Home / Politics / Policy /  The science of emotions

New Delhi: A 38-year-old man is beaten to death in Delhi after his motorbike hits a car. A young Sikh removes his turban to save a young boy bleeding after a road accident. What does it take for a person to become so violent as to beat a stranger to death, or put aside his religious customs to save another’s life?

Take another example: Think of the countless times ordinary Indians, overcome by a sense of unfairness, injustice and anger, have taken to the streets. What drove them to protest so emphatically?

And what about cricket, the great love of this country that has millions of Indians delight in a win or depressed when we lose?

Ever wondered what actually goes on inside the human brain to make it possible for such a range of emotions to appear and express themselves?

“Emotions are central to human existence, they lie at the root of societal behaviour, civilization, our moral systems and even the ways in which we conceptualize and understand the world around us," says Nandini Chatterjee Singh, a neurobiologist at Gurgaon-based National Brain Research Centre.

According to a paper published by Edmund T. Rolls in 2000, “Emotions can usefully be defined as states elicited by rewards and punishments, including changes in rewards and punishments."

Emotion, for example, explains Rolls, might be happiness produced by being given a reward, such as a pleasant touch, praise, or winning a large sum of money. Conversely, it could be the fear produced by the sound of a rapidly approaching bus or the sight of an angry expression on someone’s face. But the human brain works to avoid stimuli that are punishing, it noted.

Frustration, anger or sadness are produced by the omission of an expected reward such as a prize, or the termination of a reward such as the death of a loved one. Similarly, relief is produced by the omission or termination of a punishing stimulus such as the removal of a painful stimulus, or sailing out of danger, the paper observes.

“Emotions enable us to react to situations," says Singh. “For example, anger or fear will set your heart racing, and feeling happy will make you smile."

“One of the key areas of the brain that deal with showing, recognizing and controlling the body’s reactions to emotions is known as the limbic system," she explains.

The limbic system areas fall into two categories. Some of these are subcortical structures (the portion of the brain immediately below the cerebral cortex) including olfactory bulb (which receives neural inputs about odours); hypothalamus (responsible for the production of many of the body’s essential hormones); amygdala (plays a key role in the processing of emotions) and thalamus (relays motor and sensory signals to the cerebral cortex). Many are portions of the cerebral cortex (the outer layer of neural tissue in the brain that plays a key role in memory, attention, perception, awareness, thought, language, and consciousness). These include the hippocampus (involved in forming memory, organizing, storing and retrieving it) as well as areas of neocortex (top layer of the cerebral hemispheres) such as insular cortex (lies within the fissure separating the temporal lobe from the parietal and frontal lobes), orbital frontal cortex (a prefrontal cortex region in the frontal lobes) and cingulate gyrus (helps regulate emotions and pain.). The limbic system gets sensory inputs from the external world through sight, smell, hearing, touch, taste and the viscera (internal organs in the main cavities of the body) and emotional experiences occur when these sensations are integrated in the limbic system.

Amygdala, an almond-shaped set of neurons in the brain’s medial temporal lobe, sometimes known as the emotional centre of the brain, is “an unconscious processor because it’s just not connected with the conscious system", according to Joseph E. LeDoux, a neuroscientist and professor of neuroscience and psychology at New York University. “The amygdala gets direct sensory information and it learns and stores information on its own, and that information that’s stored then controls emotional responses," he said in a 2010 interview with digital knowledge forum Big Think.

In his book, The Emotional Brain, DeLoux argues that the brain is hardwired in the sense that the amygdala directly responds to external stimuli received from the senses, mainly in case of a dangerous situation without actually consciously knowing what it is dealing with. “Most of the time, the amygdala is quiet. But when it receives a strong stimulus, it sets sirens in motion. Hairs stand on end, the heart races and fight-or-flight hormones flood the body," he says.

Fight or flight is a reflex response by a person when in danger—whether to avoid it or face it.

“The amygdala is linked to the parts of the brain that govern your senses, muscles and hormones—enabling your body to react quickly to the sight or sound of a threat," explains Singh. “The same information can also travel via the cortex, where it is put together to get the whole picture. This route is probably slower, but allows you to modify your behaviour if the situation isn’t as dangerous as it first seemed."

“Danger can make you feel either angry or frightened: both these emotions are triggered by the same part of the brain—the amygdala," she adds. “The amygdala in turn triggers a response in the hypothalamus, a key area for many of the things your brain does without thinking, including this fight-or-flight response."

That conscious feeling of fear is different, DeLoux says in his book. It is analysed in detail, using information from many parts of the brain, and a message is sent back down to the amygdala through a second, slower pathway that travels from the ear to the amygdala and then on to the higher cortex.

In case of a situation that is pleasing, “enjoyment triggers areas in the brain known as pleasure centres". Neuroscientists refer to the nucleus accumbens region as the brain’s pleasure centre. “They release ‘feel-good’ chemicals, in particular, dopamine," says Singh. “All animals have this reward system, usually triggered by food or sex. However, the system can be affected by drugs, including nicotine and alcohol."

Researchers have found that the main centres of the brain’s reward circuit are located along the medial forebrain bundle, which includes the ventral tegmental area, the nucleus accumbens, septum, the amygdala, prefrontal cortex and certain parts of thalamus. These centres are interconnected and inform the hypothalamus of the presence of a reward.

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