Directeur : Mr S. PERREY (PR).

1. Improving Usability in Human Computer Interfaces: an investigation into cognitive fatigue and its influence on the performance of hybrid brain computer interfaces Presented by Gérard Derosière Directeur : Mr S. PERREY (PR). 06/14/2012

2. I. Supervisors of the project and partners Codirection in the context of a PhDthesis :

3. II. Introduction Brain-Computer Interfaces (BCIs): allow the control of an electrical system withoutvoluntarymovementneeded, just by the mean of the cerebralactivity(Gouy-Pailler, 2010). How isit possible? The user have to : - Do mental imagery or mental arithmetic; - Focus his attention to a light. Thesetasksrequiresustained attention. One main characteristic of the sustained attention:  The time-on-task (TOT) effect. Characterized by: - A progressive decrease of the attentional resources with time  measured through the increase of the reaction times (RTs) (Lim et al., 2010); - A modification of the cerebral activation (e.g., Paus et al., 1997)  non-stationarity. Attentionalresources

4. II. Introduction TOT effect must be reduced during the use of a BCI for 2 reasons: - Decrease of attentional capacities  exhaustion, inability to use the BCI; - Modification of cerebral activation  ↓ of classification accuracy.  Proposed solutions (Baï et al., 2010): to develop BCIs requiring minimal training, and thus, less mental load • Allison et al. (2010): development of a simultaneoushBCI. • Event-RelatedDesynchronization (ERD): mental imagery. • Steady-State Visual EvokedPotential (SSVEP): focalization of attention to a light. Pfurtscheller et al. (2010): the hybridBCIs (hBCIs)  allow to enhance classification accuracy.  Enhancement of the classification accuracy in the simultaneous condition.

5. III. Definition of the problematic • Summary •  BCIs require sustained attention; •  Sustained attention is characterized by a "Time-On-Task" effect; • TOT effect must be reduced during the use of a BCI; • A new type of BCI to enhance classification accuracy: the simultaneous hBCI; Incompatibility between simultaneous hBCI and the aim to reduce TOT effect. SimultaneoushBCIsrequiredivided attention  the mental load = higherthan a simple condition. Questions: - Does the simultaneous condition generate an early TOT effect? - If so, is it linked to an early modification of the cerebral activation? - Finally, does it generate an early decrease of the classification accuracy?

6. IV. Proposedprotocol Comments: • Session 1: Mental arithmetic only • PASAT: Paced Auditory Serial Addition Test (mental arithmetic task). • RTs: Reaction times. • Concomitant measurements: • Electroencephalography (EEG), functional NIRS. Subjective aspects of fatigue. • Classification accuracy tested in the three conditions, in a monomadal and multimodal manner. PASAT PASAT PASAT PASAT ... RTs RTs RTs RTs RTs Time Session 2: Steady State Visual Evoked Potential (SSVEP) only SSVEP SSVEP SSVEP SSVEP ... RTs RTs RTs RTs RTs Time Session 3: hybrid condition SSVEP + PASAT SSVEP + PASAT SSVEP + PASAT SSVEP + PASAT ... RTs RTs RTs RTs RTs Time

7. V. Expectedresults and conclusion Expectedresults: Tested in the threeconditons: Classification accuracy RTs Classification accuracy SSVEP + Mental arithmetic Multimodal (EEG+fNIRS) Mental arithmetic SSVEP Monomodal fNIRS Mental arithmetic SSVEP + Mental arithmetic Monomodal EEG SSVEP TOT TOT TOT Project partlyfinanced by the LABEX NUMEV  thiswillconduct to new development for pathological people.

8. Thank you for your (sustained) attention. Directeur : Mr S. PERREY (PR).