Temporo-Parietal Junction less important to abnormal body perception (like OBE) than claimed.

#1
Interesting new paper where researchers attempt to test the idea that the right Temporo-parietal Junction may play a specific role in abnormal body perception (ABP) like out of body experience (OBE). They attempted to induce an OBE using repetitive transcranial magnetic stimulation (rTMS) of the brains right Temporo-parietal Junction (rTPJ), vs a Control Site (CS) located 5cm away.

"Effects of Transcranial Magnetic Stimulation on Body Perception: No Evidence for Specificity of the Right Temporo-Parietal Junction"

https://www.researchgate.net/public...ficity_of_the_Right_Temporo-Parietal_Junction

[Updated Link to full free version of the paper above]

Even though they failed to induce a full-blown OBE, I applaud the researchers for being so open minded and actually providing a realtime hidden target just incase they had been successful...

"...The aim of the present study was therefore to investigate in a larger sample, whether repetitive transcranial magnetic stimulation (rTMS) of the rTPJ in a healthy brain can induce ABP, and to explore neurophysiological correlates of ABP. We employed MRI-based neuronavigated TMS for exact localisation of the rTPJ. Following the design of previous research, a visual target was displayed out of sight of the participant. A laptop was placed above the participant with the screen turned to the ceiling. The screen displayed a series of 5-digit numbers that changed randomly every second. The participant was instructed that if he/she experienced an ABP and was able to see the target, he/she would have to recall it after the ABP. The participant’s electroencephalography (EEG) was monitored to allow the assessment of neurophysiological correlates of ABP...."​

Highlights for me...

"...Thirteen participants (65 %) reported ABP when stimulated at the rTPJ and twelve (60 %) when stimulated atthe CS. Among the participants who reported ABP, none reported an OBE. Two participants had somatosensory tingling sensations in their arms or legs. Eight participants reported twitching sensations in their body parts (arms and/or legs). Most remarkably, three participants reported complete illusory movements of body parts. These participants did not see their body parts moving, but they felt illusory movements of body parts such as arm deflections and stretching legs..."​

and...

"...Our neurophysiological data indicate that abnormal body perception (ABP) were related to a systematic (almost independently of the rTMS cortical site and rTMS frequency: in 3 out of 4 experimental conditions) decrease of the EEG power in all frequency bands at a common left anterior and left central cortical area according statistical results in 2 conditions (15 Hz rTMS at rTPJ and CS) and according to trends (Fig. 6) in a third condition (1 Hz rTMS at rTPJ). The EEG power decrease in all frequency bands could be interpreted as a specific type of cortical deactivation due for instance to EEG desynchronisation (Mun˜oz-Torres et al. 2011; Julkunen et al. 2008) or a reduced connectivity (Julkunen et al. 2008). At a neurofunctional level, ‘‘power decrease in all frequency bands is generally seen after arousal stimuli, during orienting reactions’’ (Gamma et al. 2000, p. 160) and EEG desynchronisation has been interpreted as reflecting the perception of an incongruence (Berlyne and McDonnell 1965). Thus, the power decrease in all frequencies could reflect an orientation mechanism to the presence of an incongruent body perception that we refer to as an ABP..."
Whether it's with drugs, cardiac arrest or event related desynchronisation etc, it seems to me that a common cause of localised OBE-type phenomena continues to be a reduction in power output of the brains endogenous EM field.
 
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#2
I am worried that people tend to use computer screens (for obvious reasons) to test OBE's. The problem is that OBE sight clearly can't be exactly like normal sight - there obviously isn't a lens to focus the light, and it isn't obvious that there are any photo detectors!

I suspect that our senses are a sort of crude analogy to non-physical senses - that maybe detect physical objects directly. At the very least it would be good it they used the kind of screens that Kindle uses, that actually reflect ordinary light rather than emit it and stay visible even with the power removed (so there won't be flicker effects).

David
 
#3
It is interesting, Max thanks for posting that. There's nothing (as far as know) really new about this type of stimulation though to try to produce OBE ? Persinger's helmet would (at least he would claim) be very similar, wouldn't it ?

I don't get the "real time" hidden target bit with this type of experiment. Surely that's for prospecting dualists (or your theory) ...these guys are limited to finding a part of the brain that "produces" the feeling of being out of body, not "actually" out of body. My feelings are that if during an experiment like this, they actually had someone accurately report a target, at the same time as that person insisting they were definitely out of their body then I think they'd refuse to accept it and insist it must have happened by some other mechanism. Cynical I know but in academic circles, "really" leaving the body is a non starter.
 
#4
It is interesting, Max thanks for posting that. There's nothing (as far as know) really new about this type of stimulation though to try to produce OBE ? Persinger's helmet would (at least he would claim) be very similar, wouldn't it ?

I don't get the "real time" hidden target bit with this type of experiment. Surely that's for prospecting dualists (or your theory) ...these guys are limited to finding a part of the brain that "produces" the feeling of being out of body, not "actually" out of body. My feelings are that if during an experiment like this, they actually had someone accurately report a target, at the same time as that person insisting they were definitely out of their body then I think they'd refuse to accept it and insist it must have happened by some other mechanism. Cynical I know but in academic circles, "really" leaving the body is a non starter.
I don't think they were motivated to produce an OBE, but rather by a healthy skepticism to test claims of other researchers that the brains right Temporo-parietal Junction was the 'key' area responsible for abnormal body perception (ABP). Their research does not support that claim.

Rather this team found that ABP seemed almost independent of their choice of cortical location, and instead they found ABP was best associated with a systematic decrease of the EEG power in all frequency bands.

That's what I find exciting about this research... because it fits with what I expect... a drop in EEG power when you produce currents in the brain by high power repetitive Transcranial Magnetic Stimulation (rTMS)... in other words, external induction of a current within the brain seems to cause a generalised disruption to the networks synchronization... leading to a large and generalised drop in power output measured by EEG... and it is this latter observation that the researchers say seems best associated with ABP.

Other researchers have claimed electrical stimulation of a very particular part of the brain was the cause of ABP with very little evidence, and without checking if this is supported by perhaps stimulating a different part of the brain to see what happened, or, looking for other correlations using EEG for example. I'm pleased this team challenged that claim, and found it wanting.

I suspect that a blunt (not spatio-temporally patterned) TMS may be unable to induce sufficient current to disrupt a wakeful brains networks to such an extent that they temporarily resynchronise using better synchronized (compatible) external field data to produce a full-blown localised OBE.

I agree that many researchers approach this phenomena as if the brain is perfectly isolated, and therefore they don't even consider checking for unexplained veridical recollections using targets within the design of their experiments. A few interested researchers go the other way, and take the experients perceived location of 'self' quite literally, and only place targets up high. The first group don't get any hits because they've got no targets, the second group don't get any hits because they've used hidden and secret targets. Jerome Daltrozzo (the main author and a neuroscientist I believe) is at least open minded enough to try and gather some target data within the design of his experiment.
 
#5
You can see two heat maps showing EEG power below. The first line of heads in each image shows the EEG of subjects who did experience an abnormal body perception, in comparison to the, the second line which shows the EEG of those who did not. You can clearly see much reduced power (colder/bluer) over the centralised portion of the ABP experiencing subjects vs the non-experiencing subjects... which I claim is more likely to allow compatible external fields to affect the brain.

Those cortical areas showing reduced power IIRC include areas related to processing motor function, which seems to be the type of ABP the researchers report. But also note that the visual processing areas of the cortex (the extreme posterior of the brain) seem to continue showing reasonably high power EEG in both types of subject. Most importantly within the Alpha-Gamma and Theta-Gamma frequencies, which are thought to be related to visual processing. Hence I would say a visual experience may be less likely.

 
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#7
I am worried that people tend to use computer screens (for obvious reasons) to test OBE's. The problem is that OBE sight clearly can't be exactly like normal sight - there obviously isn't a lens to focus the light, and it isn't obvious that there are any photo detectors!

I suspect that our senses are a sort of crude analogy to non-physical senses - that maybe detect physical objects directly. At the very least it would be good it they used the kind of screens that Kindle uses, that actually reflect ordinary light rather than emit it and stay visible even with the power removed (so there won't be flicker effects).

David
You do need to read 'Apparitions'...

http://www.booksystemsplus.com/product.php?id_product=295
 
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