他者性の英語論文 推敲の4

この部分、結構書き加えた。

Multiple Track Model – a theoretical basis for the view of splitting as multiplication

In this section I will discuss some neurological basis for DID as representing the splitting of consciousness as multiplication. In the past, some authors already discussed neurobiological underpinnings of DID. It is well known that Putnam proposed the "discrete behavioral states" model (Putnam, 1997) as a groundbreaking work in search for the biological mechanism of DID. According to this model, young children's sense of self is highly discrete and state-dependent (Wolff, 1966), and their integrative capacity will yield a cohesive sense of self. However, in abusive environment, they remain disintegrated and forms a basis for the pathology of DID. 
   Scaffolding on to Putnam's model, Kelly Forrest (2001) proposes that the involvement of a specific brain structure, orbitofrontal cortex (OFC) plays a key role in the development of DID. Based on recent neurodevelopmental research, he underscores the OFC's protective inhibitory role in the organization of behavior and emotional regulation as well as the sense of self. In abusive child-caretaker relationship, the OFC attempts to protect the integrity of the organization of behavior within the immediate context by dissociating any conflicting experiences, thus creating pathology represented as DID.
  In my view, Putnam’s model describes quite well the way DID’s mind is structured; it consists of separate and “discreet” parts which coexist and structurally separated. Forrest’s view of the role of OFC is relevant in explaining how the state of disintegration is perpetuated in its attempt to “sacrifice” full coherence in order to emotionally survive. Along with their theories, what I would like to focus in this article is what actually seems to be occurring in the minds of individual with DID in their OFC-assisted characteristic discrete state of mind.

It might be plausible to assume that the neural correlate of each PP should be in a form of some kind of neural network in our central nervous system. When a PP is active, that corresponding network should be at work. If the splitting of mind in DID is in the form of division, the way that that network is structured might be quite different from in the form of multiplication. In this article, I would like to present a model of neural networks which represent the splitting as multiplication and call it the “multiple track model.”

.Neural correlate of consciousness and the “DCGW” hypothesis

Several neuroscientists have suggested neuronal correlates of consciousness on a hypothetical basis. Edelman (2005) proposes “a thalamo-cortical system, which is a dense meshwork connectivity between the cortex and thalamus and among different cortical areas” (p.25), each exhibiting synchrony in gamma frequency and call it the dynamic core.

 Edelman et al. (2011) further proposed a hub-like base with synchronizing and re-entrant connection with different contributing cortical areas, in a frequency of gamma range. They call it the Dynamic Core Model , or DCGW (Dynamic Core and Global Workspace hypothesis).

One of the characteristics of this model is that it grasps consciousness as equivalent to informational system consisting of complex neural networking system between thalamus and cortical areas which are highly frequent, synchronous, and reciprocal. The re-entrant nature of their communication based on their observation of neural system reminds us of the “backpropagation” algorithm (Rumelhart, et al, 1986) which is proved to be crucial in current enormous advance in deep learning system.

Another remarkable feature of this model relevant to our discussion is that it maintains that consciousness is “unitary and integrated” which typically characterizes its experience of qualia Edelman, 2005). Being conscious itself presupposes that it “cannot voluntarily be broken up into separate parts”(ibid, 179). It straightforwardly denies divided nature of subjective experience, even by a PP of the individual with DID, which suggests that each PP has a neurological correlate of a single dynamic core.

Obviously, Edelman et al. are talking about our ordinary single mind and they are not particularly supposing multiple consciousness. However, their theory of consciousness acknowledges a possibility of multiple existence in an individual at the same time (Baars, 2002). We can then hypothesize that there are multiple conscious systems, each with its own synchronous wave frequency which are slightly different from each other, but all are within the gamma range. They are compared to different broadcasting stations using different radio wave frequency.

One circumstantial, but quite solid and convincing evidence for the possible co-existence of multiple minds in an individual comes from the experiment of subjects with split brain (Gazzaniga, 1967). If each severed hemisphere of a subject is asked to do some tasks at the same time but separately, they can do them well. However, if control subjects by being given tasks in a same manner, they get confused and could not perform either of them (Edelman, Tononi, 2000). This practically proves that different personality/agency can exist in an individual’s brain, so long as structural separation of different “dynamic cores” is secured (in this care, by splitting the surgically) . In patients with DID, this functional separation and co-existence of multiple dynamic cores seem to be occurring in a mechanism which is yet to be known.

In this split brain paradigm, supposedly single dynamic core is artificially multiplied into two dynamic cores, representing consciousness which now are different from each other. (Diagram 2)

With the discussion above, I draw an image of the mind of DID on a neuronal model, using icon of a dynamic core that I made after Edelman’s own drawing of the dynamic core.