We are emotional creatures. The brain is not just a logic machine, but also handles emotions – some of the most powerful drivers of human behaviour
Emotion is important to how we experience life. Love, fear, anger, disgust – these are central to human experience. These raw emotions, in different combinations, add spice to our existence, define many of our goals and influence our decisions.
In their crudest form emotions help survival. Fear and disgust drive us away from possible sources of harm, such as predators or rotten food; love helps us reproduce. They have a profound impact on us, affecting almost all aspects of our behaviour and thinking.
One impact is on attention (see ‘The mind’s eye’). We detect emotional stimuli – faces with positive or negative expressions, or spiders and snakes – much more quickly than neutral ones.
Oddly, though, functional imaging (see ‘Ways of seeing’) has shown that the brain also reacts to emotional stimuli before the nature of the stimuli has been explicitly recognised, or even without any conscious recollection that we’ve seen something scary (for instance).
The key brain region here is the amygdala, which receives visual input independent of the main vision processing areas of the brain. If it detects frightening stimuli, it sends messages to other parts of the brain, triggering a series of responses – making us ‘frightened’.
Memories are made of this
As well as preferentially focusing on emotional stimuli, we also remember them better. We tend to remember not the mundane but the events that are emotionally charged – the good or the bad. Again, memory enhancement seems to depend on activity in the amygdala.
Sometimes, though, people do not want to be reminded of emotionally charged experiences. People with post-traumatic stress disorder (PTSD) suffer from unwanted flashbacks and intrusive memories of their trauma. Interestingly, creation of traumatic memories depends on a particular neurotransmitter (noradrenaline), and a drug that blocks its action – propanolol, more usually used to slow the heart – can prevent traumatic memories being laid down. There is interest in using this as a drug to treat, or even prevent, PTSD.
Feelings, nothing more than feelings
Neuroscientists see emotions as well-described and consistent brain responses. They translate into subjective experiences we know as feelings. These derive in part from the physiological changes created by the emotional stimuli, which are registered by sensors of the body’s internal state (internal organs, energy levels, etc).
It is likely that the brain systems handling emotions are not the same as those responsible for feelings. For example, some people with amygdala damage do not show emotional responses but still experience feelings.
Another distinction is that feelings seem to have more influence over long-term behaviour and decision making. So our choices depend in part on our past feeling states.
Emotion and reason are often thought of as enemies – a battle between cold, hard logic and irrational, emotional decision making.
In fact, though, emotional responses may enhance our decision-making ability, for example by helping us to make value judgements about people based on their facial expressions or because of an awareness of our current bodily state.
What governs mood?
Our mood, or predominant emotion, is governed by several neurotransmitters produced in our bodies.
Serotonin enhances mood by reducing depression and anxiety. Antidepressants that increase serotonin levels are now widely used to treat depression. Interestingly, low serotonin levels have been found in suicide victims.
Dopamine, nicknamed ‘the pleasure chemical’, promotes a feeling of bliss. This explains the attraction of alcohol, nicotine and drugs such as cocaine, all of which increase dopamine levels. Some research has found a correlation between increased levels of dopamine and schizophrenia (though other factors are also involved).
Playing sports makes us feel better due to the release of noradrenaline, another feel-good chemical. Pleasure is also increased by endorphins, the body’s natural painkillers, which are also released during exercise.
Other chemicals, such as GABA and histamine, may also influence mood. Our final mood is governed by complex interplay between all these chemicals, with each chemical’s level being modified by factors such as heredity, environment, lifestyle – and even diet.Lead image:
Danielito311/flickr CC BY NC