To Juan Antonio Micó, in memoriam
Pain is the cruelest expression of nature.
When it is intense and long-lasting, it fills the mind of the sufferer, leaving little room for anything other than feeling it or trying to relieve it.
The suffering that often accompanies him can become an invitation to leave this world.
Some parts of the body are very sensitive to pain, such as the fingers, the tibia or the cornea of the eyes.
An especially irritating pain is toothache, and among the most excruciating pains are burns and kidney stones.
The mothers maintain that there are very few pains like those of childbirth.
A problem that is difficult to solve is the one that occurs when the pain persists for weeks and becomes chronic.
Little joke, because it is estimated that one in five adults in the world has this type of pain, such as neuropathic pain, which occurs when a traumatic accident or disease damages the neurons that carry information from the body to the brain.
It occurs more often in obese or diabetic people and is related to damage to the small blood vessels that feed those neurons.
Chronic pain is also a strong initiator of disorders such as persistent stress, anxiety, depression, vulnerability to drug addiction, and memory deficits.
Disorders that, in turn, can aggravate the duration and sensitivity of the pain.
Unlike other senses, there is no specific part of the brain responsible for the perception of pain.
When we feel pain, functional magnetic resonance imaging (MRI) shows activation of various regions, both in the cerebral cortex (somatosensory cortex, anterior cingulate, insula), and subcortical regions (thalamus), which, far from being specific for pain , they can also be activated in emotional situations, such as when we feel empathy when seeing the suffering of other people or when we feel excluded and rejected in a group.
Envy also activates some of the regions involved in pain.
The brain therefore responds in a fairly generalized way to any type of pain, be it somatic (physical) or emotional.
Fortunately, the brain also has an important analgesic mechanism in the brainstem (periaqueductal gray matter) that prevents pain information from anywhere in the body from ascending to it.
This mechanism is normally inhibited, that is, paralyzed, but it is activated by the brain's own production of substances such as enkephalins and endorphins that, in this way, relieve pain, in addition to producing pleasure.
The brain itself acts, therefore, as a valve that regulates the ascent towards it of painful information.
It is the same mechanism that certain antidepressant medications and opiates such as morphine use to relieve pain, since they mimic or usurp, so to speak, the function of the enkephalins and endorphins themselves,
We also know from experience that the pain we feel at a given time and situation can be influenced by the expectations we have, the attention we pay to it, the emotional situation we live in and even the personality of each individual.
Thus, in the heat of a brawl, the pain of a blow may be less than what we feel when we are calm and relaxed.
We sometimes wonder how some soldiers can continue to fight with large wounds on their bodies, proof that intense stress can also work as an analgesic.
Similarly, the suspicion that pain is a sign of a serious illness can increase their suffering, making it unbearable.
And it is no less true that when experience tells us that the pain we have will not last long, we bear it better, even if it is intense.
In addition,
When we have analgesics to take if the pain persists, we do not suffer as much as when we do not have that remedy because we have already taken the maximum prescribed dose without feeling much relief.
These influences are possible because they act on the neuronal mechanisms that prevent pain information from any part of the body from ascending to the brain, and also, as we will see below, because of their possible influence on the cerebral cortex.
Although pain perception and analgesia mechanisms have traditionally focused on the brainstem, young researchers Linette Liqi Tan and Rohini Kuner, from the Institute of Pharmacology at the University of Heidelberg in Germany, have recently published
an excellent article in
Nature Reviews Neuroscience
review that diverts interest from the mechanisms of pain and analgesia to the cerebral cortex.
The fact that pain, as we have just explained, is modulated by motivational and emotional factors justifies, according to these researchers, the importance of this cortex to explain individual differences and the context of each person in the perception of pain.
The new data that we know are changing the classic dogma that in the cerebral cortex the areas of pain itself are segregated from those that process their emotional aspects and suggest much more complex functional subdivisions in each area that must be taken into account.
New neural pathways from the prefrontal cortex to lower areas (nucleus accumbens or insular cortex) that increase or attenuate pain (periaqueductal gray matter) have been revealed, and research is under way to differentiate between pathways mediating acute and chronic pain. those that are a consequence of the pain itself or its motor or emotional components.
On the other hand, the efficacy of repetitive high-frequency transcranial magnetic stimulation has also been demonstrated to relieve neuropathic pain by inhibiting in the thalamus, as indicated by experiments with rats, the rise of pain information, and also the possibility of reducing pain. pain through conditioned stimuli, also painful, applied to a different part of the body.
Other data indicate that
mindfulness
could suppress the intensity and discomfort of pain by acting on brain mechanisms other than those of placebo analgesia, including a strong activation of different cortical areas associated with sensory and emotional modulation of pain.
The aforementioned review by the two researchers from Heidelberg gives particular information about all this and much more.
But, in addition, new and very recent research also shows the possibility of treating neuropathic pain through bacterial toxins, proteins that can specifically adhere to pain neurons to inactivate them.
No vital experience surpasses that of pain, perhaps because it is the sentinel that warns us of damage or deterioration in some part of our body so that we prepare to avoid it.
In turn, nothing in life is more pleasurable and rewarding than pain relief, especially when it is intense and long-lasting.
Helping those who suffer from it must always be among the main objectives of science and of a caring society.
Ignacio Morgado Bernal
is Professor Emeritus of Psychobiology at the Institute of Neuroscience and at the Faculty of Psychology of the Autonomous University of Barcelona.
He is the author of "The Factory of Illusions: Getting to know each other better to be better" (Ariel, 2015).
Gray matter
it is a space that tries to explain, in an accessible way, how the brain creates the mind and controls behavior.
The senses, motivations and feelings, sleep, learning and memory, language and consciousness, as well as their main disorders, will be analyzed in the conviction that knowing how they work is equivalent to knowing ourselves better and increasing our well-being and relationships with other people.
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