Postcards from the Brain Museum The Improbable Search for Meaning in the Matter of Famous Minds

Chapter 1 The Most Complex Object in the Universe As neuroscientists never tire of pointing out, the adult human brain is the single most complex object in the universe, and one of the least understood. On average, it weighs about three and a half pounds, most of which is fragile, malleable tissueso fragile that the brain is the most difficult part of the body to access, remove, handle, and study. A Soviet neuroscientist once likened its consistency to the insides of a watermelon, but even that overstates its structural integrity. If placed on a table, a fresh brain will quickly surrender to gravity and collapse into a heap (more like gelatin than watermelon). Within eight hours, it will begin to decompose, the first part of a dead body to do so. There may indeed be nothing so complex in the universe, nor anything quite as delicate. The familiar shape of the human brain is somewhat misleading. As a ubiquitous graphic symbol, its most prominent feature, the massive, fissured cerebrum, has come to symbolize the unlimited potential of human thought, if not the very means of man's dominion over the planet. Yet it also bears an unmistakable resemblance to a comical turban, and for most of recorded history it was treated that way. Until the 1600s, anatomists drew the brain's tortuous surface as a mass of undifferentiated folds, which they likened in their randomness to the folds of the small intestine.1 After puzzling over its purpose, they concluded that the folds were nothing more than an apparatus for the manufacture of phlegm, which the brain squeezed out through the sinuses, and for producing tears, which it squeezed out through the eyes. Only in the last 150 years have scientists come to appreciate what really goes on in those folds, and that their rapid evolution, seemingly accomplished over the last million years, is easily the most impressive achievement in Darwin's universe. In hindsight, the human brain is a triumph of adaptation, so impressive both in size and reputation that until recently it has succeeded in hiding what has in common with the brains of all mammals, which turns out to be quite a bit. The principal parts of the mammalian brain are the brain stem, the cerebellum, and the forebrain. The stem houses the physical plant. It monitors and regulates unconscious physical processes such as breathing, blood flow, digestion, and glandular secretion. It consists of the medulla, an extension of the spinal cord, a nodule called the pons, and a short connector called the midbrain. The cerebellum, or little brain, lies behind this assembly, and it is aptly named. With its striated exterior and dual hemispheres (at least in primates), it hangs behind the cantilevered back porch of the forebrain like a wasp's nest. Although its role is still not completely understood, the cerebellum is believed to act as a kind of automatic pilot for fine muscle control. If recent studies are correct, it also plays a role in short-term memory, attention, impulse control, emotion, cognition, and future planning. Researchers suspect that it might be a kind of backup unit, an auxiliary brain. Its loss, while far from desirable, is not fatal. The rest of the brain seems to be able to compensate. The forebrain, on the other hand, is indispensable. It is what makes humans human, and, as a result, the search for the anatomical locus of genius, criminality, or insanity begins there. Neurologists tend to be of two minds about the forebrain. Some see it as two complementary but sometimes competing hemispheres, an uneasy coalition of rationality and impulse. Others attribute the same inner struggle to a cold brain and a hot brain, the entire cerebrum being the source of cool calculation, and a set of nested organs called the limbic system giving rise to hot instincts and urges. The left brain-right brain dichotomy originated in the 1960s when neurosurgeons intervened in acute cases of epileBurrell, Brian is the author of 'Postcards from the Brain Museum The Improbable Search for Meaning in the Matter of Famous Minds', published 2004 under ISBN 9780385501286 and ISBN 0385501285.