lecture recording on 12 March 2025 at 11.52.03 AM

Understanding Light and Color

• Nature of Light

  • Light can be measured objectively.

  • Travels in specific wavelengths, perceived by humans.

• Perception of Color

  • Colors like red, purple, and blue do not exist as physical entities; they are constructs of the brain.

  • Brain interprets environmental stimuli to create the perception of color.

Anatomy of the Eye

• Retina Composition

  • Contains rods and cones, specialized cells for light detection.

  • Cones:

    • High concentration in the macula and fovea.

    • Sensitive to details and color.

  • Rods:

    • Distributed in the periphery.

    • Sensitive to low light and motion; see in grayscale.

• Blind Spot

  • Location where axons exit the eye to form the optic nerve.

  • The brain fills in the gap from this blind spot, so it remains unnoticed.

Visual Processing

• Neural Response

  • Rods and cones are neurons reacting to light wavelengths.

  • Different wavelengths alter neuronal firing patterns.

• Visual Pathway

  • Visual information from the left field goes to the right occipital cortex; right field to left cortex.

  • Damage to any part of the visual system can lead to visual deficits.

  • Cortical blindness can occur if the primary visual cortex is damaged, despite the eyes being functional.

Saccadic Eye Movements

• Small, involuntary eye movements.

• Constantly move to scan environment, helping the brain fill in visual information around the blind spot.

Introduction to Hearing

• Nature of Sound

  • Sound is a physical phenomenon and must travel through a medium (e.g., air).

• Frequency and Amplitude

  • Measured in hertz (Hz); affects perceived sound.

  • Lower frequencies are deeper sounds (bass); higher frequencies are sharper sounds.

Anatomy of the Ear

• Outer Ear

  • Pinna: Funnels sound waves into the auditory canal.

• Middle Ear

  • Tympanic Membrane (Eardrum): Vibrates with sound waves.

  • Contains ossicles (smallest bones: hammer, anvil, stirrup).

• Inner Ear

  • Cochlea: Converts vibrations into neural signals.

  • Contains hair cells that transduce vibrations; higher frequencies detected at the start of cochlea.

• Semicircular Canals

  • Control balance, not directly related to hearing.

Sound Construction in the Brain

• Perception of sound is created in the brain, similar to color perception.

• Each sound generated is the brain’s interpretation of physical sound waves.

Smell and Taste: Chemical Senses

• Gustation (Taste)

  • Involves contact with chemicals through taste buds in papillae on the tongue.

  • Five basic tastes: sweet, salty, sour, bitter, umami.

• Olfaction (Smell)

  • Involves olfactory cilia that detect chemicals in the air.

  • Smell is linked to strong memories; particles interact with olfactory receptors in the brain.

Interaction Between Taste and Smell

• The sense of taste is highly influenced by smell.

• Loss of smell leads to a significant reduction in the ability to taste.

• Cultural and individual differences affect taste preferences.

Summary of Sensory Processing

• Sensory perceptions (vision, sound, taste, smell) are constructed by the brain, providing meaning and experience to stimuli.

• Each sense has evolved to enhance survival, influencing behaviors related to nutrition and danger.