Angelaki Lecture - Eye Movements Research Goal To...

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1 Research Goal To understand the neural basis and computational aspects of sensorimotor control Sensorimotor Transformations Sensory Signals Motor Output noise Motor Output: Eye movements Sensory Signals: Visual and Vestibular systems Eye Movements Eye Movements 1) Why do we move our eyes? 2) Why study eye movements? The main goal in systems neuroscience is to understand how the brain produces behavior. The most common questions asked: “How does a particular combination of sensory inputs lead to a particular motor output?” “What is the neural processing that converts sensory signals into motor output?” Eye movements provide an excellent example: Simple (but still interesting) -the eye has only one joint with 3 degrees of freedom (as compared to multiple joints in arm control) -unlike pointing, there’s only one configuration of the eyes that will get your gaze to a particular point in space -no load for the eye (arms must work against variable loads) -no functional stretch reflex (in the skeletomotor system, stretch reflex is believed to serve as an automatic adjustment for unexpected changes in environmental factors and loads) no co-contraction (simultaneous activation of opposing muscles across a joint; usually used to stiffer the joint and better resist destabilizing torques) is observed in eye muscles; movements are achieved through reciprocal activation of coplanar muscle pairs, where a gradual increase in tension in the agonist is matched with a decrease in tension in the antagonist Eye Movements Output is easy to measure and quantify Highly constrained, thus easier to study All of the neural circuitry controlling eye movements is located in the brainstem or higher in the CNS. At these sites, modern microelectrode techniques allow the recording of neural responses along oculomotor pathways in alert behaving animals Particularly for an engineer: -ocular responses easily observable noninvasively -stimuli (vestibular and/or visual) are controllable -central systems anatomically simple, when compared to other motor reflexes (yet strategies used in oculomotor control may be common to more complex integrated systems) -lessons to be learned for design of robotic gaze systems 3) How do we measure eye movements? Until recently: EOG. The retina has an electrical charge on it, unclear what it arises from, but moving the eye moves this charge which can be picked up and amplified to give eye movement tracing Today: Video methods and Magnetic Search Coil technique the eyes are rotated by 6 extraocular mucles there are 3 agonist/antagonist pairs
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2 What principles do we use for the study of eye movements? ? output input Engineering tools one can use: - Signal Processing - Control Systems Analysis - Calculus and Differential Equations Different Types of Eye Movements Saccades (Fast Eye Movements) – goal : Redirect gaze to a target of interest – input : Position error relative to fovea Smooth Pursuit – goal
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Angelaki Lecture - Eye Movements Research Goal To...

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