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Behavioural  Science  –  Schizophrenia  
 
Schizophrenia:  a  brief  revision:  
Schizophrenia  is  a  highly  disabling   psychiatric  illness  affecting  1%   of  the   population;  centred  around  abnormal  
thinking,  behaviour  and  perception
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 Twin   studies   have   demonstrated   that   M/Z   twins   are  more   likely   develop   it   if  
one  already  has  it
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 MRI  scans  show  that  there  is  an  enlargement  in  
the  ventricles  and  a  reduction  in  cortical  mass;  widespread  cortical  atrophy
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g
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 Thus,  they  are  not  specific  to  the  illness  
but  reflect  genetic  or  environmental  vulnerability  
There  is  a  high  degree  of  inter-­‐subject  variability  (e
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 none  of  the  abnormalities  are  found  in  all  patients)  
The   results   of   different   studies   are   often   inconsistent   with   each   other   (e
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  more   vs   less   activation),   possibly  
because  of  the  disease  heterogeneity
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This  has  contributed  to  the  notion  that  the  core  neural  deficit  of  schizophrenia  lies  in  abnormal  anatomical  
and  functional  connectivity  amongst  different  regions  

Several  studies  report  that  patients  with  schizophrenia  who  experience  auditory  verbal  hallucinations  (AVH)  tend  to  
misidentify  their  own  speech  as  that  of  someone  else
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  Using   functional  
magnetic   resonance   imaging,   we   measured   brain   responses   from   11   schizophrenics   with   AVH,   and   10   healthy  
controls
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  Participants   had   to   indicate   whether   each   word   was   spoken   in   their   own   or   another  
person’s   voice   via   a   button   press
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  In   controls   and   in   patients  
without  AVH,  the  connectivity  between  left  superior  temporal  and  anterior  cingulate  cortex  was  significantly  greater  
for   alien   than   self-­‐generated   speech;   in   contrast,  the   reverse   trend   was   found   in   schizophrenic   patients   with   AVH
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  Although   this   finding   is   based   on   external   rather   than   internal  
speech,  the  same  mechanism  may  contribute  to  the  faulty  appraisal  of  inner  speech  that  putatively  underlies  AVH  
 
 
 
 
 
 
 
 
 
 
 
 
 
 

The  Dys-­‐connectivity  hypothesis  –  Zhou  et  al
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 Specifically,  the  
 lateral  PFC  is  critical  for  the  selection,  monitoring,  and  manipulation  of  cognitive  task  sets;  the  medial  PFC  is  critical  for  
updating  these  sets;  and  the  orbitofrontal  cortex  (OFC)  is  critical  for  assigning  social  and  emotional  meaning  to  these  
 sets  in  order  to  better  guide  goal-­‐directed  behaviour
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 The  major  
 findings  in  schizophrenia  include:  spine  loss  and  dendritic  atrophy  of  PFC  neurons;  smaller  PFC  grey  matter  volume;  
profound  dysfunction  of  the  PFC  (including  deficits  in  working  memory);  and  changes  in  gene  expression
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 Diffusion  tensor  imaging  (DTI),  a  new  and  powerful  tool,  
 
affords  the  possibility  to  explore  the  anatomical  connectivity  in  the  human  brain  in  vivo
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Fractional  anisotropy  (FA)  is  the  most  commonly  used  DTI  index  to  examine  white  matter  integrity
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 The  region  in  the  left  frontal  deep  white  matter  is  traversed  by  tracts  
interconnecting  the  frontal  lobe,  thalamus,  and  cingulate  gyrus
...
 Similar  findings  
 were  obtained  when  analysing  studies  on  patients  with  first-­‐episode  schizophrenia,  in  whom  reduced  FA  in  the  white  
matter  of  the  right  deep  frontal  and  left  d eep  temporal  lobes  was  found
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 All  of  these  findings  provide  evidence  for  
 
disrupted  anatomical  connections  in  the  front  limbic  circuitry,  even  at  the  early  stages  of  schizophrenia
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 A  study  
carried   out   by   Mechelli   et   al   (2008)   found   that   individuals   with   the   high-­‐risk   allele   of   NRG1   show   less  
activation  of  the  precuneus  than  those  without  it  
Dysbindin  (DTNBP1):  Neurotropic  factor  involved  in  neural  development  and  glutamatergic  function  
DISC1:   Associated   with   schizophrenia   but   mechanistic   action   unknown   (role   in   cortical   development)
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e
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7%   and  
4
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 2006)  

Parental  separation,  loss  and  psychosis  in  different  ethnic  groups  (Morgan  et  al  2006)  
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African   Caribbean   and   black   African   populations   living   in   England   suffer   from   remarkably   high   rates   of  
schizophrenia  
For  example  schizophrenia  is  9X  more  common  in  African  Caribbean’s  and  6  times  more  common  in  black  
Africans  than  in  white  British    
Separation   from   one   or   both   parents   for   more   than   one   year   before   the   age   of   16,   as   a   consequence   of  
family  breakdown,  is  associated  with  a  2
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g
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 Increased  risk  of  viral  infections?  
But  this  finding  is  not  specific  to  schizophrenia
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