From sense of touch to tactile intelligence: Thoughts from the 2021 Nobel Prize in Physiology or Medicine

Abstract

<p indent=0mm>Human beings have highly developed sense of touch. Through touching we can perceive heat, pain, mechanical stimuli, recognize features of an object such as texture and hardness, and even understand emotion of a person. Hence, human touch is one of the most important ways to sense and adapt to the world around us. However, we had little understanding of how cutaneous perception was formed in our nervous system, until the groundbreaking discoveries were made by this year’s Nobel Prize laureates in Physiology or Medicine, David Julius from University of California, San Francisco, and Ardem Patapoutian from Scripps Research. They found that heat and mechanical stimuli can initiate specific nerve impulses for temperature, pain, and touch sensations. The quest to understand temperature sensation and pain spans millennia. In the early 20th century, the Greek physician Galen proposed that sensations were transmitted along pathways that connect the organs to the brain. It was not until 1997 that the true underlying molecular mechanism was revealed by Julius in a breakthrough work. Julius and his team found that a receptor on the cell’s membrane arranges itself from one side to the other, so that it creates a passage called a transient receptor potential (TRP) channel. This ion channel opens or closes in response to heat. Inspired by Julius’s work, Patapoutian in the early 21st century explored a mechanosensitive ion channel, called the Piezo channel, and identified that it is essential for the sense of touch. Patapoutian and his team also found that the Piezo channel is responsible for the sensing of position and motion of our body, which explains why we can balance on a steep stair. Not only did these discoveries elucidate the physiological understanding of human somatosensory, they also enlightened the researchers who work on reproducing such human functions in robotics and prosthetics. The molecular mechanisms of thermo-sensation and mechano-sensation provided a new paradigm for designing artificial cutaneous perception and constructing electronic skin for robots. Once fully armed by tactile perception and haptic feedback, smart robots and artificial intelligence may start to have consciousness and feel emotions like we humans do. With the awarding of the 2021 Nobel Prize in Physiology or Medicine to research in how humans perceive touch and pain, the research in tactile intelligence now has a clearer roadmap and gains a greater momentum. We foresee many exciting breakthroughs in this field in the near future.