Chapter 8 Epilogue Much can and has been learnt about the brain by determining where different mental tasks are performed and our ability to do so has been dramatically enhanced in recent years by the use of imaging technologies such as fMRI that allow the working brain to be functionally mapped. We should not however be seduced by beautiful pictures of the brain in action and there is the need for a mature evaluation of the contribution that localization of function by fMRI or other imaging technologies can make to an understanding of how the brain works as a whole. It is important to recall that fMRI localizes neuronal activity indirectly by detecting changes in blood flow, and may therefore seriously misrepresent it. Certainly there is a link between increased blood flow and measures of neuronal activity, but the link may not be obligatory and at best it is likely to be decidedly rough. We know for instance that the brain can perform all of the functions required for recognizing a face within about 300 milliseconds, whereas it takes seconds for blood vessels to dilate. It is possible therefore that brief bouts of functionally important neural activity do not attract a blood surge. Also, where increased blood flow is detected in a region, it might be triggered by a number of quite different distinct bouts of neural activity involving different neurons performing different functional operations. The fMRI method is also unlikely to detect important functional operations that are not highly localized but performed by diffusely distributed networks of neurons. These may go undetected because the network functions without requiring more oxygenated blood. In other words there are likely to be important operations performed by neurons that can be achieved within the capacity of the normal blood supply to accommodate them. Actively working neurons may not need to whistle up more energy resources and so they will not be detected by fMRI. Even if we grant that fMRI and other imaging technologies can produce reliable high-resolution maps of the brain’s responses to different cognitive tasks, simply knowing where something happens is not the same thing as knowing how it happens. Our next challenge in neuroscience is to explain how the brain works as a whole, processing massive amounts of information in parallel. This is a challenge that will require us to leave behind a localizational way of thinking about the problem. We are left however with a paradoxical situation in which our most sophisticated understanding of the brain comes from highly local recordings of the electrical activity of one or just a few of its countless neurons at a time. Will we ever understand completely how the brain works? If here the word ‘understand’ is used in the same sense that we can use it to indicate that we understand how a television works, I doubt it. Televisions are complicated and remarkable devices, but they were conceived by the human brain and built by the human hand. In spite of this, however, few of us would claim to have a complete understanding of how a TV works – sufficient to fix it when it doesn’t for instance. Nonetheless, we trust that some knowledgeable individuals do know everything about televisions and the workings of televisions therefore leave no philosophical questions unresolved. Our understanding of how the brain works will probably not reach this level. Some future scientist may proclaim that he or she has attained a complete understanding of the brain. But it seems improbable that the rest of us would then simply stop regarding thinking, dreaming, poetry, and the beauty of a sunset as somewhat puzzling manifestations of the brain in action and the cause of some modest philosophical reflection. Further reading General Books There are many excellent textbooks on the neurosciences but few that provide a comprehensive and accessible introduction for the nonspecialist. However, both Fred Delcomyn’s Foundations of Neurobiology (Freeman & Co., 1998) and Essentials of Neural Science and Behaviour by Eric R. Kandel, James H. Schwartz, and Thomas M. Jessell (Prentice Hall International, 1995) combine lucid text with unusually helpful illustrations and can be recommended for readers wishing to take the subject further. For a guide to the human mind see Oxford Companion to the Mind, 2nd edn., edited by Richard L Gregory (Oxford University Press, 2004). Chapter 1 For a review of some of the most important literature on the control of eye movements in reading see Keith Rayner, ‘Eye Movements in Reading and Information Processing: 20 Years of Research’, Psychological Bulletin, 124 (1998), 372–422. Chapter 2 The website http://www.bri.ucla.edu/nha/histneur.htm provides a number of useful links to authoritative resources on the history of neuroscience. At http://nobelprize.org/index.html you will find information about the Nobel Prize awarded to Golgi and Cajal for their pioneering work discussed in this chapter. Also for a scholarly and comprehensive history of concepts about the brain in action see Origins of Neuroscience: A History of Explorations into Brain Function, by Stanley Finger (Oxford University Press, 2001). Chapter 3 Both Fred Delcomyn’s book Foundations of Neurobiology (Freeman & Co., 1998) and Essentials of Neural Science and Behaviour, by Eric R. Kandel, James H. Schwartz, and Thomas M. Jessell (Prentice Hall International, 1995) will be helpful in clarifying some of the difficult concepts touched on in this chapter. For a more technical but no less clear account see An Introduction to Molecular Neurobiology, by Zach W. Hall (Sinauer Associates, 1992). Chapter 4 For a contemporary view on the animal evolution see Kenneth M. Halanych, ‘The New View of Animal Phylogeny’, Annual Reviews of Ecology, Evolution and Systematics, 35 (2004), 229–56. For more on the role of sexual selection in the rapid evolution of the human brain see The Mating Mind: How Sexual Choice Shaped the Evolution of Human Nature, by Geoffrey F. Miller (Doubleday, 2000). Chapter 5 The website of Richard L. Gregory (editor of Oxford Companion to the Mind – see above), http://www.richardgregory.org/index.htm,is thought provoking on the elusive connection between sensation and perception, with some fascinating down-loadable illusion movies. For a contemporary reconsideration of the grandmother cell idea see R. Quian Quiroga et al., ‘Invariant Visual Representation by Single Neurons in the Human Brain’, Nature, 435 (2005), 1102–7; Eric R. Kandel, ‘The Molecular Biology of Memory Storage: A Dialogue between Genes and Synapses’, Science, 294 (2001), 1030–8. Chapter 6 For the original research article on the physical consequences of spatial learning in the brains of taxi drivers see Eleanor A. Maguire et al., ‘Navigation-Related Structural Change in the Hippocampi of Taxi Drivers’, Proceedings of the National Academy of Sciences, 97 (2000), 4398–4403. Chapter 7 For more on brain–machine interfaces see Miguel A. L. Nicolelis, ‘Actions from Thoughts’, Nature, 409 (2001), 403–7, and Aileen Constans, ‘Mind over Machines’, The Scientists (14 Feb. 2005), 27–9. For the latest on overcoming obstacles to regeneration in the adult mammalian spinal cord see Fouad K. Schnell et al., ‘Combining Schwann Cell Bridges and Olfactory-Ensheathing Glia Grafts with Chondroitinase Promotes Locomotor Recovery after Complete Transaction of the Spinal Cord’, Journal of Neuroscience, 25 (2005), 1169–78. This page intentionally left blank