What makes us scratch, where does it itch?
45. Three things, once started, it is difficult to finish:
a) eat good food;
b) talk to a friend who has returned from a hike and
c) scratch where it itches.
Kozma Prutkov,
Fruits of reflection. Thoughts and aphorisms.The fact that pain, including that caused by severe scratching, temporarily suppresses itching is a well–known phenomenon.
However, scientists at Wake Forest University (Wake Forest, North Carolina), working under the guidance of Dr. Gil Yosipovitch, for the first time managed to trace the central mechanisms underlying the relief experienced when scratching.
The authors analyzed the activity of various brain areas during scratching using the functional magnetic resonance method. The test involved 13 healthy people, whose shins were brushed twice in opposite directions with a soft brush for five minutes at 30-second intervals.
Such scratching suppressed the activity of the anterior and posterior cingulate cortex associated with pain perception and memories of it. At the same time, the longer a person was scratched, the less activity was observed in these areas of the brain.
According to the authors, scratching may suppress the emotional components of itching and thus bring relief. However, each scratching causes a need for prolongation of sensations.
At the same time, scratching increases activity in the secondary somatosensory cortex, the pain center and the prefrontal cortex associated with manifestations of compulsive behavior (obsessive actions), which explains the irresistible desire to continue scratching the itchy place.
The researchers note that the results of the work are not exhaustive, because during its conduct they did not study the processes occurring in the brain when scratching a truly itchy place.
At first glance, it may seem that scientists are spending taxpayers' money on mere trifles. However, chronic itching, for example, in skin diseases, is a very unpleasant thing, and the authors emphasize that understanding the processes triggered by scratching in the brain will help in the treatment of people suffering from chronic itching, including eczema patients and patients undergoing renal dialysis.
Portal "Eternal youth" www.vechnayamolodost.ru based on ABC materials.
05.02.2008