1.6B Sensation Vision

The Visual Sensory System

  • LT2C/SC1: Explain how the structures and functions of the visual sensory system relate to behavior and mental processes.

    • Focus on how visual perception affects behavior and cognitive function.

    • Relevance to psychological and biological bases of behavior.

Accommodation

  • Function: Focus light onto the retina through the lens.

    • This process adjusts the shape of the lens for near or distant objects, aiding in clear vision.

Vision Types

  • Normal Vision: Ability to see objects clearly.

  • Nearsightedness (Myopia): Difficulty seeing distant objects clearly.

  • Farsightedness (Hyperopia): Difficulty seeing close objects.

  • Focal Points:

    • Z Point: Specific point at which light focuses on the retina.

Retina Objectives

  • Objective 01: Understanding the role of the retina in vision.

  • Objective 02 - 07: Further exploration into retinal functions and their significance in visual transduction.

Transduction in Vision

  • Process by which light is converted into neural signals by photoreceptors in the retina.

    • Essential for visual perception.

Photoreceptors: Rods and Cones

  • Rods:

    • Located in the periphery of the retina.

    • Responsible for low light vision and detecting shapes and movement.

    • Function in dim lighting, adapting to light and dark conditions.

  • Cones:

    • Concentrated in the fovea, responsible for visual detail and color detection.

Blind Spot

  • Definition: Area of the retina without photoreceptors leading to a blind spot in vision.

  • Distribution:

    • Rods and cones are unevenly distributed; predominance in specific areas of the retina.

    • Example: At the fovea, there are no rods, hence no receptor activity in that spot.

Color Vision Theories

  • Trichromatic Theory:

    • States that color vision is based on three types of cones reacting to red, green, and blue wavelengths.

  • Opponent-Process Theory:

    • Proposes that colors are perceived in opposing pairs (red-green, blue-yellow, black-white).

    • Explains afterimages when staring at a color and then looking away.

Wavelengths in Color Vision

  • Rods: Responsible for luminance, not color.

  • Cones:

    • Long Wavelength Cones: Sensitive to red.

    • Medium Wavelength Cones: Sensitive to green.

    • Short Wavelength Cones: Sensitive to blue.

Color Vision Irregularities

  • Monochromatism:

    • Total color blindness due to lack of cones.

  • Dichromatism:

    • Color vision deficiency typically affecting red/green vision.

    • Results in difficulty distinguishing between certain colors.

Disorders Related to the Visual System

  • Prosopagnosia:

    • Face blindness; inability to recognize familiar faces despite normal vision.

  • Blindsight:

    • Ability to respond to visual stimuli without conscious visual perception due to damage in the visual processing areas of the brain.