sensation

• Absolute threshold

  The lowest level of a stimulus we can detect 50% of the time
• Just noticeable difference

  The smallest amount of stimulus change we can detect
• Cocktail party effect: Not all information is filtered out
• Principles of Sensation

  1. External stimulus is converted by a sensory neuron into neural activity via transduction

  2. Activation is highest when stimulus is first detected, then sensory adaptation occurs
• Weber's law

  The stronger the stimulus, the greater the change necessary for the detection of a difference
• Explains why hands-free cellphone conversations hurt driving performance just as much as hands-held cellphone conversations
• Reasons for needing glasses: Nearsightedness (myopia) and Farsightedness (hyperopia)
• We have many more rods than cones (20:1)
• Visual illusions provide the perfect examples of the difference between sensation and perception
• Selective attention

  1. Brings whatever you are focused on into awareness

  2. Blocks out competing/ignored information
• Seemingly salient, unusual events do not automatically capture our attention
• Perception of an object

  • Brightness (intensity): How much light is reflected off the object (and reaches our eyes)
  • Hue (color): Overall lighting of the surrounding objects
• Objects can be in the spatial extent of attentional focus and still not be “seen”
• Selective attention allows us to choose which sensory inputs to focus on and which to "turn down"
• Fovea: Very high resolution (only cones)
• Perception

  Our conscious awareness of the information in the environment
• When light reaches an object, part of the waves get absorbed by the object, with the other part reflected off the object
• Blind spot: visual nerve cells leave the eyeball to go to the primary visual cortex
• Sensation

  How the information in the world is received by our sensory system
• Psychophysics

  Study of how we perceive sensory stimuli based on their physical characteristics
• Losing $5 today vs. $5 when you were 10 years old
• Inattentional blindness: Failure to notice unexpected objects that enter our direct view
• Lens helps bring objects into focus (accommodation)
• Visual system: Light - The human visible spectrum is a narrow band of light that we respond to
• Visual Pathway

  1. “Where” pathway: visual form, position, and motion

  2. “What” pathway: object and visual identification and recognition
• Fovea

  Area with very high resolution, containing only cones
• Fusiform Face Area (FFA)
• Visual nerve cells (optic nerve) leave the eyeball to go to the primary visual cortex
• Cones and Rods

  • Cones: High resolution, color vision
  • Rods: Low light vision
• Two different classes of cells: color and brightness
• No photoreceptors in blind spot area
• Blind Spot

  1. Area where optic nerve leaves the retina

  2. No photoreceptors

  3. Demonstrates brain's ability to "fill-in" missing information
• Our sense of hearing is called Audition
• Most prosopagnosics’ recognition deficits are not limited to faces
• Each cell encodes two complementary color perceptions
• Wear and tear of hair cells leads to their death as they do not regenerate
• Humans hear molecule vibration between 20 and 20,000 hertz
• Place theory: Different tones excite different areas of the basilar membrane and primary auditory cortex
• Proprioception is our kinesthetic sense, helping us keep track of where our body parts are
• Taste receptors regenerate