Linear Quadratic Tracking Control of Smooth Pursuit Eye Movements

Conventional feedback control models of the oculo motor system fail to account for the destabilizing effects of neural transmission delays. To address this shortcoming, a linear quadratic tracking algorithm used to control smoothly pursuing eye movements of various target trajectories is presented.

Based on the type of input to the system, it is shown that stability, in the presence of large motor feedback delays, can be maintained by modulating weighting factors intrinsic to the model. Conditions, such as the initial orientation of the eye relative to the location of where a target first becomes salient and the possible oscillatory nature that the reference trajectory may present, play important roles in determining the optimal cost to go motor control strategy at the onset of a tracking movement.

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An Ultrasound Based Eye Tracking System

A novel, non-contact ultrasound device is detailed for recording and analyzing 3D fast eye movements (saccades) and smooth pursuit eye movements. Saccades are studied to gain a better understanding of the human oculomotor plant and neuromuscular systems. Abnormal saccades can be indicators of both neurological disorders and mild traumatic brain injury (MTBI). Limitations in existing saccade measurement devices prevent them from being used to measure saccades immediately after a possible MTBI event or easily outside of the clinical environment. 

The device proposed is portable allowing saccade measurements in the field to immediately assess neurological dysfunction associated with MTBI. Ease of use and portability allow collection of data at times and places not possible with devices currently available. This increased database of saccades will expand our knowledge of the relationship between saccades and the neurological functioning of the brain. The focus of this paper is the development of a finite element model to establish a starting point for such a design.

Are Kinematic and Kinetic Analyses Useful to Evaluate Patellofemoral Disorders in the Clinical Practice?

Current methods for the assessment of the outcome after anterior knee pain or lateral patellar instability treatment have several limitations, for example their subjectivity. Therefore, new technologies are needed to objectively evaluate the outcomes of treatments for patellofemoral disorders. 

Kinematic and kinetic analyses during dynamic activities under realistic loading conditions that trigger or aggravate the symptoms can: evaluate the patellofemoral patient in an objective way before surgery; analyse the defense mechanisms the patient develops in order to reduce pain and/or instability; improve our knowledge of the aetiopathogeny and therefore of a suitable treatment for patellofemoral disorders; and objectively evaluate the result of the treatment. However, the kinetic and kinematic analyses are not diagnostic tools.