Bioelectric signal analysis of assistive devices

1. Bioelectric signal analysis of assistive devices Presented by : Kelly Kaneswaran 1 Supervisory Team : Professor Khalil Arshak1, Rosemary Joan Gowran2, Dr. Edward Burke3, Dr. James Condron3.

2. Background • An important factor in the rehabilitation of people with motor impairments is the provision of assistive technology systems that enhance independence by facilitating mobility, communication and control of everyday devices. In cases of severe motor impairment, a human-machine interface (HMI) must be carefully selected and adapted to make efficient use of whatever movements remain under the voluntary control of the user. Many users' needs change over time, for example due to degenerative condition (e.g. Multiple Sclerosis). Unfortunately, even in systems that have been carefully adapted to make best use of an individual user's abilities, this often leads to usability problems. • The objective of the proposed research is to investigate automatic adaptation of a HMI based on bioelectric signal analysis. Using a previously developed wheelchair navigation device, a study will be carried out to identify means of adapting the operating parameters of user interfaces over time to respond to the changing needs of the user. The additional physiological data may allow system adaptation algorithms to move beyond reaction to changes in functional performance towards more subtle behaviors (e.g. responding to a level of satisfaction frustration), providing safer, more comfortable and efficient long-term use of the device. • Significance • The primary contribution of this research to the field of rehabilitation and assistive technologywill lie in identifying novel approaches for the automatic adaptation of human-machine interfaces to facilitate safer, more comfortable and/or more efficient use of devices by people with disabilities that give rise to time-varying motor impairments. By gathering data directly from a HMI during use in conjunction with other signals emanating from the human body, it is envisaged that a better understanding can be obtained of how changes in a user's needs canbe observed in their interactions . • The creation of new test methods and advanced algorithms could facilitate the design of smarter HMIs that react to their users' changing needs, addressing a real problem experienced by many users of existing assistive technology devices. By addressing the needs of time varying motor impairments, prolonged use is envisaged, reducing device abandonment rates. It is envisioned that both Biomedical Engineers and Occupational therapists communities will benefit from the dissemination of this work through publications , conferences and demonstrations. Background and significance

3. Publication and Dissemination of work through conference proceedings and journal publications. • Goals • Specific Objectives • Work Break Down Goal and Specific Objectives Inter department collaborations and publications.

4. Research Design Method • The newly developed assistive device incorporates a capacitive based touchpad , measuring varying changes in capacitance over interwoven electrode sensor strips. An algorithm already developed gives a 200 x 200 resolution over a 23mm x 23mm square area. The system can measure capacitive changes as low as 4 femtofarads. The user makes small finger movements (as little as 2mm) in any given direction, the controller translates these movements to directional commands and conveys the commands to the power wheelchair module. • A typical BCI Paradigm in where the subject watches the screen for visual cues. Each visual cue prompts an intended movement . In order to simulate small finger movements typical of the touchpad controller four micro-switches are placed equidistant from a central location. The subjects index finger is placed in the rest position in the central location. Each micro-switch is wired to a • trigger input on the Biosemi EEG acquisition system and recorded . An auditory warning stimulus is presented for 300ms after which there is 700ms Idle time. The visual cue is presented 1 second after the onset of the warning signal. The visual cue prompts a directional command for finger movement by highlighting a directional command (Up, Down, Left, Right) lasting 500ms. When the visual cue has disappeared the user actions the prompted cue by moving the index finger of selected hand from its centred position to a button situated in the forward, back, left or right direction. The subject has 2.5 seconds to react before the next warning signal. This paradigm is known as a delayed memory task. Research design method Up

5. Previous controller design • Progress to Date • Redesigned touchpad • The controller system has been redeveloped to allow an analogue module with up to 8 channels direct interface to the microcontroller with a maximum data rate of 420ksps. The system controller also provides power, 8 digital control lines, 2 DAQ outputs , and a voltage ref. The original touchpad was also redeveloped to make it lighter, aesthetically pleasing and configurable. • In collaboration with the Occupational Therapy Department, University of Limerick ethical approval was sought and granted for testing of the novel assistive device on powered wheelchair users in the University Environment. This process is still ongoing and results are being presented at the International Seating Symposium in March of this year. • Previous controller design Progress to date

6. Stimulus Software • Progress to Date • Additional Work • A software and hardware simulation were developed to present the auditory cues, visual stimulus and digital cue signal representations using Labview Graphical Software package , National Instruments USB Data Acquisition Card and a Laptop. A 12 Digit keypad with 7 buttons removed was used to allow the user to react to the visual cues through triggered responses. • A secondary system was developed for EEG acquisition. A high speed data acquisition module was designed for the Blackfin 537 Evaluation board. The module is configurable , allowing programmable settings of gain, low pass filtering and sampling speed. The module allows sampling on 4 channels synchronously using 4 sigma delta modulators, with up to 22bit resolution. Samples can be accessed on the high speed serial port at up to 2.2khz. Remote access is available through network connection. Progress to date

7. Results • Progress to Date • Average ERPs on Scalp Map • Experiments were carried out on 8 subjects, 7 male and 1 Female in the range of 20 to 40 years of age. Over 320 trials were recorded for each subject. Datasets were band pass filtered 1-30hz and epoched from onset of cue to 500ms using 0 – 100ms as a baseline. The data was visually inspected for artefacts. For one subject the button response was activated during cue presentation so he was discarded from current analysis activities. For three other subjects data was heavily contaminated due to artefacts from eyes , loose electrodes and muscle movement and were also disregarded from current analysis. The remaining 4 underwent visual epoch rejection, and encouraging preliminary results are presented. • After visual ERP analysis it was found that a symmetrical response to intentional movement can be seen across the parietal cortex of the four subjects. The image above shows a scalp map of 128 electrode positions used during recording of each subjects EEG activities. Circled above are electrode B4 and A7 on the parietal cortex . On closer inspection we can see a peak at around 200ms and a trough at the same position on the opposite side of the brain. In fact we can see the same response across all four subjects. According to literature the parietal cortex is involved in visual path planning, and spatial awareness. As the next graphs show we can see a change of amplitude of the 200ms peak with left and right movements causing an inversion of the peak according to directional movement. Progress to date

8. Results • Enlarged Left over Right Average ERP from symmetrical electrodes • As a prevalidation half the sample set for one subject was averaged for left and right movements, the second half was also averaged in the same way. Both sets produced the same phenomenon at around the 200ms range. In order to fully validate this phenomena a classifier will be developed to determine if this feature can be used to determine left and right movement intent from the parietal lobe. This feature along with standard BCI control features such as modulation of mu and beta rhythms will be used to develop a more robust classifier in an effort to enhance the classifier accuracy. Progress to date

9. Obstacles Obstacles

10. 2 IEEE Sensor Application Symposium, Texas , 2006. EMRS Strasbourg, Nice , May 27 – June 1, 2007. 14th Nordic – Baltic Conference on Biomedical Engineering and Medical Physics, Riga, Latvia, June 16 – 20, 2008. 13th International Conference on Biomedical Engineering, Suntec, Singapore, December 3 - 6, 2008. International Seating Symposium , Florida , March 12 – 14, 2009. European Seating Symposium, Trinity College, Dublin, Ireland, 14 – 17 Sept 2009. International Seating Symposium , Vancouver, Canada, March 10-13th 2010. EMBC , 32nd Annual International Conference of the IEEE Engineering in Medicine and Biology Society, Argentina, Aug 31st – Sept 4th 1 7 3 4 5 6 1 2 Conferences Attended Conferences Planned Invited Talk, ““Applying Consumer Technology to Assistive Device Design” , Posture and Mobility – A Day of Shared Learning, Engineers Ireland Biomedical Engineering Division (Seating and Mobility Interest Group), 24th February 2009 Conferences attended

11. Publications 1 K. Arshak, D. Morris, K. Kaneswaran, O. Korostynska, A. Arshak, “Portable Real-Time Gamma Radiation Dosimetry System Using MgO and CeO2 Thick Film Capacitors”, Proc. Int. Conf. on Sensing Technology, Palmerston North, Nov. 21-23, 2005, pp. 137-142 Arshak, K.; Kaneswaran, K.; Korostynska, O.; Morris, D.; Arshak, A., "Wireless real-time Gamma Radiation Dosimetry System Using MgO and CeO2 Thick Film Capacitors," Sensors Applications Symposium, 2006. Proceedings of the 2006, IEEE vol., no., pp. 60-65, 2006 Arshak, K.; Morris, D.; Arshak, A.; Korostynska, O.; Kaneswaran, K., "Investigation into the pressure sensing properties of PVDF and PVB thick film capacitors," Electronics Technology, 2006. ISSE '06. 29th International Spring Seminar on , vol., no., pp.334-339, 10-14 May 2006. K. Arshak, D. Morris, A. Arshak, O. Korostynska, K. Kaneswaran, Development of oxide thick film capacitors for a real time pressure monitoring system, E-MRS IUMRS ICEM 2006 Spring MeetingNice, France - May 29 – June 2, 2006. Arshak, K. I. and K. Kaneswaran. 2007. "Novel Use of Capacitive Sensing Device for Investigation of GI Tract Anomalies." 30th IEEE ISSE Conference, Cluj-Napoca, Romania, 9-12 May. Poster presentation. Korostynska, O.; Arshak, K.; Gill, E.; Arshak, A.; Kaneswaran, K., "Bi2O3/Nb2O5 thick film capacitive pH sensor using AD5933 impedance converter," Sensors Applications Symposium, 2008. SAS 2008. IEEE , vol., no., pp.16-21, 12-14 Feb. 2008. Kelly Kaneswaran and KhalilArshak, "Applying Consumer Technologies to Assistive Device Design", 14th Nordic – Baltic Conference on Biomedical Engineering and Medical Physics, Riga, Latvia, June 16 – 20, 2008. Kelly Kaneswaran and KhalilArshak, "Capacitive Interfaces for Navigation of Electric Powered Wheelchairs", 13th International Conference on Biomedical Engineering, Suntec, Singapore, December 3 - 6, 2008. Kelly Kaneswaran and Rosemary Gowran, " Creatively Generating a Sustainable Template for Technology Transfer ", 25th International Seating Symposium Proceedings, pp 247, Buena Vista Palace, Orlando Florida, March 12 - 14th, 2009. Poster Presentation. Kelly Kaneswaran and KhalilArshak, "Applying a Universal Design Template in Creating a Novel Assistive Device", European Seating Symposium Incorporating Assistive Technology, September 14th -17th, 2009. In Press K.Arshak, D.Buckley, K. Kaneswaran, “Review of assistive devices for electric powered wheelchairs navigation”, Journal of the Institute of Technology Blanchardstown, Vol. 13, pp. 13-23, May 2006. Kelly Kaneswaran and KhalilArshak, "Applying Consumer Technologies to Assistive Device Design", 14th Nordic – Baltic Conference on Biomedical Engineering and Medical Physics, IFMBE Proceedings, vol. 20, pp 131 - 134, Springer Berlin Heidelberg , ISSN 1680-0737. 3 4 5 6 7 8 9 10 Journal Book Chapter Kelly Kaneswaran and KhalilArshak, "Capacitive Interfaces for Navigation of Electric Powered Wheelchairs", 13th International Conference on Biomedical Engineering, IFMBE Proceedings, vol. 23, pp 1153-1157, Springer Berlin Heidelberg, ISSN 1680-0737 Book Chapter 2 publications K. Arshak, D. Morris, A. Arshak, O. Korostynska, K. Kaneswaran, Development of oxide thick film capacitors for a real time pressure monitoring system, Materials Science and Engineering: CVolume 27, Issues 5-8, EMRS 2006 Symposium A: Current Trends in Nanoscience - from Materials to Applications, Sept 2007, Pages 1406-1410. ISSN 0928-4931 Journal

12. Questions and Answers