We sense ’stiffness’

Every day, people use their hands effortlessly to assess an object's stiffness, like the ripeness of a piece of fruit. For the first time an international team of scientists led by UCL, have discovered the area in the brain where stiffness perception is formed. The findings, published in the Journal of Neuroscience , could aid rehabilitation in patients with sensory impairments. Hands do not have sensors to directly inform the brain about an object's stiffness. To uncover the link between our brain and our hands, researchers focused their attention on how motion and sensory inputs are combined and processed. The team looked to the posterior parietal cortex (PPC); a key part of the brain which plays an important role in planning movements, spatial reasoning and attention. Could the PPC also be involved in stiffness perception? Lead researcher Dr Marco Davare (UCL Institute of Neurology) said: "There is already evidence that a position controller exists in this brain area, however it is still unknown whether this area also combines force and position information - a prerequisite for us to sense stiffness." Sensory signals such as position and force travel back to the brain and are combined with a copy of motor commands to adjust movement and provide us with a sense of the environment.