Scientists have identified a group of neurons located in an ancient region of the brain that plays a key role in helping animals concentrate. These cells appear to improve attention by filtering out distractions and directing the brain to the information that matters most.
The discovery, made in mice by researchers at Johns Hopkins University, points to a brain system shared by all vertebrates, including humans. The findings could ultimately help researchers develop more precise treatments for attention-related disorders.
“The hallmark of ADHD is that even subtle distractions distract us, and that’s exactly what we see here when these neurons are silenced,” said lead author Shreesh Mysore, a neuroscientist who studies neural circuits related to behavior. “But the next day, when the neurons are turned on again, the same animal is once again able to ignore distractions, even very strong ones.”
The federally funded study recently nature communications Selected as an editorial highlight.
Ancient brain regions associated with attention
Humans and other animals constantly sort through competing information, focusing on what matters most while ignoring unimportant signals. This ability, known as selective spatial attention, allows people to follow conversations in a noisy room or spot a friend in a crowded space. Difficulties with this process are associated with conditions such as autism and attention-deficit/hyperactivity disorder (ADHD).
Scientists have long believed that attention is primarily controlled by the prefrontal cortex. The prefrontal cortex is a particularly well-developed brain region in humans and other primates. But that explanation leaves important questions unanswered. Many animals are able to focus their attention despite lacking a highly developed prefrontal cortex.
“If you actually go back in evolution, over hundreds of millions of years, birds have had this ability, fish have had this ability, and they usually don’t have highly developed prefrontal cortex. So how does the brain solve this problem?” said lead author Ninad Kothari, a postdoctoral researcher in the university’s School of Psychological and Brain Sciences. “We were able to identify an evolutionarily ancient region of the brainstem that enables this ability.”
Brainstem neurons act as focus filters
The researchers found that the mice’s attention was also regulated by a network of inhibitory neurons in the brainstem. These neurons are present across vertebrate species, including birds and fish. The decision to study these cells in mice grew out of previous work by Mysore and other researchers studying birds, frogs, and turtles.
To test the role of neurons, the team designed an attention task similar to those used in human research. Mice watched visual cues on the screen and were rewarded when they responded correctly to information presented in front of them, while ignoring distracting cues appearing to the side.
The mice successfully performed this task until the researchers temporarily switched off the brainstem neurons.
“When you inactivate these neurons, the mice become very distracted,” Kothari said.
Disabling neurons increases distraction
The scientists conducted additional tests to determine whether the mice were failing due to visual impairment or motor difficulties. Those possibilities have been ruled out.
Instead, the experiments showed that animals specifically lost the ability to evaluate competing information and focus on the most relevant signals.
“The only thing that was compromised was the ability to retrieve and compare competing information and pay attention to where the most important information was,” Mysore said. “This part of the brain is like an attentional selection engine. It helps answer the question, ‘What is the most important information to pay attention to right now?'”
Potential impact on ADHD and autism
Researchers now want to understand exactly how these neurons influence spatial attention across vertebrate species, and whether they serve a similar function in humans.
“All evidence so far suggests that these neurons also exist in humans,” Mysore said. “But are they involved in selective spatial attention in humans? An interesting hypothesis is that they play an important role.”
Future studies could investigate the activity of these neurons in people with ADHD and autism. If researchers discover that cells function differently in these conditions, the findings could help develop more targeted drugs and treatments.
The study’s authors also include Arunima Banerjee, Qingcheng (Jessica) Zhang, and Wen-Kai You from Johns Hopkins University.
