Lecture on Visual Perception and Brain Plasticity

Introduction

• Humans are visual creatures with eyes at the front of the head, providing depth perception.
• Visual cortex is larger in humans compared to other mammals, aiding in processing visual information.
• Question raised: What happens to visual areas in the brain when someone is blind?

Understanding Fields of View

• Fields of View: Left and right fields hit different aspects of the eyes.
  • Right field of view hits the left side of both eyes.
  • Left field of view hits the right side of both eyes.
• Binocular Vision: Overlaps in the center, offering greater depth perception.
• Closing one eye reduces accuracy but not the ability to judge distance.

Retina and Photoreception

• Retina: Photoreceptive area at the back of the eye.
  • Contains rods (low light sensitivity) and cones (color detection).
• Functions with other cells to transduce photon information into brain language (sodium-potassium neurotransmitters).

Visual Pathway

• Signal passes through optic nerves, combining into optic chiasm, and then splits into optic tracts.
• Information processed in the thalamus, specifically the lateral geniculate nucleus (LGN).
  • Minimal processing in LGN, signals then move to the visual cortex in the occipital lobe.

Visual Cortex Processing

• Visual cortex subdivided into V1 to V5.
  • V1 (primary visual cortex) is identifiable to the naked eye; others require a microscope.
• Information is processed through sequential activation from V1 to V5.

Brain's Response to Blindness

• Neuroplasticity: Brain reorganizes itself structurally and functionally.
  • Changes in receptor quantity or synapse strength.
• Blindness affects brain differently based on type and age of onset.
  • Cortical blindness vs. damage to retina or optic pathways.

Types of Neuroplastic Changes

• Cross Modal Plasticity: Structural changes in the visual cortex for enhanced hearing and tactile senses.
• Multimodal Plasticity: Activation of pre-existing, unused pathways due to loss of visual processing.

Conclusion

• Brain creatively repurposes unused visual areas for other sensory enhancements.
• Emphasizes brain's adaptability and efficiency in resource utilization.
• Encouragement to explore brain plasticity and its implications further.