info day 29/9/97 MEL-ARI NANO

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Graz-Brain-Computer Interface State of Research
By Hyun Sang Suh
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Overview BCI systems
The user performs a certain task, which has a
distinct EEG signature
The specific features are extracted from the EEG
A pattern classification system uses these EEG
features to determine which task the user
performed
The BCI presents feedback to the user, and forms
a message or command
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Motor execution vs. Movement imagination
Subject 1, g3
Subject 2, f4
Execution
time
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How can we discriminate four motor imagery tasks?
Tongue
Left Hand
Right hand
Foot
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The mu-wave BCI

• Mu wave activity occurs around roughly 12 Hz.
• Alpha waves are strongest over the visual areas
  in the occipital lobe, But mu waves are strongest
  over the motor areas in the frontal lobe.
• Mu activity changes as people perform or imagine
  movement. You have ERD/ ERS patterns depending on
  the motor imagery tasks

Time
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Subjects and experimental paradigm

• Participants Six female and three male healthy
  right-handed subjects.
• Remain relaxed and avoid any motion during
  experiment.
• Imagine the experience of movement (kinesthetic,
  MIK).
• The arrow pointing represent one of the four
  different tasks (left hand, right hand, both feet
  and tongue).
• EEG signal were recorded from 60 electrodes
  referenced to the left mastoid.

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Quantification of ERD/ ERS

• First, band-pass filtering of each trial.
• Second, squaring of samples (with smoothing)
• Third, averaging of N trials.
• The ERD/ ERS pattern is defined as the percentage
  power decrease (ERD) or power increase (ERS)
  comparison to one-second reference interval
  (0.5-1.5 sec).

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Kappa coefficient and ITV

• Kappa coefficient
• - To measure distinctiveness

Where acc is the accuracy derived by confusion
matrix, n is the number of classes

• Intertask variability (ITV)
• - standard deviation of averaged ERD/ ERS

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Frequencies and band power changes
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Time-frequency maps displaying ERD/ ERS
time
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Maps displaying the topographical distribution of
averaged band power
High ITV
Low ITV
Intertask variability ITV
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Brainloop Interface for Google
R. Scherer, G. Pfurtscheller. The self-paced Graz
brain-computer interface methods and
applications. Computational Intelligence and
Neuroscience 2007, 79825, 2007.
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Mu vs. P300 BCIs
Mu BCI
P300 BCI

• Requiring training
• Work in real-time
• 2D control possible
• Continuous control
• Affected by movement

• Requiring no training
• Require averaging
• 1D control only
• Discrete control
• Affected by distraction

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Phase Synchronization Features

• Currently, BCIs system is not considered the
  relationships between EEG signals measure at
  different electrode recording.
• We can obtain the additional information from
  this relationships.
• Phase Locking value (PLV) is one of the method to
  quantify such relationships.
• The PLV can measure the level of phase
  synchronization between pairs of EEG signals.
• The PLV value of 1 means that the two channels
  are highly synchronized, whereas a value of 0
  means no phase synchronization.

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Phase Synchronization Features
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BCI Applications
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Patient with Spinal Cord Injury

• Spinal Cord Injury (SCI)
• - Damage or trauma to the spinal cord that
  result in a loss or impaired function
• - The effects of SCI depend on type of injury
  (i.e, a car accident, falls, sports injuries, or
  a disease)

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Restoration of hand movement in SCI patient
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Functional Electrical Stimulation
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BCI controlled FES
G. Pfurtscheller, G. R. Müller, J. Pfurtscheller,
H. J. Gerner, Rüdiger Rupp. 'Thought'-control of
functional electrical stimulation to restore hand
grasp in a patient with tetraplegia. Neuroscience
Letters 351, 33-36, 2003. .
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What is the Neuroprosthese?

• It is a device which replaces nerve function lost
  as a result of disease or injury.
• The neuroprosthetics can act as a bridge between
  functioning elements of the nervous system and
  damaged nerves.
• It can be used in the spinal cord to allow
  standing in paraplegics.

Hand prostheses
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AUDITORY PROSTHETICS

• most successful example of sensory prosthetic is
  the cochlear implant.
• lack the cochlear hair cells that transduce sound
  into neural activity.
• Extended to direct stimulation of the brainstem
  for those with dysfunctional cochlear nerves.

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VISUAL PROSTHETICS

• The device uses electrical signals to bypass dead
  photoreceptors and stimulate remaining viable
  cells of the retina.
• Images come from the external video camera worn
  behind the patients glasses.
• The images are transmitted through a computer to
  electrodes attached to the retina
• Reproduce the visual image in the occipital lobe.

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BCI controlled Neuroprosthese

• The BCI system is implanted his right hand and
  arm
• Detect brain pattern (ERD/ ERS) of left hand foot
  imagery movement
• Provide two graps patterns

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BCI controlled Neuroprosthesis
G. R. Müller-Putz, R. Scherer, G. Pfurtscheller,
R. Rupp. EEG-based neuroprosthesis control a
step towards clinical practice. Neuroscience
Letters 382, 169-174, 2005.
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BCI controlled Game
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Thank you for your attention