NEUROSCIENCE: VISION -- INTRODUCTION

INTRODUCTION

A. Role of the visual system: sense photons emitted by or reflected from objects in the environment and to interpret the resulting afferent input. This is accomplished by four processes:

1. Formation of a small image of the environment on retina (which contains the photoreceptor afferent neurons) by the optical apparatus of the eye (physiological optics) (==>)

2. Transduction of the image into a pattern of action potential discharge by retinal neurons (retinal transduction)

Note: Transduction is possible only for light within a limited wavelength range, approximately 400-700 nm (nanometers); the exact range depends on whether the eye is light adapted (photopic vision) or dark adapted (scotopic vision)

Note lower sensitivity of photopic vision

3. Conduction of the resulting action potentials to regions of the central nervous system (CNS) responsible for conscious sensation of visual input (visual pathways)

4. Extraction of the properties of the visual image: shape, color, brightness, movement, etc. (visual cortex and projection areas)