Placebo and nocebo work in the subcortex
Placebo treats unconsciously
The brain makes a decision about the effect of the drug even before,
how will this action be realized by usDmitry Malianov, "Gazeta.
The brain decides how this or that medicine will affect us, even before the information about this medicine is realized by us.
Unconscious mechanisms play a key role in the therapeutic effect of placebo, doctors from the Department of Psychiatry and the Center for Biomedical Research at Massachusetts General Hospital, together with specialists from Harvard Medical School working on the placebo research program PiPS, whose article "Unconscious activation of placebo and nocebo responses to pain" (Nonconscious activation of placebo and nocebo pain responses) published Tuesday Proceedings of the National Academy of Sciences (PNAS).
Placebo (from Lat. placebo – I will be pleased) is a chemically inert substance that does not have therapeutic properties, but, nevertheless, has a pronounced therapeutic effect on the patient. At the same time, the placebo effect is observed in a much wider range of cases than using the actual "pacifiers". It has been shown that "real" drugs also owe their therapeutic effect to this effect to varying degrees, although it is quite difficult to identify its real contribution, since patients can be influenced by a variety of factors, including the color and shape of tablets, the price of the drug, its inaccessibility and "prestige", publications in the media, opinions of other patients etc.
The psychophysiological mechanism of action of placebo still remains unclear. It is believed that it is based on suggestion, that is, the patient's conscious belief in the therapeutic power of the dummy drug and, again, the conscious expectation that this particular drug will cure them, or, in the case of nocebo (from Lat. nocebo – will cause harm), will worsen their condition.
Meanwhile, in clinical and laboratory practice, a lot of data has accumulated that the effects of placebo and nocebo can occur without conscious processing of verbal and visual stimuli associated with the medication taken: in these cases, improvement and deterioration of the condition occurs in people as if automatically, that is, bypassing the conscious registration of the idea that the drug should have this or that effect on their health.
As the MRI scan showed, visual and verbal stimuli in these cases can be processed by the brain at a lower, pre-conscious level in the striatum, which is an integral part of the evolutionarily older basal nuclei of the hemispheres, as well as in the subcortical amygdala, that is, in the sections of the brain in which signals are formed that render "unconscious" the effect on human behavior and perception.
The experiments carried out by the authors of the article in PNAS confirmed the hypothesis that the brain decides how a particular medicine will affect us, even before the information about this medicine is realized by us.
"Using a new experimental technique, we found that the placebo and nocebo effect is based on a mechanism that is not related to the mechanism of conscious perception. A therapeutic or negative response occurred even when the subjects did not realize that their condition could improve or worsen," the authors of the article summarize.
The experiment involved 40 healthy volunteers – 24 women and 16 men, whose average age was 23 years. The experiment took place in two stages.
At the first stage, each subject, to whose hand a heating element was attached, had to assess the level of their pain sensations on a 100-point scale, while simultaneously viewing photos of people on the monitor screen, some of whom depicted weak pain on their face, and others severe pain. The participants of the experiment did not know that the temperature of the heating element remained unchanged throughout the experiments. Despite the fact that the thermal effect on the skin was the same, the level of their pain sensations strongly correlated with the images in the photographs, that is, it depended on the associative suggestion caused by the visual stimulus. On average, the subjects rated them by 19 points when they saw a person depicting mild pain on his face (placebo effect), and 53 points when they saw a face severely distorted by a painful grimace (nocebo effect).
At the second stage of the experiment, the participants were again asked to evaluate the level of their pain sensations on the same scale, but this time photos of people experiencing pain of different intensity were shown for 12 ms each, that is, in stroboscopic mode, which does not allow recognizing and, moreover, analyzing facial expressions (in previous experience, this time was 100 ms).
And again, despite the absence of consciously perceived stimuli, the intensity of the pain experiences of the participants in the experiment clearly correlated, although not so much, with the grimaces of pain on other people's faces: participants rated their pain sensations by an average of 25 points when they were shown photos of people depicting mild pain in stroboscopic mode, and by 44 points – at the moments when they were shown faces distorted by a grimace of severe pain.
"It is an automatic and more fundamental mechanism than belief and conscious expectation that regulates our reactions and behavior. It is also important that using this experimental model in combination with functional MRI mapping of the brain, we can study the placebo effect in more detail," said Jiang Kong, one of the authors of the article.
Having understood the mechanism of this effect, it will be possible to create a new generation of drugs, the action of which will be based not on direct interference in the work of certain body systems, but on launching protective scenarios at a higher level – the brain level. Strictly speaking, such a medicine – actually a placebo – has been available to doctors for a long time, but its effect in most cases is unstable and uneven – some patients are treated with placebo, others are treated weaker, others are not treated at all.
Portal "Eternal youth" http://vechnayamolodost.ru11.09.2012