For much of history, the brain has been a mysterious ‘black box.’ The only clue to what went on inside was what came out of it. During the 20th century, a variety of approaches were used to explore how the mind functions. Today, brain imaging techniques are bringing us tantalizingly close to seeing the workings of the mind in action.
It is difficult to understand how the physical tissue of the brain can produce an apparently non-physical thing like consciousness. Mind and body (of which the brain is a part) seem so different that it is tempting to agree with the 17th-century French philosopher Descartes, who concluded that they must be entirely separate kinds of substance. The first clues about the way the brain functions came through so-called ‘natural experiments’ studies of people with brain damage caused by strokes or head injuries. The ancient Greek physician Hippocrates had noted that an injury to the left side of the brain often disrupted speech; his finding was confirmed in 1861 when the French neurologist Paul Brocade identified the brain area responsible for speech production through post-mortem examination of stroke patients.
Bumps On the Surface
Many attempts have been made to find a systematic way to match the brain and mind. The Austrian anatomist Franz Gall (1758- 1828) was convinced that human characteristics such as ‘amativeness’ ‘morality,’ ‘acquisitiveness’ and so on, were each produced by specific brain ‘organs’ in different areas of the cortex – the outer layer of the brain. Particularly well-developed characteristics supposedly caused bumps on the skull, which could be measured to give a character reading. Gall developed his theory of ‘phrenology’ by drawing up a detailed map showing the location of the various organs and selling special devices to measure them. Head-measuring became a popular pastime in the 19th century, and many towns in the USA (and in Europe) had their phrenology institute.
Phrenology was, of course, nonsense: no amount of normal brain development could cause detectable bulges on the skull. The discovery of brain areas genuinely responsible for certain functions -the two main language areas in the left hemisphere- began the discrediting of phrenology (although interest in it persisted), as they were nowhere near the brain’s organ that Gall had claimed was responsible for language.
Mind Theories
Another reason for the fall of phrenology was that, by 1900, Sigmund Freud had developed a far more sophisticated method of studying the mind – psychoanalysis. Freud focused on bringing suppressed conflicts and fears to the patient’s consciousness. With its emphasis on unconscious motivation, the method caught the public imagination. For nearly half a century, it was generally thought to offer the clearest model of the workings of the human mind. Unlike phrenology, psychoanalysis also offered the prospect of therapy to cure problems.
Freud’s success encouraged others to seek an explanation of the mind through systematic introspection. However, people’s ability to report accurately and consistently on their perceptions proved disappointing. One’ introspectionist laboratory’ reported, for example, that people could have 12,000 sensual experiences; another claimed that it was 44,000. Psychologists became embarrassed by their confusing findings and sought to put their work on a more scientific footing.
Behaviorism was a reaction to the pitfalls of psychoanalysis and introspection. The behaviorists regarded the mind as an input-output machine: in went a stimulus, and out came behavior. In describing the relationship between stimulus and behavior, they ignored anything that was not observable or measurable. The behaviorist era reached its peak in the 1920s, around the time that early computers were being developed. Scientists could see how these worked: the machine was programmed with a few rules and then fed bits of information, which the computer manipulated according to the rules. It was plausible to assume that the mind functioned similarly.
In the 1950s and 60s, cognitive psychology took the behaviorist principle a step further by emphasizing internal mental processes, such as decision-making, thinking, and language. Cognitive psychologists were concerned with the rules the brain uses to interpret information but not with the nature of the brain itself. While the approach made valuable advances in the study of the thinking process, no direct link could be made to the increasing knowledge about the anatomy of the brain. Psychology was, in effect, split into two separate areas of knowledge.
Probing Inside the Brain
Meanwhile, some scientists continued to probe the brain physically. In the 1950s, the Canadian neurologist Wilder Penfield pinpointed areas of long-term memory by stimulating the brains of patients undergoing surgery. The brain has no pain receptors, so operations can be performed with the patient awake and thus able to report what happens when different parts of the brain are touched. Penfield discovered that placing electrodes on parts of the temporal cortex (at the side of the brain) triggered vivid descriptions of long-forgotten events. In the last 20 years, the mapping of brain processes has leaped ahead with the development of techniques such as positron emission tomography (PET) and functional magnetic resonance imaging (fMRI). It is now possible to watch the workings of a normal, conscious brain on a computer monitor and match the ripples and flares of activity to the person’s reports of perceptions, thoughts, and emotions. At the same time, the development of drugs that alter behavior by targeting particular regions of the brain has. Helped to fill in the details of what is happening at the molecular level.
Insights from computer science are supplementing the biological approach. Self-learning computers that can adapt their circuits have provided a powerful new ‘neural network ‘model for investigating the brain. These models are equivalent to creating a ‘virtual’ brain that can be studied outside the body. Of course, they will never work precisely like real brains, but such systems are providing fascinating clues as to how brains develop over time.
Looking Inside the Brain Modern imaging techniques can reveal brain activity as well as structure. They allow doctors and scientists to observe the complex functioning of different regions of the brain and to diagnose where damage has occurred. Some method uses X-rays, some measure brain activity, while others record brainwaves.
CT (Computed Tomography)
CT produces detailed cross-sectional images of the brain. The CT scanner sends out an X-ray beam as it rotates around the body and uses its internal computer to create a high-quality image. CT scans can reveal tumors and other abnormalities.
EEG (Electroencephalography)
EEG measures brainwaves – the electrical activity created when large numbers of neurons fire. Each of the eight patterns above represents activity in a different part of the brain. EEG is used to study changes in brain activity, for example, in epilepsy.
PET (positron emission tomography)
PET scans evaluate the amount of metabolic activity in brain tissue. The patient is injected with a radioactive substance that is absorbed into active cells. The radioactivity detected produces an image of active brain areas.
MEG (magnetoencephalography)
MEG, like EEG, measures brainwaves, but it does so by picking up the tiny magnetic pulses produced along with the brain’s electrical activity. It is a faster scanning technique than PET or MRI.
MRI (magnetic resonance imaging)
MRI scans use magnets and radio waves to create brain images. The technique is radiation-free and one of the safest imaging methods available. It is used for imaging the spinal cord as well as the brain.
FMRI (functional magnetic resonance imaging)
fMRI measures the amount of oxygen in different brain areas, which indicates the level of activity. Several pictures are taken every second so that, over time, a ‘film’ of the brain’s activity is created.
