There’s an interesting new piece on TheEdge.org, Self Awareness: The Last Frontier by V.S. Ramachandran. Though it’s largely speculative, it’s a good read. (Be aware that there is not yet agreement in the scientific community on the significance of mirror neurons, which are Ramachandran’s specialty.)
It’s a long and rambling article. I’m going to give you a few bits that I found to be especially interesting:
… There are also: “touch mirror neurons” that fire not only when your skin is touched but when you watch someone else touched. This raises an interesting question; how does the neuron know what the stimulus is? Why doesn’t the activity of these neurons lead you to literally experience the touch delivered to another person? There are two answers. First the tactile receptors in your skin tell the other touch neurons in the cortex (the non-mirror neurons) that they are not being touched and this null signal selectively vetos some of the outputs of mirror neurons. This would explain why our amputee experienced touch sensations when he watched our student being touched; the amputation had removed the vetoing. It is a sobering thought that the only barrier between you and others is your skin receptors!
A second reason why your mirror neurons don’t lead you to mime everyone you watch or to literally experience their tactile sensations might be that your frontal lobes send feedback signals to partially inhibit the mirror neurons’ output. (It cant completely inhibit them; otherwise there would be no point having mirror neurons in the first place.) As expected, if the frontal lobes are damaged you do start miming people (“echopraxia”).
… I mention these to emphasize that despite all the pride that your self takes in its individuality and privacy, the only thing that separates you from me is a small subset of neural circuits in your frontal lobes interacting with mirror neurons. Damage these and you “lose your identity” — your sensory system starts blending with those of others.
… Let us return to Cotards syndrome — the ultimate paradox of the self negating its own existence (sometimes claiming “I am dead”, “I can smell my body rotting”, etc.). We postulate that this arises from a combination of two lesions. First, a lesion that is analogous to Capgras but far more pervasive. Instead of emotions being disconnected from just visual centers, it is disconnected from all sensations and even memories of sensations. So the entire world becomes an imposter — unreal (not just the mother). Second, there may be dysfunctional interaction between the mirror neurons and frontal inhibitory structures leading to a dissolution of the sense of self as being distinct from others (or indeed from the world ). Lose the world and lose yourself — and it’s as close to death as you can get. This is not a fully developed explanation by any means; I mention it only to indicate the style of thinking that we may need to explain these enigmatic syndromes.
Now imagine these same circuits become hyperactive as sometimes happens when you have seizures originating in the temporal lobes (TLE or temporal lobe epilepsy). The result would be an intense heightening of the patient’s sensory appreciation of the world and intense empathy for all beings to the extent of seeing no barriers between himself and the cosmos — the basis of religious and mystical experiences.
It’s a good article. [ link ]
-Julie
