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Workshop: "Brain Computer Interfaces & Haptics" …

Workshop: "Brain Computer Interfaces & Haptics"
Haptics Symposium 2014, Houston Texas

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  • 1. Haptics Symposium 2014 Haptics Symposium 2014 Exoskeleton control by Motor Imagery BCI for upper limb neurorehabilitation Michele Barsotti, Antonio Frisoli m.barsotti@sssup.it a.frisoli@sssup.it Brain Computer Interfaces & Haptics February 23-26, 2014, Houston Texas Haptics Symposium 2014
  • 2. Haptics Symposium 2014 Haptics Symposium 2014 • Brain activity acquisition methods • General Brain Computer Interfaces • Brain anatomy • Movements EEG correlates • Decoding movement intention by analyzing EEG • Feedbacks for motor-imagery-BCI • Implementing a MI-BCI paradigm OUTLINE
  • 3. Haptics Symposium 2014 Haptics Symposium 2014 BRAIN ACTIVITY ACQUISITION
  • 4. Haptics Symposium 2014 Haptics Symposium 2014 ACQUIRING BRAIN ACTIVITY Temporal Resolution [s] SpatialResolution[cm] BASED ON THE BLOOD FLOW VARIATION BASED ON THE MAGNETIC- ELECTRICAL ACTIVITY
  • 5. Haptics Symposium 2014 Haptics Symposium 2014 ACQUIRING BRAIN ACTIVITY Temporal Resolution [s] SpatialResolution[cm] ElectroCorticoGraphy (ECoG) Very good spatial and temporal resolution (firing of a single neuron) INVASIVE Surgical intervention
  • 6. Haptics Symposium 2014 Haptics Symposium 2014 ACQUIRING BRAIN ACTIVITY Temporal Resolution [s] SpatialResolution[cm] • Most widely used strategy for BCI applications • Good Temporal Resolution • Several portable, cheap systems exist •Motion artifacts and interferences can be greatly reduced by employing active electrodes EEG is the record of electrical activity of brain by placing the electrodes on the scalp.
  • 7. Haptics Symposium 2014 Haptics Symposium 2014 EEG SIGNALs FEATURES  AMPLITUDE RANGE:  Wake EEG:: Vpp = 100µV  Sleep EEG: Vpp = 300µV  FREQUENCY RANGE:  From 0.01 to 100 Hz  COMMON EEG ARTIFACTs:  Eye blinking (eye movement)  Muscular activity (EMG)  Ambient Noise + (50Hz-60Hz)  Electrodes Movement  Zero Mean
  • 8. Haptics Symposium 2014 Haptics Symposium 2014 NATURAL EEG RHITMIC ACTIVITY Band [Hz] Normaly Location Gamma 32 + Displays during cross-modal sensory processing and short-term memory Somatosensory cortex Beta 16 - 32 active thinking, focus, hi alert, anxious both sides, symmetrical distribution, most evident frontally; low-amplitude waves Alpha 8 - 16 relaxed/reflecting closing the eyes inhibition control posterior regions of head, both sides, higher in amplitude on non-dominant side. Mu 8 - 12 Shows rest-state motor neurons Sensorimotor cortex Theta 4 - 8 higher in young children drowsiness in adults and teens idling Found in locations not related to task at hand Delta up to 4 adult slow-wave sleep Has been found during some continuous-attention tasks frontally in adults, posteriorly in children; high-amplitude waves
  • 9. Haptics Symposium 2014 Haptics Symposium 2014 NATURAL EEG RHITMIC ACTIVITY Band [Hz] Normaly Location Gamma 32 + Displays during cross-modal sensory processing and short-term memory Somatosensory cortex Beta 16 - 32 active thinking, focus, hi alert, anxious both sides, symmetrical distribution, most evident frontally; low-amplitude waves Alpha 8 - 16 relaxed/reflecting closing the eyes inhibition control posterior regions of head, both sides, higher in amplitude on non-dominant side. Mu 8 - 12 Shows rest-state motor neurons Sensorimotor cortex Theta 4 - 8 higher in young children drowsiness in adults and teens idling Found in locations not related to task at hand Delta up to 4 adult slow-wave sleep Has been found during some continuous-attention tasks frontally in adults, posteriorly in children; high-amplitude waves
  • 10. Haptics Symposium 2014 Haptics Symposium 2014 GENERAL BRAIN COMPUTER INTERFACES
  • 11. Haptics Symposium 2014 Haptics Symposium 2014 GENERAL BCI FRAMEWORK SIGNAL PROCESSING FEATURES EXTRACTION 1 CSP FC3 FCZ FC4 C5 C3 C1 CZ C2 C4 C6 CP3 CPZ CP4 -0.2 -0.1 0 -0.2 -0.1 0 CSP 13 CSP FC3 FCZ FC4 C5 C3 C1 CZ C2 C4 C6 CP3 CPZ CP4VAR MAX VAR MIN SIGNAL CLASSIFICATION APPLICATION OUTPUT BIOFEEDBACK USER MENTAL STRATEGY BRAIN SIGNALs ACQUISITION
  • 12. Haptics Symposium 2014 Haptics Symposium 2014 Feedback for subject training Machine learning  BCIs represent a set of techniques to allow direct control of a software or device via brain activity – without the need of a motor output  The most common BCI approach exploits voluntary modulation of EEG activity, although more invasive approaches have been explored  These techniques have successfully been employed to aid disabled patients  Recently BCIs have also been investigated as a rehabilitation tool GENERAL BCI FRAMEWORK
  • 13. Haptics Symposium 2014 Haptics Symposium 2014 BCI CATEGORIES INVASIVE NON-INVASIVE Without penetrating the skalp, mostly EEG, rarely magnetoencephalogram (MEG) or functional magnetic resonance imaging fMRI - Several portable, cheap systems exist - Motion artifacts and interferences can be greatly reduced by employing active electrodes DEPENDING ON THE ACQUISITION SYSTEM Implanted sensors (electrode array, needle electrodes, electrocorticogram ECoG) -Control of 2-3 DoF, with good accuracy. -Implants have only been tested for months after surgery --Highly expensive
  • 14. Haptics Symposium 2014 Haptics Symposium 2014 BCI Invasive Non invasive Single recording site Multiple recording sites ECoG EEG MEG fMRI Classification: signal acquisition
  • 15. Haptics Symposium 2014 Haptics Symposium 2014  Insertion of arrays of microelectrodes in cortical tissue  Control of 2-3 DoF, with good accuracy.  Implants have only been tested for months after surgery  Highly expensive Hochberg et al., Nature, 2006 Invasive vs. non-invasive BCI  Invasive BCI  Non-invasive BCI  EEG systems range from low to high density (2 to 256 eletrodes)  Several portable, cheap systems exist  Motion artifacts and interferences can be greatly reduced by employing active electrodes
  • 16. Haptics Symposium 2014 Haptics Symposium 2014 BCI CATEGORIES INDEPENDENT DEPENDENT A Dependent BCI does not use the brain’s normal output pathways to carry the message, but activity in these pathway is needed to generate the brain activity that does carry it. Independent from peripheral nerves and muscles, using only central nervous system (CNS) activity DEPENDING ON THE MENTAL STRATEGY
  • 17. Haptics Symposium 2014 Haptics Symposium 2014 BCI CATEGORIES ENDOGENOUS EXOGENOUS Evoked Potentials: Users modulate brain responses to external stimuli SSVEP p300 Unstimulated Brain Signals: Users can voluntarily produce the required signals (Motor Imagery, Computational Task) DEPENDING ON THE MENTAL STRATEGY
  • 18. Haptics Symposium 2014 Haptics Symposium 2014 BCI CATEGORIES ASYNCHRONOUS Commands can only be emitted synchronously with external pace. The system detects when the user wants to emit a command DEPENDING ON THE COMMAND-TIMING SYNCHRONOUS The differences in EEG response following different stimuli are used to discriminate what subjects want Subjects are asked to perform visual imagery tasks and the local changes in EEG power spectra are recorded
  • 19. Haptics Symposium 2014 Haptics Symposium 2014  SSVEP  VEP  MOTOR IMAGERY  ERP (i.e.P300) BCI CATEGORIES - SUMMARY EXOGENOUSENDOGENOUSDEPENDENTINDEPENDENT
  • 20. Haptics Symposium 2014 Haptics Symposium 2014 BRAIN ANATOMY & EEG MOVEMENTS CORRELATES
  • 21. Haptics Symposium 2014 Haptics Symposium 2014 BRAIN ANATOMY [Martini, 2006]
  • 22. Haptics Symposium 2014 Haptics Symposium 2014 The Primary Somatic Sensory Cortex (Parietal Lobe) and the Primary Motor Cortex (Temporal Lobe) are the most important regions for BCI research. I III IV V II BRAIN ANATOMY: THE CEREBRAL CORTEX
  • 23. Haptics Symposium 2014 Haptics Symposium 2014 The Primary Somatic Sensory Cortex (Parietal Lobe) and the Primary Motor Cortex (Temporal Lobe) are the most important regions for BCI research. I III IV V II BRAIN ANATOMY: THE CEREBRAL CORTEX M1 S1
  • 24. Haptics Symposium 2014 Haptics Symposium 2014 The Primary Somatic Sensory Cortex (Parietal Lobe) and the Primary Motor Cortex (Temporal Lobe) are the most important regions for BCI research. I III IV V II BRAIN ANATOMY: THE CEREBRAL CORTEX M1 S1
  • 25. Haptics Symposium 2014 Haptics Symposium 2014 TYPES OF MOVEMENT Three types of movements may occur in respect of to ascending and descending signals via different pathways and at different levels: • Reflexes movement : are performed subconsciously and can occur at an exclusively spinal level • Rhythmic movement: stereotyped action involving repetitions of the same movements The control is at the spinal level without involvement of higher cortical control • Voluntary movement: usually goal directed and therefore fully conscious. It arises in the motor cortex and is executed by the spinal cord.
  • 26. Haptics Symposium 2014 Haptics Symposium 2014 TYPES OF MOVEMENT Three types of movements may occur in respect of to ascending and descending signals via different pathways and at different levels: • Reflexes movement : are performed subconsciously and can occur at an exclusively spinal level • Rhythmic movement: stereotyped action involving repetitions of the same movements The control is at the spinal level without involvement of higher cortical control • Voluntary movement: usually goal directed and therefore fully conscious. It arises in the motor cortex and is executed by the spinal cord. When a voluntary movement is started, neurons in the M1 send commands to upper and lower motor neurons. The M1 needs to be stimulated by neurons from the premotor cortex and the supplementary motor area (SMA), which support and coordinate the M1, in order to initiate a voluntary movement
  • 27. Haptics Symposium 2014 Haptics Symposium 2014 Motor imagery is a mental process by which an individual rehearses or simulates a given action. MOTOR IMAGERY Performing motor imagery or attempting a movement (i.e. for patients) influences the brain activity as the voluntary movements do.
  • 28. Haptics Symposium 2014 Haptics Symposium 2014 Why MOTOR IMAGERY is suitable for BCI? • No need of external stimulus (it could be asynchronous) • Not depend in any way on the brain’s normal output/input pathways (independent) • Possibility to provide different commands depending on which body part is evolved in the simulated action • Mental practice of motor actions via BCI training affect neuro- rehabilitation in a positive way. • the power in μ (8-12 Hz) and β (12-24Hz) EEG rhythms are affected by motor imagery: Event Related Spectral Perturbation (ERSP) • Users learn to perform motor imagery tasks • Can be employed event if the motor areas are impaired • Works mostly for digital control, has a fast response
  • 29. Haptics Symposium 2014 Haptics Symposium 2014 DECODING MOVEMENT INTENTIONS BY ANALIZING EEG
  • 30. Haptics Symposium 2014 Haptics Symposium 2014  Event Related Potential (ERP):  - Repeatedly present discrete stimulus, average raw EEG responses across presentations. Characteristic feature (eg. P300)  Event Related Spectral Perturbation (ERSP):  Frequency band changes - Average spectral features across presentation. - Characteristic suppression/increase in power (ERD/ERS: Event Related De-Synchronization). EEG PHENOMENAL USABLE FOR BCI  Event Related Spectral Perturbation (ERSP) and Event Related Potential ERP are the measured brain response that are the direct result of a specific sensory, cognitive, or motor event.
  • 31. Haptics Symposium 2014 Haptics Symposium 2014 time Frequency[Hz] epochtimechannel  X epochfrequencytimechannel  X AVERAGING time Amplitude[µV] ERP ERSP • The ERPs and ERSP should be extracted from the background noise mediating many recordings (Epochs or Trials)
  • 32. Haptics Symposium 2014 Haptics Symposium 2014 Amplitude[µV] EEG background noise ~ 1/sqrt(N) Costant Signal ERP Repetition (N) Post-Stimulus EEG Costant Signal Background Noise average ERP average Signal average Noise AVERAGING THEORY S/N ratio increases as a function of the square root of the number of trials.
  • 33. Haptics Symposium 2014 Haptics Symposium 2014 MOTOR IMAGERY CORRELATES IN EEG Performing (or imagining) a motor action influences the EEG with two main phenomena:
  • 34. Haptics Symposium 2014 Haptics Symposium 2014 SLOW CORTICAL POTENTIALS [Kornhuber and Deecke (1965) ] • Know as BereitschaftPotential (readiness potential) or Movement Related Cortical Potentials (MRCPs). • Slow oscillations preceding the movement • Localized over the supplementary motor area (SMA) • Steps for MRCP detection • Spatial filter, • LP frequency filter • Template extraction from the training data • matching with the ongoing eeg MOTOR IMAGERY CORRELATES IN EEG •Frequency close to the DC -> very challenging to detect in single trial
  • 35. Haptics Symposium 2014 Haptics Symposium 2014 SENSORIMOTOR RHYTHMS [Pfurtscheller and Lopes da Silva, (1999)] • the power in μ (8-12 Hz) and β (12-24 Hz) EEG rhythms are affected by motor imagery. •Know also as Event Related De/Synchronization (ERD,ERS) •Steps for MRCP detection • Spatial filter, • Band Pass frequency filter • Feature extraction • LDA classifier • High average classification accuracy (>80%) MOTOR IMAGERY CORRELATES IN EEG
  • 36. Haptics Symposium 2014 Haptics Symposium 2014 ERD extraction: example with motor imagery Collecting Trials from a specific electrode Bandpass on the specific frequency Squaring Signals Averaging over Trials Smoothing [Pfurtscheller and Lopes da Silva, (1999)]
  • 37. Haptics Symposium 2014 Haptics Symposium 2014 β ERD 13-30 Hz µ ERD 8-12 Hz Event Related DeSynchronization ERD Motor Imagery of right hand movement EVENT RELATED SPECTRAL PERTURBATION SENSORIMOTOR RHYTHMS
  • 38. Haptics Symposium 2014 Haptics Symposium 2014 MOTOR IMAGERY: SIGLE TRIAL DETECTION The important features of the motor imagery are:  The frequency band.  The spatial localization A priori knowledgment:  The frequency band are mu (8 -13Hz) and beta (15-30 Hz).  The spatial localization is over the sensory motor Very high intersubject variability! Need of optimized spatial filters
  • 39. Haptics Symposium 2014 Haptics Symposium 2014 The aim of spatial filtering is to improve the signal-to-noise ratio by creating a virtual channel which is a (linear, in the following cases) combination of the input channels of the filter. A spatial filters can optimize the data extracted from an high number of electrodes reducing the dimension of the features'space to only few significant dimensions. N-channel input (ex. 16 ch) 1-optimized channel output 1 CSP FC3 FCZ FC4 C5 C3 C1 CZ C2 C4 C6 CP3 CPZ CP4 C SPATIAL FILTERING y(t) = a*ch1(t) + b*ch2(t) ....
  • 40. Haptics Symposium 2014 Haptics Symposium 2014 Optimized Spatial filter: Common Spatial Pattern – CSP VAR MAX VAR MIN VAR MIN RAW CHANNELS FIRST AND LAST CSP FILTER PROJECTED DATA REST MOVERESTMOVE Trial i Trial i+1 Trial i Trial i+1 VAR MAX [Pfurtscheller 1999] Common Spatial Pattern (CSP) is a supervised spatial filtering method for two-class discrimination problems, which finds directions that maximize variance for one class and at the same time minimize variance for the other class. 1 CSP FC3 FCZ FC4 C5 C3 C1 CZ C2 C4 C6 CP3 CPZ CP4 -0.2 -0.1 0 -0.2 -0.1 0 CSP 13 CSP FC3 FCZ FC4 C5 C3 C1 CZ C2 C4 C6 CP3 CPZ CP4 1 CSP FC3 FCZ FC4 C5 C3 C1 CZ C2 C4 C6 CP3 CPZ CP4 -0.2 -0.1 0 -0.2 -0.1 0 CSP 13 CSP FC3 FCZ FC4 C5 C3 C1 CZ C2 C4 C6 CP3 CPZ CP4
  • 41. Haptics Symposium 2014 Haptics Symposium 2014 WHITENING MATRIX TRIALS CLASS A TRIALS CLASS B COVARIANCE CLASS A COVARIANCE CLASS B i Ti A i A Ti A i A A XXtrace XX R )(  i Ti B i B Ti B i B B XXtrace XX R )(  BAc RRR  T CCCC UUR  T CC UW 1  T AA WWRS  T BB WWRS  T AA UUS  T BB UUS  IBA  WUP T  PXZ  COMPOSITE COVARIANCE Transformed Covariance A Transformed Covariance B EIGENVECTOR PROJECTION MATRIX EIGENVALUES Common Spatial Pattern – Algorithms
  • 42. Haptics Symposium 2014 Haptics Symposium 2014 • The scalp-plot of the Common Spatial Pattern can be also used to give a physiological interpretation of the data Common Spatial Pattern: advantages • Since variance of band-pass filtered signals is equal to band-power, CSP filters are well suited to discriminate mental states characterized by spectral perturbations (ERD and motor imagery based BCIs).
  • 43. Haptics Symposium 2014 Haptics Symposium 2014 The log-scaled band-power values in the mu and beta band of the resulting two projected channels, can be used as a two- dimensional feature of the brain activity. Classification is performed using a linear discriminant classifier (LDA) or a support vector machine (SVM) CLASSIFICATION
  • 44. Haptics Symposium 2014 Haptics Symposium 2014 CSP VARIANTS  CSP – Pfurtscheller 1998  FWM – Liu 2010  CSSSP – Blankertz 2006  CSSP – Lemm 2005  SPEC-CSP – Tomioka 2006  SB-CSP – Novi 2008  FB-CSP – Ang 2008  dCSP – Wang 2010  SSCSP – Arvaneh 2011  I-CSP – Blankertz 2008 With Frequency Optimization Furhter Spatial Optimization
  • 45. Haptics Symposium 2014 Haptics Symposium 2014 FEEDBACKs for motor imagery - BCI
  • 46. Haptics Symposium 2014 Haptics Symposium 2014 FEEDBACK FOR MOTOR IMAGERY The biofeedback provided as a response to the mental activity can improves the usability of motor imagery BCI. The congruency of the provided feedback with the mental task is expected to ease the performance of motor imagery. Game Illusion Virtual reality Exoskeleton VISUAL PROPRIOCEPTIVE
  • 47. Haptics Symposium 2014 Haptics Symposium 2014 motor imagery – BCI in neurological rehabilitation
  • 48. Haptics Symposium 2014 Haptics Symposium 2014 BCI in neurological rehabilitation Daly & Wolpaw, Lancet, 2008
  • 49. Haptics Symposium 2014 Haptics Symposium 2014 Daly & Wolpaw, Lancet, 2008Goal: The subject should be able to control muscle activity through brain activity BCI in neurological rehabilitation
  • 50. Haptics Symposium 2014 Haptics Symposium 2014 Daly & Wolpaw, Lancet, 2008 Strategy 1: Train subjects to modulate brain activity via visualization and voluntary control of relevant features BCI in neurological rehabilitation
  • 51. Haptics Symposium 2014 Haptics Symposium 2014 Daly & Wolpaw, Lancet, 2008 Strategy 2: Train subjects by using brain activity to aid motion with assistive devices BCI in neurological rehabilitation
  • 52. Haptics Symposium 2014 Haptics Symposium 2014 A new multimodal architecture for gaze-independent brain–computer interface (BCI)-driven control of a robotic upper limb exoskeleton for stroke rehabilitation to provide active assistance in the execution of reaching tasks in a real setting scenario. Object 1 Object 2 Work plane Kinect Eye tracker BC I
  • 53. Haptics Symposium 2014 Haptics Symposium 2014 VAR MIN OPTIMAL CHANNELS MOVE VAR MAX REST MOVE REST VAR MAX VAR MIN ORIGINAL CHANNELS CSP FILTERS SVM CLASSIFIER TRAINING PHASE VISUAL CONDITION ROBOT CONDITION  Involving the BCI module only and the visual feedback of a virtual arm controlled through motor  The subject performed a test session with the complete system: Kinect – EyeTracker – BCI – ArmExos
  • 54. Haptics Symposium 2014 Haptics Symposium 2014 BCI-REHABILITATION PROTOCOL BCI EEG acquisition & processing L-EXOS proprioceptive feedback MONITOR visual feedback • TRAINING PHASE: visual and proprioceptive feedback are provided accordingly to the task • EXERCISE PHASE: the real-time classification output of the BCI was used for driving the proprioceptive and visual feedback ALL PATIENTS WERE ABLE TO CONTROL THE BCI SYSTEM AFTER THE FIRST TWO SESSION 5 right hemiparetic stroke patients enrolled SESSION STRUCTURE: • MOVEMENT: the patient have to perform motor imagery of his impaired arm • REST: the patient have to hold a resting mental state TASKs REQUIRED:
  • 55. Haptics Symposium 2014 Haptics Symposium 2014 BCI paradigm based on Motor Imagery
  • 56. Haptics Symposium 2014 Haptics Symposium 2014 EEG acquisition Signal filtering and conditioning Features extraction Features classification Online operations: User Offline BCI training Frequency bands and artifact removal parameters Spatial Filter parameters Classifier weights Real-time feedback MOTOR IMAGERY BCI: WORKFLOW
  • 57. Haptics Symposium 2014 Haptics Symposium 2014 EEG CONFIGURATION  EEG channels: minimal configuration Frontal ground electrode Reference ear lobe electrode Electrodes covering the motor cortex Electrode for eye-blink detection and removal  Feature extraction The power in the mu (8-12 Hz) and beta (16-24 Hz) bands is computed over 500 ms windows.
  • 58. Haptics Symposium 2014 Haptics Symposium 2014 TRAINING PHASE Training paradigm Subjects are asked to perform several motor imagery trials. 1. Feature classification Acquired data is classified into two or more classes via machine learning techniques, to optimize feature classification 2. Subject training The subject is trained again with the output of the feature classifier as a feedback signal, in order to optimize its motion imagery TRIAL STRUCTURE
  • 59. Haptics Symposium 2014 Haptics Symposium 2014 DATA PROCESSING TRAINING • Import data with the channel location • Subdivide data into epochs for the two classes • Remove artifactuated epochs • Train the Common Spatial filter • Extract Features • Train the classifier it is possible to predict the BCI performance by a visual inspection of both the time-frequency plot of the CSP-projected channels and the features plot
  • 60. Haptics Symposium 2014 Haptics Symposium 2014 DATA PROCESSING: Visual Inspection
  • 61. Haptics Symposium 2014 Haptics Symposium 2014 Time Frequency plot raw channels Time [ms] Frequency[Hz] C3 -2000 0 2000 4000 10 20 30 -2 0 2 Time [ms] Frequency[Hz] CZ -2000 0 2000 4000 10 20 30 -2 0 2 -2 0 2 CHANNELS ERD MAPS - MOVE Time [ms] Frequency[Hz] C4 -2000 0 2000 4000 10 20 30 Time [ms] Frequency[Hz] C3 -2000 0 2000 4000 10 20 30 -2 -1 0 1 2 Time [ms] Frequency[Hz] CZ -2000 0 2000 4000 10 20 30 -2 -1 0 1 2 -2 -1 0 1 2 CHANNELS ERD MAPS - REST Time [ms] Frequency[Hz] C4 -2000 0 2000 4000 10 20 30 Click on electrodes to toggle name/number Click on electrodes to toggle name/number Click on electrodes to toggle name/number
  • 62. Haptics Symposium 2014 Haptics Symposium 2014 Time Frequency plot CSP projected channels Time [ms] Frequency[Hz] MOVE - First CSP -2000 -1000 0 1000 2000 3000 4000 10 20 30 -5 0 5 Time [ms] Frequency[Hz] MOVE - Last CSP -2000 -1000 0 1000 2000 3000 4000 10 20 30 -2 0 2 Time [ms] Frequency[Hz] REST - First CSP -2000 -1000 0 1000 2000 3000 4000 10 20 30 -2 0 2 -2 0 2 Time [ms] Frequency[Hz] REST - Last CSP -2000 -1000 0 1000 2000 3000 4000 10 20 30 FC3 FCZ FC4 C5 C3 C1 CZ C2 C4 C6 CP3 CPZ CP4 FC3 FCZ FC4 C5 C3 C1 CZ C2 C4 C6 CP3 CPZ CP4 First CSP First CSP Last CSP Last CSP REST trials MOVE trials
  • 63. Haptics Symposium 2014 Haptics Symposium 2014 0 1000 2000 3000 0 20 40 60 80 100 Time [ms] CorrectRate[%] CLASSIFIER PERFORMANCE 'Rest' ->89.65% 'Move'->99.95% 'Total' ->95.10% 1.8 2 2.2 2.4 2.6 2 2.5 3 3.5 1st CSP - Log Features 2ndCSP-LogFeatures 0 1 Support Vectors PREDICTING RESULTS Analysis of the BCI output calculated with parameters extracted from the same dataset Plot of each trial in the features space
  • 64. Haptics Symposium 2014 Haptics Symposium 2014 MODEL EEG amp CSP and LDA weights Spatial Filtering Features Extraction Classifier User Interface
  • 65. Haptics Symposium 2014 Haptics Symposium 2014 SHOWING RESULTs [Frisoli et al. 2012]
  • 66. Haptics Symposium 2014 Haptics Symposium 2014 email: a.frisoli@sssup.it m.barsotti@sssup.it thank you!