An Invisible Touch

Delusions and hallucinations are often one and the same. From hearing voices to seeing a physical manifestation of the consciousness brought to life, delusions and hallucinations deal with a peculiar type of trickery; believing that something is there when it is not. The concept of phantom limbs is no different. 

 

In a 2001 PBS documentary, Secrets of the Mind, Indian-American neuroscientist Vilayanur Subramanian (V.S.) Ramachandran met with various patients who experienced unusual aftereffects of bodily accidents. One of his patients claimed that he could feel the absence of an amputated left arm. Derek Steen sustained serious injuries from a motorcycle incident. Steen had pulled his motor nerves out of his spinal cord, rendering his left limb useless. Consequently, Steen and his family were informed that he would no longer be able to use his arm again. Interestingly, however, after his surgery, Steen claimed sensations in his left arm, as if his limb was still attached to his body.

 

In the documentary, Dr. Ramachandran explains that the body is essentially a construct in the mind. Through the somatosensory cortex, the brain maps each part of the body from the face to various limbs. In fact, Dr. Ramachandran noted the region of the brain that represents the face and left hand were close in location. And this jumpstarted Ramachandran’s hypothesis for Steen’s phantom limb. 
 

Oftentimes, when Steen’s left cheek would come in contact with a sensation that would send an input signal to the brain, he would be able to sense it on his phantom limb, as well. Dr. Ramachandran is seen dragging the end of a Q-Tip across Steen’s left cheek, to which Steen reports that he can feel a “stroking sensation” on his left arm. After undergoing a brain scan to further support his suspicions, Dr. Ramachandran was able to come to a conclusion. Prior to Steen’s motorcycle incident, the map of his body in his brain was a complete system that represented each part of the body. However, after his accident, the region in Steen’s brain that represented his left arm ceased to receive further sensory signals; in other words, that specific region of his brain was no longer active. But in order to proceed with its mental functions, the region was “hungry for a new sensory input.” Therefore, due to the close proximity of the face and arm regions in the somatosensory cortex, the face region had invaded the arm region, causing Steen to feel sensations of the left cheek in his phantom limb. According to Dr. Ramachandran, this opened up new pathways in Steen’s brain.
 

In addition to his conclusion, Ramachandran says that all parts of the body, except for the brain, are susceptible to phantom sensations. Whether it is phantom menstrual cramps after a hysterectomy, or in the appendix after an appendicitis surgery, the absence of a body part causes a disruption in the brain’s mental construct of the human body. And in turn, this causes the invisible sensations that the seeing eye does not perceive. 

 

Sources
“Secrets of the Mind Phantom Limb.” YouTube, 29 Aug. 2012, https://youtu.be/iv2O6B6SOEc. Accessed 30 Apr. 2022.