Many writers on the brain focus on the astonishing discoveries that have been made in recent years, usually with the implication that we are coming ever closer to an understanding of how the brain works. Cobb's impression is rather different. Yes, there have been enormous technical advances, but we still have no explanatory theory in which to accommodate them. If we step back for a moment and ask 'so what?', no obvious answer is forthcoming. This has been the case for more than fifty years.
This period has seen immense, Nobel prize winning discoveries—astonishing new techniques have given researchers an amazing degree of precision and control of brain activity, massive computer simulations capture the activity of millions of neurons and we now appreciate the role of chemistry in controlling the activity of neural networks. All of this gives us a far richer understanding of what is happening where in the brain, compared with past generations, but we still think about brains in the way our scientific grandparents did (emphasis added).In part this is due to the sheer complexity of the brain, 'with its 90 billion neurons, 100 trillion synapses, and its billions of glia (these figures are all estimates).' We've heard these figures before, but here is something I hadn't come across previously that points up the brain–computer difference even more clearly.
Brain actvitiy depends not only on the well-known neurotransmtters that act between neurons at synapses but also on slower-acting neurohormones. These are small molecules (peptides) and they modify behaviour either temporarily or permanently.
The way in which these peptides are secreted is very different from the action of neurotransmitters. Vesicles containing the neurohormones can appear anywhere on the body of a neuron, not just at a synapse; they are particularly prevalent on dendrites and can contribute to the functional reorganisation of parts of the nervous system during repeated stimulation.Complexities of this kind are one reason why the computer–brain analogy is merely that—an analogy. As Cobb emphasises repeatedly, brains are not computers. Neural networks are often cited as the basis for understanding the brain, but a fundamental difficulty with this idea is that those who construct such networks admit that in many cases they don't know how they work.
This should be a warning to any neuroscientist who looks to neural networks to provide a theoretical explanation of how the brain works.There are some simple organisms for which we know exactly how many neurons there are in their brains and how they are connected, yet these are not simple automata and the behaviour of different individuals can vary even though they have identical brains.
So we need a larger vision of how the brain works than we can frame at present and probably for a long time to come, but Cobb is clear that the answer will come from science not mysticism. He quotes a Cambridge neuroscientist, Horace Barlow, who said in 1972 that he had 'difficulty even imagining anything scientific that would explain the personal and subjective aspects of perception'. This is the famous 'hard question' of how consciousness emerges from neural activity. Cobb is confident that it can be solved scientifically. and we don't need to look beyond science for an answer.
No matter how difficult it might be to imagine how it works, the facts are stubborn; there is no evidence for anything immaterial in our heads, or in the heads of any other animal.Some neuroscientists are less uncompromising. A few still favour dualism (mind–body separation) while others prefer panpsychism (all matter, or all living organisms, are conscious). '[Panpsychism] has the great advantage of not requiring any specific explanation of the human or animal mind, but it explains nothing and often leads to untestable mystical beliefs… .'
One such scientist is Chistof Koch, who collaborated with the late Francis Crick. He 'suggests that there is some kind of urge in matter to become conscious and enthusiastically references the Jesuit mystic Teilhard de Chardin. It is hard to imagine Crick appreciating such company.' (See Koch's book, Consciousness: Confessions of a Romantic Reductionist.)
As well as rejecting the introduction of mysticism into neuroscience, Cobb also dismisses the 'triune brain' hypothesis put forward by Paul MacLean starting in the 1960s and 1970s. This postulated that the human brain is really three brains in one: a 'reptilian' brain, an 'old mammalian' brain (the limbic system), and an evolutionarily 'new' brain, the neocortex. This 'entirel erroneous' idea was never taken seriously by other neuroscientists but it was adopted enthusiastically by two influential writers of the time, Arthur Koestler and Carl Sagan, who introduced it to popular consciousness, since when it has appeared in many different contexts.
While MacLean's desire to put the functiong of the human brain into an evolutionary context was laudable, his fundamental idea never had a leg to stand on. As the Oxford anatomist Ray Guillery suggested in Nature, it should have been classified as neuromythologyCobb's book has been widely praised and rightly so. It's more than popular science; it's a contribution to the subject it describes. Cobb has succeeded brilliantly in combining academic seriousness with readability (I particularly enjoyed some of his footnotes.)
Just one suggestion: it might have been worth providing a glossary for readers who are unfamiliar with the terminology used.
22-05-2020