NOTE THAT the brain’s motor cortex directs the contralateral muscles in our body because the UMN nerve impulse crosses to the other side at the cervico-medullary junction. That’s why if we have a stroke on the right side of the brain, we get paresis on the left side of the body. And if we have a stroke on the left side of the brain, we get paresis on the right side of the body.
We direct our upper motor neuron to wriggle our toe. Lo! The (opposite) toe wriggles.
(Caveat. The above discourse is a short oversimplification.)
All seems well. Until we ask ourselves, what triggers the upper motor neuron to fire?
You might say offhand, our mind of course. We will it to happen; it happens.
In the philosophy of the mind there is a thing called goal-directedness. We sense, perceive, integrate in memories, emotions, and aspirations, and after all that we use the data we had perceived to direct our actions in ways that can achieve our goals.
But the devil is in the details. We have learned that there is a well-defined process by which the UMN directs the LMN to direct the muscle to move.
So what is the process by which the mind directs the upper motor neuron to fire?
That’s a blackhole in between the mind and volitional movement.
For generations medical students have been hearing countless lectures on the following process: Upper motor neuron fires. Lower motor neuron fires. Muscle moves. And none on what fires before the upper motor neuron.
As far as I know, there is nothing much in literature that offers testable hypotheses on the subject of how the mind creates volitional movement.
Perhaps it’s because we ourselves do not fully comprehend the mind. Even if it’s our mind.
The most popular hypothesis that I have heard of is that from monist materialists (who believe that everything is material), that the mind is some kind of emergent phenomenon from the physical existence of neurons, the stuff that composes them, and the stuff they do.
There are historically other types of monism and materialism, but the monist materialists are the ones that presently dominate discussions on the mind.
If we were to follow monist materialism, then we would have to entertain the hypothesis that it is the brain’s electrochemical activities that create the mind.
It is a given that we all know subjectively that it is our mind that chooses to move our muscles.
Thus, the brain’s constantly changing electrochemical activity creates the mind, which triggers the UMN to fire.
The blackhole before the UMN is the mind itself. And all its putative characteristics that are hot philosophical issues such as inward accessibility, subjectivity, intentionality, goal-directedness, creativity, and consciousness.
That doesn’t make much sense to me. Rather it is more sensible to think that it is changes in the electrochemical activity of the brain, specifically the cortical neurons, that directly triggers the UMN to fire. It is still the mind that causes that electrochemical activity to change. (To be continued)/PN
