How is it Possible for Brain to Quickly Detect Relevant Stimuli?

Researchers from the University of Queensland have found an amazing mechanism in the brain which enables it to rapidly focus attention. Brains are the only organ which is on and on bombarded with information due to our senses. Therefore, response to every information varies as our brain selectively focuses on only one conversation.

Professor Stephen Williams of the Queensland Brain Institute at UQ explains, “If we want to give our full concentration, something happens in the brain to enable us to focus and filter out distractions. There must be a mechanism that signals the thing we want to focus on.” He also said that still, more research has to be done in order to understand this mechanism better.

According to the research, the neocortex of the brain shows electrical changes as the person focuses attention. Neurons stop sharing its signals with one another in a synchronized manner and start working out of the sync. According to Williams, this activity in the brain is significant as it helps the body to respond to sensory information in various ways. For example, one can easily observe a car riding at high speed or listen to what the person is trying to say in a crowded room.

It is the cholinergic system present in the brain which helps in desynchronization. In a cholinergic system, there are special neurons which produce and release a neurotransmitter called acetylcholine. These clusters are widespread making long connections in the brain. Neurotransmitters are the signaling molecules.

The recent research has highlighted and put light on the fact that the cholinergic system not only releases neurotransmitter but also helps the brain to identify which stimulus is more worthy of attention at that moment. Professor William said: “The cholinergic system broadcasts to the brain, ‘this thing is really important to be vigilant to’.” He also explained that the cholinergic system plays a very significant role on the person’s cognitive abilities.

“Destruction of the cholinergic system in animals profoundly degrades cognition and the formation of memory. Importantly, in humans a progressive degeneration of the cholinergic system occurs in devastating diseases that blunt cognition and memory, such as Alzheimer’s disease,” he says. However, still more research has to be done in order to know which neurons are stimulated by acetylcholine and how its affect its function.

William and Queensland Brain Institute researcher Lee Fletcher predicted that both the layer 5 B-pyramidal neurons and neurons of the cortex might play their role in this as they are involved in how the person perceives its surroundings. “The output neurons of the neocortex perform computations that are thought to underlie our perception of the world,” says Williams.

Both the researchers were eager to know if this cholinergic system also influences the function of output neurons. In order to understand this, the researchers used optogenetics to reform the neurons in the cholinergic system of the mice so that they can release the neurotransmitter acetylcholine on the flash of blue light. By this, they were able to closely look and observe the interaction between the cholinergic system and the output neurons.

Fletcher said, “It’s as if the cholinergic system has given a ‘go’ signal.” It ultimately makes the output neurons of the neocortex to respond energetically. The activity of neurons was restricted and was only observable when energetic input was in action in the dendrites of output neurons. “We have known for some time that the dendrites of the output neurons of the neocortex only become active when animals are actively performing a behavior and that this activity is correlated with perception and task performance,” says Williams.

“We suggest that this switch also occurs in the human neocortex, allowing us to rapidly switch our state of vigilance and attention. Our work, therefore, provides important insight into how the progressive degeneration of the cholinergic system in disease blunts human cognition,” says William.

Adeena Tariq

Adeena's professional life has been mostly in hospital management, while studying international business in college. Of course, she now covers topics for us in health.

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