Introduction to Perception

Question 1

What are the organising principles of visual perception?

Answer 1

• Visual perception follows a pathway from senses to dedicated cortical receiving areas.
• In the case of the visual system, the pathway is: Eye → Retina → LGN (Lateral Geniculate Nucleus) → Visual System (V1) → V2 → V3 → V4 → V5.
• Different types of ganglion cells, including midget cells, bistratified cells, and parasol cells, play specific roles in visual perception.

Question 2

What are the functions of midget cells, bistratified cells, and parasol cells?

Answer 2

• Midget Cells: They code for redness, greenness, and edges in visual perception.
• Bistratified Cells: These cells code for blue/yellow information
• Parasol Cells: They code for the information on luminance

Question 3

How many layers does the LGN (Lateral Geniculate Nucleus) have, and what are the functions of each layer?

Answer 3

• The LGN consists of six layers.
• Magnocellular Layers (1, 2): These layers process luminance information.
• Parvocellular Layers (3, 4, 5, 6): They primarily code for red/green information.
• Koniocellular Layer: This layer is involved in blue/yellow coding, contributing to the color perception process.

Question 4

Describe the layers of V1 (Primary Visual Cortex) and their functions.

Answer 4

• V1 is located in the occipital lobe and comprises six layers.
• It sorts visual information into different ‘drawers,’ including colour contrast (blobs), achromatic contrast, and ocular dominance columns.
• Each layer processes specific aspects of visual information, contributing to the overall perception of the visual scene.

Question 5

What are the functions of cells in V1, V2, V3, V4, and V5 in visual perception?

Answer 5

• Cells in these visual areas are selective for various visual features, including orientation, colour, binocular disparity, and motion direction.
• They play crucial roles in processing and interpreting visual information, contributing to our perception of the surrounding environment.

Question 6

Describe the visual processing streams and anatomical pathways in the brain.

Answer 6

• There are two main streams: dorsal and ventral.
• The magnocellular and parvocellular pathways contribute to these streams.
• The dorsal stream is concerned with “where” information and perception-action coordination, while the ventral stream is involved in “what” information and object recognition.
• These pathways and streams facilitate efficient communication and integration of visual information in the brain.

Question 7

Why is visual perception important, and how does it contribute to survival?

Answer 7

• Perceptions are crucial for daily functioning as they actively inform us about important aspects of our environment.
• Representations of objects are constructed by specialized subsystems in a layered manner, allowing us to make sense of the visual world.
• Visual perception is unique as it conveys messages about distant objects, aiding in navigation and spatial awareness.
• Perceptions aid in survival by enabling decision-making and actions, such as spotting predators, finding food, or selecting healthy mates, highlighting the interplay between memory and perception in deciphering potentially dangerous stimuli.