Interesting talk just posted on Ted of VS Ramachandran's The Neurons that shaped civilization.
What he considers is mirror neurons in my prefrontal cortex allowing me to sense when somebody touches something. They mirror the neurons that are fired when I (not somebody else) touch something.
Ramachandran says that when I actually touch something, my hand (say I am touching with the hand) sends signals of touching to my prefrontal cortex and that's how I differentiate direct neurons from mirror neurons.
Now Ramachandran says that if my arm is anesthesied, my direct neurons don't get the usual signals but are still looking for them so they get them from me seeing the other hand. Therefore my brain concludes that I am touching with the hand of somebody else. Ramachandran says that I have just assumed somebody else's consciousness.
But Ramachandran doesn't say: what happens with the mirror neurons then?
I think that the answer is that there are not both direct and mirror neurons, but rather one set of neurons that reacts to touching. However, that set can be linked to a representation of my hand (that's for direct touching) or/and to the representation of somebody else's hand (that's for mirror touching). If I see both my hand and that of somebody else each touching something, my neurons are activated, with a link to my hand (strong because reinforced by my hand signals) and another link to the other hand (weak). If my arm is anesthesied and the strong signal disappears, the only signal around is that from the other hand, even if weak, and it takes the place that would normally be taken by my own hand's signal.
That assumes that seeing my own hand, anesthesied or not, primes my neurons for searching signals from it. That sounds right, but now somebody needs to tell me if my explanation fits the neurological evidence. From what I have read of the original litterature on mirror neurons (see the reference in Computer Theology, p. 420: Mirrors in the Mind, by Giacomo Rizzolati, Leonardo Fogassi and Vittorio Gallese, Scientific American, November 2006), it is. In their original discovery, the authors had a monkey's neuron monitored by sound when the monkey touched a banana. One day the operator, instead of the monkey, touched a banana and the monkey's neuron resonated. I was actually the same neuron, which is what I say in my explanation.
Now a final point. My touching neurons get input from both the image of my hand and that of somebody else, but how do they themselves communicate where the input was from? The only explanation I see to that is that the recipients for the strong signal out (which means that my touching neurons think, rightly or not, that I am actually touching something) and those for the weak signal out (which means that I am watching somebody else touching) are, in the former case, far from my touching neurons, and in the later, close to them. Attenuation would make the difference. I have no idea whether that's a realistic hypothesis. If not, what else?
Bertrand du Castel
What he considers is mirror neurons in my prefrontal cortex allowing me to sense when somebody touches something. They mirror the neurons that are fired when I (not somebody else) touch something.
Ramachandran says that when I actually touch something, my hand (say I am touching with the hand) sends signals of touching to my prefrontal cortex and that's how I differentiate direct neurons from mirror neurons.
Now Ramachandran says that if my arm is anesthesied, my direct neurons don't get the usual signals but are still looking for them so they get them from me seeing the other hand. Therefore my brain concludes that I am touching with the hand of somebody else. Ramachandran says that I have just assumed somebody else's consciousness.
But Ramachandran doesn't say: what happens with the mirror neurons then?
I think that the answer is that there are not both direct and mirror neurons, but rather one set of neurons that reacts to touching. However, that set can be linked to a representation of my hand (that's for direct touching) or/and to the representation of somebody else's hand (that's for mirror touching). If I see both my hand and that of somebody else each touching something, my neurons are activated, with a link to my hand (strong because reinforced by my hand signals) and another link to the other hand (weak). If my arm is anesthesied and the strong signal disappears, the only signal around is that from the other hand, even if weak, and it takes the place that would normally be taken by my own hand's signal.
That assumes that seeing my own hand, anesthesied or not, primes my neurons for searching signals from it. That sounds right, but now somebody needs to tell me if my explanation fits the neurological evidence. From what I have read of the original litterature on mirror neurons (see the reference in Computer Theology, p. 420: Mirrors in the Mind, by Giacomo Rizzolati, Leonardo Fogassi and Vittorio Gallese, Scientific American, November 2006), it is. In their original discovery, the authors had a monkey's neuron monitored by sound when the monkey touched a banana. One day the operator, instead of the monkey, touched a banana and the monkey's neuron resonated. I was actually the same neuron, which is what I say in my explanation.
Now a final point. My touching neurons get input from both the image of my hand and that of somebody else, but how do they themselves communicate where the input was from? The only explanation I see to that is that the recipients for the strong signal out (which means that my touching neurons think, rightly or not, that I am actually touching something) and those for the weak signal out (which means that I am watching somebody else touching) are, in the former case, far from my touching neurons, and in the later, close to them. Attenuation would make the difference. I have no idea whether that's a realistic hypothesis. If not, what else?
Bertrand du Castel
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