Research Interests:

I am interested in understanding principles of movement generation. Given the continuous stream of movements that biological systems exhibit and their enormous capacity to learn new skills, an account for such versatility and creativity has to assume that movement sequences consist of segments, executed either in sequence or with partial or complete overlap.

My research revolves around the existence and formalization of discrete and rhythmic movement primitives in human arm control. We study this hypothesis using psychophysical experiments and Dynamics Systems modeling

In psychophysical experiments we use Sensuit or Visual Tracking system to record joint angle and endpoint position while performing rhythmic and discrete tasks. One such experiment involves interaction of discrete and rhythmic movements in single joint, dual joints of the same arm and bimanual tasks. In another set of experiments we investigate online movement correction using target switching paradigm. We have a 3-D visual display using anaglyph glasses.

In Dynamics System modeling, we study Dynamic Motor Primitives (DMP). DMPs are units of action that are formalized as stable nonlinear attractor systems. They are useful framework for biological motor control as they are highly flexible in creating complex rhythmic (limit cycle) and discrete (point attractor) behaviors that can quickly be adapted to the inevitable perturbations of a dynamically changing, stochastic environment. We use our Dynamic System framework to model and interpret our human behavioral studies.

Research Interests:

Motor Control, Robotics, Machine learning

Curriculum Vitae
Links

Email:

Phone:

(213) 740 6717

Publications:

Mohajerian, P.;Mistry, M.;Schaal, S. (submitted). Cerebral or spinal level interaction of rhythmic and discrete movements during two-joint arm task, Journal of Neurophysiology.
[Detail] [BibTeX]

Mohajerian, P; Hoffmann, H.; Mistry, M.; Schaal, S. (2007). A Computation Model of Arm Trajectory Modification Using Dynamic Movement Primitives, Society of Neuroscience.
[Keywords: online movement correction, target switching, movement primitives, computational model, motor control]
[Detail] [BibTeX] [PDF]

Schaal, S; Mohajerian, P.; Ijspeert, A. (2007). Dynamics systems vs. optimal control — a unifying view, Progress in Brain Research, 165, pp.425-445.
[Keywords: discrete movement; rhythmic movement; movement primitives; dynamic systems; optimization; computational motor control]
[Detail] [BibTeX]

Schaal, S.;Mohajerian, P.;Ijspeert, A. (2007). Dynamics systems vs. optimal control--a unifying view, Prog Brain Res, 165, pp.425-45.
[Detail] [BibTeX] [PDF]

Mohajerian, P.;Hoffman, H.;Mistry, M.;Schaal, S. (2007). A computational model of arm trajectory modification using dynamic movement primitives, Abstracts of the 37st Meeting of the Society of Neuroscience.
[Keywords: motor control, computational neuroscience, behavior, movement primitives, trajectory formation]
[Detail] [BibTeX]

Mistry, M.;Mohajerian, P.;Schaal, S. (2005). Arm movement experiments with joint space force fields using an exoskeleton robot, IEEE Ninth International Conference on Rehabilitation Robotics, pp.408-413.
[Keywords: computational motor control trajectory planning inverse kinematics force control human motor control torque perturbations]
[Detail] [BibTeX] [PDF]

Mistry, M.;Mohajerian, P.;Schaal, S. (2005). Force field learning in joint space with a 7-DOF exoskeleton, 12th Joint Symposium of Neural Computation.
[Keywords: force fields, motor primitives, computational motor control. inverse kinematics]
[Detail] [BibTeX]

Mistry, M.;Mohajerian, P.;Schaal, S. (2004). Force Field Learning in Joint Space with a 7-DOF Exoskeleton, Abstracts of the 34st Meeting of the Society of Neuroscience.
[Keywords: computational motor control trajectory planning inverse kinematics]
[Detail] [BibTeX]

Mohajerian, P.;Mistry, M.;Schaal, S. (2004). Neuronal or spinal level interaction between rhythmic and discrete motion during multi-joint arm movement, Abstracts of the 34st Meeting of the Society of Neuroscience.
[Keywords: movement primitives behaviors dynamic systems computational motor control discrete rhythmic trajectory planning]
[Detail] [BibTeX]

Mohajerian, P.;Peters, J.;Ijspeert, A.;Schaal, S. (2003). A unifying computational framework for optimization and dynamic systemsapproaches to motor control, Proceedings of the 10th Joint Symposium on Neural Computation (JSNC 2003).
[Keywords: computational motor control, optimization, dynamic systems, formal modeling]
[Detail] [BibTeX] [PDF]

Mohajerian, P.;Ijspeert, A.;Schaal, S. (2001). Arm motor control based on superimposed rhythmic and discrete movement primitives, Abstracts of the 31st Meeting of the Society of Neuroscience.
[Keywords: movement primitives, behaviors, dynamic systems, computational motor control, discrete, rhythmic, trajectory planning]
[Detail] [BibTeX]

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