Out of body experiences Flashcards
OBE?
The feeling of being outside one’s physical body, look from parasomatic body onto physical body
Autoscopy
Seeing one’s body in extrapersonal space from the habitual visuospatial perspective. Consciousness stays in the physical body, you see the parasomatic body.
Parasomatic body
the perceived new body.
he-autoscopy
Either 1 or 2 visuospatial perspectives, either simultaneously or
alternation between them.
associations with OBE
- OBE/AS related to neurological diseasessuch as epilepsy, migraines, neoplasia, infection
- And psychiatric diseases such as schizophrenia, depression, anxiety.
- Also drug induced, kettyboi (maybe look up).
- Not restricted to psychiatric patients though, healthy population 1-2x in lifetime ~10%.
- But hard to study, spontaneous, hard to induce, unpredictable, transient/short.
Blanke et al 2004
- describes the correlates of OBE/AS in 6 patients
- Semi structured interview: – phenomenological information, perspectives, body characteristics
- Repeated or Long-Term EEGs
- Neurological (e.g. visual field tests) and Neuropsychological (e.g. oral/written language tests)
- Structural MRI (group lesion analysis)
Subjective results
• 3 patients OBE, 4 AS, one patient reported both at same time.
• Seen own body posture congruent with real posture before experience
• Self-recognition preserved and immediate even if face not visible
Visual phenomenology
• OBE – Visuospatial perspective: in a second (parasomatic) body outside the physical body
– Immediately elevated (variable distance)
– Inverted by 180 degrees, lying to rotated immediately.
– “vivid” and veridical: in colour, high-detail
– Lying down
• AS – In their own physical body
– Either 1 or 2 visuospatial perspectives, either simultaneously or alternation between them (Heautoscopy?)
– “vivid” (apart from patient 6 – pseudo-dreamlike)
– Sitting or standing
Non-Visual phenomenology (e.g. vestibular)
• Visual part illusions – illusory flexion or transformation of limbs
• Emotions – not consistent, fear/elation/neutral
• OBE – All experienced flying or floating during OBE
– No feelings of rotating (therefore was immediate)
• AS – 3 of 4 reported vestibular sensations
– Prior, during, independently
– More variable than in OBE
Objective results
• 4/6 had epileptic seizures
• partial consciousness related to transitory ischemic attack/migraine in two cases
• Could not identify lesion in one patient
• Overlap analysis showed lesions centred on the Temporo-Parietal junction (TPJ)
• Cortical Stimulation could produce, gives some causation.
electrical stimulations of OBEs
Penfield (1941)
• Patient GA: epileptic female
• Electrical stimulation under local anaesthesia
• OBEs linked to vestibular illusions rather than visual/auditory ie flying
Blanke et al. (2002)
• 43 year old, right-handed woman
• Temporal lobe epilepsy for 11+ years
• Sub-dural electrodes to treat.
• Electrical stimulation of right angular gyrus gave rise to vestibular sensations – like falling from a height
• Different illusions were created if different sites were stimulated, ie motor cortex motor effects. LOOK EXAMPLES UP ON PAPER
De Ridder et al. (2007)
• Accidental induction of OBE.
• Tinnitus patient - conventional therapy had failed
• Implanted electrode – overlaying right superior temporal gyrus
• Electrical stimulation did not suppress tinnitus, but did reliably produce “OBE”s: disembodiment 50 cm behind his body, to the left.
• They describe no autoscopy but they seem to describe it, as patient experienced form own visuospatial pov.
Blanke theory of how OBEs produced
- Multisensory disintegration - Failure to integrate visual, tactile and proprioceptive information about the body
- Vestibular dysfunction
Evidence for multisensory disintegration:
• Visual body-part illusions during OBE, ie bending or stretching of limbs.
• AP are reliant on posture, suggesting influence of proprioceptive/tactile mechanisms.
• AP are reliant on posture, suggesting influence of proprioceptive/tactile mechanisms, posture usually remains the same, e.g. OBE = supine; AS = sitting/standing.
• Experienced self corresponds to that posture.
• TPJ involvement – Combines tactile, proprioceptive and visual information into coordinated reference frame in healthy people (e.g., Calvert et al., 2000, Bremmer et al., 2001, Ladavas, 2002)
• Could be that seeing our body in a position that does not correlate to ones felt/perceived position is what gives rise to the feeling of OBE.
• Supernumerary phantom limbs (SPL) – (e.g. Ramachandran & Hirstein, 1998). Additional limb, maybe related to multisensory integration. But different, so different mechanism or additional mechanism must be occurring.
Evidence for vestibular dysfunction:
• Semicircular canals filled with fluid, give rotation info.
• Otoliths – utricle and saccule “acceleration” info about head
• Info -> vestibular cortex, located at the TPJ.
• TPJ also implicated in hemispatial neglect. (e.g., Halligan et al., 2003)
• TPJ also active during ego centric perspective changes in healthy people (Blanke et al., 2005: Reading group paper).
Blanke et al. (2005)
Methods:
• Mental own body transformation task, which hand is gloved? Front or back, left or right hand glove.
• Compared to which side of screen is the glove on? Requires no transformation.
• Extra control task (TMS task?), using external objects rather than bodies – letter F. which side of F is the bump on? F and backwards F, left or right side bump. Requires rotation.
Results healthy adults:
• Faster on side of screen task, no difference for different conditions
• Faster on back facing condition with no rotation compared to front, both longer RT than screen task.
• EEG: P5 electrode 300-400ms. Approx. over TMJ. Different activity between conditions, EEG measures sync firing, difference.
• TMS: interfere with neural activity at either TPJ or control site IPS.
- In back facing/easy task, no change when TMS applied to TPJ/IPS.
- In front facing task, RT increased for TMS applied to TPJ.
- Letter task, no change for unturned F.
- Letter task, RT increased when TMS applied to IPS on turned F.
- Therefore TPJ only applicable to rotating own body. But still why did IPS increase? Wouldn’t it stay the same?
Conclusions healthy adults:
• Selective activation of the TPJ 330-400 ms after stimulus onset in the mental own-body transformation task (evoked potentials analysis).
– Healthy volunteers imagine themselves in a position and visual perspective usually reported during spontaneous OBE, involves TPJ.
• Interference of the TPJ using TMS selectively impaired mental own-body transformations, but not transformations of external objects.
– Suggests selective and causal role for the TPJ in transformations of one’s own body.
Epileptic patient with OBEs
• Same patient reported in Blanke et al. (2004)
– 22 year old, right handed female
– Subdural electrodes allowed easy stimulation
– Complex partial seizures since childhood
– Seizures originating in the TPJ
• Same RT effects as controls (slower RTs for front-facing figures)
• In basal temporal lobe/inferior temporal gyrus no effect if stimulated between front/back (control).
• If TPJ stimulated, increased activation in back facing condition.
Mechanisms of OBEs:
Blanke et al. (2004)
Double disintegration between
• Personal space (multisensory integration) – in all Aps, disintegration in personal space (tactile, proprioceptive, visual).
• Personal and extrapersonal space in the TPJ – the difference between autoscopy, he-autoscopy and OBE arises. The strength of vestibular dysfunction determines strength.
TPJ and prefrontal cortex (PFC) are implicated in self-processing ie Agency, ToM, perspective taking, switching perspective.
Hypothesise that PFC and TPJ (and their connections) are implicated in OBEs – OBEs have been linked to frontal lesions (e.g., Devinky et al., 1989)
Easton, Mohr, & Blanke (2009)
- Never exp OBE/nOBE n=36, previous OBEs but not currently n=11.
- Switched between OBT-task and mirror task (same as OBE but imagine it’s a mirror).
- For mirror front facing is now easier.
- Task switching component relies on PFC e.g., Kumada & Humphreys (2006), Passingham et al., (2000)
- Switching depends on interplay between PFC and TPJ (and parietal lobe in general) ie Dove et al. (2000), Ruge et al (2005)
Results:
• No RT difference between nOBE and OBE.
• OBE reduced accuracy when switching between conditions, especially when new task was the easier viewpoints.
• If same task as the previous then no change in accuracy.
Conclusions:
• Fronto-parietal integration compromised in OBE vs nOBE individuals.
• Therefore OBEs do not relate only to disintegration of multisensory integration at the TPJ (as suggested by Blanke et al., 2004, 2005), but that the PFC also contributes to impaired self-processing.
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