Visual Computation Psy 5612 Lecture Review

Physiological Foundations

• Visual perception: The perception of visual information does not reflect the external environment directly; it represents the brain's interpretation of sensory stimuli.

Visual Computation Process Steps

1. Rod & Cone Cells: Responsible for the initial detection of light.
2. Horizontal & Bipolar Cells: Involved in preprocessing visual information.
3. Ganglion Cells: Further preprocessing to generate neural spikes.
4. Lateral Geniculate Nucleus (LGN): Functions as the relay station for visual information.
5. Visual Cortex: Engages in conscious visual perception.

Elements of Visual Computation

• Receptive Fields (RF): The specific area of the retina that influences the firing of a neuron.
• ON-Center/OFF-Surround RF:
  • ON-center: Neurons fire when light is present in the center of the receptive field.
  • OFF-surround: Neurons are inhibited when light is in the surrounding area.
• Edge Detection: Ganglion cells fire more when there is a contrast (edge) between light and dark.
• Orientation Detectors: Neurons tuned to specific orientations of visual stimuli, with selectivity for a narrow range.

Neural Oscillation in Visual Cortex

1. Sensory Binding Problem: Refers to the challenge of how the brain integrates different sensory attributes (e.g., color, shape) to form a single perception of an object.
2. Neural Assembly Coding: Groups of neurons that work together to represent specific features/attributes of stimuli.
3. Synchronized Neural Assembly: Neurons fire in synchrony, which helps in integrating various sensory features and solving the binding problem.

Rods and Cones in Vision

• Rods:
  • Allow for vision in low light but do not detect color.
  • Contribute to peripheral vision.
• Cones:
  • Responsible for color detection and function best in bright light.
  • There are three types of cones sensitive to different wavelengths (S-cones, M-cones, L-cones) corresponding to blue, green, and red light, respectively.

Visual Projection System

• Visual information is processed through several key pathways:
  • Right and left visual fields process through the optic chiasm to the lateral geniculate nucleus, then to the visual cortex for processing and perception.