Psych 6

• Sensation


  Stimulation of the sense organs by physical stimuli from the environment
• Perception


  Subjective selection, organization, and interpretation of sensory input

  
• Transduction


  The process where sensations are translated to electrochemical transmission
• Even if stimulus intensity changes linearly, our perception of that change is not linear

  
• Fechner's law


  Subjective sensation is proportional to the logarithm of the stimulus intensity
• With constant increases in stimulus intensity, smaller and smaller increases are perceived in the magnitude of that sensation
• Signal-detection theory


  Detection of stimuli involves decision processes as well as sensory processes

  
• Signal-detection theory outcomes


  • Hit
  • Correct Rejection
  • Miss
  • False Alarm
• Sensory receptors


  Specialized cells that transduce specific types of sensory energy into neural activity

  
• Receptive field


  Area in which a stimulus modifies a receptor's activity
• Unequal distribution of receptors allows for increased sensitivity in important areas
• Higher density of receptors gives better resolution
• Sensory pathways

  • Sensory information modified at various stages in the neural relay (pathway)
  • Allows interactions between systems

  
• Sensory coding


  Sensory information encoded by action potentials traveling along peripheral nerves to the central nervous system

  
• Presence and intensity of a stimulus can be encoded by an increase or a decrease in firing rate

  
• Topographic map

  Neural–spatial representation of the body or the areas of the sensory world perceived by a sensory organ

  
• Retinotopic map


  Neural map of what is detected at the retina projected on the cortex

  
• Points close together on an object and on the retina will activate neurons close together in the brain

  
• Cortical magnification


  Small area of fovea is represented by large area on visual cortex

  
• Light


  Form of electromagnetic radiation that travels as a wave

  
• Properties of light


  • Amplitude (perception of brightness)
  • Wavelength (perception of colour)
  • Purity (mix of wavelengths; perception of saturation)
• Structures of the eye

  • Cornea
  • Iris
  • Pupil
  • Lens
  • Retina

  
• Retina


  Light-sensitive surface at the back of the eye that consists of neurons and photoreceptor cells

  
• Fovea


  Region at the center of the retina that is specialized for high acuity

  
• Myopia


  Nearsightedness; inability to see distant objects clearly

  
• Hyperopia


  Farsightedness; inability to see nearby objects clearly

  
• Blindspot


  Region of the retina (optic disc) where axons forming the optic nerve leave the eye and where blood vessels enter and leave

  
• Photoreceptors


  • Cones
  • Rods
• Cone pigments


  Three types that absorb light over a range of frequencies, with maximal absorptions at 419 nm (blue), 531 nm (green), and 559 nm (red)
• Types of retinal neurons

  • Bipolar cell
  • Horizontal cell
  • Amacrine cell
  • Ganglion cells
• Types of ganglion cells

  • Magnocellular cell (M-cell)
  • Parvocellular cell (P-cell)
• Optic chiasm


  Junction of the optic nerves from each eye where axons from the nasal half of each retina cross over to the opposite side of the brain

  
• Visual pathways


  • Geniculostriate system
  • Tectopulvinar system
  • Retinohypothalamic tract

  
• Lateral geniculate nucleus (LGN)


  Receives signals predictably from the right and left halves of each retina

  
• Occipital cortex input


  • Primary visual cortex (V1)
  • Secondary visual cortex (V2-V5)

  
• Occipital cortex processing


  • Information segregated into categories of colour, form, and motion in V1
  • Information from V1 flows to the thick, thin, and pale zones of V2

  
• Fusiform face area (FFA)


  Located in the fusiform gyrus, identified as specialized for processing faces
• Interblobs


  Spaces between the blobs
• All categories kept separate as they move from V1 to nearby V2
• Occipital Cortex Processing in V2

  • Thick stripes: Receive information from movement-sensitive neurons
  • Thin stripes: Receive information from color-sensitive neurons
  • Pale zones: Receive information from form-sensitive neurons