Following are the take-home messages from the NOVA documentary “Secrets of Mind” that I found noteworthy;
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For every part of the body, there is a sensory area or map of that part of the body in the brain called the somatosensory cortex. In the documentary, two phantom arm subjects were presented as case studies by Dr. V. S. Ramachandran. Based on the “somatosensory cortex” idea, except for the brain itself, we can get the phantom of any body part. For instance, Dr. Ramachandran mentions phantom appendix pain following appendectomy.
I found the application of knowledge in solving the phantom problem interesting. For instance, the use of a mirror box for solving a phantom limb problem was outstanding because it was non-invasive, inexpensive, quick, and used as a common tool available in every home.
The brain map of the body creates severe problems when there is a disruption in the bidirectional messaging system. For instance, when James -one of the subjects in the phantom limb case- lost one of his arms, his brain sent a signal to clench his fist because of the pain. But since there was no physical arm to send a signal back to the brain that there is too much clenching, the brain kept sending even more signals to the phantom arm. Normal medical interventions such as painkillers or traditional interventions such as mind control weren’t working in the case of Mr. James. A visual feedback to the brain in the form of a mirror box restored the bidirectional messaging and the clenching messaging to the phantom arm stopped.
Separate pathways (more conscious vs. more reflexive) to the visual cortex help patients notice/see even when their visual cortex is damaged. One pathway is an evolutionarily new pathway that goes from the eyeballs to the thalamus to the visual cortex and helps us see consciously. Another evolutionary older pathway that is more prominent in evolutionary older vertebrates than primates such as other mammals, reptiles, and birds going to the cortex via the brainstem is more reflexive. This reflexive pathway helps people see/notice movements even when their visual cortex is damaged in a phenomenon known as blind sightedness. This documentary, the case of Mr. Young Graham from Oxford, England was presented who lost vision on his right side due to an accident during his childhood which damaged his visual cortex. But still, he notices movements, though not the color, shapes, etc of the objects.
I found Dr. Ramachandran’s question based on conscious vs. reflexive pathways a fascinating and very important question about the nature of consciousness. Why is one pathway equal to consciousness and another to Zombie-like response? What consciousness is, anyway?
Peggy, another subject, had a stroke that damaged her brain's parietal lobe and caused a condition known as visual or hemi-spatial neglect. When asked to draw a shape, she draws half of the shape, for instance, a flower. According to Dr. Ramachandran doesn't have only visual problems but also a problem of consciousness. Since the parietal lobe is responsible for 3D representation or layout of the physical world and helps us navigate our environment, the damage in one part of the lobe results in the inability of the patient to respond to stimuli coming from the opposite side -contralateral- of the damaged area.
While navigating, the visual stimuli go through two pathways, the “how pathway” - which goes from the eyeballs to the parietal lobe area-, and the “what pathways”-which goes from the eyeballs to the temporal lobes, and then relayed to the amygdala, an area associated with emotions. David, another subject, suffered damage in the connection between the “temporal lobe-amygdala” part, hence occasionally does not invoke the emotional responses normally a person has upon seeing his parents. This damage caused “capgras delusion” in which the subject perceives his real parents as imposters. Since the auditory pathway to the “auditory cortex-amygdala” is intact in David he doesn't have a “capgras delusion” on the phone.
The case of John Sharon who suffers from temporal lobe epilepsy/seizure is particularly interesting. According to Dr. Ramachandran, the pathway between the temporal lobe-amygdala has sensory neural connections that determine the importance or emotional significance of things and is unique in each individual. Something that might be unimportant or trivial to a person might be emotionally very important to someone else. A landscape -mountains, valleys, plain areas- can as an analogy for the relative importance of things based on the strength of these connections. The seizure or epilepsy of the temporal lobe increases the strength of these connections indiscriminately. These exaggerated connections strengthen the significance of everything -not just what is important for our survival such as relations we love or threats we fear. This cosmic importance of everything is what Dr. Ramachandran calls a religious or mystic experience.
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