How the brain forms categories

October 20, 2012
Credit: Research Institute of Molecular Pathology

Neurobiologists at the Research Institute of Molecular Pathology (IMP) in Vienna investigated how the brain is able to group external stimuli into stable categories. They found the answer in the discrete dynamics of neuronal circuits. The journal Neuron publishes the results in its current issue.

How do we manage to recognize a friend's face, regardless of the light conditions, the person's hairstyle or make-up? Why do we always hear the same words, whether they are spoken by a man or woman, in a loud or soft voice? It is due to the amazing skill of our brain to turn a wealth of sensory information into a number of defined categories and objects. The ability to create constants in a changing world feels natural and effortless to a human, but it is extremely difficult to train a computer to perform the task.

At the IMP in Vienna, neurobiologist Simon Rumpel and his post-doc Brice Bathellier have been able to show that certain properties of in the brain are responsible for the formation of categories. In experiments with mice, the researchers produced an array of sounds and monitored the activity of nerve cell-clusters in the auditory cortex. They found that groups of 50 to 100 neurons displayed only a limited number of different activity-patterns in response to the different sounds.

The scientists then selected two basis sounds that produced different response patterns and constructed linear mixtures from them. When the mixture ratio was varied continuously, the answer was not a continuous change in the activity patters of the , but rather an abrupt transition. Such dynamic behavior is reminiscent of the behavior of artificial attractor-networks that have been suggested by computer scientists as a solution to the categorization problem.

The findings in the activity patters of neurons were backed up by with mice. The animals were trained to discriminate between two sounds. They were then exposed to a third sound and their reaction was tracked. Whether the answer to the third tone was more like the reaction to the first or the second one, was used as an indicator of the similarity of perception. By looking at the activity patters in the , the scientists were able to predict the reaction of the mice.

The new findings that are published in the current issue of the journal Neuron, demonstrate that discrete network states provide a substrate for category formation in brain circuits. The authors suggest that the hierarchical structure of discrete representations might be essential for elaborate cognitive functions such as language processing.

Explore further: Unraveling the mysteries of the maternal brain: Odors influence the response to sounds

More information: Brice Bathellier et al. "Discrete neocortical dynamics predict behavioural categorization of sounds". Neuron 76, 435–449, October 18, 2012.

Related Stories

Unraveling the mysteries of the maternal brain: Odors influence the response to sounds

October 19, 2011
Motherhood is associated with the acquisition of a host of new behaviors that must be driven, at least in part, by alterations in brain function. Now, new research published by Cell Press in the October 20 issue of the journal ...

Interaction between auditory cortex and amygdala responsible for our response to unpleasant sounds, research finds

October 10, 2012
(Medical Xpress)—Heightened activity between the emotional and auditory parts of the brain explains why the sound of chalk on a blackboard or a knife on a bottle is so unpleasant.

Researchers connect neurons to computers to decipher the enigmatic code of neuronal circuits

July 12, 2011
Machine logic is based on human logic. But although a computer processor can be dissembled and dissected in logical steps, the same is not true for the way our brains process information, says Mark Shein of Tel Aviv University's ...

Recommended for you

Physicist reports binary marker of preclinical and clinical Alzheimer's disease

August 23, 2017
A new technique shows high potential for providing a discrete, non-invasive biomarker of Alzheimer's disease (AD) at the individual level during both preclinical and clinical stages. The proposed biomarker has a large effect ...

Firing of neurons changes the cells that insulate them

August 22, 2017
Through their pattern of firing, neurons influence the behavior of the cells that upon maturation will provide insulation of neuronal axons, according to a new study publishing 22 August in the open access journal PLOS Biology ...

Study suggests serotonin may worsen tinnitus

August 22, 2017
Millions of people suffer from the constant sensation of ringing or buzzing in the ears known as tinnitus, creating constant irritation for some and severe anxiety for others. Research by scientists at OHSU shows why a common ...

Activating brain region creates intense desire to use cocaine

August 22, 2017
Researchers have identified a portion of the brain that intensifies one's desire for certain rewards—in this case, mimicking addiction to cocaine.

Brain region mediates pleasure of eating

August 22, 2017
Providing the body with food is essential for survival. But even when full, we can still take pleasure in eating. Researchers at the Max Planck Institute of Neurobiology in Martinsried and the Friedrich Miescher Institute ...

Chronic stress induces fatal organ dysfunctions via a new neural circuit

August 22, 2017
Hokkaido University researchers revealed that fatal gut failure in a multiple sclerosis (MS) mouse model under chronic stress is caused by a newly discovered nerve pathway. The findings could provide a new therapeutic strategy ...

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

Tausch
not rated yet Oct 20, 2012
The brain does not create constants.
Why do we always hear the same words, whether they are spoken by a man or woman, in a loud or soft voice?


Think about this boys and girls.

For the same reason you can recognize a melody despite what originates the sound, what key used, what octave used, what tempo used -the list is endless.

They found that groups of 50 to 100 neurons displayed only a limited number of different activity-patterns in response to the different sounds.


Well that is because you did not eliminate the possibility that groups larger than this do NOT display an only limited number of different activity in response to the different sounds.

Good work.
Go back to the drawing board anyway. Not a watertight thesis.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.