When I tell people I study rodent whiskers I’m often met with a slightly puzzled look. More often than not, I get asked ‘why?’ which is probably fair enough since to the general population it might seem like a slightly odd thing to do. Unlike my colleagues studying Alzheimer’s disease or chronic pain, there’s no obvious reason why we should be interested in the whisker system- after all humans don’t have whiskers (hipster beards aside) and at first glance there’s no obvious medical benefit. However, there are in fact many amazing features of the rodent whisker system which could provide fundamental insights in neuroscience, alongside many opportunities for technological and medical advances.
One key problem in neuroscience is understanding how the sense organs (eyes, ears, nose, tongue and skin) take information from the outside world and translate it into something we can perceive. Take olfaction for example: a smell begins life as a small number of air borne chemicals hitting receptors in our nose. But, from these humble beginnings it can – with the help of a bit of brain power – become so much more; the appetising aroma of freshly baked bread or the memories of summers long-past engrained in the smell of petrol and freshly cut grass.
Another sense we sometimes take for granted is our sense of touch, how do we manage to distinguish between smooth and rough surfaces? Rodents are experts at navigating the world in the dark using only their sense of touch and they use their whiskers in much the same way that we would use our fingertips – to get information about something in front of them. Rodents rhythmically brush and tap about 60 large vibrissae (whiskers) against objects to determine their size, shape, orientation, and texture. This behaviour is called ‘whisking’. When a whisker bends against an object, forces and torques are generated at the whisker base. By quantifying these mechanical signals we are able to understand what information the rat’s brain is receiving.
The fact that the whisker system uses mechanical information is a great advantage for scientists as it means that we can measure the exact inputs coming into the receptors at the base of the whisker (forces and bending moments are easier to measure than the equivalent input for every other sensory system). For example, the equivalent in the visual system would be attempting to measure every single photon of light hitting the retina- something that is currently impossible. Furthermore, the whisker system has a well-defined neural pathway, meaning we know the route that information takes from the base of the whisker, through the brainstem and thalamus all the way up into the cortex. In this pathway, each whisker is faithfully represented so that at any stage along the neural pathway, you will find neurons that fire to the movement of a single whisker and no other. These features provide an unparalleled opportunity to study how the neurons ‘code’ information from the external world and how the brain ‘decodes’ it.
If we can understand the way information from the outside world is transduced within the nervous system, we can use this knowledge for a surprisingly wide-range of applications. One of the most promising applications is the construction of robotic whiskers which can be used in situations where visual information is difficult to obtain. For example, fog, darkness and glare can all interfere with optical sensors. A tactile based sensor, however, could provide crucial information where optical sensors fail. For example, fault detection in piping, machinery or ducts.
Another potential application is in the field of intravascular surgery. This application would require our robotic whiskers to be miniaturized in a biocompatible manner. An increasing number of surgeries are being conducted non-invasively. Although there are several optical sensing methods available to the surgeon, none of these methods can replicate the sense of touch that is lost when performing non-invasive surgery.
Whilst there is a still a way to go before whisker based technologies can be fully used in the situations outlined above, we are certainly making significant headway – for example take a look at the following video showing ‘Whiskerbot’- a robotic active touch system created by scientists at the University of West England and the University of Sheffield.
Hopefully, projects like this will not only inspire others to study this fascinating sensory system, but also pave the way for innovative technological advances.
Post by: Michaela Loft