|Ph.D Student||Boris Yazmir|
|Subject||Error Related Potentials Evoked by Disturbances during|
|Department||Department of Mechanical Engineering||Supervisor||Professor Reiner Miriam|
|Full Thesis text|
This study looks at the nature of - Error related Electroencephalography (EEG) signals in response to distinctly different errors during three-dimensional (3D) motion. More specifically, this study attempts to answer the following: What are the EEG correlates of different error types during execution of continuous 3D motor task - are they distinct? What are their characteristics? What are EEG correlates of successful motion? How is EEG activity affected by congruence/incongruence visuo/proprioceptive feedback? Can humans predict success of motor acts that were not yet completed - and which of the two, prediction of success or failure, is faster?
Errors in motion can be classified as follows: (1) Target error elicited by unexpected change of target location, motion direction or environment conditions; (2) Execution error elicited by unintended movement of controlled agent or human limb; and (3) Outcome error elicited by unachieved goal of the movement. Also, errors can be classified as internal, if originating in the user, and external, if inflicted by external factors.
During the experiment participants played in virtual 3D tennis game against computer player. The game world was highly-ecologically-valid due to immersive, multimodal, virtual-3D gameplay and haptic device control. Valid comparison of Event related potentials (ERPs) evoked in EEG in response to successes and errors, was achieved by use of the same experimental environment. Correct repel or miss of the tennis ball in the game was considered, as user internal repelling outcome success or error, respectively. Scoring a goal or not scoring a goal in the game was considered, as user internal throwing outcome success or error, respectively. External execution interface errors were presented by random shifts of user's virtual racket on the screen or of the controller end effector handle with a hand holding it, for incongruent and congruent proprioceptive feedback, correspondingly. The external target error was induced by unexpected inclination of the incoming tennis ball.
Research results for each event type showed well-defined ERPs with distinct waveforms, scalp signal distribution maps, source estimation results (sLORETA) and time-frequency patterns. Neural responses to self-induced internal user outcome errors and successes were different from other types of externally induced errors, indicating possible self-awareness related to error classification. In addition, it was possible to discriminate between internal outcome success and errors. Results showed significant dependence on the availability of congruent proprioceptive feedback. Incongruence between visual and proprioceptive feedbacks caused marginally significant Stroop effect, accompanied by differences in ERPs characteristics. Only users' internal throwing outcome success (“Goal”) related ERP had pre-event peaks indicating possible outcome prediction process. The significant delay in latency between positive peaks of internal outcome error and success (earlier) related ERPs suggested a cross-talk between top-down and bottom-up processing, represented by an outcome recognition process, in the context of the game world.
Results can be applied to check how users interprets errors, to assess user success experience and to build a more efficient Brain computer interfaces (BCIs) with error feedback based on a smart classifier of errors, providing a tailored correction according to the nature of the error.