2.2 Modern Understanding of Consciousness
Not all biological systems give rise to consciousness.
- The human body contains a complex immune system that performs its functions silently. Our immune system can even retain “memories” in the form of antibodies, but we have no conscious access to them.
- Even within the nervous system there are networks that are not conscious. The enteric nervous system controls the gut and can function without any connection to the brain, but does not seem to give rise to consciousness.
Consciousness is independent of behavior, emotion, and language.
- Consciousness does not require behavior or action. We are able to experience consciousness even when we are dreaming and our muscles are temporarily paralyzed.
- Catatonia, a state of motor immobility and behavioral abnormality, provides another piece of evidence that consciousness does not require action. Patients with MPTP toxicity who have gone into a state of catatonia are still able to experience consciousness.
- While emotion enormously enriches the conscious experience, it is also unnecessary for it. Many individuals with affective disorders, who have lost the capacity for normal emotional experience due to loss of underlying brain regions, continue to have conscious experiences.
- Pre-linguistic children and patients who are aphasic (have lost the ability to speak) have conscious experiences.
Even self-consciousness and the ability to learn are not essential aspects of consciousness.
- Self-consciousness, or self-awareness, is the ability to recognize oneself as a distinct individual and to think about oneself from an outside perspective. It is overdeveloped in humans, particularly adults. Self-awareness is thought to develop relatively late in life due to the late stage myelination of the projection systems into the prefrontal cortex.
- Self-awareness is not required for basic consciousness, it is just one highly-developed aspect of it. Despite an incomplete development of self-awareness, children are still able to have conscious experiences.
- Even in adults, self-awareness decreases with increased situational awareness. Intense conscious engagement with an external activity has the effect of silencing self-consciousness.
- Patients with severe memory impairment have revealed that memory and learning are not necessary for consciousness.
- Clive Wearing is a British musicologist who suffers from chronic amnesia due to a viral infection. He lacks the ability to form new memories, and also cannot recall many past memories. Despite his severe memory impairment Wearing is fully conscious; he experiences love for his wife, can still play piano, and even seems to be somewhat aware that his mind is impaired.
Consciousness is not present in many of our actions and behaviors.
- People perform many “zombie behaviors,” such as typing, walking through a crowd, or driving, without conscious awareness of their specific actions. Experiments have shown that if we performed these behaviors consciously, we would be slower and make more mistakes.
- Consciousness is still necessary for these behaviors, but only at the early stages of our learning. Once a behavior is over-trained our brains execute it without conscious thought. At this stage, trying to consciously perform these behaviors is counter-productive.
- Consider speech: when we speak, we do not plan each word in our sentence, nor do we analyze speech word by word when we listen. Speech comprehension occurs subconsciously so that our conscious minds can focus on the actual information being exchanged.
Only specific brain regions are directly associated with consciousness.
- So-called “split brain” patients who have had their corpus callosum (the fibers that link the two hemispheres of the brain) severed are still fully conscious, as are patients who have had whole brain hemispheres removed.
- Nonetheless, many neurologists have shown that damage to certain brain regions can be linked to loss of specific conscious experiences such as familiarity, feeling emotions or perceiving faces. This suggests that there is a certain locality to consciousness.