How brain filters out irrelevant information decoded

Ever wondered how people are able to read in a noisy cafe, ignoring the ambient chatter and clattering of cups? Scientists have discovered how the brain filters out irrelevant information in such circumstances.

To explain how we are able to focus on a particular sound or information ignoring others, New York University (NYU) researchers offer a new theory, based on a computational model.

"It is critical to our everyday life that our brain processes the most important information out of everything presented to us," said Xiao-Jing Wang, professor at NYU and NYU Shanghai.

"Within an extremely complicated neural circuit in the brain, there must be a gating mechanism to route relevant information to the right place at the right time," said Wang.

The analysis focuses on inhibitory neurons - the brain's traffic cops that help ensure proper neurological responses to incoming stimuli by suppressing other neurons and working to balance excitatory neurons, which aim to stimulate neuronal activity.

"Our model uses a fundamental element of the brain circuit, involving multiple types of inhibitory neurons, to achieve this goal," Wang said.

"Our computational model shows that inhibitory neurons can enable a neural circuit to gate in specific pathways of information while filtering out the rest," he said.

In their analysis, led by Guangyu Robert Yang, a doctoral candidate in Wang's lab, researchers devised a model that maps out a more complicated role for inhibitory neurons than had previously been suggested.

Of particular interest to the team was a specific subtype of inhibitory neurons that targets the excitatory neuron's dendrites - components of a neuron where inputs from other neurons are located.

These dendrite-targeting inhibitory neurons are labelled by a biological marker called somatostatin and can be studied selectively by experimentalists.

The researchers proposed that they not only control the overall inputs to a neuron, but also the inputs from individual pathways-for example, the visual or auditory pathways converging onto a neuron.

"This was thought to be difficult because the connections from inhibitory neurons to excitatory neurons appeared dense and unstructured," said Yang.

"Thus a surprising finding from our study is that the precision required for pathway-specific gating can be realised by inhibitory neurons," added Yang.

Researchers used computational models to show that even with the seemingly random connections, these dendrite-targeting neurons can gate individual pathways by aligning with excitatory inputs through different pathways.

They showed that this alignment can be realised through synaptic plasticity-a brain mechanism for learning through experience.

The study appears in the journal Nature Communications.