BRAIN

Let’s Learn About Touch

Receptor cells all over the body tell the difference between petting a cat and a cactus.

Careful there! If you poke your finger on a cactus, your sense of touch will let you know the plant is covered with sharp spines.

By Bethany Brookshire

Four of your senses are located just on your head. Taste is in your mouth. Smell is in your nose. Sight in your eyes and hearing in your ears. But touch? Touch is all over your body. Your fingertips and face can sense touch, and so can the bottoms of your feet and the backs of your knees. It’s completely essential. Without it, we wouldn’t know if we stubbed our toes or burned our skin. 

Your skin (and your organs, bones, and muscle) is full of receptor cells for different aspects of touch. These cells might respond to pressure or heat. They could respond to something that causes pain. Some of these receptor cells can also respond to cold and different chemicals. Each of the receptor cells connects to a sensory neuron. These are cells that send information back to the spinal cord and brain. There, your brain processes the touch your receptors felt, and determines whether you just tried to pet a cat or a cactus. Some areas of your body are more sensitive to touch than others, which is why you pet a cat with your hand and not with your back.

It’s pretty easy to fool our eyes, ears, or noses with sights, sounds, and scents. But touch? That’s tougher. Scientists are working on haptic devices — technologies that can mimic our sense of touch. Some use stretchy fabrics to make our skin feel something that’s not there. Others are using sound waves that we can’t hear to make illusions real to the touch.

Touching allows octopuses to pre-taste their food: Special sensory cells in suckers in the animals’ arms sense chemicals. Those cells allow them to taste the difference between food and poison.

This artificial skin feels ‘ghosts’ — things you wish were there: Engineers have developed a wearable device that simulates the sense of touch. It may benefit robotic surgery and deep-sea exploration. 

Testing the power of touch: We pet dogs with our fingers, not our arms or backs. Our fingers are more sensitive to touch. But how do we know? Here’s how you can test that.

Virtual reality is mostly sight and sound right now. But with the power of haptics, it could be touch, too.