The human brain is one of the most complex organs of the body and has yet to be fully understood. The capability of the human brain goes beyond what we actually perceive. So what makes this organ so interesting?
Human brain has three basic divisions – fore brain, mid brain and hind brain. This is a common division in all vertebrate (animals with backbone in simple terms).
Fore brain controls – body temperature, eating, reproductive functions, sleep and display of emotions. Fore brain is formed and the face begins to develop in the fifth and sixth weeks of human pregnancy. This is one of the crucial development in human pregnancy – a disorder where fore brain fails to develop in two hemispheres (Holoprosencephaly) is observed to be so severe that babies die before birth.
The mid brain is associated with hearing, vision, sleep / wake, motor control, alertness and temperature regulation.
The hind brain is the region from which the brain and spinal cord originate during early stages of human embryonic development. This region is responsible for functions like blood pressure and heart rate. Damage to the hindbrain produces uncoordinated and delayed motor responses, as well as cognition / thinking difficulties.
Brain lobes are anatomical classification. Cerebrum and cerebellum both are divided into lobes; however, if not specifically mentioned the lobes refer to cerebrum lobes. There are six lobes –
|Frontal lobe||These are most uniquely human.|
|Parietal lobe||Integrates sensory information from various senses|
|Occipital lobe||Sense of sight|
|Temporal lobe||Sense of smell, sound, processing of complex scenes.|
|Limbic lobe||Emotion and memory|
|Insular cortex||Pain and other senses|
Evolution of brain from ice age:
During the ice age the tree-dwelling animals adapted to their new environment. As a part of this change some Hominine started walking on their hind legs(to get greater elevation to eyes), this also freed forelimbs from walking and made ‘hands’ available for food collection, picking up sticks etc … eventually this led to ‘handedness’. These predictions are dated to period 7 to 5 million years ago. From this stage the Hominine brain started developing in size and different functions. There has been a gradual increase in brain volume as humans progressed along the timeline of evolution. This might lead to the understanding that – in general there is a correlation between brain volume and intelligence. (However, comparison with ‘Neanderthals’ and ‘hobbits’ (Flores Man – Hominine known for small body and brain) also indicate that rather than the size the structure is more important for intelligence).
The evolution of a larger brain created a problem for early human – a larger brain requires a larger skull, and thus requires the female to have a wider birth canal (for the newborn’s larger skull to pass through). With too wide birth canal female would loose the ability to run (a necessity during that time) … thus the solution was to give birth at an early stage of foetal development (when the skull has not grown too large to pass through the birth canal). Thus to take care of infants for longer duration, human bands started staying in one place for long periods and as a result, humans became more dependent on tool-making to compete with other animals and also other humans.
There are different hypothesis that try to explain the evolution of the brain.
Social Brain Hypothesis:
British anthropologist Robin Dunbar proposed social brain hypothesis. This hypothesis states that – human intelligence evolved as a means of surviving and reproducing in large and complex social groups. When hominids started living in large groups, selection favoured greater intelligence. However, meerkats have more social relationships than the capacity of their brain.
Geoffrey Miller proposed that positive feedback loop of sexual selection would have led to the evolution of human intelligence in a relatively short period. With this approach and inferior individual will find an inferior mate and in turn their joint offspring is less likely to survive.
Evolution of the brain has also something to do with flexibility of the brain.
Recent study discusses flexibility and lopsided nature of brain. Asymmetry and specialization of the brain’s hemispheres were thought to be distinctly human traits, but primates and other animals possess them as well. Gómez-Robles and her colleagues compared the differences between live human brains and chimpanzee brains using MRI scans.
- Compared with the chimpanzee brain, human brains showed even more variation in structure size between individuals in the population.
- Overall, human brains had enlarged frontal and parietal lobe.
- The lack of symmetry in the brains of both animals, but especially humans, may be a sign of the flexibility, or plasticity, of their brains.
With such a structural information and understanding on human brain one may feel that we have captured good amount of information on human brain. However the reality is far different… according to us, the more we explore the more and more challenges are being faced while understanding Human Brain, the following pointers illustrate the same:
- Understanding the relationship between the brain and the mind is a great challenge. How mental entities (such as thoughts, emotions) could be implemented by physical entities (such as neurons, synapses)?
- Number of projects like the ‘humanbrainproject’ understand this challenge and hence are directed towards finding more details.
- Many scientist believe that we lack the tools and technology to measure and understand the complete capacity of Human brain.
However, power to innovate and explore is after all what brain gives us; so one day we will definitely succeed.