Our ability to perceive heat and cold. The touch that makes us feel contact with others. They are sensations essential to survival and support our interaction with the world around us. In our daily life we take them for granted, but behind all this there is a sophisticated mechanism. How nerve impulses are initiated so that the temperature and pressure can be felt? The winners of this year’s Nobel Prize in Medicine or Physiology, David Julius and Ardem Patapoutian, answered this question.
Julius used capsaicin, a pungent compound in chilli that induces a burning sensation, to identify a sensor in the skin’s nerve endings that responds to heat. Patapoutian instead used pressure-sensitive cells to discover a new class of sensors that respond to mechanical stimuli in the skin and internal organs.
These “revolutionary discoveries”, as they have been defined by the experts of the Nobel Assembly, have given rise to intense research activities that have led to a rapid increase in our understanding of how the nervous system perceives heat, cold and mechanical stimuli.
And so the importance of ‘warmth’ and tact is rewarded, precisely in the era in which human beings had to put them aside, the era of social distances due to the Covid pandemic.
Award winners have identified critical links missing in understanding the complex interaction between the senses and the environment. One of the great mysteries humanity faces is the question of how we perceive the environment. The mechanisms underlying the senses have triggered our curiosity for thousands of years: how light is detected by the eyes, how sound waves affect our inner ears, how different chemical compounds interact with the receptors in our nose and mouth generating smell and taste. We also have other ways to perceive the world around us. For example, walking barefoot on a meadow on a hot summer day, you can feel the warmth of the sun, the caress of the wind and the individual blades of grass under your fingers. These impressions of temperature, touch and movement are essential for adapting to the ever-changing environment.
In the 17th century, the philosopher René Descartes imagined threads connecting different parts of the skin with the brain. The findings then revealed the existence of specialized sensory neurons that record changes in our environment. Joseph Erlanger and Herbert Gasser received the Nobel Prize in Medicine in 1944 for their discovery of different types of sensory nerve fibers that react to distinct stimuli, for example, in painful and non-painful responses to touch. Since then it has been shown that nerve cells are highly specialized in detecting and transducing different types of stimuli, allowing a nuanced perception of our surroundings; for example, our ability to perceive differences in surface texture through our fingertips, or our ability to discern both pleasant and painful heat. Before Julius and Patapoutian’s discoveries, the understanding of how the nervous system perceives and interprets the environment was not complete. There was a fundamental unsolved question: How are temperature and mechanical stimuli converted into electrical impulses in the nervous system?