alas I do not.  

Vintage paper:

Neuropediatrics. 1984 Oct;15(4):220-5.

Neurophysiological studies on conjoined twins.

Hughes JR, Fino JJ.

EEG, VEP and BAEP studies were performed on conjoined (craniopagus

parieto-occipitalis) twins, born prematurely without any common neural tissue,

but with shared venous channels and contiguous posterior poles. At thirty-three

wks (CA) the EEG of one of the twins showed higher amplitudes and less

quiescence, suggesting a more mature cerebrum but the same twin also showed

longer latencies in the BAEP, suggesting a less mature brainstem. Sleep spindles

at four and a half months frequently occurred at the same time in both of the

twins, at times synchronous and at other times with a latency of onset 0.5-0.8

sec from one to the other, providing further evidence for a circulating

"sleep-promoting factor". VEPs were recorded that were distinctive of each of the

twins. Flash stimulation of one twin produced VEPs in the other that were

characteristic, not of the stimulated twin, but of the other, suggesting that

evoked responses from one area can activate non-volume conducted responses from

another region characteristic of that latter region, presumably by physical

contiguity alone.

My Dear Alfredo, you remember that some time ago I replied to one of always interesting question just presenting my hypothesis of Brain Function based on the introduction of a "mechanical component" ascribable to the vascular network (my Hyper-oscillator Brain Model). A new kind of signaling channel in the vascular network. The very interesting study you have showed seems to support strongly this hypothesis...very interesting Alfredo. This give me more energy to go ahead in this direction. Thank you

Right at the begining of theEEG (1936) identical twins ere studied and it was found that the alfa generation pattern was"stricling similar" (sic) . The mos numerous study I found was of lennox, 1945. identical 55 twin pairs, 16 non-identical twins. EEGs were examined by naive interpreter 85% were ranked "identical", 4% non-identical and 11% as dubious.Lennox, W.G et als,,The brainwave pattern an hereditary trait. evidence from 74 "normal" pairs of twins. J.heret., 36:233-243

Dear Alfredo,

There are no many EEG studies on Siamese twins.

We find the following:

H.G. LENARD AND F.J. SCHULTE. Polygraphic sleep study in craniopagus twins. Journal of Neurology, Neurosurgery, and Psychiatry, 1972, 35, 756-762 (however it is sleep, and twins are very small - may be self is not developed yet...)

To check your hypothesis it is interesting to contrast EEG of twins joint at somewhere in the body with EEG of twins joined at the head (craniopagus). Then again the effects may be different depending on which part of the brain is shared...

Check please the following link for the popular article and the video on twins joined at the head.

http://www.nytimes.com/2011/05/29/magazine/could-conjoined-twins-share-a-mind.html?_r=0

Several years ago we watched British documentary about adult twins (females) joined at the head (if we remember correctly they sheered frontal lobe). Nothing was told in this film about EEG... But what was interesting that they had different hair stiles and very different personalities. Each of them had her own room to rest with different stiles...

If you will find something please share it with us.

Best,

Alex & Andrew

From the NY Times article suggested by Alex and Andrew: 

"Twins joined at the head — the medical term is craniopagus — are one in 2.5 million, of which only a fraction survive. The way the girls’ brains formed beneath the surface of their fused skulls, however, makes them beyond rare: their neural anatomy is unique, at least in the annals of recorded scientific literature. Their brain images reveal what looks like an attenuated line stretching between the two organs, a piece of anatomy their neurosurgeon, Douglas Cochrane of British Columbia Children’s Hospital, has called a thalamic bridge, because he believes it links the thalamus of one girl to the thalamus of her sister. The thalamus is a kind of switchboard, a two-lobed organ that filters most sensory input and has long been thought to be essential in the neural loops that create consciousness. Because the thalamus functions as a relay station, the girls’ doctors believe it is entirely possible that the sensory input that one girl receives could somehow cross that bridge into the brain of the other. One girl drinks, another girl feels it....From the very beginning, doctors wondered if the twins shared sensation; an early video shows one girl being pricked for a blood test as the other starts to cry, her face a perfect mirror image of her sister’s....in one of the many idle moments of the five days I spent with the family, the girls were watching television, and I absent-mindedly gave Tatiana’s foot, which Krista could not see, a little tickle. She turned to me and smiled, and then Krista spoke: “Now do me,” she said. Had she felt the sensation but wanted the emotional experience of knowing that she, too, was receiving that kind of playful attention?"

Dear All:

According to Todd Feinberg (Professor of Clinical Psychiatry), who studied the above case of craniopagus twins, the Self is related to a nested hierarchy in the brain (see Abstract below). As each of the girls has a brain, the consequence of his hypothesis would be that each one has a Self. However, as the brains are connected, it may be the case that they share conscious experiences.

In the Merleau-Pontyan view of the case, as I interpret his philosophy, there is only one Self (because there is just one body/same flesh) with two cognitive/sensorimotor systems, which allow the girls to elaborate different representations of reality and execute different actions, but not to have opposite feelings at the same time. If one feels pain, the other feels too, as above reported.

Conscious Cogn. 2011 Mar;20(1):4-15. doi: 10.1016/j.concog.2010.09.016.

The nested neural hierarchy and the self.

Feinberg TE(1).

Author information:

(1)Albert Einstein College of Medicine, New York, NY, USA. [email protected]

In spite of enormous recent interest in the neurobiology of the self, we

currently have no global models of the brain that explain how its anatomical

structure, connectivity, and physiological functioning create a unified self. In

this article I present a triadic neurohierarchical model of the self that

proposes that the self can be understood as the product of three hierarchical

anatomical systems: The interoself system, the integrative self system, and the

exterosensorimotor system. An analysis of these three systems and their

functional features indicates that the neural hierarchy possesses features of

both non-nested and nested hierarchies that are necessary for the creation of a

unified consciousness and self. These functional properties also make the central

nervous system a biologically unique entity unlike anything else in nature.

Dear Alfredo,

Thank you very much for the information and interesting thoughts.

We do familiar with Prof. Todd Feinberg theory of Self as a nested hierarchy in the brain. We also support the concept of a nested hierarchy, but not the concrete implementation of it. Considering the Merleau-Pontyan view of the Self as related to a body, we agree with this only partly. In fact we have developed the three dimensional construct model for the complex experiential selfhood, where the frontal DMN (default mode network) module/subnet is responsible for the first-person perspective and the sense of agency (the witnessing observer), the posterior right DMN module is responsible for the experience of self as an localized embodied entity, emotion-related thoughts, and autobiographical memories (representational-emotional agency), and the posterior-left DMN module is responsible for the experience of thinking about oneself, including momentary narrative thoughts (reflective agency). Together, such trinity of the DMN subnets provides a coherent representation of complex selfhood (Fingelkurts & Fingelkurts, 2011; Fingelkurts et al., 2012; Fingelkurts, Fingelkurts, & Kallio-Tamminen, 2015). We attached three papers of ours related to the issue.

Conceptualizing the DMN as a functional integration of three subnet modules, each contributing specific functions or qualities characterizing self-referential processing, may allow to interpret such case of craniopagus twins as having common representational-emotional agency, that relates to the experience of self as localized embodied entity, but having two witnessing observers :) of course this is just speculation, which need to be tested in the actual cases of craniopagus twins.

Best,

A&A

Dear Alex and Andrew:

Many thanks for the papers and comments.

I appreciate your conclusion about two witnessing observers in the craniopagus - this is a consequence of your model, since they have different frontal DMN.

In regard to the other modules of the DMN (the right and left posterior areas) the connection of Tatiana and Krista is peculiar. From their photo available in the site (they also have a Facebook page made by their mother, with more recent photos), it seems that the left parietal region of one is directly connected to the right parietal region of the other. EEG studies while they are performing cognitive and affective tasks could clarify if these circuits/modules operate independently.