Making sense of our senses

Imagine you’re driving a car. There are myriad sensations, from the noise of sirens, to vibrations from driving over a bump, to the colour of traffic lights. The brain constantly monitors these sensations and instantly works out what to pay attention to and what to ignore.

Yet we know very little about how the brain does this, despite more than one hundred years of neuroscience research. But that is changing as Professor Ehsan Arabzadeh and his team from the Eccles Institute of Neuroscience at JCSMR investigate how neurons in the brain process sensory perception.

“A key goal in neuroscience is to understand how the brain generates a representation of the world around us. We call this the neural code,” says Professor Arabzadeh.

“You would think after so many years we would know what the neural code is. But there are lots of gaps in knowledge in exactly how neurons generate perception and process sensory experience.”

Professor Arabzadeh is exploring sensory perception by investigating how rats respond to changes in their environment such as rough or smooth surfaces, and changes in the amount of light.

As nocturnal animals, rodents rely heavily on their sense of touch through their array of whiskers. They move their whiskers back and forth to navigate their environment and to collect information about the objects around them.

Arabzadeh’s research team found that the rodent brain does not process sensory information the same way all the time, it changes its priorities based on the context.

Professor Arabzadeh’s group discovered this by developing a model for studying perception by changing a rat’s experiences of vision or touch.

The rats were exposed to two types of sessions: a whisker session, which was primarily about detecting vibrations, and a light session, which was mostly about detecting flashes of light. In the whisker session, 80 per cent of trials involved a brief vibration to the rat’s whiskers and the remaining 20 per cent of trials involved a change in light levels. The reverse was applied to the light sessions.

Professor Arabzadeh expected the rats to prioritise the whisker sensory pathway in the whisker session and the visual sensory pathway in the light session.

Not surprisingly, in the whisker session the rats were quicker to respond to vibrations than to light flashes. The researchers could also see increased neuronal activity in the part of the sensory cortex that processes whisker vibrations.

The reverse happened for the light sessions.

“The next step is to better understand the link between circuitry and behaviour in paradigms such as sensory prioritisation,” says Professor Arabzadeh.

Professor Arabzadeh’s work ultimately may prove to be useful in understanding brain disorders.

“If you understand what the properties of a healthy functioning circuit are, you can then understand diseases such as epilepsy or schizophrenia, where the circuits malfunction,” says Professor Arabzadeh.

“In the long run it could have applications for prosthetic devices. If you understand the neuronal language you can bypass the part that is not functional. For example if a signal from the eye to the brain is broken, one could wire the visual signal directly to the brain.”

Published in Research Highlights – John Curtin School of Medical Research, ANU, May 2017.


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