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Lecture Notes
Chapter 6

Perception: detection of more complex properties of a stimulus (including its location and nature); can involve learning

Not a clear boundary.

• Receptor cells (e.g., rods/cones, cilia, etc.) ... sensory neurons ... brain

• e.g., 1/40 weight, 1/60 light

• Magnitude of sensation with JNDs

Threshold Theory:

• JND = difference threshold
  • Minimum detectable difference
• Absolute threshold
  • Minimum detectable value
• 50 percent detection rate
• Neurons fire spontaneously and randomly

• "Signal to noise"
• Response bias: personal
• Receiver operating characteristics

• Part of the electromagnetic spectrum (EMS)

The Human Eye

• Optic nerve and retina part of the CNS
• Cross sectional view

Eyes of other mammals:

• Specialized for function

• Rods/cones ---> bipolar cells ---> ganglion cells ---> brain
• Compression of data

Photopigment and Adaptation

• Four kinds
  One for rods, three for cones
• Light splits photopigment (bleaching) ---> activates neural signal ---> receptor sends signal
• Requires energy to recombine parts of photopigment
• Dark adaptation
  • Rhodopsin requires time to recombine
• Fovea: high concentration of cones

Eye Movements

• Conjugate movements
  • Keeps eye on particular target
• Saccadic movements
  • Small, rapid shifts of gaze
• Pursuit movements
  • Tracking moving objects

Colour Vision

• Hue: determined by wavelength
• Brightness: determined by intensity
• Saturation: purity

• Light of all hues
• Completely desaturated

Colour Mixing

• Additive process
• Different from pigment mixing
  • A subtractive process
• Perception vs. reality

• Cones
• Three colour receptors
  • Blue (420 nm), green (530 nm), red (560 nm)
• Analyzes colours
  • White: stimulates all three receptors
  • Yellow: stimulates red and green

• Ganglion cells
  • Red/green and yellow/blue cells
• When not stimulated fire at a steady rate
• Shine red ---> red cones excited ---> increases red/green firing rate
• Shine green ---> excites green ---> suppresses red/green firing rate
• Yellow excites, blue suppresses yellow/blue ganglion cells

• Primarily in males
• Protanopia: lack of red cone photopigment
• Deuteranopia: lack of green cone photopigment
• Tritanopia: lack of blue cones

• Rhythmic pressure changes in air

• Human auditory range: 30-20,000 Hz

Human Ear

Basal membrane: sound detection apparatus

• Cilia

Basilar Membrane

• Pitch: different frequencies stimulate different cilia along membrane
  • High: base; medium: middle
  • Low: causes tip of basilar membrane to vibrate
    • Temporal coding
• Loudness
  • High/medium: alter firing rate; positive correlation
  • Low: number of cells firing
• Timbre: overtones, multiples of basic pitch
  • Causes different parts of basilar membrane to flex together

Flavour: taste and odour

Papillae: taste buds; contain receptor cells

• On roof of nasal sinuses, under base of brain

• First analysis of olfactory information
• "Lock and key"
• Straight into limbic system
  • Amygdala, limbic cortex or frontal lobe

• Different endings to dendrites
• Free nerve endings; surround hair folicles
• Pacinian corpuscle; vibrations

Pressure

• Only while being moved
• Two point discrimination threshold (a JND)

• Complex
• Sensation and emotional component
• Effective motivator
• Survival mechanism