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Role of the Prefrontal Cortex in Pain Processing - Coggle Diagram
Role of the Prefrontal Cortex in Pain Processing
Neuroanatomy :silhouette:
Prefrontal cortex :
anterior portion of the frontal lobe
Includes executive functions (planning and functioning out of the routine + inhibiting an inappropriate thought, distraction, emotion or feeling)
Important for pain processing
Medial prefrontal cortex (mPFC)
Pariaqueductal gray (PAG)
Primary control center for descending pain modulation and pain relief
The connections going to the PAG mainly come from the prefrontal cortex
Thalamic Nuclei
Under normal conditions, the connection btw the PFC and thalamic nuclei is what is guiding you to avoid dangerous situations
Under pathological conditions, an over communication btw both may be contributing to chronic pain
increased thalamocortical activity could result in increased activity of the insula and the constant perception of pain
Amygdala
also involved in fear
Basal Nuclei
A lot of loops connecting the basal ganglia with thalamus and prefrontal cortex
Studies have shown that an increased connectivity btw the PFC and the basal ganglia is predictive of pain persistence and chronicity
Neurochemistry :fire:
GLUTAMATE: An increased neuronal excitation due to glutamate receptor activation in the medial PFC has shown to result in antinociception (inhibitation of the pain sensitivity)
GLUTAMATE: When a pain is induced, we see an enhancement of glutamate release in the medial PFC
GLUTAMATE: A reduction in glutamate in the medial PFC shows an increase of chronic pain
GABA : More GABAergic neurons in the medial PFC lead to 1. inhibition of principal neurons in medial PFC that project to the PAG and 2. increased pain
OPIOIDS :In the contrary, if we have an activation of opioid receptors on GABAergic neurons: disinhibition of neurons in mPFC projecting to PAG and decreased pain
CANNABINOIDS: With cannabinoids, we observe a reduction of the excitation of inhibitory neurons in the mPFC, because of an increased amygdala output.
DOPAMINE: There would be a rôle of dopamine with pain since it has been associated with the recalled efficacy of placebo
NORADRENALINE: We ca nsee an increase of the innervation of PFC with noradrenaline in case if injury
ACETYLCHOLINE: We can see the impairment of cholinergic neurons one week after an injury by reduction of the receptors of the neurons, impairing the efficacy of drugs and opioids
Changes in the PFC during acute pain :red_flag:
Study by EEG on humans: tonic pain: gamma oscillations : oscillations encoding pain intensity
PFC is sending signals to other parts of the brain in case of pain but also when a loved one is experiencing pain
Having a continuous and untreated pain could lead to neuroinflammation and loss of neuronal process in the medial prefrontal cortex, leading to a decreased modulation of pain
Chronic pain could also be linked to a persistant activation of the medial prefrontal cortex connectivity with the nucleus accumbens
How to deal with chronic pain :question:
Repetitive transcranial magnetic stimulation of the PFC has a potential to relieve chronic pain, increasing the connection of the PFC with other parts of the brain and activating the modulating effect of the PFC over pain
Transcranial direct current stimulation, helps with the pain perception by inducing an analgesic effect and help patients avoid opioids
Tricyclic amtidepressant is related to reduced pain related activation in the PFC. The brain response is basically reduced in case of pain
Acunpuncture was tested and showed in fMRI a reduction of the pain network in the brain
Transcutaneous Electrical Nerve Stimulation shows a significant decrease in pain intensity perception, and increase the conncetivity between PFC and PAG wich result in modulation of the pain
Depression and anxiety can predispose to pain, treating them will help deal with chronic pain
Mindfulness pactitioners may be able to reduce pain and related anxiety during a mindful state…
Music can increase the functional connectivity of the PFC and produce analgesia
Greater physical activity is associated with decreased pain rating and again a greater activity of the PFC to modulate pain after exercice
Same thing with viewing romantic partner pictures, reducing experimental pain by increasing the modulation of pain by the PFC
Contrary to all previous activities, increasing activity of modulation, mediation seems to make the whole brain work more calmly, having less inhibition but also less excitation of the pain network. The activity of the brain after 5 months practice is lowered of 40 to 50% in the PFC and thalamus!!!!!
Religious prayers may have an effect similar to medication , attenuating pain through a reduction of the general processing of pain in the pain network of the brain
risk factors :warning:
Depressive mood is increasing the pain sensation and vice versa. This interaction involves the PFC with an overactivation of the thalamus and PFC, and the amygdala. This is showing a correlation between emotion regulation and pain affect. In animals, we could see that a 28 days injury provoquing pain is also provoquing depressive and anxiogenic behavior, worsening the pain sensation.
Pain is often associated with anxiety but there is not much proof of why.
Painful stimuli may affect cognition, since in chronic pain states, the mPFC is deactivated and tasks related to the mPFC, such as attention and working memory are impaired. !!! Careful, not all tasks related to the mPFC are impaired, and memory functions can also be in other parts of PFC.
After the treatment of pain, luckily, it seems that the PFC may recover fully from all decreased cognitive functions and misconnections with other parts of the brain. The decrease in grey matter is stopping and patients are showing a recovery in cortical thickness.
I would like to finish by pointing on the importance of prevention and treatment of chronic pain, depression and anxiety
Changes in the PFC during chronic pain:red_flag:
Loss of grey matter in the PFC as a result of chronic pain
We could observe a loss of matter of 5 to 11% in some parts of the PFC and also in the thalamus, which is equivalent to a 10 to 20 years of aging normal loss
With this PFC athrophy, we also observe a reduced white matter integrity and connectivity in basal ganglia
Description of specific patterns depending on illnesses in the article, i let you check if interest
As we saw earlier, the PFC interact with the PAG to deal with the pain and regulate it. In chronic pain, we see the PFC less communicate with PAG and less regulate the pain