Touch signals are processed earlier in the neurobiological pathway than once believed

David Ginty’s asking the same fundamental questions he set out to answer more than a decade ago: 

Where do the various touch neurons go, what are their end structures, and how do they capture the richness of the physical realm? 

“We’ve gotten a pretty good handle on who’s who in the skin and what their response properties are,” Ginty said. 

But what about the heart, lungs, larynx, esophagus, stomach, intestines and kidneys? What are the neurons that make muscles ache and fatigue, or trigger migraines, or cause milk to flow in a mother’s breast when her baby suckles?

Ginty also wants to know how all these neurons connect to the brain to generate perceptions: 

How does pressure and vibration across millions of nerve endings become a hug? How do we feel wetness, slipperiness or elasticity? “Think about squeezing a balloon,” he said. “Presumably no one sensory neuron type is going to encode squeeziness.”

His work has transformed our understanding not only of individual touch sensors, but also of their connectivity. 

Until recently, the canonical view was that touch signals, like a telephone conversation, travel along fixed lines all the way to the somatosensory cortex, the part of the outer brain associated with sense information. “So any higher-order feature of the tactile world was seen as an emergent property of the cortex,” Ginty said. 

But his research and that of others has caused a paradigm shift: 

It’s now clear that a great deal of information carried by touch neurons converges in the spinal cord and brainstem before reaching the cognitive parts of the brain, suggesting that the touch signals are processed earlier in the neurobiological pathway than once believed.