ミラーニューロンと解離 35

Discussion　を少し書き直したが、だいぶ考え方が変わってきた。DIDというネーミングそのものが間違っている可能性があると考えるようになった。

So far, I take a second look at how personalities in DID are conceptualized in modern psychiatric diagnostic criteria such as DSM-5 and ICD-11 and delineated current trend of regarding the identities in DID as partial and fragmentary.

Presumably, DID is characterized as having a disruption of identity (DSM-5, ICD-11), which is cogently expressed in the name of the “dissociative identity disorder”, a diagnostic nomenclature which first appeared in 1994 (DSM-IV, American Psychiatric Association) and seems to have gained its citizenship well enough afterward. If we trace the way the diagnostic naming is switched from MPD (multiple personality disorder) to DID, the rationale for the change was to remind clinicians with this name that patients’ problem is not having many real personalities as MPD connotes, but having identity disorder with inability to have a wholesome personality (i.e.,) as a result of the failure of integration.

David Spiegel, who chaired the committee for DSM-IV dissociative disorder spoke the rationale for the change from MPD to DID, with a rather pejorative tone, as follows:

 Indeed, the problem is not having more than one personality, it is having less than one (Spiegel, 2006 p567.)

Spiegel, D. (2006) Editorial. Am J Psychiatry 163:566-568.

It might be a surprise for those who are used to this diagnostic name DID that it implies that personalities are parts or fragments as this view might not altogether consistent with their clinical manifestations. I imagine that many clinicians including myself are treating these personalities as a regular and wholesome human being until we have a chance to be reminded of their experiences reflecting disruption of identity in one way or other.

I would venture and ask if it is really a problem for a person to have more than one mind so long as he is coping with it well? Imagine that there is a population of people who happen to have two or more personalities while possessing a shared body? Some might argue that it is a problem, or “disorder”, but this is equivalent to the state of Siamese twins, a comparison that I already made to the state of DID earlier in this paper. In fact, example of Hensel sisters look quite healthy and normal although they share a single body (Russell, Cohn, 2012). This topic even goes back to the question of whether the condition of DID is an illness or a normal variant.

Russell, J,., Cohn, R. (eds.)(2012) Abigail and Brittany Hensel. Book on Demand Ltd. 

 （以下省略）

 

ミラーニューロンと解離 34

 討論の部分の推敲をしていて、いろいろ気になることがある。

Discussion

In this article, I take a second look at how personalities in DID are conceptualized in modern psychiatric diagnostic criteria such as DSM-5 and ICD-11 and delineated current trend of regarding the identities in DID as partial and fragmentary.
　Presumably, DID is characterized as having a disruption of identity (DSM-5, ICD-11), which is cogently expressed in the name of the “dissociative identity disorder”, a diagnostic nomenclature which seems to have gained its citizenship well enough after its first appearance in 1994 (DSM-IV, American Psychiatric Association).　If we trace the way the diagnostic naming is switched from MPD(multiple personality disorder) to DID, the rationale for the change was to remind clinicians that personalities are not whole ones, but parts as result of the failure of integration.
　David Spiegel, who chaired the committee for dissociative disorder spoke the rationale with a pejorative tone, as follows: “People with this disorder do not have more than one personality but rather less than one personality. (The name was changed recently from ‘multiple personality disorder’ to ‘dissociative identity disorder.’) “

Spiegel, D expert Q&A: dissociative disorders American Psychiatric Association https://www.psychiatry.org/patients-families/dissociative-disorders/expert-q-and-a

改めて思うことだが、1994年に発表されたDSM-IVで、MPDからDIDに変わった時、実は大きな意識の変化があったのだが、このことを今日まで十分把握していなかった。つまり多重人格障害（MPD）に示唆された「人格が沢山ある」という表現は誤解を招くという。DSMの解離部会の委員長だったDavid Spiegel はこんなことを言っていた。私はこれまでシュピーゲル先生を尊敬していたが、これはひどすぎる。

「彼らはたくさんの人格を持つことが問題ではない。一つも【正常な】人格を持てないことだ。」

私はこれに断固反対したい。これほどDIDの患者さんを誤解した文章はないだろう。

I proposed that this view is not altogether consistent with their clinical manifestations and proposed an alternative way of looking at these personalities has having their sense of self on their own, furnished with all its component delineated by Japers.

サクレの件、ミラーニューロンと解離 33

結局こちらにはハマらなかった。どうしてだろう？

何となく論文は完成に向かっている。見直しを繰り返すといろいろ考える材料が見つかる。つくずく解離をめぐる議論は誤謬に見している。大家の多くが唱える「交代人格は断片であり、部分的である」、という理屈はどう考えてもおかしい。今日は以下の文を付け加えた。 

How about the issue of partial or fragmented personality? I consider that we need to take a second look at this concept seriously. What many individuals with DID suffer is conflict among personalities, which indicates that they are emancipated and independent enough to have different views from others, rather than their being partial and fragmentary, achieving a view only when fused and integrated.

問題は私たちがある体験をする(正式にはクオリアを持つ、体験する)という事はそれ自身が統一であり、単回であり、決して部分的ではないという事だ。(これはWauchope 安永理論にも通じる。）人格が部分的、断片的という事はあり得ない。もしそうなら体験を持てない、という事になる。するとそれは人格でない。このような誤りを多くの解離の大家たちが犯している。

ミラーニューロンと解離 32

 Abstract　書いてみた。

In this paper the author examines current problems in understanding and conceptualizing “personalities” of the individual with DID (dissociate identity disorder). In seeking biological correlate of these personalities, he attempts to give a second look at the understanding of this issue. He first delineates current theoretical ambiguity and potential problem about how we understand the personality, by examining current international diagnostic criteria and views proposed by leading experts on the topic. The general trend is to not to acknowledge each personality as having independent sense of self, but rather partial and fragmentary, which the author does not think matches well with the clinical manifestations of individuals with DID. Then the author proposes that each personality has its independent neurological correlate, a neural network which is proposed with the notion of Dynamic Core by G. Edelman and J. Tononi. Although their theory is not designed to explicate personalities of DID, it can be applied to personalities of DID based on the superimposed nature of these networks, which is partially exemplified by the brain functions in the so-called split-brain experiments. The author then draws on current understanding of mirror neuron system (Giacomo Rizzolatti, G., Vittorio Gallese, V. et al.) which forms a basis for the understanding of how our sense of self is formed. He proposes that potential dysfunction of mirror neuron system in a traumatic and critical situation might explain how different personalities are formed. The author then discussed how this neurological understanding might be reflected on our understanding and treatment of individuals with DID.

サクレのあずき

 もう確実に３年以上毎晩食べ続けている。(冬も置いている店あり。）おいしさ変わらず。ただし売っているところが限られているので、地方にいる間は味わえないのが残念だ。時々あずきの量が多いカップがあり、「ラッキー！」となる。まあ晩酌よりはいいか。

ミラーニューロンと解離 31

 What could we learn from these theories on the biological basis of personalities in DID?

Perhaps we should assume that our neural system has a readiness, or a leeway for multiple existence of conscious mind. Many phenomena, including imaginary companionship, possessing phenomena, hidden observers described by Hilgard (1977) and rather sudden formations of personalities in DID might corroborate that situation.  

Hilgard, E. (1977). Divided consciousness: Multiple Controls in Human Thought and Action. New York, John Wiley and Sons.

 　　One metaphor that I care for in describing this situation is radio stations. Each station broadcasts programs based on a band of radio frequency assigned by the authority. If station A is joined by station B with different frequency band on its own, it can get its activity started without hindering A’s program. They can coexist, besides multiple other stations with different frequency on their own. If you allow me to expand my imagination and share a fantasy that our brainwaves are Fourier series and can be divided into different waves with different frequency, can’t they harbor multiple selves? In ‘dynamic core’ theory by Edelman, probably two dynamic cores, each functioning at the frequency of 40, and 42 Hertz, for example, can coexist and form two different minds.
　Or, dynamic cores can be superimposed and can exist in layers, as I designed in the previous paper. If a situation like what Stephen Porges suggests, where two other autonomic system fail and the remaining dorsal vagal system gets activated, there could be extra dynamic core ready for these emergency situation (like “spare” network) and get activated and function in the place of frozen subject. In DID that can occur multiple times due to repeated crisis, each producing extra dynamic core. The theory of mirror neuron gives us a tool to speculate how our mind can host other mind virtually (Ramachandran) and allows us to imagine what can happen if MNS fails, as I did in this paper.
　　The reason why I consider that this model can be of help in better and more realistic understanding of DID is that by imagining that each personality possesses an independent neural system, a dynamic core which is basically isomorphic to our own, we can more readily accept that each personality is a stand-alone mind, like ourselves. 

ミラーニューロンと解離 30

 One of the problems of the current diagnostic criteria of DID is that alleged disruption of the identity is rather ambiguous, and what it seems to implicate, the discontinuity of the sense of self is not altogether what people with DID appear to be experiencing. Hearing voices, or intrusive and ‘made’ experiences can be part of their symptoms and they sometimes feel that they are switching or merging into other personality without their sense of control. However, these symptoms of discontinuity may be experienced rater intermittently or episodically. In fact, individual with DID might spend their time without these problems for a quite long time. Therefore, clinicians might need to look elsewhere in order to locate the essential pathology of DID, which might be the structure and the sense of self in each personality. One of the candidates is that these identities might be partial or fragmentary, which was demonstrated by texts written by many major figures in the study of dissociation.  

Russell, J,., Cohn, R. (eds.)(2012) Abigail and Brittany Hensel. Book on Demand Ltd. 

 One of the ways of looking at this issue from a different perspective is to consider the biological basis of these personalities. Perhaps the biological mechanism of personality formation is so complicated that rough sketching with a broad brush is at best available. In modern psychiatry, brain function should be understood on a neural network approach instead of focusing on anatomically separated areas Durstewitz, D. Koppe, G, and Meyer-Lindenberg, A (2019). In their brain graph model, multiple neuronal networks exist in a superimposed way, allowing multiple networks still sharing same neuron and subnetworks (Pol, Bullmore, 2013).. One of the most hopeful candidates of the methodology is that of neural network model proposed by Edelman and Tononi which can exist in a superimposed way, practically providing us with the neurological basis for the existence of multiple personality

Pol, HH, Bullmore, E (2013) Neural networks in psychiatry. European Neuropsychopharmacology. 23.1-16

Durstewitz, D. Koppe, G, and Meyer-Lindenberg, A (2019) Deep neural networks in psychiatry

Molecular Psychiatry (2019) 24:1583–1598.

 This type of model is necessary to better understand the mechanism of DID and dissociative pathology where a very large mass of neural networks are the subject of dissociative phenomenon.

 

ミラーニューロンと解離 29

 Discussion

So far I challenged the current trend of regarding the identities in DID as something partial and fragmentary which is inconsistent with their clinical manifestations and proposed a new way of looking at them as a whole in their own sense, if not altogether sophisticated and generally furnished with all the component of the sense of self. When we examined the current definition of DID in DSM or ICD, there is ample room for multiple and possibly mutually contradictory understanding of the personalities in DID. We assume that clinicians agree that there is some kind of disruption of identity (DSM-5, ICD-11)in DID, which is cogently reflected on the name of the “dissociative identity disorder”, a diagnostic naming which seems to have gained its citizenship well enough. However, what is the nature of the disruption of identity is nothing but simple and clear. Is it the fact that there are independent identities switching back and forth (and hence, discontinuity in the sense of self), instead of having one, which itself is the problem, at least from observers’ point of view? However, is it really a problem for a person to have more than one mind so long as he is coping with it well? Imagine that there is a population of people who happen to have two or more personalities while possessing a shared body? Some might argue that it is a problem, or “disorder”, but this is equivalent to the state of Siamese twins, a comparison that I already made to the state of DID earlier in this paper. In fact, example of Hensel sisters look quite healthy and normal although they share a single body (Russell, Cohn, 2012). This topic even goes back to the question of whether the condition of DID is an illness or a normal variant.

Russell, J,., Cohn, R. (eds.)(2012) Abigail and Brittany Hensel. Book on Demand Ltd. 

ミラーニューロンと解離 28

 Let us imagine a traumatic situation where a baby is harshly beaten by the mother, instead of engaging in mutual smiling with her. The baby might experience a serious emotional trauma with intense fear and anxiety. As we saw above, in such situations, in dissociative cases, some areas of the baby’s brain, especially prefrontal cortex, are activated in order to suppress related areas, such as amygdala in his limbic system in order to avoid sensual and emotional experiences (van der Kolk, 1994, Reinders, et al, 2003,3006). The baby might be “dazed” and is in trans-like dissociated state) and his passive experience of being beaten is not formed properly as there is a lack of sensation, such as pain, terror and anxiety. The baby might wonder what he is going through, as though he might not be living that experience, like his anesthetized hand being touched.

van der Kolk, B. (1994) The body keeps the score: Memory and the evolving psychobiology of post-traumatic stress. Harvard Review of Psychiatry. 1(5):253-65.

In this situation where the MNS faces paradoxical input of information of visually being beaten, but no matching sensation and is unable to form a passive experience, suddenly a new center of consciousness might be formed on an emergency basis, which observes himself from outside, in a form of so-called out-of-body state. It is suggestive that many reports of out of body experiences come from those who undergo surgical operation with general (but probably insufficient) anesthesia. This was eloquently described by the author such as Putnam,etc.

(deleted from this point.) .................................................................................................................................................................................................................................................................................................................................................................................................................................................

ミラーニューロンと解離 27

 

Mirror neuron and its dysruption

There are studies indicating that MNS is closely related to imitation (Rozzi, Buccino, Ferrari, 2013). Among primates, there are species which are good at imitation (e.g., orangutans) and not so good (e.g., monkeys)(Arbib, Bonaiuto, 2009). Human beings are extremely good at imitating others and that is considered to be related to our highly elaborated and sophisticated social and communication skills (Ramachandran, 2011).　

Ramachandran, VS. (2011) The tell-tale brain. Norton & Company.

Rozzi, S., Buccino, G and Ferrari, PF. (2013) Mirror neuron and imitation. In Routledge Handbook of Motor Control and Motor Learning By Albert Gollhofer, Wolfgang Taube, Jens Bo Nielsen. Chapter 9 pp.175-194.

Arbib, M, Bonaiuto, J (2009) From grasping to complex imitation: Mirror systems on the path to language. Mind & Society 7:43-64.

Let us examine more closely how mirror neurons are involved in our act of imitation. When a person A smiles at another person B, naturally B has the same experience in its passive voice; he has the experience of being smiled at. However, at the same time, B is also observing A’ s actively smiling and with the help of MNS, B is also experiencing A’s smiling vicariously. Thus, if B observes A doing something toward B, his experience is always twofold, and what is important is that B is with his readiness for the imitation of A’s behavior. When B actually imitates A’s behavior by smiling back at A, it is no longer a simple imitation, but starts A and B’s bidirectional interaction. That interaction may continue, by A’s smiling back at B, and B’s response to it, and so on. In order to show that this imitative exchange is based on MNS and involves multimodal experiences and reward system, let us make this interaction more concretely.  

Suppose that this interaction is between mother and her baby. The baby is on the receiving end of mother’s smiling, while at the same time, with the help of MNS, he vicariously experiences mother’s actively smiling at him. Most likely, the baby feels good, as mother’s smile might come with her tender tone of voice, gentle sensation of her stroking hand, warmth of her body and good smell, which are all experienced by the baby in a multi-modal way. He then smiles back at his mother, and their mutual smiling begins to form their emotional exchange. As I suggested, this interchange is strongly mobilized by the involvement of their reward system: they repeat them as they feel basically very good. When the baby smiles back at her, most of the additional sensation, such as tender voice and warmth of his hand, might be experienced by the mother on the receiving side. The child experiences vicariously through MNS the mother’s experiences of them. Thus the baby experiences this bi-directional exchange with his mother (or any significant caretaker) with its all recipes necessary for the child to gain sense of self, sense of agency, self-other differentiation with the help of mirror system; his passive experience is backed by all sorts of additional sensation. He has the sense of agency by vicariously experiencing mother’s reception of the sensation in the same kind. He feels that he and his mother are different subjects as his observation of an action and his actually doing are sensed differently, with the help of MNS and mu-neuron.(when he is actually doing, there is an activation of μsystem which tell the subject that he is not doing but observing it.

 

ミラーニューロンと解離 26

 Dissociation and the dysfunction of mirror neuron system

In the last part of this particle, I would like to propose a hypothesis that formation of personalities in the individual with DID can be related to some type of disruption of the mirror neuron system.

Although we can hypothesize that each personality has its own dynamic core as its neurological correlate, it is still unknown how and in what situation these multiple dynamic cores are formed. It is our clinical observation that many personalities are formed rather suddenly in a critical and traumatic situation where an individual is under an extreme stress. When an extreme emotion is experienced and dissociated, they become a part of “some personality” who came for rescue (McDougall, 1926, P543, van der Hart et al., 2006, p29) and this is how a personality forms. But how can it happen?McDougall, W. (1926). An outline of abnormal psychology. London: Methuen.
van der Hart, O, Nijenhuis, E.R.S, Steele, K. (2006) The Haunted Self. W.W.Norton & Co. New York, London.
 There have been theories regarding the process of “identification” as a crucial mechanism for the formation of personalities (Howell,2014), especially aggressive ones when abusive situation occurs. Although the original notion such as “the identification with aggressor” (Ferenczi, 1933/1949) was psychoanalytic and not on a biological basis, some type of cognitive error might be involved in the behaviors of other person (especially the “aggressor”) in the process, which might give rise to the formation of a novel dynamic core. In this context, I consider that the theory of mirror neuron system is a very useful tool in delineating this mechanism.   

Ferenczi, S. (1933/1949) Confusion of the tongues between the adults and the child (The language of tenderness and of passion). International Journal of Psycho-Analysis, 30, 225–231.
Howell, E (2014) Ferenczi’s Concept of Identification with The Aggressor: Understanding Dissociative Structure with Interacting Victim and Abuser Self-States. The American Journal of Psychoanalysis 74(1):48-59.

 There has been an explosion of the studies related to mirror neuron for the past decades. Mirror neuron was discovered in 1996 by Italian neurophysiologists in the University of Parma, led by Giacomo Rizzolatti, Leonardo Fogassi, and Vittorio Gallese (Rizzolatti, Craighero, 2004, Rizzolatti, Fabbri-Destro,2010). They found that some neurons in the ventral premotor cortex of the macaque monkey responded when the monkey observed a person picking up food, the same neurons that are activated when monkeys do the same behaviors. By definition, A mirror neuron is a neuron that gets activated both when an animal acts and observes the same action by another, thus "mirroring" the other’s behaviors of the other, as though the observer itself is acting (Rizzolatti, Craighero, 2004,). Reportedly, mirror neurons have been found in human, primate species, and birds.

Rizzolatti, G., Craighero, L. (2004). "The mirror-neuron system" (PDF). Annual Review of Neuroscience. 27 (1): 169–192. 
Rizzolatti G, Fabbri-Destro M (2010). "Mirror neurons: from discovery to Autism". Experimental Brain Research. 200 (3–4): 223–37. 

Iacoboni (2009) indicates that mirror neurons forms a system of neurons (Mirror neuron System) with its relationship to various locations in the brain, suggesting that it allows the subject to differentiate between self and others, active and passive voice and fantasy and imagination. What is to be stressed is that we acquire these distinctions through imitative activities.

Iacoboni, M. (2009) Mirroring People: The New Science of How We Connect with Others. Farrar, Straus and Giroux.

ミラーニューロンと解離 25

 Split brain - A putative biological model for the multiplicity of personality

I propose that so-called “split-brain experiment” (Gazzaniga, 1970) , indicates something akin to the multiplicity of the personalities in different locations in the brain, and I consider that state as a step toward the biological model of DID.

Gazzaniga, M. S. (1970). The Bisected Brain. Appleton Century-Crofts.

There seems to be an increase of attention to the issue of split brain (Haan, et al. 2020). It is because the surgical disconnection of the cerebral hemispheres creates a splendid opportunity to study the neurological mechanisms of consciousness in its potential dual states (Gazzaniga, 2000).
Gazzaniga, MS (1995) Principles of Human Brain Organization Derived from Split-Brain Studies. Review Neuron, Vol. 14, 217-228.

After the two hemispheres are disconnected, the person verbal IQ of a patient remains intact (Nass and Gazzaniga, 1987) and problem-solving capacity remains unchanged for the left speaking hemisphere (Ledoux, et al.,1988). However, with a proper set of examination, each hemisphere has a separate mind. “Cortical disconnection produces two independent sensory information processing systems … (Gazzaniga, 1995)”, with each hemisphere having its own set of specialized capacities, e.g., language and speech, problem solving capacities for the left, and facial recognition, attentional monitoring, etc for the right. When tested separately, right hemisphere is seriously impoverished in cognitive tasks. It is poor at problem solving and may other mental activities (Gazzaniga.2000). Therefore, it has been debatable whether the right, mute hemisphere has its conscious equal to its counterpart.
Gazzaniga M (2000) Cerebral specialization and interhemispheric communication - Does the corpus callosum enable to human condition? Brain. 123:1293-1326. 
Nass, R, Gazzaniga, M (2011) Cerebral Lateralization and Specialization in Human Central Nervous System. Handbook of Physiology. 
Ledoux, JE, Risse GL, et al. (1977) Cognition and commissurotomy. Brain. 100.87-104.

Joseph LeDoux tackled this issue and stated that brain bisection produces a state of double consciousness (Ledoux, et al.1977). In their experiment with a patient “P.S.” with a split brain, they concluded that the right hemisphere in that patient has a sense of self with its own feeling.

Personally, the author considers that it is still debatable if this state of right brain is emancipated enough to be called a conscious mind. It sounds much more like a part of personality, needing the counterpart (left brain) to be supplemented to function as a while, just as van der Hart defined as a “part of personality”.

Haan, EHF, Corballis, PM. et al (2020) Split-Brain: What We Know Now and Why This is Important for Understanding Consciousness Neuropsychology Review (2020) 30:224–233.
LeDoux, JE, Wilson,DH, Gazzaniga, MS (1977) A Divided Mind: Observations on the Conscious Properties of the Separated Hemispheres. Ann Neurol. 2:417-421. 

To summarize, the split-brain states seems to create two independent minds. The speaking left hemisphere appears normal with intact intelligence, which is largely unaware of its counterpart, right brain, except for the “emotional significance” of its experience (LeDeux, 1996).

Ledoux, J.(1996) The Emotional Brain. The Mysterious Underpinnings of Emotional Life. The Touchstone.

   Although it is still debatable whether the right brain can claim that it is emancipated enough to be called a “personality”, at least two issues are obvious.
   When dissected, the neural network consisting of two connected hemispheres would become two independent minds. It appears to be crucial for a mind to be conscious to have a set of one hemisphere, one thalamus, and a limbic system including amygdala and hippocampus which are connected to each other. As Tononi’s information system asserts, it is not the localization but the connection of system that creates the mind. In order to consider the neural correlate of a personality, this “set” is a crucial component.

ミラーニューロンと解離 24

 少しリライトした

Neurological basis of dissociative symptoms

 The difficult problem that we discussed above, as to whether we should understand personalities in DID as independent individual or “partial” or “incomplete” might be easier to handle if there is any neurological basis or “neural correlate” of these personalities. If a personality A happens to be “located” in one side of the hemisphere whereas the personality B resides in the other without any overlapping area or communication between them, for example, we could assume that they are different and independent consciousnesses. Unfortunately, no study has so far indicated that each personality in DID has its distinct localization or neural network.
    However, there has been a considerable number of studies that are suggestive of biological basis of trauma-related or dissociative mechanism of PTSD and dissociative disorders. In 1980s, Bessel van der Kolk discussed biological basis for the formation of traumatic memories which underlies clinical manifestation of flashbacks and dissociated memories. He stressed that intense emotional experiences affect amygdala and hippocampus, and trauma-related memories are dissociated on the body/visceral level on a traumatized individual, in a way quite different from the ordinary formation of episodic memories.

　More recently, dissociative symptoms in PTSD has been the focus of study, which led to the notion of dissociative subtype of PTSD (PTSD + DS). The study suggests that PTSD+DS has the mean prevalence of 20.35% among PTSD population (Hansen et al.,2016) and are found to be related to increased re-experiencing symptoms, male sex, history of childhood trauma, history of trauma prior to the index trauma (Stein, et al, 2013). Studies found that PTSD+DS is to be associated with greater activity of areas of the frontal cortex that are involved in inhibiting brain areas that coordinate fear responses, such as the amygdala, as the study of van der Kolk suggested, but also it spans multiple brain areas, particularly those involved in sensory integration, giving rise to the complex subjective sense of dissociation (National Center for PTSD, 2018).  

Hansen, M., Műllerová, J., Elklit, A., & Armour, C. (2016). Can the dissociative PTSD subtype be identified across two distinct trauma samples meeting caseness for PTSD? Social Psychiatry and Psychiatric Epidemiology, 51, 1159-1169.
National Center for PTSD (2018) PTSD Research Quarterly. VOLUME 29/ NO. 3. ISSN: 1050 -1835.Stein, D. J., Koenen, K. C., Friedman, M. J., Hill, E., McLaughlin, K. A., Petukhova, M., . . . Kessler, R. C. (2013). Dissociation in posttraumatic stress disorder: Evidence from the world mental health surveys. Biological Psychiatry, 73, 302-312.

Along with these studies, Polyvagal theory proposed by Porges (2011) made a contribution in elucidating close relationship between autonomic nervous system and dissociation. He proposed three branches of our autonomic nervous system, including what he calls ventral vagal system (VC) which has been developed in mammalian animals but has never been delineated until his discovery. When in real crisis, this VC shuts down and if fight-flight response based on the sympathetic nerve fails, the dorsal vagal system activates which is largely responsible for dissociative process. Recent biological studies including Porges’ research help us understand how much dissociative mechanism in involved in our traumatic response and this led to the proposal of dissociative type of PTSD which now appears in the last version of DSM (DSM-5, 2013).
　Although this view helps clinicians understand the involvement of different area of the brain in the formation of dissociative experiences it remain still unclear how this mechanism is translated to the way massive entity such as a personality structure can be dissociated in the case of DID.

ミラーニューロンと解離 2３

 

Let us imagine a totally different situation where a baby is harshly beaten by the mother, instead of engaging in mutual smiling. The baby might experience an intense emotional trauma with strong fear and anxiety. As we saw above, in such a traumatic situation, the baby’s brain, especially prefrontal area is activated in order to suppress areas related to emotional experiences, such as amygdala and other areas in his limbic system. The baby’s mind is in a sense “hypnotized” (i.e., dissociated) and the imitative response of the mother’s behaviors based on the MNS cannot be followed through with. What the baby would experience, instead, is depersonalization and derealization, or out-of-body type of experiences. Why would these experiences occur? The baby might lose a sense that he is passively beaten-up by his mother, as there is no pain or tactile sensation which should accompany and establish that passive experience. Then a new center of consciousness, a new personality is established on an emergency basis, which observes himself from outside, in a sort of out-of-body state.

Another situation which might occur in a more severe cases is that baby’s passive experience of being beaten might translate into an active experience of beating (himself). As I stated, the experience of passivity and passivity has a dual nature. One as a real experience and the other as a vicarious experience of the other through MNS. Being smiled at, for example, is doubled by the counterpart of smiling, etc. In a situation of being beaten, the passive experience would be obliterated through dissociative process and the only active experience remains, establishing that experience primarily as the active one. This process is considered the “identification with the aggressor”.

To schematically describe, this is what might happen in the baby’s psyche:

Experiences of being beaten (actively, virtually beating experience + direct experience of being beaten + lack of physical experiences of passive experience = establishment of by-stander personality, or establishment of aggressive personality ←　overactivation of MNS.　

 

 

ミラーニューロンと解離 22

 　Let us examine this interaction more concretely, say, between mother and her baby. The baby virtually experiences mother’s actively smiling at him, with the help of his MNS while being on the receiving end. He then smiles back at his mother, and their mutual smiling begin to form their mutual emotional exchange. This interchange is strongly backed by the involvement of their reward system: they repeat them as they feel good. When the mother smiles at the child, she does with her tender tone of voice, gentle sensation of her stroking hand, warmth of her body and good body smell which are all experienced by the baby in a multi-modal way. When the baby smiles back at her, most of these additional behaviors, such as tender voice and warmth of his hand, might be experienced by the mother on the receiving side. The child naturally experiences through MNS the mother’s experiences of them vicariously. Thus the baby experiences this bi-directional exchange with his mother (or any significant caretaker) which is strongly motivated by the involvement of reward system. We should understand that this interchange implies all the recipes necessary for the child to gain sense of self, sense of agency, introject of object images, obviously with the help of mirror system.

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Mirror neuron system and dissociation

The purpose of this section is to give a hypothesis that formation of personalities in the individual with DID can be related to some type of disruption of the mirror neuron system.
　There has been an explosion of the studies related to mirror neuron for the past decades. Mirror neuron was discovered in 1996 by Italian neurophysiologists in the University of Parma, lead by Giacomo Rizzolatti, Leonardo Fogassi, and Vittorio Gallese. They found that some neurons in the ventral premotor cortex of the macaque monkey responded when the monkey observed a person picking up food, the same neurons that are activated when monkeys do the same behaviors. By definition, A mirror neuron is a neuron that gets activated both when an animal acts and observes the same action by another, thus "mirroring" the other’s behaviors of the other, as though the observer itself is acting. Reportedly, mirror neurons have been found in human, primate species, and birds.
　Iacoboni indicates that mirror neurons forms a system of neurons (Mirror neuron System) with its relationship to various locations in the brain, suggesting that it allows the subject to differentiate between self and others, active and passive voice and fantasy and imagination. What is to be stressed is that we acquire these distinctions through imitative activities.

Iacoboni, M.(2009) Mirroring People: The New Science of How We Connect with Others. Farrar, Straus and Giroux.

Mirror neuron and imitation

There are studies indicating that MNS is closely related to imitation. Among primates, there are species which are good at imitation (orangutans) and not so good (chimpanzees). Human beings are extremely good at imitating others and that is considered to be related to our highly elaborated and sophisticated social and communication skills.
　　Let us do some thought experiment. When A smiles at B. B has an experience of being smiled at. A’s experience of smiling at and B’s being smiled are different and independent. However, B who is smiled at might by A might smile back at A. That interaction is bi-directional and therefore not a simple imitation. In the mind of B, being smiled at and smiling back are a pair of experience, one is passive and the other is active, occurring successively and are tightly connected. Their behaviors paired up together is not by accident. Those who are smiled at typically smile back, which is readily observable when you look at people interacting. Smiling at someone almost automatically induce being smiled at. It is a beautiful imitation of someone’s behavior immediately forms a basic emotional interaction.

 

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There have been some studies focusing on the neurological background of the formation of personalities in DID. Already in 1980s, Bessel van der Kolk discussed biological basis for the formation of traumatic memories which underlies clinical manifestation of flashbacks and trauma-related memories. He stressed that intense emotional experiences affect amygdala and hippocampus, and trauma-related memories are ingrained on the body/visceral level on a traumatized individuals, in a way quite different from the ordinary formation of episodic memories.

Bessel van der Kolk (2015) The Body Keeps the Score: Mind, Brain and Body in the Transformation of Trauma. Penguin.

Although this view helps clinicians understand quite well the way traumatized individuals suffer from flashbacks and sudden recollection of past atrocious memories, this does not help us explain how this mechanism is translated to the way different memory systems are formed for the each personality in DID.

　In this context, studies by Reinders et al. are of our great help and interest.In their studies in 2003, Reinders et al. used functional neuroimaging (PET scan) and demonstrated particular changes in localized brain activity and other biological markers of eleven individuals with DID who are able to switch between normal personality state (NPS) and traumatized personality state (TPS). In the state of TPS, they showed the deactivation of a brain network including the mPFC, which is involved in conscious processing of experience. In contrast, in the NPS, they demonstrated disturbances in the parietal and occipital blood flow, indicating an inability to integrate visual and somatosensory information. This way, the NPS in DID exerts some defense mechanism against traumatic stimuli that prevents further emotional processing (2003).

　Reinders et al. in their 2006 study, had their DID individual listen to trauma script as well as neutral script in their NPS and TPS states. They found that in response to the trauma script, the TPS showed increased heart rates and blood pressure, as well as strong emotions and sensory reminders of the traumatic event. In their NPS, however, they did not show that response, possibly due to its own defense mechanism discussed above. When the neutral script was shown, neither TPS nor NPS displayed any cardiovascular activation.　

Reinders, AA.T.S., Nijenhuis, E.R.S., Paans, A.M.J., Korf, J., Willemsen, A.T.M.,& den Boer, J.A. (2003). One brain. two selves. Neurolmage. 20, 21 19-2125.
Reinders, A.A.T.S., Nijenhuis,E.R.S., Quak,J., Korf,J.,Paans, A.M.J., Haaksma,J., Willemsen, A.T.M., & den Boer, J.A. (2006). Psychobiological characteristics of dissociative identity disorder: A symptom provocation study. Biolog1cal Psychiatry, 60,730-740.

In my view this study suggests that these two personality states might engage in two different neural networks, or “dynamic cores.” This would explain why NPS state shows no difference in response to either trauma script or neutral script. Reportedly, NPS shows practically no response to trauma script, indicating that it does not particularly inhibit (or “repress”) that stimuli. Thus NPS acts practically as a bystander, an individual unrelated to past traumatic events.  

When we hypothesize a presence of only one mind or a single dynamic core shared by different personalities in DID, there should be some type of communication on a sub-conscious or unconscious level, in this case between TPS and NPS, responding to each other’s experiences at least on a unconscious, physical, or emotional level. The “nonchalant” response of NPS to trauma-related stimuli strongly speaks to the fact that two different personality states have biological correlate of two independent dynamic cores.

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In contrast, self-disturbance in schizophrenia has been studied and discussed throughout the history of modern psychiatry. Recently it is often discussed also in the context of“ipseity disturbance”

Sass, LA (2013) self-disturbance and schizophrenia: structure, specificity, pathogenesis. Association Recherches en psychanalyse 16;119-132.

The self-disturbances in schizophrenia is far more distinct and severe. Take for example a schizophrenic person, Mr. A who observes a man walking on a street, noticing another pedestrian, a stranger  approaching him from a different direction.. Suddenly a voice in his head says “He is an enemy. He will attack you!” Mr. A immediately takes an offense for that person as the voice is his own thought. This type of hearing voice often referred to as “command hallucination” characterizes the nature of the self-disturbance of schizophrenics, where the individual experiences the voice of someone as though that someone is almost seamlessly merged with himself. This condition might instantly meet the criterial of the self-disturbance in four domains delineated by Jaspers.

Neurological basis of dissociative symptoms

The difficult problem that we are facing, as to whether we should understand personalities in DID as independent individual or “partial” or “incomplete” might be easier to handle if there is any neurological basis or “neural correlate” of these personalities. If a personality A happens to be “located” in the right hemisphere whereas the personality B resides in the left hemisphere, without any overlapping area or communication between them, we could assume that they are different and independent consciousnesses. However, no study has so far indicated that each personality has its distinct localization. The author would still make a case that so-called “split-brain experiment” (Gazzaniga,et al) , indicates something akin to the multiplicity of the personalities in different location in the brain, I will save this topic for any future opportunity for further elaboration.)

In the past I approached this issue with the concept of dynamic core model proposed by Edelman and Tononi.

In this article, I discuss what I call ‘‘the problem of otherness’’ in dissociative identity disorder, which addresses the extent to which we validate and recognize the perception of otherness in each part of personality (PP) regarding other PPs. The general trend is considered to not fully validate it, which seems to stem from the era of the Freud–Janet controversy, partly due to the conceptual ambiguity of the splitting of the mind in the sense of division vs. multiplication. Consequently, we tend to consider dissociation as a defensive and intentional act, at least when it was initiated, with an understanding that PPs are not structurally separated from each other, but are rather internally and dynamically connected to each other, and that a PP is somewhat causative to and responsible for another PP’s thoughts and behaviors. Here, I consider the hypothetical neuro-cognitive model that is based on the ‘‘dynamic core’’ model proposed by G. Edelman, where the neurological correlate of dissociative identity disorder is conceived as a simultaneous and multiple existence of a

‘‘dynamic core’’, which represents each PP as a unique and wholesome existence in the conscious.

Okano (2019) Problem of ‘‘otherness’’ in dissociative disorder European Journal of Trauma and Dissociation