Our problem-solving abilities depend mainly on a part of the brain called the cerebrum, which is divided into two parts called the left and right cerebral hemispheres. These hemispheres are formed by the division of the cerebral cortex by a longitudinal fissure that is a deep grove that runs down the centre of the brain front to back. There are other grooves that divide the surface of each hemisphere neatly into four parts called lobes: frontal lobes, temporal lobes, parietal lobes and occipital lobes. The temporal lobes, named so because of their location at the temples, analyze much of the auditory inputs from the environment and are involved in memory, while the occipital and parietal lobes (in the rear and upper regions respectively) provide information about where objects are . The frontal lobes in each hemisphere play a vital role in thinking and planning of actions.
The left and right hemispheres have different functions and specialties. The left hemisphere is important for all forms of communication and is responsible for ‘logical’ thinking, speech, written language, number skills and understanding scientific concepts. We known this because when the left hemisphere is damaged, perhaps as a result of an accident or a stroke, there can be serious problems in speaking. The left hemisphere specializes in controlling certain movements, which include the movements we use to communicate. Studies by the Frenchman Paul Broca have revealed that a piece of the left frontal lobe works as a centre for producing speech. Further, a German neurologist name Kari Wernicke discovered an area on the left temporal lobe, near to the Broca’s area, that was a centre for understanding speech. There certainly occurs an interdependence of different lobe functions that helps to coordinate various brain activities.
The right hemisphere, on the other hand, specializes in receiving and analyzing information from the outside world. Therefore, damage to the right hemisphere may result in difficulty in identifying a face or any other sensory perception received by the five sense organs which connect us to the world around us. The right half of the brain is involved in ‘creative’ thinking, imagination and artistic insight. The left and right cerebral hemispheres are connected by fibres running crosswise between them called commissures. The largest and most important commissure is called the ‘corpus callosum’. The commissures are useful in exchanging information between the two hemispheres. That is why the left half of the brain controls the right side of the body whereas the right half of the brain controls the left side. A s most people are right handed, their left brain takes control and is dominant because logic and reasoning are important for our survival today than simply being imaginative and having artistic talents, as even schools focus mostly on subjects such as maths and science instead of art and music. Ideally, both the right brain and the left brain, working in unison, is the key to healthy brain activity.
Normally, the various systems of the body like digestion, blood circulation, breathing, reproduction, growth etc.., occur involuntarily under the control of both nervous system and the endocrine system. The latter comprises various ductless glands – pineal, pituitary, hypothalamus, thyroid, parathyroid, thymus, pancreas, adrenals and gonads – that produce different chemical messages in the form of hormones, which travel through the circulating blood to reach particular tissues and alter the cellular functions. These basic life processes are controlled by the brain stem and the structures connected with it, namely the medulla and pons. The seat of emotion in the brain happens to be the limbic system that comprises the top part of the brain stem and the region bordering the lower brain that is involved in instincts and inherent drives, and the higher brain areas that comprise the cerebral cortex.
The structures namely, amygdale, hippocampus and hypothalamus are considered to be the parts of limbic system that are predominantly engaged in charging our lives with various emotions like love, hate, anger, greed, lust, envy etc. For example, persons with some damage in the limbic system, particularly the amygdale, show behavioral disorders as such persons typically show sudden outbursts of emotion on slightest provocation.
Male And Female Brains
Interestingly, sex hormones are necessary both for forming the genitals and for the behavioral and brain differences between the sexes. The hypothalamus, which is a tiny structure at the base of the brain, regulates many basic functions, such as eating, sleeping, temperature control, and reproduction. A specific part of the hypothalamus, responsible for sexual behavior, is larger in male brains than in female brains, and also in human and non-human animals. Actually during embryonic development, the male hormone called testosterone is known to affect the action of certain brain chemicals in the male fetus. This perhaps predisposes men to react more strongly to stress and causes greater aggressiveness in them.
Although male and female brains largely function in the same way, there are subtle differences in their brains. For example, if the task is to define words, men appear to use only their left hemisphere, while women use both. The area of the anterior commissure seems to be larger in women, and some researchers have found that the back part of the corpus callosum is larger in women, and this could perhaps make the male and female brains work differently. Men are generally better at handling gadgets and have spatial navigational skills like map reading and judging distances, whereas women have a better memory for words and objects, and have finer motor skills.
Experiments carried out on mice have shown that for development of parts of the brain which, in humans, are responsible for intelligence, mother’s genes play the dominate role, whereas the parts of brain which control the basic instincts and influence the emotional make-up of an off-spring take proper shape due to the father’s genes. Could this astonishing finding be true for humans as well? If so, women again would get the credit of endowing the human species with an intellect unparalleled in any other living organism. An interesting repercussion that this finding could have on our society is that men would look for smart and brainy wives for bearing intelligent offsprings! Although there is no direct evidence that this finding is true in humans, genes which carry a tag of their parental origin have been discovered in human beings.
Normally, all genetic traits of an individual, be they defining the colour of eyes or the texture of hair are controlled by pairs of genes. Of the two genes responsible for a particular characteristic, one comes from the father and the other from the mother. The one which is dominant becomes active. However, a different set of genes called ‘imprinted’ genes are active only if they happen to inherited from a particular parent. So, the genetic information buried in these genes is decoded in the form of proteins – the vital functional molecules to run the cellular machinery, only if they are inherited from the right parent. Experiments in mouse embryos have shown that imprinted genes descending from the mother are vital for early development of an embryo that includes the formation of neural connections, while those which came from the father are essential for development of tissues that provide the growing embryo nourishment, namely placenta.
Needless to say, the existing knowledge on the functional intricacies of the human brain is breathtaking. Understanding of the various aspects of brain evolution, as the human species evolved through the ages, clearly sheds light on the fact that human beings enjoy superiority over all other life forms only because the human brain is endowed with astounding abilities that are unique to our species.