Story of Psychology - Morton Hunt [342]
And a word from the cognitive psychologist George Mandler: “The mind has functions that are different from those of the central nervous system, just as societies function in ways that cannot be reduced to the function of individual minds.”21
Most cognitive psychologists thus believed that a word retrieved from memory could not be equated with the firing of millions of neurons and the resultant millions or billions of synaptic transmissions, but was the product of the pattern or structure of those firings and transmissions. The neurobiological study of memory, valuable as it was, did not tell us how we learn anything, recognize things we have earlier experienced, or retrieve items from memory as needed—the words we use in speech, to give one example. Such phenomena, they insisted, were governed not by the laws of cognitive neuroscience but by those of cognitive psychology.
Martha Farah, a distinguished neuroscientist and director of the Center for Cognitive Neuroscience at the University of Pennsylvania, recalls that in 1980, when she was a graduate student of psychology at Harvard, “I asked to take a course in neuroanatomy—and got lectured. I was ‘supposed to be studying how the mind worked, and looking at how the brain works was simply not relevant.’ That was the received wisdom in those days. The ’70s and ’80s were the last hurrah of brain-free psychology.”22
What ended the reign of brain-free psychology? Many things, including:
—the growing mass of data on neuronal transmission, on the functions of brain substructures, and on the molecular and other factors that strengthen synaptic connections in learning;
—the shortcomings of the computer model of cognition (it was becoming apparent that although computers could simulate some aspects of cognition, the mind processes information in vastly more complex ways than the linear step-by-step fashion of computer programs);
—the weakening resistance of some leading cognitive psychologists to valuable neuroscientific findings about brain processes; and
—the growing sense among neuroscientists by the late 1970s that they were doing far more than exploring brain biology and that their domain should be called “cognitive neuroscience.”
But as has been the case in various other sciences, it was a new tool (actually a set of tools) that transformed the domain of neuroscience and produced a second revolution in the cognitive sciences. The tools were an array of brain scan devices—machines that could produce various kinds of images of the working brain and, most importantly, of the physical changes or events taking place in it when mental processes were in progress.
Prior to the 1980s, physiologists had been able to use EEG (electroencephalography) to show the form of brain waves; this was useful in studying the differences in brain wave activity during various wakeful and sleep states and the distortions of the waves during epileptic seizures. The method, however, was poor at localizing the brain activity of specific cognitive processes because it reflected overall electrical activity, not that of specific regions or structures of the brain.23
But in the 1980s several dramatic advances were made. One was the development of PET (positive emission tomography) scanning after many years of experiments in measuring blood flow in the brain. In a PET scan the subject lies supine on a narrow table which rolls into a large tubular machine. A nearby cyclotron generates a weakly radioactive isotope with a half-life of only two minutes which is then injected into the patient. The scanner, sensitive to the isotope, records blood flow in a “slice” (narrow cross-section) of the brain, the isotope showing where the brain is active. From a number of slices, a computer assembles three-dimensional images of the brain. The PET scan can be used clinically to study physical damage to, and abnormalities in, the brain, but cognitive psychologists and neuroscientists soon began using PET scans to see what areas of the brain had increased blood flow during—and thus were involved in—various