Cynic
Well-Known Member
A Journey into the Mind and Inner Self
For thousands of years, humanity has been consumed with questions about the world around them. Many of these questions have plagued humanity with an undying thirst of curiositya curiosity which has driven men and women to explore the ends of the globe. And now, we continue our journey as we gaze upon the stars and the infinite depths of space. But as we continue to explore the cosmos in search for answers, another journey still remainsa journey into territory so mystifying, stupefying, and full of complexity. What remains is the greatest journey of them all: the journey into the mind and the inner self.
From a neuroscientific perspective, there are many aspects of the self. According to neuroscientist Vilayanur S. Ramachandran of the University of California, Its defining characteristics are fivefold. First is, continuity: a seamless and continual fabric with a sense of passing time. Second, is coherence of self. We each experience ourselves as a single entity. Third is a sense of embodiment and ownership of a body. Forth is agency: a sense of free will. And fifth, is self awareness. I am going to cover the third aspect, the sense of embodiment and ownership.
Our Sixth Sense
Despite what you have been told in high school, we have more than five senses. There is a hidden sense that we take for granted. In fact we are so unconscious of it, that we do not realize that it is there. It is the sense that we have a body, which involves the sense of proprioception and kinesthesis: the sense of position and movement.
Now consider the visual system in the brain. We have the eyes, the thalamus, and the visual receiving area in the visual cortex. Reflected light from the environment hits the retina, which is then converted into nerve impulses that travel down the optic nerve, exciting neurons in the thalamus and visual cortex in its wake. Your entire field of vision is mapped out in the visual cortex. We have a "theater" in the mind. With sensory input from the eyes, the neurons in the thalamus and visual cortex fire to represent everything we see.
Analogically, the parietal lobes consist of body maps, which are involved in the representation of your body. Most notable is the somatosensory receiving area, where the homunculus or little man resides. These neurons fire to represent each part of your body, with the help of sensory feedback that travels from your peripheral nerves, through your spinal cord, and into your brain. Skin sensation, pain, proprioception, and kinesthesis emerge from this region.
Imagine what would happen if your optic nerves were severed. You would go blind, because your visual cortex could no longer receive sensory input. Now imagine what would happen if the rest of your body is somehow disconnected from the parietal lobes via the spinal cord. It would be analogical to ablating the optic nerve that travels to the visual cortexresulting in blindness. However in this sense, it would result in the discontinued sense of having a body.
A Ghost in the Machine
In Oliver Sach's book, The Man Who Mistook His Wife for a Hat, he describes a patient named Christina, who suffered from an infection in her spinal fluid. The result was a loss of proprioception, which created a sense of disembodiment. Although she had a physical body, she had no internal sense of a body. Christina would flail and overshoot her limbs. She would flop around like a rag doll or a severely intoxicated person. Standing or sitting straight was nearly impossible for her. The sense of disembodiment is hard to imagine. It is better explained in her own words: "
I may lose my arms. I think theyre one place, and I find theyre another. This 'proprioception' is like the eyes of the body, the way the body sees itself. And if it goes, as it's gone with me, it's like the body's blind."
Conversely is the phenomenon of Phantom Limb syndrome. People who are born without arms or legs can sense the presence of their missing limbs. Imagine a little girl, born without arms, doing arithmetic by counting fingers that arent really there. Also, many amputees, who have lost parts of their own body, continue to feel the presence of them. Often, patients will attempt to step on a foot that isnt there, or pick up cups with their missing hand. Sometimes these phantom limbs get stuck in unusual positions. Imagine an amputee with an extended phantom arm, turning sideways as he walks through doorwaysin fear that his phantom arm would hit the door frame. Its obviously impossible, but the presence of the phantom is so convincing.
According to V.S. Ramachandran, motor signals contribute to phantom limb phenomenon. The frontal lobes (I.E. the pre-motor and motor cortex) are primarily responsible for voluntary movement. When motor signals are sent to muscles from these regions, a duplicate signal is sent to the parietal lobes as well in a sort of feedback loop, thereby eliciting a sense of proprioception and kinesthesis in the missing limbs.
Lastly, I should mention the phenomenon of out-of-body-experiences. By electrically stimulating the angular gyrus in the parietal lobes, the self can be decoupled from the physical body and take on a phantom existence of its own. One woman being treated for epileptic seizures by Dr. Olaf Blanke, a neurologist in Switzerland, felt herself float out of her body and hang from the ceiling. The angular gyrus integrates vision with proprioception, resulting in a coherent sense of self. But when the angular gyrus is stimulated with mild electrical currents, the two senses become decoupled, giving the perception of an out-of-body-experience.
As you can see, the self is a jungle full of staggering perplexity and mystery. But it is a jungle that will nonetheless be fully chartedperhaps within the next century. And when the mind and the nature of self is completely unraveled, it will be the end of one of the greatest chapters in human historyit will be the end of the greatest journey, a journey into the mind and our innermost selves.
Works Cited
Goldstein, B. Sensation and Perception. California: Wadsworth Group, 2002.
Melzack, R. Phantom Limbs. Scientific American, Secret of the Senses. 2006: 53-59.
Ramachandran, V., S. A Brief Tour of Human Consciousness. New York: Pearson Education, 2004.
Ramachandran, V.S. and D. R. Its All Done with Mirrors. Scientific American Mind, August 2007: 16-18
Sachs, O. The Man Who Mistook His Wife for a Hat. New York: Simon and Schuster, 1985.
Victor, M., and Ropper, A. Principles of Neurology. McGraw-Hill, 2001.