Welcome to our new reality. Panic in the shops as the supermarket shelves are emptied of toilet paper and bottled water. Whole continents in lock-down. Our older people dying rapidly, or needing increasingly scarce intensive care resources to help them through. Three months ago, who would have thought it? In the UK, employment was up, wages were up. In my town, we’ve had a long dry scorching summer. And now…? It’s all about Covid-19. At least science is once again gaining respectability. Even in the guttersnipe Press. And in the White House. Who would’ve thought that a few months ago?
We are constantly trying to make sense of what’s around us. Reality is perception and perception is reality and we have to perceive so we can act. If we perceive something to be a threat, we become stressed. Psychological stress is useful as it heightens our senses and makes us ready to flee or change our goals to prepare for the worst. Like stocking up on toilet paper or bottled water. Sometimes these responses appear illogical. But there is always a reason we do things, and it depends on how we perceive our world.
I have written about perception in my book How the Brain Thinks, also available here. It is one of the cornerstones that determines how we relate to the world. Sensory information is anlaysed in the periphery and transferred centrally for more detailed analysis. The amygdala produces a rapid emotional response, producing a label of ‘good’ or ‘bad’ within 1/10 of a second. The medial prefrontal cortex (mPFC), with its connections to memory, analyses this information and helps us to decide how to make moral judgments and act appropriately. All of this is out the window now as our moral framework is under threat and we are struggling to make sense of what we should do.
It is interesting to read a recent research paper in Science that sheds new light on the neural circuits involved in our response to psychological stress. Psychological stress activates the sympathetic nervous system producing a variety of responses, but how the brain does this is poorly understood.
‘Stress-induced sympathetic stimulation of heat production in brown adipose tissue (BAT) and changes in cardiovascular function is common in mammals and is a stress-coping response to boost physical performance in fight-or-flight situations. However, excessive stress may cause aberrant sympathetic symptoms.’ For instance, patients with post-traumatic stress disorder show an ‘increased risk of developing hypertension and cardiovascular diseases. Vigorous psychogenic cardiovascular responses are also observed in panic disorder, a severe anxiety disorder.’
‘In a rat model, Kataoka et al. combined anatomical tracing, immediate early gene expression analysis, pharmacology, optogenetics, electrophysiology, and genetic cell ablation to provide evidence for the prominent role of a ventral part of the medial prefrontal cortex,’ the DPP/DTT, ‘in sympathetic responses to social defeat stress. This brain region sends excitatory projections to the dorsomedial hypothalamus as a central coordinator of the psychosocial stress responses. This pathway is crucial for understanding how psychosocial stress influences a variety of body functions.’
But, they ‘propose that there are two functional units in the mPFC: the ventral (DP/DTT) unit that drives stress responses and the dorsal (PrL/IL) unit that inhibits these responses. The inhibitory unit may constitute the negative feedback mechanism in which the stress hormones, glucocorticoids, act in the PrL and IL to mitigate or terminate stress responses. This feedback inhibition might involve stress-activated PrL/IL→DMH neurons and/or local inhibition of DP/DTT neurons from the PrL/IL.’
If this second, dorsal, PrL/IL region can be selectively stimulated or the DP/PTT signals selectively blocked, then we may be able to change our minds response to stress and relieve us of the increased risk of the negative consequences of heart disease and mental illness. Fascinating stuff.
So, once again ‘Goodbye’, and once again, ‘Good Luck’ and may your God bless.
Dr Graham Desborough is a general practitioner, writer, mountaineer and photographer. If you like this post, you can join his mailing list at drgrahamdesborough.com or check out his book How the Brain Thinks.
