Stress is an interesting body response that is stimulated by our brain due to incoming auditory, visual and/or somatosensory signals. It is how we feel and how our body reacts when we encounter an imbalance in the normal rhythm of life. Watching a horror movie, coming face to face with a deadly creature or simply feeling overwhelmed due to daily tasks may all evoke stress. How does our brain respond to a stimulus that elicits fear and anxiety?
The key areas of the brain that are involved in stress are the thalamus, hippocampus, amygdala, and the prefrontal cortex. The thalamus located in the forebrain processes the incoming visual and auditory signals and relays them to the prefrontal cortex and the amygdala. The prefrontal cortex is the hub for executive function. With respect to stress, it gives meaning to the relayed signals and makes us conscious of what we see and hear. This part of the brain is also critical for ‘turning off’ the stress response once the condition is passed.
The amygdala is the emotional center of the brain and is responsible for triggering the stressful response. It is a part of the limbic system and is located deep within the temporal lobes of the brain. The amygdala also drives the body’s sympathetic nervous system to initiate anxiety that is associated with stress. This includes increasing the heart rate, blood pressure, hyperventilation of the lungs and increasing perspiration.
Finally, the hippocampus located in the medial temporal lobe stores the memory linked to a particular stress response and allows the brain to access these memories when the same visual and auditory triggers of stress are encountered later on.
It is also essential to mention the role of the hypothalamus and the linked pituitary gland that pumps out high levels of cortisol – “the stress hormone”. Recent studies suggest that cortisol can damage and kill brain cells, especially that in the hippocampus. (The hormonal response of stress is in fact a huge area of study with lots of factors involved.)
A critical question in this area of study that interests me is, “How much stress is bad for us? Can a little stress actually be helpful?” It turns out that acute stress (short-lived, unlike chronic stress) may actually be good for us. New research suggests that it conditions the brain for improved performance by inducing an increased level of alertness, behavioural and cognitive performance. This may explain why we get most of work done when we’re under pressure!