PSY 86

• Visual Cues


  Depth, Form, Motion, Constancy

  
• Binocular Cues


  • Retinal disparity (eyes are 2.5 inches apart)
  • Convergence – things far away, eyes are relaxed. Things close to us, eyes contract
• Monocular Cues


  • Relative size
  • Interposition (overlap)
  • Relative height (things higher are farther away)
  • Shading and contour
  • Motion parallax (things farther away move slower)
• Constancy


  Our perception of object doesn't change even if it looks different on retina

  
• Types of constancy


  • Size constancy
  • Shape constancy
  • Color constancy
• Sensory Adaptation


  • Hearing - inner ear muscle: higher noise = contract
  • Touch - temperature receptors desensitized
  • Smell – desensitized to molecules
  • Proprioception – mice raised upside down would accommodate over time, and flip it over
  • Sight – down (ex. Light adaptation, pupils constrict, rods and cones become desensitized to light) and upregulation (dark adaptation, pupils dilate)

  
• Weber's Law


  The threshold at which you're able to notice a change in any sensation is the just noticeable difference (JND)
• 2 vs. 2.05 lb weight feel the same, 2 vs. 2.2 lb weight difference would be noticeable
• Delta I/I = k (Weber's Law)


  Delta I (JND) is proportional to the intensity of the stimulus (I)
• Absolute threshold of sensation

  The minimum intensity of stimulus needed to detect a particular stimulus 50% of the time
• Absolute threshold can be influenced by expectations, experience, motivation, and alertness
• Subliminal stimuli


  Stimuli below the absolute threshold
• Vestibular System


  • Responsible for balance and spatial orientation
  • Focuses on the inner ear, particularly the semicircular canals and otolithic organs

  
• Endolymph in the semicircular canals shifts to allow detection of head movement and rotation
• Otolithic organs detect linear acceleration and head positioning
• Signal Detection Theory


  Looks at how we make decisions under conditions of uncertainty, discerning between important stimuli and unimportant "noise"
• d'


  Strength of a signal, hit > miss (strong signal), miss < hit (weak signal)
• c


  Strategy, conservative (always say no unless 100% sure signal is present) or liberal (always say yes, even if get false alarms)
• The difference between means of the noise and signal distributions is d'
• C strategy

  Minimizes miss and false alarm, ideal observer when C = 0
• Beta

  Ratio of height of signal distribution to height of noise distribution, sets the threshold value
• Bottom-up processing

  Stimulus influences our perception, processing sensory information as it comes in
• Top-down processing


  Background knowledge influences perception, driven by cognition
• Gestalt Principles


  • Similarity
  • Pragnanz
  • Proximity
  • Continuity
  • Closure
• Structure of the Eye

  • Conjunctiva
  • Cornea
  • Anterior chamber
  • Pupil
  • Lens
  • Suspensory ligaments and ciliary muscle
  • Posterior chamber
  • Vitreous chamber
  • Retina
  • Macula
  • Fovea
  • Choroid
  • Sclera

  
• Phototransduction Cascade


  Process by which light is converted to neural impulses in rods and cones
• Steps in Phototransduction Cascade

  • Light hits retinal in rhodopsin
  • Rhodopsin changes shape
  • Transducin breaks from rhodopsin, alpha subunit binds phosphodiesterase
  • Phosphodiesterase converts cGMP to GMP
  • Decrease in cGMP causes Na+ channels to close
  • Rods hyperpolarize and turn off, glutamate no longer released
  • Bipolar cells turn on, retinal ganglion cells fire action potentials
• Photoreceptors (Rods and Cones)


  • Specialized nerves that convert light to neural impulses
  • Rods are more sensitive to light, cones detect color
• Rods are concentrated in the periphery, cones are concentrated in the fovea
• Visual Field Processing


  Right visual field goes to left side of brain, left visual field goes to right side of brain

  
• Feature Detection and Parallel Processing


  Simultaneous processing of different visual features like color, form, and motion
• Auditory Structure


  Requires pressurized sound waves and hair cells to convert sound to neural impulses

  
• Parts of the Auditory System

  • Pinna
  • External auditory meatus
  • Tympanic membrane
  • Malleus, incus, stapes
  • Oval window
  • Cochlea
  • Organ of Corti

  
• Basilar Tuning


  Different hair cells in the cochlea are activated by different sound frequencies, allowing the brain to distinguish them

  
• Cochlear Implants


  Surgical procedure to restore hearing in individuals with sensory neural hearing loss
• Types of Somatosensation


  • Temperature (thermoception)
  • Pressure (mechanoception)
  • Pain (nociception)
  • Position (proprioception)
• Sensory Adaptation


  Change over time in receptor response to a constant stimulus, downregulation
• Sensory Amplification


  Upregulation of receptor response
• Somatosensory Homunculus


  Map of the body in the sensory cortex of the brain

  
• Adaptation


  Change over time of receptor to a constant stimulus - downregulation