Blue Mars - Kim Stanley Robinson [317]
So he switched his emphasis to the memory problem, abandoning the quick decline and all the rest of the senescence issues. He was only mortal after all.
3
Recent memory work was fairly suggestive of avenues of approach. This particular scientific front was related in some of its aspects to the work on learning that had enabled Sax to (partially) recover from his stroke. This was not surprising, as memory was the retention of learning. All brain science tended to move together in its understanding of consciousness. But in that progression, retention and recall remained recalcitrant crux issues, still imperfectly understood.
But there were indications, and more all the time. Clinical clues; a lot of the ancient ones were experiencing memory problems of varying kinds, and behind the ancient ones came a giant generation of nisei, who could see the problems manifesting in their elders, and hoped to avoid them. So memory was a hot topic. Hundreds, indeed thousands of labs were working on it in one way or another, and as a result many aspects of it were coming clear. Sax immersed himself in the literature in his usual style, reading intensively for several months on end; and at the end of that time he thought he could say, in general terms, how memory worked; although in the end he, like all the rest of the scientists working on the problem, ran into their insufficient understanding of the underlying basics— of consciousness, matter, time. And at this point, as detailed as their understanding was, Sax could not see how memory might be improved or reinforced. They needed something more.
The original Hebb hypothesis, first proposed by Donald Hebb in 1949, was still held to be true, because it was such a general principle; learning changed some physical feature in the brain, and after that the changed feature somehow encoded the event learned. In Hebb’s time the physical feature (the engram) was conceived of as occurring somewhere on the synaptic level, and as there could be hundreds of thousands of synapses for each of the ten billion neurons in the brain, this gave researchers the impression that the brain might be capable of holding some 1014 data bits; at the time this seemed more than adequate to explain human consciousness. And as it was also within the realm of the possible for computers, it led to a brief vogue in the notion of strong artificial intelligence, as well as that era’s version of the “machine fallacy,” a variant of the pathetic fallacy, in which the brain was thought of as being something like the most powerful machine of the time. The work of the twenty-first and twenty-second century, however, had made it clear that there were no specific “engram” sites as such. Any number of experiments failed to locate these sites, including one in which various parts of rat’s brains were removed after they learned a task, with no part of the brain proving essential; the frustrated experimenters concluded that memory was “everywhere and nowhere,” leading to the analogy of brain to hologram, even sillier than all the other machine analogies; but they were stumped, they were flailing. Later experiments clarified things; it became obvious that all the actions of consciousness were taking place on a level far smaller even than that of neurons; this was associated in Sax’s mind with the general miniaturization of scientific attention through the twenty-second century. In that finer-grained appraisal they had begun investigating the cytoskeletons of neuron cells, which were internal arrays of microtubules, with protein bridges between the microtubules. The microtubules’ structure consisted of hollow tubes made of thirteen columns of tubulin dimers, peanut-shaped globular protein pairs, each about eight-by-four-by-four nanometers, existing in two different configurations, depending on their electrical polarization. So the dimers represented a possible on-off