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Cross-talk between conscious and non conscious mind:

Cross-talk between conscious and non conscious mind: Cortical mechanisms and clinical implications Rajendra D. Badgaiyan, MD Departments of Psychiatry and Radiology, Harvard Medical School Department of Psychology, Harvard University Massachusetts General Hospital, Boston.

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Cross-talk between conscious and non conscious mind:

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  1. Cross-talk between conscious and non conscious mind: Cortical mechanisms and clinical implications Rajendra D. Badgaiyan, MD Departments of Psychiatry and Radiology, Harvard Medical School Department of Psychology, Harvard University Massachusetts General Hospital, Boston

  2. ‘Normal’ cognitive experience requires: • intact conscious and non conscious processes • balanced information sharing between the two processes • To understand neural basis of cognitive impairments, we need to know • neural network of conscious and non conscious processes • neural network that allows two processes to share information

  3. Memory: a model for the study of conscious and non conscious processes • Classical concept: • short term memory (STM) • long term memory (LTM) • Stimulus  STM  LTM(Attkinson & Shiffrin, 1968) • Problems: • patients with STM deficits may have normal LTM (Braddley & Hitch, 1974) • amnesics with both STM and LTM deficits show normal performance in a variety of tests of memory (Milner, 1966) • Current concept:(Graf & Schacter, 1985) • explicit: conscious and intentional • implicit: non conscious and incidental

  4. 1. Word-stem completion task: STUDY TEST institution pic picture ins faculty fac Instructions: explicit: remember words complete word-stems using a studied word implicit: count vowels complete word-stems using the first word that comes to mind 2. Picture recognition test: STUDY TEST pictures shown for 3 sec studied and non studied pictures flashed for 16 msec Instructions: explicit: remember picturesindicate whether the picture was studied implicit: look at the pictures indicate if you can recognize the picture

  5. Memory is a good model for the study of neural basis of conscious and non conscious cognitive processes and their interaction: • it has a conscious and a non conscious component • two components are dissociable in neuropsychiatric disorders • schizophrenia • depression • parkinsonism • evidence suggest that the two components interact with each other

  6. Interaction between explicit and implicit processes…. Remember following words: candy sour sugar bitter good taste nice honey soda chocolate heart cake eat fruit pie

  7. Louis Wain (1860-1939) The ‘King of cat art’

  8. Did you see following word in the list just studied? TASTE

  9. Did you see following word in the list just studied? POINT

  10. Did you see following word in the list just studied? SWEET

  11. So, we had three words….. TASTE POINT SWEET

  12. Explicit memory (false memory) conscious action  encoding and retrieval of studied words nonconscious action  semantic organization of studied words Implicit memory (stem-completion task) conscious action  finding a word beginning with word stem nonconscious action  retrieval of a studied word conscious action/cognition non conscious processing

  13. conscious cognition non conscious processing • ‘altered’ non conscious processing  ‘altered’ conscious cognition • false memory  delusional disorder • PTSD • hallucination • ‘resetting’ of non conscious processing ‘resetting’ of conscious cognition • cognitive techniques (e.g., Crovitz technique in psychogenic amnesia) • ? Neurophysiological/neurochemical techniques

  14. conscious behavior/cognition •  conscious behavior/cognition could be altered by impairments of • conscious processing • nonconscious processing • interaction between conscious and nonconscious processing •  using neuroimaging methods, we studied • sites of conscious (explicit) memory • sites of nonconscious (implicit) memory • sites of interaction

  15. Neuroimaging techniques used Event-related potentials (ERP): high-density EEG recording  high temporal but poor spatial resolution Positron emission tomography (PET): changes in regional cerebral blood flow (rCBF) estimated using radioactive tracer inhalation  high spatial but poor temporal resolution Functional magnetic resonance imaging (fMRI): changes in rCBF estimated by measuring ratio of oxygenated/ deoxygenated blood  high spatial but poor temporal resolution

  16. Conscious retrieval Studied pictures Activations sup/ mid frontal gyrus (BA 9/46) hippocampus Deactivations extrastriate cortex (BA 19) R

  17. Badgaiyan & Posner, 1998

  18. Badgaiyan & Posner, 1998

  19. Conscious retrieval: studied words BESA algorithm a single dipole source located in the right hippocampus was responsible for 84 % of activity between 164 - 200 ms Badgaiyan & Posner, 1997

  20. Processing sequence: conscious retrievalextrastriate cortex: 64 - 600 ms hippocampus: 164 - 200 ms prefrontal cortex: 200 - 600 ms

  21. Implicit retrievalPicture recognition Deactivations extrastriate cortex (BA 19) Badgaiyan, 2000

  22. Implicit retrievalWord stem completion Deactivations extrastriate cortex (BA 19) Schacter, Badgaiyan & Alpert, 1999

  23. Auditory priming (implicit retrieval) to ascertain that the extrastriate involvement is associated with implicit retrieval and not with some aspect of visual perceptual processing Auditory word stem completion task Study Test listen: words listen: word-stems (first syllable) Instruction: complete word-stems using the first word that comes to mind

  24. Auditory priming Deactivations extrastriate cortex (BA 19) medial prefrontal cortex (BA 9/10) Experiment 1 Experiment 2 Badgaiyan, Schacter & Alpert, 1999

  25. Cross-modality priming to understand cortical mechanism of non-perceptual priming, we examined implicit memory under cross-modality priming condition Visual-to-auditory Study Test see: words listen: word stems (first syllable) Auditory-to-visual Study Test listen: words see: word stems (first 3-letters) Instruction: complete word-stems using the first word that comes to mind

  26. Cross-modality (visual  auditory) priming Activation superior frontal gyrus (BA 9/10) Badgaiyan, Schacter & Alpert, 1999

  27. Cross-modality (auditory  visual) priming Activation superior frontal gyrus (BA 9/10) Schacter, Badgaiyan & Alpert, 1999

  28.  extrastriate deactivation during conscious retrieval of studied items  prefrontal activation during non conscious retrieval under cross modality condition  suggest cross-talk….

  29. Neural evidence of interaction between explicit and implicit memory • Reduced activation in the extrastriate cortex (BA 19) during: • implicit retrieval • explicit retrieval of studied items Retrieval of studied pictures Conscious retrieval Non conscious retrieval

  30. Time course of extrastriate deactivation Nonconscious retrieval Nonconscious retrieval Baseline 2 µ V 200 800 - 2 µ V

  31. Time course of prefrontal and late extrastriate activity

  32. Cortical processing of memory Nonconscious Conscious Cortical activity extrastriate (early)  extrastriate (early)  extrastriate (late)  prefrontal cortex Cognitive component retrieval of studied  retrieval of studied items items  conscious awareness of retrieval Late extrastriate deactivation and prefrontal activity associated with conscious awareness ?

  33. Processing sequence: conscious retrievalextrastriate cortex: 64 - 200 ms (early) extrastriate cortex: 200 - 600 ms (late) hippocampus: 164 - 200 ms prefrontal cortex: 200 - 600 ms • 64-200 ms: implicit retrieval • 200-600 ms: extrastriate cortex holds implicitly retrieved information • re-entrant circuit sets up between extrastriate and Prefrontal cortex • conscious awareness

  34. Neuropsychiatric conditions associated withimpaired explicit but preserved implicit memory • schizophrenia (implicit ‘better than normal’) • severe PTSD • MPD/psychogenic amnesia (fugue state) • amnesia (hippocampal lesion) • post-ECT • Alzheimer’s disease • organic depression • anesthetic recovery tests of implicit memory could be useful diagnosis aids for these conditions

  35. Cognitive impairments associated with ‘altered’ signal transmission Increased activity of… extrastriate -prefrontal connectivity: hallucination hippocampal -prefrontal connectivity: loose association

  36. Cognitive impairments associated with ‘altered’ signal transmission Decreased activity of … extrastriate -prefrontal connectivity: negative symptoms dementia delirium hemineglect

  37. Future prospects... • if the physiological nature of the communication between implicit and explicit processes is known, it can be manipulated to ‘reset’ the impaired communication which can theoretically alleviate cognitive symptoms • tests of implicit memory may help objective diagnosis of conditions like, PTSD, MPD • functional neuroimaging studies may help definitive diagnosis of a variety of neuropsychiatric conditions until then, psychiatric conditions will continue to have low inter rater reliability ...

  38. Thank you...

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