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THE VISUAL SYSTEM

THE VISUAL SYSTEM. direction of light. Eccentricity. 0 °. 5 °. 10 °. direction of light. direction of light. Midget ganglion cells (P cells). Small bistratified ganglion cells (K cells). Parasol ganglion cells (M cells). direction of light. L and M cones. L and M cones. Rods.

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THE VISUAL SYSTEM

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  1. THE VISUAL SYSTEM

  2. direction of light

  3. Eccentricity 0° 5° 10°

  4. direction of light

  5. direction of light

  6. Midget ganglion cells (P cells) Small bistratified ganglion cells (K cells) Parasol ganglion cells (M cells)

  7. direction of light

  8. L and M cones L and M cones Rods S cones K cells P cells (midget) M cells (diffuse)

  9. Competing Goals for Visual System Design Maximize spatial resolution Maximize field of view Minimize neural resources

  10. Solution High resolution foveal vision Low resolution peripheral vision Eye movement system

  11. Types of Eye Movements • •Saccadic Movements: • –Scanning movements where the gaze is abruptly shifted from one point to the next: conjugate, ballistic, no visual feedback • •Vergence Movements: • –Cooperative movements that keep both eyes fixed on the target; converge or diverge • •Pursuit movements: • –Smooth tracking movements that keep an object’s image fixed in place on the retina • •Vestibulo-Ocular Reflex (VOR) • –Stabilize image during head and body movements • •Micro movements • –Tremor, drift, microsaccades

  12. Relating Neuron Responses and Behavior Define the task and stimuli Measure behavioral responses Measure responses of single neurons or populations to same stimuli (preferably in same species and while behaving the task) Test linking hypotheses; for example, Most sensitive neuron hypothesis Optimal pooling hypothesis Sub-optimal pooling hypotheses Invariance hypothesis (read Parker & Newsome 1998)

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