[VERSION 2] COMPLETE Perception and Behavior Notes: Part 1 -- 4.0ed this course!

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Psychological & Brain Sciences
CAS PS 222
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Exam  I  Study  Guide     Chapter  1-­‐  Introduction  to  Perception     The  Perceptual  Process       • Stimulus  on  the  receptors-­‐  representation  of  the  object  formed  as  an  image  on  the   retina.     • Transduction-­‐  transformation  of  one  form  of  energy  to  another.   o Light,  mechanical  or  chemical  in  the  environment  to  electrical  in  brain.   • Transmission-­‐  signals  reach  the  brain.   • Processing-­‐  communication  within  the  brain.   • Perception-­‐  conscious  sensory  experience.   o Brain  processing  allows  for  the  experience  of  sensing  the  object.     • Knowledge  of  previous  sensory  experiences   o Bottom-­‐up  processing:  processing  based  on  incoming  data.     o Top-­‐down  processing:  processing  based  on  previous  knowledge.   o Bottom-­‐up  starts,  top-­‐down  follows  and  both  work  in  unison  to  create   perceptual  experience.     Approaches  to  the  Study  of  Perception   • Physiological  Approach-­‐  relationship  between  physical  stimuli  and  the  generated   perceptual  experiences.     • Physiological  Approach-­‐  stimulusà  processing  of  stimulusà  perception  of  stimulus.     • Cognitive  Approach-­‐  effects  on  perception  by  knowledge,  memories  and   expectations.     Measuring  Perception   • Descriptive-­‐  phenomenological  approach -­‐  describing  what  we  perceive.   • Recognition-­‐  recognize  and  categorize  a  stimulus.   o Visual  agnosia  patients  can’t  do  this.   • Detection-­‐  quantitatively  measuring  relationship  between  stimulus  and  perception.   o Absolute  Threshold-­‐  smallest  amount  of  stimulus  energy  needed  to  detect   it.     Limits   Adjustment   Constant  Stimuli   Stimuli  presented  in   Stimuli  adjusted  until  subject   Stimuli  of  different   ascending  or  descending   can  barely  detect  it.     intensities  presented  in   order  until  crossover  point.   random  order.  Threshold  is   defined  as  intensity  felt   during  50%  of  the  trials.     o Difference  Threshold -­‐  smallest  difference  between  two  stimuli  a  person  can   detect.     • Magnitude  Estimation-­‐  relationship  between  intensity  and  perceived  magnitude.     o Steven’s  Power  Law-­‐  relationship  between  the  physical  intensity  of  a   stimulus  and  the  perception  of  the  subjective  magnitude  of  the  stimulus.   • Visual  Search     Chapter  2-­‐  Introduction  to  the  Physiology  of  Perception     The  Brain   • Cerebral  cortex-­‐  machinery  of  perception à  higher  order  functioning.   • Modular  organization -­‐  specific  functions  for  specific  areas     Neurons   Communicate  within  cells:  electrically   Communication  between  cells:  chemically   (neurotransmitters)   Recording  from  a  neuron   • Recording  neuron-­‐  records  passing  of   action  potential.   • Reference  neuron-­‐  outside  of  axon   • Difference  in  voltage  at  rest:   -­‐70  mV.   • Action  potential  difference:  +40  mV.                   • Action  Potential-­‐  electrical  impulse  passing  through  the  axon  and  causing  release  of   chemicals  from  the  terminal  buttons.     Properties  of  APs   • Propagated  Response-­‐   travel  all  the  way  down   without  decreasing  in  size.   • Intensity  doesn’t  affect   size.   • Intensity  affects  rate  of   fire.   • Number  of  impulses   depends  on  refractory   period.     • All-­‐or-­‐none  law:  happens   or  it  doesn’t  happen.   • Saltatory   • Excitatory  neurotransmitters  cause  depolarization  (become  positive).   o If  enough  excitatory  transmitters  released,  then  there  is  an  action  potential.   • Inhibitory  neurotransmitters  cause  hyperpolarization  (become  negative).     o Inhibits  reaching  the  action  potential  threshold.     • When  both  received  by  the  neuron,  the  neuron  combines  them  in  different   intensities.     • Lock  and  Key  Model-­‐  if  it  fits  then  it  has  an  effect.   • Terminating  neurotransmission:  reuptake,  destruction  by  an  enzyme  or   autoreceptors.     • Agonist  drug-­‐  enhances  actions  of  a  neurotransmitter.   • Antagonist  drug-­‐  inhibits  actions  of  a  neurotransmitter.                   Chapter  3-­‐  Introduction  to  Vision     • Visible  light:  400-­‐700  nm,  which  is  all  reflected  from  objects.       • Normal  vision  results  from  light  coming  in  parallel  from  20  feet  away.     • Moving  object  closer  pushes  the  focus  point  back  and  makes  the  lens  flatter.   • Moving  object  further  accommodates  the  eye  (making  lens  fatter)  and  brings  the       focus  point  back  forward.       Myopia-­‐  cornea  or  lens  bends  too  much  light   or  eyeball  is  too  long.     Hyperopia-­‐  eyeball  is  too  short   Cornea  accounts  for  80%  of  focusing,  while   lens  accounts  for  the  other  20%.                       Retinal  Receptors   Rods   Cones   Located  in  peripheral  area  of  retina   Located  mostly  in  fovea   120  million   5  million   Large  and  cylindrical   Small  and  tapered   Responsible  for  black  and  white  vision   Responsible  for  color  vision   Vision  at  low  light  levels   Vision  at  high  light  levels   Low  spatial  acuity   High  spatial  acuity   Achromatic-­‐  absorb  best  at  500  nm   Tri-­‐chromatic-­‐  absorb  best  at  short,  medium   More  photopigment   and  long  wavelengths.     High  convergence   Less  photopigment   High  amplification   Low  convergence   Less  light  to  respond   Low  amplification   More  light  to  respond     • Blind  spot-­‐  area  on  retina  where  there  are  no  receptors .     o Optic  nerve  leaving  the  eye.   o One  eye  covers  the  blind  spot  of  the  other.   o Located  at  edge  of  visual  field.     o The  brain  fills  in  that  spot.       • Disks  contain  rhodopsin -­‐  a  visual  pigment                                                                                                             molecule.  They  have  two  components:   o Opsin-­‐  large  protein  that  loops  back   and  forth  across  the  disk  membrane.     o Retinal-­‐  light  sensitive  molecule  that   has  one  in  each  rhodopsin.                         Transduction  of  Light  into  Nerve  Impulses   • Retinal  absorbs  one  photon  of  light.   • Isomerization-­‐  retinal  changes  shape.   • Visual  pigment  bleaching -­‐  retinal  separates  from  opsin  molecule  and  retina  lightens.     • Enzyme  cascade  is  triggered.   Proof  of  Transduction:  Hec ht’s  Psychophysical  Experiment   • Objective:  how  many  visual  pigments  need  to  be  isomerized  for  a  person  to  be  able   to  see.     • Method  of  constant  stimuli  where  a  subject’s  absolute  threshold  for  seeing  a  brief   flash  of  light  is  measured.     • Results   o Person  can  detect  100  photons   o Half  of  those  bounce  off  the  cornea  or  are  absorbed  by  the  lens.     o Only  7/50  photons  reaching  the  back  of  the  retina  are  absorbed  by  the   retinal.  43  photons  hit  the  opsin.     o Only  1  visual  pigment  molecule  per  receptor  was  needed  for  isomeriza tion.   Dark  Adaptation   • Sensitivity  to  light  increases  because  of  regeneration  of  rod  and  cone  visual   pigments.     • Measuring  dark  adaptation   o Subject  is  adapted  to  light.   o Light  is  turned  off.   o Subject  turns  a  knob  to  adjust  intensity  of  test  light  so  that  it  can  barely  be   seen.     o When  vision  shifts  from  cones  to  rods  we  become  sensitive  to  short -­‐wave-­‐ length  light.     § Enhanced  perception  to  blue  and  green  end  of  spectrum.           • Dark  adaptation  curve -­‐  as  dark  adaptation  proceeds  the  subject  becomes  more   sensitive  to  the  light.       • Measuring  cone  adaptation -­‐  in  dark  the  subject  looks  directly  at  test  light  so  the   image  falls  on  the  all-­‐cone  fovea.     • Measuring  rod  adaptation -­‐  on  people  who  have  no  cones à  once  light  is  turned  off   the  rods  increase  their  sensitivity  and  reach   their  adapted  level  in  25  minutes.     • Process  of  dark  adaptation   o Once  light  is  turned  off,  both  rods  and  cones  increase  in  sensitivity.   o Cones  adapt  in  3  to  5  minutes,  determining  early  part  of  the  curve.     o Rods  catch  up  to  cones  at  about  7  minutes  and  then  be come  even  more   sensitive.     o Once  rods  become  more  sensitive,  they  start  controlling  the  person’s  vision.   Visual  Pigment  Regeneration   • In  normal  light  levels  there  is  a  certain  balance  of  intact  and  bleached  visual   pigments.     • When  light  is  turned  off  there  wo uld  be  no  more  isomerization,  and  only  intact   visual  pigment  molecules.     • As  retinal  recombines  with  opsin,  the  color  comes  back  to  the  retina.     • Cones  take  6  minutes  to  regenerate,  while  rods  take  30  minutes.   Convergence  in  the  Retina -­‐  done  by  five  cells  in  the  retinal  layer   • Rods  and  cones,  bipolar  cells  and  ganglion  cells  send  signals  vertically.   • Horizontal  cells  send  signals  between  receptors.   • Amacrine  cells  send  signals  between  bipolar  and  ganglion  cells.                       • Different  convergence  patterns   o 120  rods  to  1  ganglion   o 6  cones  to  1  ganglion   o 1  foveal  cone  to  1  ganglion   Lateral  Inhibition  (inhibition  that  is  transmitted  across  the  retina)  and  Lightness   Perception  (perception  of  shades  from  white  to  gray  
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