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HMB200 2014 Lecture 24.pdf

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Human Biology
Course Code
John Yeomans

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  Lecture  24:  Classical  Conditioning:  From  Reflex  to  Consciousness   Pavlov  and  Search  for  Engram   • Hippocampus  is  important  in  some  aspects  of  Pavlovian  conditioning   • Visceral  reflexes:  Salivation  and  gastric  acid.   • Unstable  à  can  be  altered  à  animals  can  change  responses  with  pairing  of  CS  and  US   • Events  can  change  visceral  relaxes  and  Pavlov  condition  reflexes   • Conditioned  Reflex:  Tone  (CS)  plus  food  (US)   • Laws  of  conditioning:  CS-­‐US  pairing,  extinction,  recovery,  generalization,  etc.   • Conditioning  in  cortex?  Higher  human  functions ?   • Pavlov  speculated  classical  condition  occurred  in  the  cortex  à  proposed  humans  learn  in  the  cortex   • Thought  higher  human  functions  were  due  to  classical  conditioning  in  the  cortex   • Search  for  engram:  Lesions  of  cortex  don’t  block  learning  of  mazes  or  conditioning  (Lashley).   • Conditioning  is  not  blocked  when  u  remove  the  cortex  (Lashley)   • 40  years  of  failure   • Discovered  later  that  its  learnt  in  hippocampus,  not  cortex   • Whole  brain  is  active,  but  in  Pavlovian  conditioning,  changes  of  activity  occurs  in  hippocampus,  cerebellum,  and   amygdala   • Correlates  of  learning:  Whole  cortex  active  initially.     Eyeblink  Conditioning   - Easy  to  measure  in  rodents  and  humans.   - Slow  acquisition  and  extinction.   - Unconditioned  reflex  (US -­‐shock  and  UR)  in  brain  stem   (two  synapses).   - Aversive  stimuli  to  the  eye  leads  to  eye -­‐blink  à  eye  blink   conditioning  is  acquired  by  pairing  tones  and  puffs  =   unconditioned  reflex,  but  can  produce  classical   conditioning  by  pairing  a  tone  (CS)  with  a  shock     - Tone  (paired)  with  the  shock,  can  then  produce   the  eye  blink  response     - After  repeated  trials,  CS  alone  (with  shock)  can   result  in  the  eye  blink  response  =  conditioned   response   - Activity  in  hippocampus  and  cerebellum  correlates  with   acquisition  of  delay  conditioning.   - Hippocampus  not  critical;  ipsilateral  cerebellum  is.   - Pathway:  brainstem  pathway   - touch:  mediated  by  the  trigeminal  nucleus   - response:  mediated  by  the  eyeblink  (occurs  in  2   cranial  nerves:  facial  and  abducens)   - Areas  activated  with  conditioning:  Ventral  Straitum,  Inferior  thalamus/red  nucleus,  anterior  cerebellar  vernis   - There  is  a  pathway  in  the  brain  stem  for  eye  blink   - Pathway  in  cerebellum  for  the  learning   - Isilateral  to  trained  eye:  left  cerebellar  cortex.  Anterior  cerebellar  vernis   - Cerebellum  has  ipsilateral  control  =  left  eye  activates  left  cerebellum   - Left  cerebellum  is  important  for  sim ple  eyelid  conditioning  (delayed  conditioning)   - Contralateral  to  trained  eye:  right  middle  temporal  gyrus,  right  hippocampal  formation   - Activity  in  right  hippocampus   à  important  for  learning  of  trace  conditioning   - Activity  in  humans  is  found  in  the  contralate ral  hippocampus  and  the  ipsilateral  cerebellum   - Activity  correlates  with  conditioning   à  better  conditioning,  the  more  acitivity  in  cerebellum  and   hippocampus     - Cerebellum  is  critical  (removal  of  hippocampus  still  results  in  conditioning)   - Conditioning  with  the  bell  is  not  in  brain  stem  pathway,  its  in  the  cerebellum   à  remove  cerebellum  =  no  Pavlovian   conditioning   - Tone/bell  +  air  puff  =  eye  blind   à  conditioned  reflex   - Conditioned  circuit  involves  the  cerebellar  pathway     Delay  Conditioning       - involves  a  long  tone  with  a    shock  at  the  end  of  the  tone   - shock  occurs  maybe  2second  later   - activity  in  cerebellum  proceeds  and  predicts  the  response  à  necessary  and  sufficient  for  the  response   - activity  of  cerebellum  occurs  befo re  the  response,  right  before  the  reflex   - lesion  of  this  area:  no  response,  no  conditioning   - eyeblink  reflex  is  dependent  on  cerebellar  neuronal  activity   responsible  for  change  in  response  in  trained  brain     Cerebellar  Cortex   • output  neurons:  giant  purkinjie  cell  à  goes  down  to  deep   nuclei  to  inhibit  deep  nuclei  à  produces  a  response  in  the   red  nucleus  and  motor  nerve   • pathway  involves  2  stimuli:  ton(cs)  and  shock  (us)   – shock  (us)  comes  in  by  way  of  red  mossy  fibers  
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