Computational and Neurological Considerations
4. The CSS/CCS Distinction and Out-of-Body Experience
Some Brain-Image studies suggested a correlation between the misattribution of the ownership of the rubber hand and the Posterior Parietal Cortex (PPC) (Ehrsson et al, 2004). The PPC is a brain region known for multi-modal sensorial- motor integration much in the way here proposed trough coordinate transformations (Anderson et al, 1997; Pouget & Sejnowski, 1997). Now, if we assume the claim according to which the FBI is conceived as a generalization of RHI to the totality of the body (see, for instance, Lenggenhager et al, 2007) then, the computational model for Core-Self Simpliciter I have been deploying, gains empirical credibility and the same is valid for the tentative explanation of FBIs in terms of pre-specified coordinate transformations.
It seems, therefore, that CSS’s properties, achieved through multisensory-motor coordinate transformation (recall: 1) a self-perspective first person position (1PP), 2) the postulation of an external independent world and 3) an image of body [a Body-Image] where the origin of the subjective perspective is located) is capable of sustaining all the phenomenological features of FBI’s experiences.
OBEs, in clear contrast to FBIs, is a non-coincidence between 1PP and an image of the body. What and how can such a difference be supported? According to the main hypothesis/claim suggested in this article and stated in the first section, OBEs are a consequence of the computational and phenomenological properties of CCS as much as FBIs are consequence of CSS’s proprieties.
Recall that it was suggested that, at the phenomenological level the CCS adds cognitive complexity to CSS, namely the capacity for imagery. On the computational level this is achieved probably by processing the contents of CSS off-line.
In line with this hypothesis it makes sense to suppose that OBEs are the result of a capacity to provide a sort of meta-representation of instances and contents made possible by CSS. For instance, the capacity to imagine a first-person visual-spatial perspective as independent of the body could explain the disembodiment feeling typical of OBE. In fact, this hypothesis seems to be supported by a series of empirical findings regarding OBE.
I will briefly sort out some of those findings: In recent years, some neuroscientists have stressed the crucial role of the Temporal Parietal Junction (TPJ) on the occurrence of OBE. More particularly, this structure seems crucially responsible for two distinct cognitive capacities with an important role in the occurrence of OBE:
1) the generation of mental imagery of body location (Blanke 2005) and 2) as providing an internal multi-modal off-line representation of the body. Regarding the first capacity, in a study conducted by Blanke and colleagues it was shown that, in an evoked potential study, 10 out of 11 healthy subjects activated their TPJ when mentally imagining their visual-spatial point of view (that is, their first person perspective (1PP)) in a location different from the ‘normal’ one. They conclude that:
”Our evoked potential data show (in healthy subjects who have never experienced an OBE) that mental own-body transformations, which mentally simulate the body position and visuospatial perspective that is experienced spontaneously during OBEs, selectively activate the TPJ at 330-400 ms. In addition, we show that this activation correlates with behavioural measures and phenomenological characteristics of OBEs (…)” (Blanke et al 2005, 555) On what concerns the second cognitive capacity, a series of experiments undertaken by Tsakiris and colleagues evaluated the role of TPJ in the production and maintenance of an ‘off-line internal body-model’.
”Recent studies suggest that the right temporal and parietal lobes and in particular the right temporo-parietal junction (rTPJ) underpins an internal model of the body that could allow the brain to maintain a coherent representation of ones body” (Tsakiris et al 2008, 3014)
They devised an experimental protocol, which modifies the Rubber Hand experiment discussed in the previous section. This new setting was conceived to address the role of TPJ in the proprioceptive drift of the real hand to a fake rubber hand or, instead to a neutral object that doesn’t look like a hand at all. They found that, by disrupting the TPJ trough transcranial magnetic stimulation, there was a much more higher probability of subjects to report a proprioceptive drift to a neutral object. Tsakiris and his team suggested that:
”[T]he rTPJ is involved in updating and maintaining [a] body-model by testing which stimuli are relevant to one’s own body. We suggest that the rTPJ is actively involved in testing the fit between current sensory input and a stored body-model (…) [t]his model describes the pre-existing visual, anatomical and structural features of the body”. (Ibid, 3017)
These two cognitive capacities made possible by the TPJ are of crucial importance for the occurrence of OBEs. The first capacity, regarding the ability to manipulate mentally a dislocation of the first-person visual-spatial perspective, can support and explain phenomenological proprieties 1 and 2 of the above definition of OBE (the sense of disembodiment and the experience of the world from an non-corporeal visual-spatial perspective). The second capacity, the off-line representation of the body, can help in understanding phenomenological propriety 3 of OBEs (i.e., autoscopy).
Now, each of these two capacities seem to assume some other capacities and contents already being provided. The first capacity assumes a previous first person perspective (1PP) in order to be capable to mentally manipulate it. The second assumes an on-line image of the body that is capable of being modelled off-line. As it happens, and as we have seen, a 1PP and an (on-line) image of the body are precisely the two features attributed to CSS (and ‘expressed’ in FBIs). If so, then a first important consequence can be extracted, namely that that CCS (as defined in the first section) supports OBEs by providing the additional off-line and imagery processing to CSS contents and cognitive capacities responsible for FBIs. A second consequence is the backup to the idea that CSS is a necessary condition to CCS. That is, as stated in section 1, just like ‘photo-reception’ (‘Vision Simpliciter’) is structurally and functionally necessary for the more elaborate and complex Cortical Vision the same applies to CSS in relation to CCS. We have just testified this necessary relation more specifically at the functional and phenomenological levels.
But this suggestion implies that a similar relationship between CSS and CCS should be expected to occur also at the structural level. Although to my knowledge no empirical confirmation to this claim seems to exist, important neural pathways seem to link the Posterial Parietal Cortex and the Temporo-Parietal-Junction (the areas suggested to correspond to CSS and CCS respectively). The structural
dependence relation between the two is an empirical consequence of my general hypothesis and suggests the need for further experimental inquiry. Thus, the idea is that whereas the PPC provides a multi-modal sensorial- motor integration through coordinate transformations which in turn is phenomenologically responsible for 1PP, the notion of an external world and an on-line image of the body, the TPJ adds complexity to these contents by computationally re-represent (or meta-represent) these contents turning phenomenolgically possible the capacity to imagine off-line the 1PP, the external world and the image of the body. These
‘extra’ cognitive capacities, in turn, make possible the detachment of the 1PP from the image of the body by ‘suppressing’ the pre-specified coordinate transformation establishing the coincidence of these two features (still present in FBIs) and, therefore enabling the phenomenological feeling of disembodiment typical of OBEs. If this is the case, then some strength is given to the notion that FBIs are a constitutive and necessary part of OBEs. As Lenggenhager et al say regarding their study in FBIs:
”Because the present illusion was neither associated with overt disembodiment nor with a change in visuospatial perspective, we argue that we have induced only some aspects of out-of-body experiences (…). [T]he present data suggest that other mechanisms in addition to conflicting visual-somatosensory information (…) are involved in generating full-blown out-of-body experiences and a more complete transfer of selfhood to an illusory body.” (Lenggenhager et al 2007, 1098)
My own conclusions and hypothesis seem to support this dependence/necessary relationship between Full-Body-Illusions and Out-of-Body-Experiences. On the other hand, taking both this relationship between FBIs and OBEs and the characteristics of both illusions, the very proposed taxonomical distinction between CSS and CCS gains empirical and conceptual strength.
Conclusion
At the end of the first section it was stated the main hypothesis that guided this article: that FBIs and OBEs are, respectively, manifestations of (malfunctioning) CSS and CCS.
The point of departure was a suggested taxonomical fragmentation of the concept
‘Core-Self’ into ‘Core-Self Simpliciter’ (CSS) and ‘Cognitive Core-Self’ (CCS), with a certain relation of dependence where CCS adds neural, computational and phenomenological complexity to the more basic CSS.
In sections 2 and 3, it was proposed the relation between CSS and FBIs. CSS was presented as the result of evolution’s ‘answer’ to the Stability Problem in complex vertebrate bodies. This solution was identified as a multi-modal and motor integration through coordinate transformation. It was argued that, the result from
this solution, was the emergence of a first person perspective, a notion of an
‘external world’ and a image of the body (a ‘Body-Image’). The suggestion was that FBIs could be viewed as a result of a misjudged pre-specified coordinate transformations brought about by the illusory body visual-tactile synchronization.
1 As a matter of fact, Björn Merker never uses the phrases ‘Core-Self’ or ‘Minimal-Self’ in his writings. Nevertheless, it is quite clear that he is referring to the set of properties usually identified with such concepts.
2 This distinction is a contentious one in current Cognitive Science. Several authors use these notions in very different ways, sometimes inconsistently. Here I am using this distinction as suggested by Gallagher (see especially: Gallagher 2005, 17-39)
References
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Neuropsychologia 46(12), 3014-3018 Endnotes