GCHSR 2016 Junior Journal Club May 18, 2016 Erol Ozmeral

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

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

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.

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.

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.”

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.

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

The guts of the system

Electrophys Results

BCI Results

Continued…

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.