The Mind and the Brain Read Online Free PDF Page B

worst anillusion. In this school of philosophy, at least among those who don’t dismiss the reality of mind entirely, the mind is the software running on the brain’s hardware. Just as, if you got right down to the level of logic gates and speeding electrons, you could trace out how a computer told to calculate 7 x 7 can spit out 49, so you could, in principle, determine in advance the physical, neural correlates in the brain of any action the mind will ever carry out. In the process, every nuance of every mental event would be explained, with not even the smallest subtlety left as a possibly spontaneous (from the Latin sponte , meaning “of one’s free will, voluntarily”) occurrence.
    A friend of mine, the neurosurgeon Joseph Bogen, recalled to me a remark that the Nobelist David Hubel made to him in 1984: “The word Mind is obsolete.” Hubel was stating exactly the conclusion of researchers who equate their brain scans and neuronal circuit diagrams with a full understanding of mental processes. Now that we understand so much about the brain, this reasoning holds, there’s no longer any need to appeal to such a naïve term, with its faint smack of folk psychology. As Hubel said to Bogen, the very word mind “is like the word sky for astronomers.” It’s only fair to note that this view has not been unanimous. In fact, no sooner had brain imaging technology produced its neat maps than neuroscientists began to question whether we will “understand the brain when the map…is completely filled with blobs,” as the neurobiologists M. James Nichols and William Newsome asked in a 1999 paper. “Obviously not,” they answered. Still, in many sophisticated quarters, mind was becoming not merely an obsolete word but almost an embarrassing one.
    But if you equate the sequential activation of neurons in the visual pathway, say, with the perception of a color, you quickly encounter two mysteries. The first is the one that befuddled our alien commander. Just as the human brain is capable of differentiating light from dark, so is a photodiode. Just as the brain is capable of differentiating colors, so is a camera. It isn’t hard to rig up aphotodiode to emit a beep when it detects light, or a camera to chirp when it detects red. In both cases, a simple physical device is registering the same perception as a human brain and is announcing that perception. Yet neither device is conscious of light or color, and neither would become so no matter how sophisticated a computer we rigged it up to. There is a difference between a programmed, deterministic mechanical response and the mental process we call consciousness. Consciousness is more than perceiving and knowing; it is knowing that you know.
    If it seems ridiculous even to consider why a handful of wires and transistors fails to generate subjective perceptions, then ask the same question about neurons outside the brain. Why is it that no neurons other than those in a brain are capable of giving the owner of that brain a qualitative, subjective sensation—an inner awareness? The activity of neurons in our fingertips that distinguish hot from cold, for example, is not associated in and of itself with conscious perception. But the activity of neurons in the brain, upstream of the fingertips’ sensory neurons, is. If the connection linking the fingers to the brain through the spinal cord is severed, all sensation in those fingers is lost. What is it about the brain that has granted to its own neurons the almost magical power to create a felt, subjective experience from bursts of electrochemical activity little different from that transpiring downstream, back in the fingertips? This represents one of the central mysteries of how matter (meat?) generates mind.
    The second mystery is that the ultimate result of a rain of photons falling on the retina is…well, a sense. A sense of crimson, or navy blue. Although we can say that this wavelength of light stimulates this