For several unsuspecting Americans each year, this scenario represents something all too real. The man in the abstract I was referring to was the actor Christopher Reeve and it is his paralysis that I will be examining in relation to the 'self'. We will be looking at the role of the spinal cord injury in various types of paralysis, while focusing primarily on quadriplegia. This essay is not trying to give a concrete answer to whether there is a self, ego or I-function but to analyze the self as a possible separate entity from the central nervous system.
The spinal cord plays a major role in the individual's ability to receive and respond to information from the periphery. It takes in sensory information from the environment and relays that information to the brain. After the information has been processed in the brain, the brain sends motor information via the spinal cord (which has nerves that innervate muscles) to produce a contraction. A spinal cord injury occurs when the vertebral column is crushed or bent. Extreme pressure on the spinal cord makes the inside severely bruised and compressed; causing localized injury to nerve fibers (1). and cell death.
A picture of the spinal cord shows that it is comprised of four sets of nerves: cervical, thoracic, lumbar and sacral nerves (2). Each section sends and receives information from certain parts of the body. For example, the cervical nerves (3) which are located at the most rostral end of the vertebral column, correspond with the hands and the diaphragm. On the other hand, the sacral nerves (4) located at the caudal end of the spinal cord connects for example, to the bowel and bladder. Injury to any point along the spine can result in a loss of functional ability to the corresponding body part and parts associated with lower vertebrae. The locality of the damage determines the level of functioning left to an injured person (1) and the type of paralysis.
Damage to the lumbar nerves, located in the lower back, will inhibit sensory information from the legs to the brain. Therefore, motor information can not be sent from the brain (which makes the person aware of the sensory information) directly to the spinal cord to initiate motor activity in the legs. This individual is considered paraplegic. As nerve fibers and cells die in the rostral regions of the vertebral column, the damage renders the person quadriplegic. For example, injury at the C1 cervical nerve (3), which transmits information to the head and neck, incapacitates the person from the neck down. Two other types of paralysis are incomplete and complete spinal cord injury. Incomplete spinal cord injury entails partial sensory and motor function performed by the spinal cord. Complete spinal cord injury refers to the level of vertebrae, which remains intact for sensory and motor information.
People with impaired motor and sensory function as a result of spinal cord injuries are classified by the location of where a vertebrae innervating with another is interrupted. If a break is at the cervical nerve C3, then the person is considered a C2 quadriplegic. With this information one can attempt to classify paralyzed persons by their observable behavior. Using Christopher Reeve as an example, we can notice from television appearances that he is ina wheelchair attached to a respirator, suggesting a loss of lower and upper body function. There seems to be damage to the neck muscles supporting Reeve's head because he wears a neck brace accompanied with a headrest. By these simple observations one could asses that there is nerve damage to the cervical C1 area of the spine because it is this region which is involved with upper body functioning like the arms, legs and respiratory activity.
Even without 'self' control over lower body functioning, the legs of a quadriplegic when presented with a stimulus render a reflex without their awareness. Unless a quadriplegic is attentive with their eyes, to the stimulus, there is no acknowledgment of stimulus-leg contact. The vertebra interruption on the spinal cord inhibits sensory information from reaching the brain for the quadriplegic to say, "I am feeling[some external stimulus]." This phenomena of seeing but not sensing raises the question of a 'self' in relation to whether there is something outside of the central nervous system.
Since, the spinal cord can induce a reflex without the use of the brain there arises the possibility that the self and brain are separate entities. For ages, philosophers, like Rene Descartes, have discussed the mind-body problem and developed theories to support their view. Descartes, in his 6th meditation, implies that the mind and body are two separate entities. His point of view was based on his inability to assign an 'extension' to the mind because its purpose is to produce thought; Descartes could not conceive the idea of thought has having boundaries or being 'extended'. However, he sees the body as a concept in which 'extension' is capable.
The central nervous system (CNS) is assumed by some, to be the end all solution to behavior. The CNS is comprised of the brain and spinal cord; their nerves forming an interconnective highway for sensory information to the brain. In a person without a spinal injury, the brain-spinal cord pathway facilitates the individual's ability to distinguish whether a stimulus has occurred without sensory information from the eyes unlike the quadriplegic who needs to be attentive. The ability to acknowledge a stimulus and sense the experience, when the pathway is intact, suggests that the brain and spinal cord are the end all to the mind-body problem. However, in a quadriplegic where the brain and spinal cord pathway is interrupted, the sense of experience is lost. This sense of experience is what people in general refer to as the 'self'; the part of the individual capable of saying, "I am feeling."
Markus and Kitayama performed a cross-cultural research about people's conceptual view of the 'self'. They found two types of self: interdependent and independent. For our purposes we will focus on the latter. The independent view, predominantly found in North America and parts of Western Europe, emphasized a separation between the 'self' and the rest of the world (5). In addition, people within this cultural group define a 'me', which has its influence from western philosophy. The sense of independence or 'me' state that is lacking in quadriplegics because the brain-spinal cord pathway is interrupted questions the role of the CNS. By questioning the functioning capacities of quadriplegics, one notices a separation between 'self' and the central nervous system. An interrupted spinal cord ( in quadriplegia) can elicit a muscle contraction, as long as the ventral and dorsal roots are intact, without direct aid from the brain. However, if brain equals mind, then without direct input from the brain to the spinal cord a muscle contraction, then the 'self' or 'I-function' in the individual should not exist. However, the 'self' does exist for the fact that the individual can decipher and mention that their 'self' is not receiving sensory information. An existent 'self', 'I' or 'me' appears to be present because the individual's acknowledgment of an external stimulus continuously elicits a response with and without direct brain involvement which suggests the CNS and 'self' are two separate entities.
2) Spinal Cord Injury Resources
3) More detailed look: cervical spine
4) More detailed look: lumbosacral spine
5) Gray, Peter. Psychology. 2nd Edition, 1994. page 507.
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This paper reflects the research and thoughts of a student at the time the paper was written for a course at Bryn Mawr College. Like other materials on Serendip, it is not intended to be "authoritative" but rather to help others further develop their own explorations. Web links were active as of the time the paper was posted but are not updated.