Breakthroughs in Brain Research
Ottoson, David, UNESCO Courier
Breakthroughs in brain research
In the last two decades there has been adramatic development in brain research, only rivalled by the advances in molecular biology in the early 1950s and the progress in physics at the beginning of this century. The introduction of new biophysical and biochemical techniques has made it possible to tackle problems that until recently were beyond experimental investigation. All evidence indicates that these techniques will open up a world hitherto unknown to us and give us new insight into the complexity of the higher functions of the brain. This development is at present progressing at a rapid rate, but the results already obtained have provided us with unprecedented data on many aspects of the brain involving information processing, perception, brain control of pain, neuro-transmitter actions, brain plasticity, regeneration, learning, memory, behaviour and emotion.
The major breakthrough in our understandingof the higher functions of the brain was the discovery of Roger Sperry, Professor of Psychology at the California Institute of Technology, of the functional specialization of the two hemispheres of the brain. Since the two hemispheres are anatomically almost identical, it had long been generally assumed that in principle the two brain halves had similar functions. However, it is interesting to note that as early as 1861 it was demonstrated by a French neurologist, Pierre-Paul Broca, that the centre for speech is localized in the left hemisphere. When presenting his observations to the Societe d' Anthropologie in Paris, he made the now famous dictum: "Nous parlons avec I'hemisphere gauche'.
Later observations, particularly on soldierswounded in the two world wars, indicated that the two hemispheres have different functions also in other aspects, but the functional differences between them remained largely unknown until the early 1950s when Roger Sperry made his pioneering discoveries which soon received world-wide attention and for which in 1981 he was awarded the Nobel Prize in Physiology or Medicine.
Sperry's research thus established thateach of the two hemispheres are specialized, each having its own specific functional characteristics. The left hemisphere is analytical, sequential and rational while the right is synthetic, holistic and intuitive. The left hemisphere is, to quote Sperry, "the more aggressive, executive, leading hemisphere with control of the motor system'. This is the hemisphere that we mainly see in action and the one with which we communicate. The right hemisphere is "the silent passenger who leaves the driving of behaviour to the left hemisphere'. The right hemisphere cannot express itself in language, is therefore unable to communicate any experience of perception or consciousness.
More recently a number of new methodshave been employed for the study of brain functions which have given us new and exciting insights into the performance of the brain in health and disease. One of these techniques provides for measurements of the regional blood flow in the brain. With this technique it has been demonstrated that at rest in a quiet room, the cerebral flow is the same in the two hemispheres. It is interesting to note that the highest flow is found in the frontal lobe. Simple visual perception consisting of opening the eyes results in an incresse in the primary visual area of the cortex, while visual stimuli which require discrimination tasks are followed by an increase in other areas.
Cerebral blood flow measurements havealso provided interesting information on regional activation of the brain during voluntary movements in man. When programming a sequence of movements without actually executing them, there is a selective increase in a special area called the supplementary motor area. During the execution of a movement there is in addition an increase in another area, the so-called primary motor area. …