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Hybrid BCI controlled FES for rehabilitation of the hand in acute tetraplegic patients

Hybrid BCI controlled FES for rehabilitation of the hand in acute tetraplegic patients. Aleksandra Vuckovic Centre for Rehabilitation Engineering, University of Glasgow, Leslie Wallace, David Allan Queen Elizabeth National Spinal Injuries Unit Southern General Hospital, Glasgow. Background.

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Hybrid BCI controlled FES for rehabilitation of the hand in acute tetraplegic patients

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  1. Hybrid BCI controlled FES for rehabilitation of the hand in acute tetraplegic patients Aleksandra Vuckovic Centre for Rehabilitation Engineering, University of Glasgow, Leslie Wallace, David Allan Queen Elizabeth National Spinal Injuries Unit Southern General Hospital, Glasgow

  2. Background Motivation for the study: • Associative learning: ' Cells that fire together, wire together’ • Combined simultaneous stimulation of efferent of the motor pathways and afferent sensory pathways might strengthen the existed synapses in the CNS on the bases on Hebbian learning [Kujirai et al. 2006]

  3. System Requirements Hypothesis Voluntary activation of motor neural pathways combined with FES may result in a stronger training effect than each of these two approaches alone [Barsi et al. 2008]. Requirements • System has to enable mental rehearsal of movements providing a (neuro)feedback of imagination through Graphical User Interface (GUI) • System needs to control an electrical stimulator used for functional electrical stimulation (FES) of the hand User BCI Stimulator GUI FES

  4. BCI-FES in Sensory/Motor Rehabilitation • SCI patients receive rehabilitation therapy programmes within weeks after the injury : • Control strategy is based on movement imagination of the limb under therapy • Control feature are extracted during motor imagination (not on post-movement synchronisation) • Initial learning period should be short • Small number of electrodes • Limited training time

  5. System Configuration 1 • EEG CAP& ELECTRODES (BCI) • EEG AMPLIFIER (BCI) • GUI (BCI) • STIMULATOR • ELECTRODES (STIMULATOR)

  6. Brain Computer Interface • Asynchronous BCI switch to control a stimulator • Hybrid BCI: • Motor imagination (mu rhytm) to activate the stimulator • Occipital alpha (closed eyes) to deactivate the stimulator

  7. Methods • Session 1-3 FES activated by mu rhythm, deactivated automatically after 10s • Session 4 FES activated by mu rhythm, deactivated by occipital alpha Sensory and motor functions

  8. Clinical Case Study EEG recordings: Motor area: 1 bipolar recording (CF3-CP3 or CF4-CP4), mu rhythm Occipital area: 2 monopolar recordings (O1 and O2), alpha rhythm Control Variable On-line Power spectral density (PSD) over 1s, of the mu rhythm and of the occipital alpha Functional Electrical Stimulation bipolar, hand extensor muscles (ramp pulse, 15 ma, 250 s, 33Hz)

  9. ERD/ERS maps to define frequency band 30 30 Subject 1, left hand imagination CF3-CP3 CF4-CP4 25 25 20 20 Frequency [Hz] 15 15 10 10 5 5 1 2 3 4 5 6 7 1 2 3 4 5 6 7 Time [s] Time [s] 30 30 Subject 1, right hand imagination CF3-CP3 CF4-CP4 25 25 20 20 Frequency [Hz] 15 15 10 10 5 5 1 2 3 4 5 6 7 1 2 3 4 5 6 7 Time [s] Time [s] 30 30 Subject 2, right hand imagination CF4-CP4 CF3-CP3 25 25 20 20 Frequency [Hz] 15 15 10 10 5 5 1 2 3 4 5 6 7 1 2 3 4 5 6 7 Time [s] Time [s]

  10. Alpha frequency band Close eyes and relax Threshold estimation Eyes closed EEG <Threshold (1s)? No Yes Eyes opened EEG <Threshold (60s)? No Yes Set threshold Methods: Defining a Threshold Choose a frequency band Imagine to move the hand Threshold estimation Imagination EEG <Threshold (1s)? No Yes Spontaneous EEG <Threshold (60s)? No Yes Set threshold SENSORY MOTOR RHYTHMS TO ACTIVATE FES OCCIPIAL ALPHA TO DEACTIVATE FES

  11. Methods: Neurofeedback GUI SCREEN 1 Screen 1: Setting the SMR threshold and choosing a frequency band Screen2: Setting the occipital alpha threshold Screen3: Simultaneous presentation of different frequency bands over the motor area SCREEN 2 SCREEN 3

  12. PSD mu rhythm Current 25 20 PSD [V2] 15 10 5 0 0 20 40 60 80 100 120 140 Time [s] 25 PSD mu rhythm Current 20 PSD [V2] 15 10 5 0 300 400 500 600 Time [s] Sessions 1-3, Subject 1 Left Hand No wrist control preserved sensation Preserved proprioception FES without BCI Manual control BCI activates FES Deactivation after 10 s

  13. 30 25 PSD [V2] 20 15 10 5 0 0 80 120 160 200 40 20 18 16 14 PSD [V2] 12 10 8 6 4 2 0 0 40 80 120 160 200 240 280 Time [s] Session 1-3, Subject 1, Right Hand Preserved motor functions No sensations Weak proprioception PSD mu rhythm Current FES without BCI Manual control Time [s] BCI activates FES Deactivation after 10 s

  14. Session 4: Hybrid BCI-FES Control PSD Current Subject 1, left hand Mu rhythm 50 PSD [V2] FES ON CF3-CP3 0 0 20 40 60 80 100 120 140 160 Time [s] Occipital alpha rhythm 300 PSD [V2] 200 O1 FES OFF 0 20 40 60 80 100 120 140 160 Time [s]

  15. Session 4: Hybrid BCI-FES Control Subject 2, right hand PSD Current 30 Mu rhythm 25 20 PSD [V2] 15 FES ON 10 5 0 80 0 20 40 60 100 120 140 160 Time [s] Occipital alpha rhythm 200 FES OFF 150 PSD [V2] 100 50 0 160 0 20 40 60 80 100 120 140 Time [s]

  16. Conclusions and Directions for Future Work • Acute tetraplegic patients can learn to reliably control BCI-FES within one training session • Proprioception crucial for successful imagination • Long term studies needed to establish functional relevance of the therapy • Strategies to facilitate motor imagination • Sensory rehabilitation? • Influence of the frequency of stimulation on cortico-spinal coherence (15-30 Hz)

  17. Thank you for your attention Aleksandra.Vuckovic@glasgow.ac.uk

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