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Wireless EEG and
fNIRS recordings
by Gerald Hirsch
email: gh.hirsch@gmail.com
fNIRS
•Functional near-infrared spectroscopy (fNIRS) is a non-
invasive optical imaging technique that indirectly assesses
neuronal activity by measuring changes in oxygenated and
deoxygenated haemoglobin in the brain tissue using light
of two different wavelengths (760 nm and 850 nm).
fNIRS Principal
Continous Wave fNIRS Principal
HBO and HBR
•oxygenated hemoglobine
(HBO)
•deoxygenated hemoglobine
(HBR)
•SNR in general better for
HBO
•clear visible pulsatile
fluctuations (quality
indication)
HBO Response
•averaged HBO respones
from MI experiment:
•dotted line: task onset
•task duration: 10s
•initial dip (~2-3s)
•peak (~8s)
•undershoot
HBR Response
•averaged HBR respones
from MI experiment:
•dotted line: task onset
•task duration: 10s
Filtered EEG Signal
fNIRS and EEG –But why?
•utilizing an additional source of information
•improving solely EEG based BCI
•increase performance
•increasing robustness
•neurovascular coupling
•low- cost complement to an EEG system
g.Nautilus fNIRS: Hard Facts
•EEG: g.Nautilus
•up to 64 channels
•24 bit
•up to 500Hz sampling rate
•fNIRS: Artinis OctaMon
•8 channels
•50Hz sampling rate
•760nm and 850nm
Signal Acquisition
Signal Quality Assesment - EEG
•VIDEO
Signal Quality Assesment - fNIRS
•VIDEO
BCIs with fNIRS + EEG
•Motor Imagery (MI) Experiment
•Stroop Experiment
BCIs with g.Nautilus fNIRS
BCI –Processing Steps
•data acquisition
•quality assesment
•pre-processing
•feature extraction
•classification
•feedback
MI Experiment
MI Experiment
MI Experiment - Paradigm
MI Experiment - Setup
MI Experiment –Simulink Model
MI Experiment
MI Experiment –HBO Response
Left Hand Grasp MI
Right Hand Grasp MI
MI Experiment –HBR Response
Left Hand Grasp MI
Right Hand Grasp MI
MI Experiment - Results
Stroop
Experiment
Stroop Test
STAGE
EXPLENATION
EXAMPLE
TASK
Rest
Nothing
is shown
-
Relax
Control
Not
colored
GREEN
Say
the word
Colour
Correctly coloured
GREEN
Say
the colour (green)
Shuffled
Wrongly
coloured
GREEN
Say
the colour (red)
Stroop - Paradigm
Stroop Experiment - Results
Recap
•g.Nautilus fNIRS:
•up to 64 channel EEG + 8 channel fNIRS (2 wavelenghts)
•HBO + HBR
•Hemodynamic response
•Neurovascular coupling
•robustness + accuracy imrpovement
•multitude of BCI applications
Thank you for your
attention!
Gerald Hirsch
mail: gh.hirsch@gmail.com