#myesthetics | Explore Tumblr Posts and Blogs

aestherians · 5 years

Text

What the medical literature says about supernumerary phantom limbs

I’ve bolded the parts that are most important to this discussion, but I suggest you read the full quotes (and preferably the papers) to gain a better understanding of supernumerary phantom limbs. Any italics were included by the original authors, not by me. Content warning for slight ableism, such as referring to able-bodied/neurotypical people as ‘normal’:

“Finally, the parapsychological literature provides a rich source of phenomenological documents of supernumerary phantom limbs in more or less normal individuals.“

“Experiments on the evocation of phantom limbs in healthy individuals lend support to this clinical observation [mentioned earlier in the article; the observation being that phantom limbs can be induced in amputees via “immersion of the inner ear with water” which “activates the vestibular system”]. Thus, Parker and Schilder (1930) elicited the transitory feeling of a pair of phantom feet while subjects were rapidly decelerated in accelerators, while their subjects felt a phantom head when the accelerator was decelerated during an upward movement.”

“Healthy subjects can also be fooled about the position of a limb with the aid of tendon vibrations. This principle of “vibratory myesthetic illusions (Jones, 1988, for an overview) was applied by Lackner (1988) to evoke phantom sensations of various body parts. One intriguing demonstration involved the illusory elongation of the lower arm via biceps vibrations while each subject was touching his own nose with the fingers. As a result of this conflict - the hand was felt some 30 cm [about 1 ft] away from the face, yet the sensation of contact with the nose was maintained - subjects reported a phantom nose up to 30 cm long! Apparently, the brain “filled in” the gap between the perceived hand location and the tip of the nose.”

P Brugger. Supernumerary phantoms: a comment on Grossi, et al.’s (2002) spare thoughts on spare limbs. Perceptual and Motor Skills 2003.

In conclusion, Brugger, as well as his cited sources, acknowledge that supernumerary phantom limbs do occur in people without any underlying cause, that they can easily be induced in able-bodied people, and that they might sometimes be a way for the brain to fill in a gap between the physical body and the subject’s perception of the physical body.

[After a skiing accident, a patient is left with a spinal chord injury which causes him to feel a supernumerary phantom arm that is described as being always disagreeable and occasionally painful. To study this phenomenon, the patients undergoes the rubber hand illusion]

“A rubber hand illusion (RHI) paradigm was applied to assess the patient’s illusory displacement of his touched hand. In the RHI, tactile stimulation is provided simultaneously to the same location on a participant’s invisible hand and visible rubber hand (see Figure 4). The visual observation of a rubber hand being touched at a corresponding location to the real hand leads to a proprioceptive drift towards the rubber hand. Ultimately, the real hand of the participant appears to be displaced towards the visible rubber hand. Based on our clinical findings, we predicted enhanced illusion susceptibility because of the breakdown in proprioceptive-tactile integration, presumably at the basis of the supernumerary phantom limbs. The local Ethics Committee had approved the study and informed consent was obtained from the patient before testing (Botvinick & Cohen. 1998) (Tsakiris & Haggard. 2005).”

“Physiological kinesthetic illusory limb movements can be induced in healthy subjects (for example, by tendon vibration), and activate complex sensory-motor networks (as assessed by functional MRI activation of cortical and subcortical areas) with a limb specific somatotopic representation similar to real movements (Naito et al. 2007).”

A Curt, C Ngo Yengue, L M Hilti & P Brugger. Supernumerary phantom limbs in spinal cord injury. University Hospital Zurich. Nature 2010.

In summary, though the phantom limb belonging to this patient appeared due to spinal chord injury, the neurologists conducting this study were well aware that SPL’s can be induced and even used this knowledge to conduct part of the study. Supernumerary phantom limbs in able-bodied people have been described phenomenologically and have been observed via MRI scans.

“The illusion is most often experienced as a somesthetic phantom, but rarer SPLs may be intentionally triggered or seen. ”

A Khateb PhD et al. Seeing the phantom: A functional magnetic resonance imaging study of a supernumerary phantom limb. Annals of Neurology 65 2009.

Unfortunately I couldn’t find a full version of this paper online, but that one line from the summary speaks for itself.

#otherkin #therian #fictionkin #alterhuman

62 notes · View notes