1. GCHSR 2016 Junior Journal Club
May 18, 2016
Erol Ozmeral

2. Brain-computer interfaces (BCI)
A BCI is a setup in which a device is directly controlled by neural pathways.
Can be used to communicate, manipulate objects, and steer computational processing.
Typical BCI’s are:
Visual paradigms
Binary classifiers
Aimed to treat ALS and CLIS patients

3. Previous Auditory BCI Hill et al (2005) Kanoh et al (2008)
Measured ERPs
Binary BCI
Two sequences in each ear (different ISIs in each stream)
Kanoh et al (2008)
ERPs to two oddball streams in right ear only
Purported the ability to extend to more than two streams

4. P300
Described as the positive deflection in the EEG signal roughly 300 ms after the onset of an event.
Typically in response to rare events among more common events (i.e., oddball)
P300 has been shown to be stronger for overt fixation both in auditory and visual domain.

5. Spatial Hearing and Attention
Our ability to localize auditory objects in space are subject to selective attention (Mondor and Zatorre 1995; Teder-Salejarvi and Hillyard 1998).
Spatial separation has been shown to be a reliable parameter for differentiating standard (common) and deviant (rare) sounds (Sonnadara et al 2006; Deouell et al 2006).
These studies used the mismatched-negativity measure, not P300.
The present experiment looked at a P300 evoked response to an spatially deviant auditory stimulus.

6. Experimental setup
“A multichannel, low-latency firewire soundcard from M-Audio (M-Audio Firewire 410) was used to individually control the low-budget, offthe-shelf computer speakers.”

7. Electrophysiology (7 subjects)
Presentation level: ~58 dB
Stim: 75 ms BPN (0.15-8kHz)
Conditions
C1000: random presentation from 1 of 8 speakers, 1 s ISI, subjects were asked to focus on a target direction.

8. BCI setup (5 subjects) Only 5 frontal speakers
Stimuli were now discriminated by pitch and spatial location
3 Conditions
C300: ISI = 300 ms
C175: ISI = 175 ms
C300s: Pitch property only

9. The guts of the system

10. Electrophys Results

11. BCI Results

12. Continued…

14. Discussion Current setup was offline, not real-time
Subject were “healthy”, and not many were used
Environment was barely controlled for
Nevertheless, most data was reliably (>70%) used to make target selections after very few iterations.