Can the mind believe what the eye sees


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Can the mind believe what the eye sees

  1. 1. The sign wasn’t placed there By the Big Printer in the sky Prof. A.V. SRINIVASAN. Prof. A.V. SRINIVASAN. M.D, D.M, PhD, F.I.A.N, F.A.A.N ,, M.D, D.M, PhD, F.I.A.N, F.A.A.N EMERITUS PROFESSOR OF NEUROLOGY EMERITUS PROFESSOR OF NEUROLOGYFORMER HEAD AND PROFESSOR OF NEUROLOGYFORMER HEAD AND PROFESSOR OF NEUROLOGY Institute of Neurology Institute of Neurology Chennai Chennai
  3. 3. Shri Uttambhai Nathalal Mehta 1924 - 1998 A visionary par excellence The pioneer of neuropsychiatry in India The mind behind some of the blockbuster drugs in the neuropsychiatry segment; the founder and guiding force behind Torrent Group A perfect epitome of business excellence, scientific integrity and benevolence unparalleledSHRI US MEHTA ORATION
  4. 4. Thomas Elbert Basic Principles Cortical representation expands linearly with use. Synchronous inputs lead to fusion of cortical zones Asynchronous inputs lead to segregation of cortical zones. Disuse or De-afferentation leads to invasion of unused cortical area by nearby neurons.
  5. 5. Sensory modulation in spatial neglect Novel Techniques Peripheral somatosensory- Magnetic stimulation Repetitive optokinetic stimulation Neck Vibration training Drug Treatment is currently unsuccessful
  6. 6. Sensory modulation and Stroke Rehabilitation aimed to increase use of paretic hand Virtual reality Motor imagery Prof. V.S..Ramachandran’s virtual reality box  Phantom limb phenomenon
  7. 7. Other techniques Caloric tests for balance  Brings awareness of illness to patient. Kinesthetic, visual, and auditory cues to improve Parkinsonian gait.
  9. 9. BACKGROUND Allesthesia and extinction of referral sensation in brachial plexus lesions A.V. Srinivasan and V.S. Ramachandran et al (1998) Intermanual referral of sensations after central lesions of the somato sensory system K. Sathian et al (2000)
  10. 10. METHODS8 patients (19-51 years) Brachial plexus lesion – one Amputation – two Stroke – five Patients were video filmed in the movement disorder clinic. Pinprick, cold, vibration and kinesthesis were tested MRI & ENMG in all cases
  11. 11. CENTRAL LESION Stroke Thalamicstroke - three Temparo parietal - two Three to four months later  Ipsilateral arm - no referral to leg
  12. 12. STROKE Contd… Intense pressure on the normal hand resulted in extinction of pain in the stroke side Pain returned within one minute of the pressure Intense pressure improved sensory and motor phenomenon
  13. 13. AMPUTATION Both the patients (below elbow & knee amputation) showed intermanual referral of sensation within 10 days. The referred sensations of touch and vibration lacked spatial organization and poor localization with a relatively high threshold
  14. 14. CASE VIGNETTE (BRACHIAL PLEXUS LESION) 21 year old girl, after total brachial plexus lesion was examined 6 months, 1 ½ & 2 ½ years after the lesion She had sensations intermanually referred in a topographically organized manner in the phantom limb
  15. 15. INTERMANUAL REFERAL AND EXTINCTION OF PAIN SENSATION Hemiparesis with Brachial hemisensory deficit Amputation plexus Spatial organi- Poor Poor Excellent sation Localisation Good Poor ExcellentTime of occurance After 3 to 4 months Immediate Immediate with in 7 days with in 7days Pain After a delay of Immediate Immediate Extinction 3 - 5 seconds
  16. 16. DISCUSSIONAnatomical facts 1. Primary somato sensory area 3b 2. A. Primary somato sensory area 1 & 2 2. B. Second somato sensory cortex and parietal operculumIn 2a & 2b the receptive fields are largerbilateral and callosal connection areabundant
  17. 17. DISCUSSION Contd… Contralateral referral of sensations was not found in normal subjects or in hemiparetic patients without hemi sensory loss Neural mechanisms for perceptual alteration not clear
  18. 18. DISCUSSION Contd…It appears that a decrease insomatosensory input to onecerebral hemisphere from thecontralateral hand allowsresponsiveness of neurons inthis hemisphere tomoderately intense tactilestimuli on the ipsilateral handto exceed perceptualthreshold (which does notnormally occur).
  19. 19. CONCLUSION Intermanual referral & extinction of pain occurred immediately in amputation and brachial plexus lesions and after a delay in stroke Intermanual referral of sensation occurred topographicaly organised manner in brachial plexus lesions but not in amputation and stroke
  20. 20. HemineglectAn Interesting Case fromProf.A.V.Srinivasan’s Unit
  21. 21. Can the mind believewhat the eye sees ?On vision, visuospatial dysfunction and body image perception in right hemispherical dysfunction Dr.K.Bijoy Menon (Senior Resident)Dr.Sundar, Dr.Saravanan, Dr.Ramakrishnan Dr.Nithyanandan (Asst.Prof) , Prof. A.V.Srinivasan
  22. 22. We thank Prof. V.S.Ramachandran, M.D., Ph.D., Direct or Centre for Brain and Cognitive Sciences University of California, San Diego, USA
  23. 23. Indrani. 50 year old female Presents with sudden onset of weakness of left upper and lower limb O/E.  Conscious, oriented to time, place and person  Mild left UMN facial paresis  Left hemiplegia  All peripheral pulses palpable
  24. 24.  CT Brain – P – Shows a (R) Occipitotemporal infarct
  25. 25. Higher mental function evaluation MMSE : 28/30 She was very attentive and quite clear in her conversation with us, though she would be complaining of a vague left sided shoulder painOn lobar testing, she had Left visual neglect with (L) hemianopia No auditory neglect Absent sensory perception in (L) upper limb and (L) tactile neglect in the lower limb
  26. 26. On cold caloric tests and its effect on neglect
  27. 27. Video of Neglect
  28. 28. Video of caloric test and Nystagmus
  29. 29. Video of disappearance of neglect
  30. 30. On ‘ Mirror Agnosia’Mirror Agnosia on the Right
  31. 31. After caloric test, Mirror Agnosia on the Left
  32. 32. ‘Mirror Agnosia’ to front
  33. 33.  On Anosognosia, Body neglect (Hemisomatognosia) and somatoparaphrenia Anosognosia – our patient has it Body neglect by Bisiach’s test – our patient does not have it Somatoparaphrenia – our patient has it
  34. 34. Somatoparaphrenia
  35. 35. On the somatophrenic arm and mirrors
  36. 36.  On Allesthesia, tactile neglect and ‘blind touch’ ‘Touch your left arm’ Bisiach’s test of body neglect. Absent proprioception and touch in the left upper limb Patient is still able to touch her left arm whatever position the examiner keeps the arm in.
  37. 37. Blind Sight Vs Blind Touch
  38. 38.  On visual imagery, neglect and caloric tests Visual imagery Bisiach’s test Our test
  39. 39. Results
  40. 40. Unconscious awareness in a person with Blind Sight And Blind TouchConscious mind and unconscious mindTheories of consciousness and the soul.