First up – what is the Left Prefrontal Cortex?
The brain’s cortex is the thin outer layer of the brain, covering most of the other brain structures. It’s known as our grey matter – this is because the nerve cells are not covered with white insulating material like most other areas of the brain.
It’s the most recent part of our brain to have evolved and is the most advanced part.
The cortex for each hemisphere of the brain (the left and right hemispheres) is divided into 4 sections known as lobes. The lobe we are interested in is the frontal lobe which is located at the front part of the cortex, in each hemisphere. The frontal lobes are responsible for our higher level thoughts and emotions.
The front of the frontal lobe is known as the prefrontal cortex.
So, the prefrontal cortex is at the very front of the outer layer of the brain.
What does the Left Prefrontal Cortex Do?
In the past, scientist thought that our emotions were governed by the action of an older part of the brain, the limbic system, the bit we had before the cortex evolved. Particular emphasis was placed on the fight-flight-freeze action of the amygdala.
However, more recent studies using functional MRI (fMRI) and PET scanning have shown links between the limbic system and the frontal lobes.
Neuroscientist, Dr Richard Davidson, has shown that the left prefrontal cortex is more active when people are happy. Conversely, the right prefrontal cortex is more active when people experience negative emotions.
In some of the experiments, participants were shown images designed to evoke different emotional responses. As might be expected when participants were shown negative images, fMRI scans showed that the amygdala was activated. PET scans also indicated changes to the activity of the right prefrontal cortex.
In another study participants were grouped into those with a high level of activity in the left prefrontal cortex and those with a high level of activity in their right prefrontal cortex. Each group was shown a list of positive and negative adjectives and they were asked to select which words best described their mood most of the time.
Left-prefrontal participants selected words such as ‘strong, enthusiastic, excited’. Their right prefrontal counterparts selected ‘nervous, scared, distressed’.
It’s important to realise that people with a left prefrontal bias, still have a fully functioning amygdala. It’s not that the amygdala doesn’t register a potential threat, it seems that the left prefrontal cortex dampens the response to the negative stimulus, quickly shutting off the negative response before it can develop inappropriately.
Developing the left prefrontal cortex
So what’s to be done? If you have the misfortune to have a highly developed right prefrontal cortex, you might be thinking that you are doomed to a life of misery caused by habitual negative thinking, at the mercy of your fearful amygdala.
The good news is that neuroscience has demonstrated that our brains are ‘plastic’, malleable, they can be moulded and trained to think differently. All we need to do, is do more of what stimulates the left prefrontal cortex and actively avoid doing things that strengthen the right prefrontal cortex.
Research into positive psychology techniques demonstrates that we can change the balance in favour of the left prefrontal cortex through repeatedly and consistently:
· thinking healthy thoughts
· avoiding unhealthy thoughts
· engaging in healthy behaviours, eg
o meditation / trance
o having plenty of social interaction
o enjoying pleasurable activities
o getting enough physical exercise
Repeatedly performing these actions strengthens the left prefrontal cortex, and makes us feel good.
Want to know more? Treat yourself to a copy of Dr Richard Davidson’s marvellous book: The Emotional Life of Your Brain