Brain-Computer Interfaces for Communication in Paralysis: A Clinical Experimental Approach

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Brain-Computer Interfaces for Communication in
Paralysis A Clinical Experimental Approach

• By
• Adil Mehmood Khan

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TTD Feedback and Communication System

• The current version of TTD software is derived
  from BCI2000 standard

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TTD Software
Data acquisition and storage
Online signal processing
Classification
Feedback and application interface
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Spelling by Brain-Computer Communication
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Contents ? Web surfing with BCI ?
Auditory-controlled BCI ? Visual and
auditory feedback comparison ? BCI using
ECoG ? Comparison of non-invasive BCI
approaches
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• Brain Controlled Web Surfing
• ? Allow patients to surf the web by
• concious changes of brain activity
• ? Enables a completely paralyzed patient to
  participate
• in the broad portion of life reflected by
  the WWW.
• ? History of providing WWW access to ALS
  patients dates back to 1999
• TTD was used to operate a standard web browser,
  i.e. Descartes
• ? Descartes was controlled by binary
  decisions
• ? Services provided

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Setup of EEG-controlled web brwoser Descartes
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Web surfing with Descartes - A
? Patient views a list of predefined WebPages. ?
Each webpage is offered successively at the
bottom of the screen for selection. ? Page
selection through positive SCPs whereas page
rejection by negative SCPs.
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Web surfing with Descartes - B
? Page loaded after its selection and shown for a
predefined period of time.
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Web surfing with Descartes - C
? The links on the previous page are offered
alphabetically as a dichotomous tree . ?
Subject will select or reject each item by
regulating SCPs
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Nessi An Improved Graphical
Brain-Controllable Browser
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BCI-software communication with Nessi
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Nessis email interface
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Nessis virtual keyboard
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An AuditoryControlled BCI

• ? Feedback
• Visual
• Auditory
• High pitch tones indicate cortical negativity
• Low pitch tones indicate cortical positivity
• Hybrid (Visual and Auditory)

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AuditoryStimulation in EEG
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AuditoryStimulation in EEG
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AuditoryStimulation in EEG
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AuditoryStimulation in EEG
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An AuditoryControlled BCI Paradigms
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Comparison between Visual and Auditory Feedback
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Functional MRI and BCI
? BCI combined with FMRI to uncover relevant
areas of brain activation during regulation
of SCPs. ? EEG from 12 healthy subjects was
recorded inside an MRI scanner while they
regulate their SCPs. ? Successful positive SCP
shift was related to an increase of blood
oxygen level dependent (BOLD) in the anterior
basal ganglia. ? While negativity was related to
an increased BOLD in the thalamus.
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SVM Classification of Autoregressive Coefficients

• ? In contrast to SCPs
• Frequency range below 1Hz
• Classified according to their time domain
  representation
• ? EEG correlates of an imagined-movement as best
  represented by oscillatory features
• of higher frequencies, i.e. 8-15 and 20-30 Hz
• Desynchronization of µrhythm over motor areas.
• ? Coefficients of a fitted autoregressive (AR)
  model were used to realize this
• phenomena.
• ? SVM was them employed for the classification
  of these AR coefficients.

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SVM Classification of Autoregressive Coefficients
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BCI using ECoG signals

• ? EEG
• Limited signal-to-noise ratio
• Low frequency range
• ? Invasive ECoG signals
• Broader frequency range (0.016 to 300 Hz)
• Increased signal-to-noise ratio
• 3 out of 5 epilepsy patients were able to spell
  their names within only one or two training
  sessions.
• ? ECoG signals were derived from a 64-electrode
  grid placed over motor-related areas.
• ? Imagery of finger or tongue movements was
  classified with SVM classification of
• AR coefficients.

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BCI using ECoG signals
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Comparison of Noninvasive Input Signals for BCI

• ? Noninvasive BCI
• Sensorimotor rhythms (SMR)
• Slow cortical potentials (SCPs)
• P300
• ? Extensively studied in healthy participants and
  to a lesser extent in patients.
• ? For this reason SCP-, SMR-, and P300-based BCIs
  were compared for free spelling.

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Background Information for All Patients
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Comparison Study

• ? SCPs
• None of the seven patients showed sufficient
  performance after 20 sessions.
• ? SMR
• Half the patients showed an accuracy ranging from
  71 to 81 .
• ? P300
• Performance ranged from 31.7 to 86.3

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Thanks