There is a long history of looking to technology to help us to understand the brain. Descartes in 1645 compared the transmission of pain information from skin to brain to a man pulling a bell rope and ringing a bell in the tower. With the invention of the telephone and the telephone exchange a new technological metaphor became available: one that allowed for the representation of more complex activities. In our own day the digital computer has proved seductively powerful as a metaphor, and more than a metaphor: many researchers have taken it as axiomatic that the brain is indeed just a biological computer, the mind being its software. As McCrone makes clear, this view neglects a number of important differences between brain and computer. For example, neurons don't remain silent when they are doing nothing in particular, but maintain a background rate of firing; this is quite unlike what happens in a computer, yet, as McCrone remarks, it is often forgotten.
The modern era in neuroscience, McCrone believes, started in 1958 with the discovery by Hubel and Wiesel that individual cells in the visual cortex responded to specific stimuli. This ushered in the technique of recording from single cells, and led to the fanciful notion of the "grandmother cell"—the idea that there could be a particular cell in your brain that was primed to respond to the sight of your grandmother and no one else. There were clearly difficulties with this: what would happen if the cell died, and would you need innumerable cells to represent your grandmother from every possible angle and in different clothes? As time went by it became evident that the brain cells are hierarchically ordered, the information being mapped in successively more "abstract" layers.
Single cell recording was a very important development in neuroscience, but others followed in the second half of the twentieth century, notably the introduction of imaging techniques, such as positron emission tomography (PET) and functional magnetic resonance (fMRI) that allowed researchers to see what the brain was actually doing while it was carrying out different kinds of mental function. However, probably the most dramatic event of all was the demonstration, by Benjamin Libet, that it was possible to detect electrical activity in the brain of volunteers several hundred milliseconds before the subjects themselves were aware of deciding to move. This raises serious philosophical questions for our ideas of consciousness and free will, and could be taken as evidence that mind is an epiphenomenon, although Libet himself resisted this interpretation. Libet's work is well discussed by McCrone and its implications continually recur as the book goes on, which is hardly surprising, for it could plausibly be claimed to be the single most important discovery in neuroscience in the twentieth century.
The role of unconscious processing emerges in another context, where McCrone discusses the way in which the brains of tennis players and other sportsmen allow such remarkably fast responses to events. This is apparently mainly the result of prediction based on reading the body language of the opponent, but the players themselves are not aware of how they do this. The process can be generalized in a much wider context and it appears to explain some basic facts about the way that all of our brains work: we are constantly making guesses about the future. The brain, in other words, doesn't wait passively for information to arrive and then try to make sense of it; rather, it constantly anticipates and imagines what is going to happen and then adjusts and updates its pictures as new information becomes available.
The book is extensively researched and the notes at the end make it clear that McCrone is drawing on a very wide range of reading as well as on interviews with many of the researchers whose ideas he cites. Unfortunately he doesn't provide a reference for one statement which I found surprising: that the hippocampus is so called because of its coiled structure in cross-section. Most sources seem to assume that it is its longitudinal structure that occasioned its name, although admittedly it doesn't look much like a seahorse when seen from that angle.
The concluding chapters approach the difficult question of consciousness, which is today, at long last, a legitimate subject for neuroscience to deal with. (In the heyday of behaviourism talk about consciousness was inadmissible.) This part of the book is inevitably more speculative than the preceding sections, and I felt that some corners were being cut in the sketching in of the development of modern consciousness in the Palaeolithic. It seems at least possible that modern consciousness is much more recent than we suppose, as suggested by Julian Jaynes, Nicholas Humphrey, Antonio Damasio and others. Contrariwise, not everyone is convinced that the Neanderthals were incapable of sophisticated language.
It's practically impossible today to write about consciousness without referring to the philosopher David Chalmers and his "Hard Question", which is the problem of qualia: how does the brain give rise to the experience of sights, sounds, and sensations that make up conscious experience? Chalmers doubts that science can ever bridge the explanatory gap, but McCrone is optimistic that we can begin to do this progressively as brain imaging techniques become ever more sophisticated.
This book provides a good overview of a considerable number of developments and trends in our knowledge of the brain and anyone interested in modern neuroscience and the problem of consciousness would like to have it in their collection.