Audio Evoked Potentials - AEP

BBCI / Machine Learning / Intelligent Data Analysis Group 

Overview

Purpose of this website is to provide, share and collect resources related to auditory experimental paradigms for Brain-Computer Interface (BCI) applications, such as for

• auditory evoked potentials (AEP, special case of event related potentials ERP)
• steady state auditory evoked potentials (SSAEP) 

and other related paradigms. By sharing resources, we would like to stimulate the growth of the currently small group of researchers interested in these paradigms.

We would appreciate if you also want to contribute by sharing your fancy stimuli and other tricks of the trade.
The provided materials are free to use under the condition that you reference the original contributors of the materials you profited from in your own publications.

    Berlin in June 2011,
    Michael Tangermann, Martijn Schreuder and Johannes Höhne

Contact

Dr. Michael Tangermann,
Berlin Institute of Technology
Email: michael.tangermann@tu-berlin.de
Phone: +49(0)30.31478624

Materials

AMUSE paradigm: brisk mono auditory stimuli for circular location encoding

For auditory ERP BCI experiments that make use of the oddball effect, eight [2] or six [3] spatially located mono sound stimuli were presented in rapid sequences via six/eight loudspeakers. Stimulus duration is 40 ms, including 3 ms for onset and offset. Stimuli are combined of high-frequent wide-band noise + low-frequent, fixed-frequeny tone. Frequencies for both, noise and tone vary in the stimuli.

Hardware

For our experiments [2],[3] we used the M-Audio Firewire 410 soundcard. It is ASIO compatible and can operate in low-latency settings such as needed for the auditory P300 paradigm. The Firewire 410 card has 8 analogue outputs that allows for the individual operation of 8 different speakers. We used low-cost, off-the-shelve computer speakers.

Software

The paradigm was implemented in Matlab. The PsychToolbox [1] (which is available online) provides an easy interface for multi-channel soundcards such as the M-Audio Firewire card. When using an ASIO compatible sound card, the latency can be kept relatively low and constant. For this, an additional ASIO driver is needed which is not included in the PsychToolbox for licensing reasons (but can be obtained from Mario Kleiner. Our M-Audio card provides 8 channels which can be individually controlled by sending an 8 x N matrix, where N is the number of sound samples.
For the Matlab commands we refer to the PsychToolbox manual.

Stimuli

For stimulation we found that a combination of bandpass filtered white noise and a tone (with multiple harmonic) was best discriminable in space. The broad frequency content of the noise allows for spatial discrimination based on phase differences at both ears. The tone gives an extra cue for each location. Although the noise alone is enough to reliably discriminate the locations, the tone gives an extra cue to the subject. Using these cues, a stimulation length of 40 ms sufficed for all subjects.

• Download of stimuli (8 speakers) (.zip)
• Download of stimuli (6 speakers) ()

Upon use please reference:

• [1] Brainard, D. H., The Psychophysics Toolbox, Spatial Vision, 10: 433-436. 1997.
• [2] Schreuder M, Tangermann M, Blankertz B, Initial results of a high-speed spatial auditory BCI. Int J Bioelectromagnetism, 11(2):105-109, 2009 [pdf] [url]
• [3] Schreuder M, Blankertz B, Tangermann M, A New Auditory Multi-class Brain-Computer Interface Paradigm: Spatial Hearing as an Informative Cue. PLoS ONE, 5(4):e9813, 2010 [pdf]

PASS2D paradigm: brisk stereo stimuli for 2D encoding

Description

• Download of stimuli (zip)

Upon use please reference:

• Höhne J, Schreuder M, Blankertz B, Tangermann M, Two-dimensional auditory P300 Speller with predictive text system. Conf Proc IEEE Eng Med Biol Soc, 1:4185-4188, 2010 [pdf] [url]