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Consciousness during sleep and the effect on the appearance of dreaming Bachelor thesis Nathasja Hartog Supervisor: Prof. Dr. D.G.M. Beersma Head of the Department of Chronobiology Director of the Center for Behavior and Neurosciences University of Groningen

Consciousnessduringsleepand) theeffectontheappearanceof) dreaming)fse.studenttheses.ub.rug.nl/10302/1/Bachelor_thesis... · 2018. 2. 15. · ! 4! Introduction! Sleep!and!dreaming!have!always!aroused!our!curiosity!and!theories!as!to!their!

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Page 1: Consciousnessduringsleepand) theeffectontheappearanceof) dreaming)fse.studenttheses.ub.rug.nl/10302/1/Bachelor_thesis... · 2018. 2. 15. · ! 4! Introduction! Sleep!and!dreaming!have!always!aroused!our!curiosity!and!theories!as!to!their!

   

   

Consciousness  during  sleep  and  the  effect  on  the  appearance  of  

dreaming    

Bachelor  thesis  

 

 

Nathasja  Hartog  

 

Supervisor:  Prof.  Dr.  D.G.M.  Beersma  

Head  of  the  Department  of  Chronobiology  

Director  of  the  Center  for  Behavior  and  Neurosciences  

University  of  Groningen  

 

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Abstract    This  study  focuses  on  sleep  and  consciousness  during  sleep  to  see  what  the  effect  of  consciousness  is  on  the  appearance  of  dreams  and  lucid  dreams.  Dreams  seem  to  be  experienced  the  most  during  REM  sleep,  but  they  also  appear  during  non-­‐REM   sleep.   Thanks   to   neuroimaging,   the   activation   and   deactivation   of   brain  areas   during   REM   sleep   has   been   made   visible.   The   (de)activation   of   certain  areas  might  give  a  possible  explanation  of  some  of  the  features  of  dreams,  such  as  emotionality,  lack  of  control  and  visual  elements.  Consciousness  during  sleep  is  an  interesting  factor,  that  also  can  be  related  to  (de)activation  of  certain  brain  areas.   Lucid   dreaming   is   an   interesting   example   of   the   coherence   of  consciousness  and  dreaming.      Keywords:  Sleep,  consciousness,  REM,  non-­‐REM,  dreaming,  lucid  dreaming,  neuroimaging

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Table  of  Contents  Abstract  .................................................................................................................................  2  

Introduction  ........................................................................................................................  4  

Sleep  .......................................................................................................................................  4  Non-­‐REM  sleep  .............................................................................................................................  5  REM  sleep  ......................................................................................................................................  5  Consciousness  during  sleep  ....................................................................................................  6  

Dreaming  ..............................................................................................................................  7  History  of  dream  research  .......................................................................................................  8  Dream  recall  .................................................................................................................................  9  Neuroimaging  of  REM  sleep  .................................................................................................  10  Neuroimaging  of  non-­‐REM  sleep  ........................................................................................  11  

Lucid  Dreaming  ...............................................................................................................  12  

Conclusion/Discussion  .................................................................................................  13  References  .........................................................................................................................  15    

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Introduction  Sleep  and  dreaming  have  always  aroused  our  curiosity  and  theories  as   to   their  cause  and  function  have  been  described  since  the  beginning  of  recorded  history.  In   general   people   don’t   remember   what   they   dreamt   of   and   this   might   be  important   for   sleep’s   functions.   There   are,   however,   people   that   do   remember  what  they  were  busy  with  during  their  sleep.  In  general  this  isn’t  a  problem,  but  sometimes  it  can  be  a  cause  of  sleeping  problems.  This  might  be  good  reasons  to  investigate  the  relation  between  consciousness  and  sleep  more  thorough.    Within  this  thesis  sleep  and  its  components  will  be  discussed  together  with  the  component  of  consciousness  during  sleep.  Dreaming  is  an  interesting  component  of  sleep  and  within  this  review  it  will  be  discussed  together  with  the  history  of  dream  research,  the  possibility  to  recalling  dreams  and  the  neuroimaging  of  REM  and  non-­‐REM  sleep.  The  phenomenon  of  lucid  dreaming  will  also  be  discussed.  All  of  these  components  form  an  interesting  topic  to  look  at,  in  my  opinion.    I   think   that   sleep   research   can   give   interesting   points   of   view   regarding   the  appearance  of  dreaming;  not  only  when  looking  at  the  activation  of  brain  areas,  but  also  when  analyzing  dream  reports.  The  standard  features  of  dreaming  (the  components   a   dream   standard   consists   of)   are,   as   found,   equal   for   everyone;   I  think   that’s   an   interesting   point   to   look   at.   These   features,   however,   aren’t  researched  much  until  now.  

Sleep  Sleep  is  a  behavior  that  is  displayed  every  day  for  a  considerable  amount  of  time.  Apparently  sleep  is  important  for  us;  but  why  is  so  little  understood.    Phenomenologically,   sleep   can   be   described   as   a   readily   reversible   state   of  reduced   responsiveness   to,   and  interaction   with,   the   environment  (Bear  et  al.  2007,  Dang-­‐Vu  et  al.  2010,  Czisch   et   al.   2004).   It   is   known   that  sleep  consist  of  two  stages:  Rapid  Eye  Movement  sleep  (REM  sleep)  and  non-­‐REM   sleep.   Non-­‐REM   sleep   is   further  classified  into  stages  1  (N1),  2  (N2),  3  (N3)   and   4   (N3)   according   to   the  degree  of  EEG  slowing  (Rechtschaffen  et   al.   1968).   These   differences   are  shown   in   figure   1.   In   the   figure   EEGs  during  waking,  during  REM  sleep  and  during   the   different   phases   of   non-­‐REM   sleep   are   shown.   When   looking  at   sleep,   the   time  spent   in  a   state  can  also   be   quantified:   it   is   known   that  roughly   75%   of   total   sleep   time   is  spent   in   non-­‐REM   and   25%   in   REM.  The   periodic   cycles   which   are   executed   during   the   night   last   for   about   90  minutes  (Bear  et  al.  2007,  Kajimura  et  al.  1999,  Hobson  2009).    

Figure  1:  EEG  rhythms  during  sleep  (Bear  et  al.  2007)  

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The  periodic  cycles  thus  consist  of  two  states:  non-­‐REM  sleep  and  REM  sleep.  In  the   following   part   of   this   thesis   both   non-­‐REM   sleep   and   REM   sleep   will   be  further   defined   and   there   will   also   be   looked   at   the   phenomenon   of  consciousness  during  sleep.    

Non-­‐REM  sleep  Non-­‐REM   sleep   seems   to   be   the   period   of   sleep   for   rest.   Muscle   tension  throughout  the  body  is  reduced  and  movement  is  minimal,  but  during  non-­‐REM  sleep  muscles   are  not  paralyzed   (Bear  et  al.   2007,  Hobson  et  al.  2000).  During  non-­‐REM  sleep  consciousness  is  most  likely  to  fade  (Nir  et  al.  2010).  Non-­‐REM  sleep  consists  of  compromising  stages  stage  1  (N1),  stage  2  (N2),  stage  3  and  4  (N3)  (slow  wave  or  delta  sleep).    Stage  N1   is   characterized   as   the   stage   of   sleep  where   the   EEG   is   intermediate  between   wake   and   deep   sleep,   with   presence   of   theta   activity   (4-­‐7   Hz),  occasional  vertex  sharp  EEG  waves  and  slow  eye  movements  (figure  1).      Stage  N2  sleep  occurs  throughout  the  night,  where  the  EEG  can  contain  spindles,  K-­‐complexes  and  occasional  slow  waves  (figure  1).  K-­‐complexes  represent  slow  biphasic  waves  of  high  voltage  (Czisch  et  al.  2004).    Stage  N3  occurs  mostly  early  at   the  night   (Dang-­‐Vu  et  al.  2010,  Nir  et  al.  2010,  Bear  et  al.  2007)  and  it   is  characterized  by  spindles  and  slow  high-­‐voltage,  EEG  waves   hence   the   name   (Slow   Wave   Sleep)   due   to   synchronized   activity   of  neurons   (figure   1)   (Hobson   et  al.  2000,   Nir   et  al.   2010,   Hobson   2009,  Maquet  2000).    Slow  waves  (Delta  waves)  are  oscillations  of  cortical  origin  that  have  frequencies  below  4  Hz;  spindles  are  waxing  and  waning  oscillations  of  thalamic  origin  that  have   frequencies   around   12-­‐15   Hz   (figure   1)   (Nir   et   al.   2010,   Dang-­‐Vu   et   al.  2010,  Czisch  et  al.  2004).      

REM  sleep      REM   sleep   has   been   discovered   in   1953   (Aserinsky   et   al.   1953)   and   it   is   also  known  as  ‘paradoxical’  sleep,  ‘active’  sleep  or  ‘desynchronized’  sleep  (Hobson  et  al.  2000).    Contrary  to  non-­‐REM  sleep,  REM  sleep  is  considered  as  a  state  of  high  cerebral  and   low  physical  activation   that  would  provide  a  neurophysiological  marker  of  dreaming   (Desseilles   et   al.   2011,   Maquet   2000,   Hobson   2009,   Hobson   et   al.  2000)   and   REM   sleep  is   also   related   to   the  homeostatic  control  of  body   temperature,  including   the  temperature   of   the  brain   (Hobson   et   al.  2012).    REM   sleep   occurs  mostly   late   at   night  and  it  seems  to  consist  of   an   active,  hallucinating   brain   in   Figure  2:  REM  sleep  development.  (Hobson  2009)  

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a   paralyzed   body,   which   is   characterized   by   movement   of   the   eyes,   fast   low-­‐voltage  EEG  and   low  muscle   tone;   this   evoked  activity  propagates  much   like   it  does  during  wakefulness  (Nir  et  al.  2010,  Hobson  2009).  REM   sleep  might   act   as   a   general   “virtual   rehearsal  mechanism”,  which  would  play  an   important   function   in   the  early  brain  development,   congruent  with   the  prominent   presence   of   REM   sleep   in   newborn   babies   and   infants   (figure   2)  (Desseilles  et  al.  2011,  Hobson  2009).      Both   in   animals   and   humans,   REM   sleep   is   believed   to   be   generated   by  cholinergic   processes   arising   from   brainstem   structures   that   mediate   some  widespread   cortical   activation   via   a   ventral   pathway   innervating   the   basal  forebrain  and  a  dorsal  pathway   innervating   the   thalamus   (Steriade  et  al.  2005,  Maquet  2000).    REM  sleep  has  been  studied  because   it   is   the  stage  during  which   intense  visual  dream  activity   is  most  prevalent   (Braun  et  al.   1998,  Hobson  2009).  REM  sleep  may   present   a   state   in   which   the   brain   engineers   selective   activation   of   an  interoceptive   network,   which   is   dissociated   from   primary   sensory   and  heteromodal  association  areas  at  either  end  of  the  visual  hierarchy  that  mediate  interactions  with  the  external  world  (Braun  et  al.  1998).      

Consciousness  during  sleep  Since   primary   sensory   areas   are   connected   to   consciousness   and   REM   sleep  shows   a   dissociation   of   primary   sensory   areas,   how   can   consciousness   during  sleep   be   defined?   To   start   there   are   two   types   of   consciousness:   primary  consciousness  and  secondary  consciousness.    Primary   consciousness   can   be   defined   as   simple   awareness   that   includes  perception  and  emotion,  where  perception  is  defined  as  detailed  visuomotor  and  other  sense  modality  information  that  constitutes  the  representational  structure  of   awareness.   Such   awareness  must   involve   the   interaction   and   integration   of  emotion  (Hobson  2009,  Hobson  et  al.  2012).    Secondary   consciousness   depends   on   language   and   includes   such   features   as  self-­‐reflective  awareness,  abstract  thinking,  volition  and  metacognition  (Hobson  2009,  Hobson  et  al.  2012).    An   interesting  point  of  view  might  be   that  homeothermy  may  be  necessary   for  normal   consciousness;   even   small   variations   of   brain   temperature   are  devastating  to  consciousness  (Hobson  et  al.  2012).  The   level   and   nature   of   a   person’s   conscious   experience   varies   dramatically  during   sleep;   during   slow  wave   sleep   consciousness   can   nearly   vanish   despite  persistent  neural  activity  in  the  thalamocortical  system  (Nir  et  al.  2010,  Hobson  et   al.  2000).   It   is   useful   to   consider   both   similarities   and   differences   between  waking   consciousness   and   dreaming   consciousness   and   to   relate   these  differences  to  changes  in  brain  activity  and  organization  (Hobson  2009,  Nir  et  al.  2010).  In  this  case,  the  differences  between  waking  consciousness  and  dreaming  consciousness  are  of  interest  the  most..  Dreaming  consciousness  differs  from  waking  consciousness  by  showing  reduced  attention   and   voluntary   control,   lack   in   self-­‐awareness,   altered   reflective  thought,  occasional  hyper-­‐emotionality  and   impaired  memory  (Nir  et  al.  2010).  Perhaps  the  most  striking  feature  of  conscious  experiences  during  sleep  is  how  similar  the  inner  world  of  dreams  is  to  the  real  world  of  wakefulness  (Hobson  et  

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al.  2000,   Nir   et  al.   2010,   Hobson   2009).   The  most   obvious   difference   between  dreaming   and   waking   consciousness   is   the   profound   disconnection   of   the  dreamer  from  their  current  environment;  such  disconnection  is  a  key  feature  of  sleep   (it   is   also   known   as   ‘high   arousal   threshold’)   (Nir   et   al.   2010).   In   adult  humans,   dreams   have   features   of   primary   consciousness   but   do   not   strongly  evince  the  characteristics  of  secondary  consciousness  (Hobson  2009).  

Dreaming  Dreaming:   a   phenomenon   almost   everybody   has   heard   and   one   that   everyone  has  experienced  at  least  once  in  his  or  her  live.  But  what  is  ‘dreaming’  and  what  is  a  ‘dream’?    Dreaming  represents  a  major,  universal  facet  of  human  experience  that  offers  a  unique  view  of  consciousness  and  cognition  (Desseilles  et  al.  2011,  Hobson  et  al.  2000,  Nir  et  al.  2010,  Hobson  2009,  Hobson  et  al.  2012).  In  the  early  decades  of  the  psychoanalytic   era,   dreaming  was   regarded  as   the  meaningful   reflection  of  unconscious  mental   functioning   (Palagini  et  al.  2011).  The  scientific  analysis  of  dreaming  is  made  somewhat  prohibitive  because  the  nature  of  the  dream-­‐state  is  highly  subjective  and  a  genuinely  personal  experience.  Several   theories   include  the  affirmation  that  dreaming  is  a  random  by-­‐product  of  REM  physiology,  which  could   possibly   be   related   to   some   “unlearning”   mechanisms   in   an   otherwise  overloaded  brain  (Desseilles  et  al.  2011,  Hobson  et  al.  2000).    But  other  studies  include  that  dreaming  is  a  state  of  consciousness  characterized  by   internally   generated   sensory-­‐motor,   verbal,   cognitive   and   emotional  experiences,   which  may   unfold   in   actions   and   events   forming   imaginary   plots  (Desseilles  et  al.  2011,  Nir  et  al.  2010,  Hobson  2009,  Marzano  et  al.  2011,  Hobson  et  al.  2012).  Dreams,  similar  to  one’s  personality  in  general,  are  quite  stable  over  time  in  adulthood  and  they  might  share  many  characteristics  across  cultures  (Nir  et  al.  2010).  Emotional  experiences  in  dreams  are  frequent,  intense  and  possibly  biased   toward   negative   emotions.   Probably   all   the   categories   of   dream  experience   described   are   also   subject   to  many   alterations   and   distortions   that  are  unlikely  to  occur  in  real  waking  life  (Maquet  2000,  Desseilles  et  al.  2011,  Nir  et   al.   2010).   Dreaming,   especially   in   religious   contexts,   was   thought   to   be   a  supernatural  manifestation,  and  considered  premonitory  or  prophetic  (Palagini  et   al.   2011).   Dream   productive   activity   is   submitted   to   unconscious   and  conscious  processes  (Cicogna  et  al.  2001,  Hobson  et  al.  2012).  Findings  suggest  that  REM  sleep  might  reasonably  be  considered  as  a  facilitating  neurophysiological   state   for   dreaming   to   occur,   even   though   dreams   are   not  exclusively  experienced  during  this  state  of  sleep  (Desseilles  et  al.  2011,  Nir  et  al.  2010,  Hobson  et  al.  2012).  More   recent   models   involve   that   dreams   echo   dynamic   functions   like  reactivation   and   further   consolidation   of   novel   and   individually-­‐relevant  features   encountered   during   previous  waking   experience   (Hobson   et   al.   2012,  Desseilles   et   al.   2011)   Such   models   of   dreaming   might   be   consistent   with  accumulating   evidence   showing   the   potential   benefit   of   reprocessing   freshly  encoded  information  for  long-­‐term  storage  (Hobson  et  al.  2012,  Desseilles  et  al.  2011,  Hobson  et  al.  2000).    

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In  REM  sleep,  dreaming  is  characterized  by  the  following  remarkably  consistent  set  of  features  (Hobson  et  al.  2000):    ü Dreams   contain   formed   hallucinatory   perceptions,   especially   visual   and  

motoric,  but  occasionally  in  any  and  all  sensory  modalities  ü Dream  imagery  can  change  rapidly  and  is  often  bizarre  in  nature  ü Dreams  are  delusional  ü Self-­‐reflection   in  dreams   is  generally   found  to  be  absent  relative   to  waking  

and   it   often   involves   weak,   post   hoc   and   logically   flawed   explanations   of  improbable  or  impossible  events  and  plots  

ü Dreams  lack  orientational  stability  ü Dreams  create  story  lines  to  explain  and  integrate  all  the  dream  elements  in  

a  single  confabulatory  narrative  ü Dreams  show  increased  and  intensified  emotions,  especially  fear  and  anxiety  ü Dreams  show  increased  incorporation  of  instinctual  programs  ü Volitional  control  is  greatly  attenuated  in  dreams  All   these   features   can   be   found   in   REM  dreams   and  most   dreams   during  REM  sleep   contain   a  majority   of   these   features   (Hobson   et   al.  2000).   Contrastingly,  these  features  are  rarely  found  in  non-­‐REM  dream  reports  (Hobson  et  al.  2000,  Maquet  2000,  Perogamvros  et  al.  2012).    

History  of  dream  research  The  first  written  record  of  dream  interpretation  came  from  the  Egyptians  around  1275   B.C.   (Palagini   et   al.   2011).   The   first   steps   toward   modern   dream  interpretation  and   their  relationship   to  emotions  were   taken   in   the  5th  century  B.C.   when   the   Greek   philosopher   Heraclitus   suggested   that   a   person’s   dream  world  was  created  within  his  own  mind   (Palagini  et  al.  2011).    During   this  era  dreams  were  thought  to  have  prophetic  properties  (Palagini  et  al.  2011).    During  medieval  times  theologians  practiced  a  more  careful,  and  to  some  extent  more   scientific,   study   of   sleep   and   dream   phenomena.   Their   interpretations,  however,   were   still   constrained   by   superstition   and   witchcraft   (Palagini   et   al.  2011).  Towards  the  end  of  the  1800s  dream  interpretation  centered  on  the  new  psychological  approach  of  psychoanalysis   in  which   the  content  of  a  dream  was  analyzed  to  reveal  its  underlying  or  ‘latent’  meaning  about  the  dreamer’s  psyche  (Palagini  et  al.  2011).    During   the   1950s   there   was   a   turning   point   for   the   science   of   dreaming;   an  objective   indicator   of   the   dreaming   state  was   discovered   and   a   new   cognitive  approach   to   the   phenomenology   of   dreams   was   developed   (Desseilles   et   al.  2011).  Since  the  1970s  several  authors  have  shown  that  dreaming  may  promote  the   resolution   of   emotional   conflict   and   reduce   next-­‐day   negative   mood  (Desseilles   et   al.   2011,   Palagini   et   al.   2011).   Since   the   1990s   human   brain  imaging   became   a   key   player   in   the   field   of   sleep   research   (Desseilles   et   al.  2011).   Most   modern   dream   research   tries   to   relate   neuronal   activity  retrospectively   to   dream   form   rather   than   to   dream   content;   they   focus   on  properties   of   all   dreams   rather   than   to   investigate   the   neural   correlate   of   a  particular  dream  (Nir  et  al.  2010).    

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Dream  recall    Because  of   the  development  of  brain  research,   it   is  now  possible   to   investigate  the  phenomenon  of  recalling  dreams.    According  to  Fell  et  al.  2006,  the  quantity  of  dream  recall  was  found  to  correlate  with   functional   coupling   between   rhinal   and   hippocampal   cortices   They  measured  the  activity  within  these  cortices  during  dream  recall  and  looked  at  the  correlation.   They   found   that   the   coupling   between   these   cortices   led   to   better  dream  recall   (Fell  et  al.  2006).  Because  the  processing  of  declarative  memories  relies   on   these   structures   of   the   medial   temporal   lobe,   increased   interaction  between   those   structures   might   be   a   key   factor   in   determining   declarative  memory  formation  during  REM  sleep  and  thus  increase  dream  recall  (Desseilles  et   al.   2011,   Fell   et   al.   2006).   Memory   is   altered   for   the   dream   and  within   the  dream;  unless  the  dreamer  wakes  up,  most  dreams  will  be  lost  forever  (Nir  et  al.  2010,  Fell  et  al.  2006).  Most  children  and  young  adults  remember  their  dreams  at   least   sometimes   (84%),  only  5%  reported  no  dream  recall   at   all   (Voss  et  al.  2012).  It  seems  to  be  that  girls  have  a  slightly,  but  significantly,  higher  recall  of  their  dreams  (Voss  et  al.  2012).    Dream   reports   contain   a   variety   of   sensations   across   different  modalities:   the  most  prevalent  are  vision  (nearly  100%  of  all  dreams  contain  at  least  one  visual  element)   and   audition   (40-­‐60%),   while   movements   and   tactile   sensation   (15-­‐30%)  and  smell  and  taste  (less  than  1%)  are  less  frequent  (Desseilles  et  al.  2011,  Nir   et   al.   2010).   The   neurocognitive   model   claims   that   dreams   are   internal  narratives;   unless   internal   experiences   are   tied   to   external   cues   (i.e.   times   and  places)   they   are   bound   to   be   forgotten   (Nir   et   al.   2010).   Dream   recall   was  significantly  correlated  with  frequent  lucid  dreaming  (Voss  et  al.  2012).  Not  only  after  awakening   from  REM  sleep,  but  also  after  awakening   from  non-­‐REM  sleep  dream  recall  is  obtained,  with  some  differences  in  the  frequency  and  content  characteristics  (Marzano  et  al.  2011,  Hobson  et  al.  2000,  Maquet  2000).  

A  positive  relationship  of  both  word   count   and   subjectively  estimated   dream   duration  with   the   length   of   preceding  REM   sleep   exists   (Hobson   et  al.   2000).   Reports   from   REM  sleep   awakenings   are   longer,  more  perceptually  vivid,  more  motorically   animated,   more  emotionally   charged   and   less  related   to   waking   life   than  reports   from   non-­‐REM  awakenings   (Hobson   et   al.  2000).   In   contrast   to   REM  sleep   reports,   non-­‐REM   sleep  reports   contain   thought-­‐like  mentation   and  representations   of   current  concerns   more   often   than   do  REM  sleep  reports  (Hobson  et  

al.  2000).   In   figure   3,   the   tomographic   distribution   of   correlation   values   (rho  

Figure  3:  tomographic  distribution  of  brain  activity  (Marzano  et  al.  2011)  

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values)  between  the  actual  number  of  dreams  recalled  after  morning  awakenings  with  the  amount  of  theta  activity  in  REM  sleep  (top  of  the  figure)  and  with  alpha  activity  in  stage  2  non-­‐REM  sleep  (bottom  of  the  figure)  are  shown  (Marzano  et  al.   2011).  The  values  are  expressed   in   terms  of   rho  values:  positive   rho  values  indicate   the   presence   of   a   positive   correlation   and   vice   versa.   The   maps   are  based   on   19   unipolar   EEG   derivations   of   the   international   10-­‐20   system  with  averaged  mastoid  reference  (Marzano  et  al.  2011).    

Neuroimaging  of  REM  sleep  Neuroimaging  studies,  using  PET  and  fMRI,  have  shown  that  the  distribution  of  brain  activity  during  REM  sleep  is  not  homogeneous,  which  provides  important  insights   into   the  putative   cerebral  underpinnings  of  dreaming   (Desseilles  et  al.  2011,  Hobson  et  al.  2000).  Unlike  PET,   fMRI  allows  repeated,  non-­‐invasive  and  high-­‐resolution   measurements   of   functional   changes   in   the   human   brain  (Desseilles   et   al.   2011).   An   advantage,   for   example,   is   that   with   help   of   fMRI  correlations  between  spontaneous  eye  movements  and  regional   cerebral  blood  flow   in   the   cortices   and   thalamus   have   been   found   (Desseilles   et   al.   2011).  However,   fMRI   is   associated   with   some   constraints   that   make   this   method  relatively  complicated  for  sleep  studies  (Desseilles  et  al.  2011).  Early   neuroimaging  data   confirmed   the  sustained   neuronal  activity   observed  with   EEG,   by  showing  a  high-­‐level  of   cerebral   energy  requirements   and   a  widespread   increase  of   cerebral   blood  flow   during   REM  sleep   (Desseilles   et  al.   2011,   Hobson   et  al.  2000).   Compared  to   wakefulness   and  non-­‐REM  sleep,  REM  sleep   is  characterized   by   a  specific   pattern   of  brain  activation  (Desseilles  et  al.  2011).  During  REM  sleep  in  humans,  compared  to  wakefulness,  a  significant  increase  in  regional   brain   activity   has   been   found   in   the   following   brain   areas:   Pontine  tegmentum,  Thalamus,  Basal   forebrain,  Anterior  cingulate  cortex   (ACC),  Limbic  and   paralimbic   structures,   including   Amygdaloid   complexes   and   Hippocampal  formation   (figure   4)   (Desseilles   et  al.   2011,   Braun   et  al.   1998,   Nir   et  al.   2010,  Marzano   et   al.   2011,   Dang-­‐Vu   et   al.   2010,   Hobson   et   al.  2000,   Maquet   2000).Activation   of   these   regions   suggest   that   memory   consolidation   processes,   in  particular   emotional  memories,   may   occur   during   REM   sleep   (Desseilles   et   al.  2011).  

Figure  4:  Functional  neuroanatomy  of  human  REM  sleep  (PET  study)    (Desseilles  et  al.  2011)  

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Several  motor  regions  are  activated  during  REM  sleep,  including  primary  motor  and  premotor  cortices,  as  well  as  the  cerebellum  and  basal  ganglia.  These  results  are  in  line  with  the  motor  content  of  dreams  (Desseilles  et  al.  2011).  Braun  et  al.  (1998)  found  that,  during  REM  sleep,  activation  within  the  temporo-­‐occipital   regions   showed   some   functional   dissociation.   The   activation   of   the  extrastriate   cortex   (visual   association   areas)   significantly   correlated   with   the  deactivation   of   the   striate   cortex   (primary   visual   cortex)   during   REM   sleep  (Braun  et  al.  1998).    The  correlation  between   these  regions   is  given   in   figure  5;   the  more  active   the  extrastriate  cortex  is,  the  less  active  the  striate  cortex  is.  In  figure  5A,  REM  sleep  

is   compared   to   wakefulness;   within   this  figure   the   correlation   between   the   lateral  occipital   cortex   and   the   striate   cortex   is  given.  In  figure  5B,  REM  sleep  is  compared  to  Slow   Wave   Sleep;   within   this   figure   the  correlation   between   the   inferotemporal  cortex   and   the   striate   cortex   is   given  during  REM   sleep   compared   to   Slow   Wave   Sleep.  Activity  in  both  regions  is  usually  found  to  be  positively   correlated   during   wakefulness  (Braun  et  al.  1998).  Several   regions   are   significantly   hypoactive  during   REM   sleep   when   compared   to  wakefulness.   The   regions   that   are  significantly  hypoactive  are  in  particular:  the  Dorsolateral   prefrontal   cortex   (DLPFC),  Orbitofrontal   cortex,   Posterior   cingulate  gyrus,   Precuneus   and   the   Inferior   parietal  cortex   (figure   4)     (Desseilles   et   al.   2011,  Dang-­‐Vu   et   al.   2010,   Czisch   et   al.   2004,  

Maquet  2000,  Hobson  et  al.  2000).  Besides  these  regions,  other  regions  also  are  hypoactive   compared   to  wakefulness,  but  not   this   significant.  Maybe   the  hypo-­‐activity  of  these  brain  regions  play  an  important  role  in  dream  amnesia  (Nir  et  al.  2010,  Maquet  2000).    

Neuroimaging  of  non-­‐REM  sleep  Neuroimaging  studies  also  strongly  support  a  distinction  between  REM  and  non-­‐REM  sleep  as  states  whose  differing  neuroanatomical  activation  patterns  predict  their   observed   phenomenological   differences   (Hobson   et   al.   2000).   Several  studies  on  cerebral  metabolism  during  sleep  have  indicated  that  global  cerebral  energy  metabolism   is  decreased  during  non-­‐REM  sleep   (Andersson  et  al.  1998,  Hobson  et  al.  2000);  global  blood  flow  compared  to  wakefulness,  however,  didn’t  seem   to   be   affected   by   sleep   (Andersson   et   al.   1998).   PET   and   fMRI   have  consistently   found   a   drop   of   brain   activity   during   non-­‐REM   sleep   when   its  activity  is  compared  to  wakefulness;  this  decrease  has  been  estimated  at  around  40%   during   slow   wave   sleep   compared   to   wakefulness   (Dang-­‐Vu   et   al.   2010,  Palagini   et   al.   2011).   The   reductions   in   activity   were   located   in   subcortical  regions   (the   brainstem,   thalamus,   hippocampus,   basal   ganglia   and   basal  

Figure  5:  Correlation  between  extrastriate  cortex  and  striate  cortex.  A  shows  REM  sleep  compared  to  wake,  B  shows  REM  sleep  compared  to  SWS  (Braun  et  al.  1998)  

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forebrain)  and  cortical   regions   (the  prefrontal   cortex,   anterior   cingulate   cortex  and   precuneus)   (Hobson   et  al.  2000,   Palagini   et  al.   2011,   Dang-­‐Vu   et  al.   2010,  Andersson  et  al.  1998).  

Lucid  Dreaming  Since   this   thesis   is   about   the   consciousness   during   sleep   and   the   effect   on   the  appearance   of   dreaming,   lucid   dreaming   is   an   extremely   interesting   kind   of  dreaming.  Lucid  dreaming  is  the  experience  in  which  the  dreamer  is  conscious  of  being  in  a  dream  (Cicogna  et  al.  2001,  Voss  et  al.  2009,  Hobson  2009,  Voss  et  al.  2012)  and,  to  some  extent,  capable  of  modifying  the  content  of  the  ongoing  dream  (Voss  et  al.   2009,   Voss   et   al.   2012).   The   occurrence   of   lucid   dreaming   in   adulthood   is  rather   rare   and   difficult   to   maintain   (Voss   et   al.   2012).   Several   authors   have  reported  an   inverse   relationship  of   age   and   frequency  of   lucid  dreaming:   lucid  dreaming  occurs  primarily  in  childhood  and  puberty  (Voss  et  al.  2012).  Frequent  

lucid   dreaming   occurs  most   often   before   the  age   of   17   years,   incidence   rates   seem   to  remain   at   similar   levels   until   the   age   of   13  years,   after   which   it   steadily   declines.   Older  students   (ages   17-­‐19   years)   appear   to  experience   lucid   dreams   only   very  infrequently   (Voss   et   al.   2012).   EEG   findings  indicate   that   lucid   dreaming   might  correspond  to  a  hybrid  state  of  consciousness,  with   some   EEG   features   similar   to  wakefulness  and  some  to  REM  sleep;  with  the  rare   but   instructive   co-­‐activation   of   both  primary  and  secondary  consciousness  circuits  (Voss  et  al.  2009,  Hobson  2009).  Some  studies  have   shown   that   it   is   possible   to   let   the  participants   signal   lucidity   by   horizontal   eye  movements   (Voss   et   al.   2009).   As   shown   in  figure  6,  the  eye  movement  signals  (EOG)  are  recorded   for   three   different   states:   Waking  with  Eyes  Closed  (WEC),  Lucid  and  REM  sleep.  The  EOG  refers  to  two  channels,  one  for  each  eye  as  indicated  by  the  separate  colors.  Eye   movements   in   lucid   dreaming   are  systematic,   repetitive   and  more   pronounced  

than   in   REM   sleep   (Voss   et   al.   2009).   Low   EMG   (figure   6)   is   found   in   lucid  dreaming   and   REM   sleep,   highlighting   the   muscle   relaxation   common   to   both  states  (Voss  et  al.  2009).  Quantitative  EEG  studies  comparing  brain  activity  during  waking,  lucid  dreaming  and  REM  sleep  show  a  difference  in  activity  of  the  brain.  Frontal  areas  are  highly  activated   during   waking   but   show   deactivation   during   REM   sleep   (figure   7).  During   lucid   dreaming   there   is   an   increase   in   40   Hz   power   and   coherence   in  frontal  areas  compared  with  non-­‐lucid  REM  sleep/  In  lucid  dreaming  additional  electrical   activation   of   the   brain   is   needed   to   activate   the   dreamer’s   forebrain  

Figure  6:  Signaling  lucidity  (Voss  et  al.  2009)  

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enough   to   recognize   the  true   state   without   causing  waking   and   thus  terminating   the   dream  (Hobson   2009).  Differentiated   regional  activation   (figure   7)   may  underlie   the  phenomenological  distinction   between   the  states  REM  sleep,   lucid  dreaming  and  waking;   scale  bars   indicate   standardized  power  based  on  scale  potentials  (Hobson  2009).    

Conclusion/Discussion  When  looking  at  all  the  components  of  sleep,  consciousness  and  dreaming  there  can  be  concluded  that  all  of  these  show  a  clear  coherence.  Sleep  is  a  phenomenon  that,  in  general,  everybody  experiences  every  night.  Consciousness  and  dreaming  seem  to  be  related  to  each  other,  but   the  exact  relationship  between  these  two  components   is   not   yet   clear.   Lucid   dreaming   is   an   interesting   example   of   the  coherence  of  consciousness  and  dreaming,  but  also  in  this  case  still  a  lot  has  to  be  done.  Dreams  seem  to  be  experienced  the  most  during  REM  sleep,  but  they  also  appear  during  non-­‐REM  sleep.  Thanks  to  neuroimaging,  the  activation  and  deactivation  of   brain   areas   during   REM   sleep   has   been  made   visible.   The   (de)activation   of  certain  areas  might  give  a  possible  explanation  of  some  of  the  features  of  dreams,  such  as  emotionality,  lack  of  control  and  visual  elements.  The   secondary   aspects   of   consciousness   rarely   appear   during   dreams.   And   if  they  appear,   it  will  most   likely  be   in   the  dream  of  a  child;   lucid  dreaming   is  an  example   of   this.   The   appearance   of   secondary   consciousness   during   dreaming  (e.g.  being  aware  of  dreaming)  might  be  artifacts  that  only  appear  under  special  conditions,  e.g.  brain  development   in  children.   If   this  were   true,   the  absence  of  secondary   consciousness   during   sleep   would   be   a   normal,   healthy   situation.  Consciousness   would   be   active   again   during   wakefulness,   when   sensory  information  begins  to  play  a  role  again.    When   looking   at   brain   activity,   certain   brain   areas   have   to   be   active   when  waking  but  not/less  active  during  sleep.  The   interpretation  of  what  happens   in  the  brain  and  the  behavioral  reactions  that  would  appear  when  wake,  have  to  be  diminished.  If  this  were  not  the  case,  one  would  jump  out  of  his/her  bed  for  even  the   slightest   thing.   This  means   that   is  would   almost   be  necessary  not   to   know  what  you  think  during  your  sleep  to  have  a  good  night  rest.    When  looking  at  all  of  the  authors  and  studies  I  have  used,  I  think  I  have  seen  a  lot  of  different  views  regarding  sleep,  consciousness  and  dreaming.    Allan  Hobson  seems  to  be  an  important  person  within  the  dream  research,  but  I  do  think  that  some  of  his  claims  are  a  little  odd.  Sometimes  he  tries  to  convince  his   readers   of   the   necessity   of   dreaming.   If   dreaming   really   was   necessary,   I  think   also   adults   should   remember   what   they   dreamt   of.   Children   often   do  

Figure  7:  Comparison  of  activity  during  different  stages  (Hobson  2009)  

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remember   what   they   dreamt   of,   but   they   don’t   seem   to   rate   this   at   high  importance.  The   studies   of   Ursula   Voss,   I   really   liked,   because   they   double-­‐checked  everything.   For   example  with   the  questionnaires,   students   executed   them  with  the   children   that   participated,   because   students   are   ‘closer’   to   children   than  professors   are.   Besides   this   they   also   used   antipodal   questions;   if   a   child  answered  ‘yes’  on  the  first  question,  it  had  to  answer  ‘no’  on  the  next  one.  Voss  et  al.  used  large  experimental  groups,  so  outliers  wouldn’t  conflict  the  data  too  much.  I   also   used   some   reviews;   these   articles   gave   an   overview   of   a   big   number   of  studies.  I  think  the  reviews  were  a  good  source  of  information,  because  it  gave  a  good  overview  without  a  too  obvious  opinion  in  it.  I  found  two  types  of  researchers:  the  ones  with  a  clear  view  that  will  use  all  the  date  they  can  to  proof  they’re  right  and  the  ones  that  are  curious  and  willing  to  change  their  view  for  a  different  one  of  the  data  need  them  to  do  so.  I  think  that  Hobson  is  an  example  of  the  first  type  of  researches  and  Voss  of  the  second  type.    

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