 was averaged over 404 epochs for
offline analysis.
 Sound delivered by Sennheiser HD 380 PRO
headphones
3. Results
3a. Epoch-averaged P300 from both target and standard stimuli
 Anticipated P300 ERP component
pertaining to positive identification
of target stimuli. Observe the apex of
the green line at 350 ms, this is con-
sistent with known latency of the
P300.
 The aqua line is indicative of stand-
ard stimuli flashing. Note the ab-
sence of a distinct signal peak. Thus,
no P300 evoked during standard
stimuli intensification; as expected.
3b. Scalp topography for oddball paradigm
 Here, scalp topographies evince the
distribution of voltage across the
scalp.
 Observe the high voltage activity 350
ms succeeding target stimuli onset.
 Stimuli successfully elicits strong
electrical activity measured from
posterior electrodes.
target standard
4. Conclusions
The oddball paradigm successfully elicited the P300 signal. As per the results, the P300 originates
from the frontal lobes and peaks at the occipital lobes. Latency of P300, otherwise known as the
delay after stimulus onset, is also consistent with expected morphology of the P300. No real-time
capability determined as study performs offline analysis.
1. Introduction
Brain-computer interfaces (BCIs) facilitate a means by which incapacitated and “locked
-in” patients can communicate with others and become self-sufficient *1+. The domi-
nant technology used to achieve this is by electroencephalography (EEG), whereby
neurophysiological signals are recorded by electrodes placed on the scalp’s surface *2+.
The foremost BCI, the P300-Speller, uses flashing characters in a matrix to elicit a tran-
sient electrical signal known as P300 *3+. P300 is elicited when a task-relevant rare
stimulus is mixed with frequently presented stimuli; known as an oddball task. Origi-
nating from the frontal lobe, this signal proceeds to travel to the centro-parietal lobe
where it apexes with a latency of 300ms.
5. References
*1+ G. Townsend, B. K. LaPallo, C. B. Boulay, D. J. Krusienski, G. E. Frye, C. K. Hauser, et al., "A novel P300-based brain–computer interface stimulus presentation
paradigm: Moving beyond rows and columns," Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology, vol. 121,
pp. 1109-1120, 2010.
*2+ S. Ikegami, "Operation of a P300-based brainâ“computer interface by individuals with cervical spinal cord injury," Clinical Neurophysiology, vol. 122, pp. 991-
996, 2011.
*3+ S. Sanei and J. A. Chambers, EEG Signal Processing. England: John Wiley & Sons Ltd., 2007.
BY: CARLOS QUIJANO 13653112