Why we recognise the smell of a scent

December 17th, 2007 - 1:13 pm ICT by admin  

London, Dec 17 (ANI): US researchers have described a mechanism called dynamic connectivity, which explains why, when we notice a scent, the brain quickly sorts through input and determines exactly what that smell is.

In the mechanism of dynamic connectivity neuronal circuits are rewired on the fly allowing stimuli to be more keenly sensed.

The study, led by Nathan Urban, associate professor of biological sciences at Carnegie Mellon, stated that by understanding how the brain does this, the mechanism could be applied to other problems faced by the brain.

If you think of the brain like a computer, then the connections between neurons are like the software that the brain is running. Our work shows that this biological software is changed rapidly as a function of the kind of input that the system receives, Nature quoted Urban, as saying.

When a stimulus such as an odour is encountered, many neurons start to fire. When many neurons fire at the same time, the signals can be difficult for the brain to interpret.

The stimulated neurons send cease-fire messages during lateral inhibition to the neighbouring neurons, which reduce the noise and makes it easier to precisely identify a stimulus. This process, in many sensory areas of the brain, also facilitates accurate recognition of stimuli.

In the study, researchers examined the process of lateral inhibition in olfactory bulb, an area of the brain responsible for processing scents.

The analysis of the study found that the connections are not set but rather able to change dynamically in response to specific patterns of stimuli.

In the experiments, they found that when excitatory neurons in the olfactory bulb fire in a correlated fashion, it determines how they are functionally connected.

The team showed that dynamic connectivity allowed lateral inhibition to be enhanced when a large number of neurons initially respond to a stimulus, filtering out noise from other neurons. By filtering out the noise, the stimulus can be more clearly recognized and separated from other similar stimuli.

This mechanism helps to explain why you can walk into a room and recognize a smell that seems to be floral. As you continue to smell the odour, you begin to recognize that the scent is indeed flowers and even more specifically is the scent of roses. By understanding how the brain does this, we can then apply this mechanism to other problems faced by the brain, Urban said.

Researchers converted this new biologically inspired algorithm into an algorithm and used computer modelling to further show that dynamic connectivity makes it easier to identify and discriminate between stimuli by enhancing the contrast, or sharpness, of the stimuli, independent of the spatial patterns of the active neurons.

The study will appear in Nature Neuroscience. (ANI)

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