image: Johns Hopkins reserachers found that attention in mice is controlled within the brainstem, by a circuit of inhibitory neurons that all vertebrates have, including birds and fish.
Credit: Johns Hopkins University
Neurons tucked away in an ancient part of the brain control the ability to pay attention by suppressing distractions and directing focus.
The discovery of these neurons in mice by Johns Hopkins University researchers, in a part of the brain that exists across all vertebrates including humans, could be an initial step toward more targeted treatments for attention disorders.
“A hallmark of ADHD is that even faint distractors draw attention away—and that’s exactly what we see here when these neurons are silenced,” said senior author Shreesh Mysore, a neuroscientist who studies neural circuits tied to behavior. “But the very next day, when the neurons are turned back on, the same animal can ignore distractors again, even very strong ones.”
The federally-funded work is newly published in Nature Communications, and has been selected as an editorial highlight.
Most animals and people can focus on the most relevant information at any given moment while filtering out distractions. It helps people find a friend in a crowd or follow a conversation in a noisy room. That ability, selective spatial attention, is affected in conditions like autism and Attention-Deficit/Hyperactivity Disorder (ADHD).
It’s long been thought that matters of attention were driven only by the prefrontal cortex, a region of the brain that’s only highly developed in humans and primates. But that doesn’t explain how many other animals can also pay attention and focus.
“If we really go back in evolution, for hundreds of millions of years, birds have had this ability, fish have had this ability. And they do not typically have a highly developed prefrontal cortex, so how does the brain solve this problem?” said lead author Ninad Kothari, a postdoctoral fellow in the university’s Department of Psychological and Brain Sciences. “We were able to identify an evolutionarily old region in the brainstem which affords this ability.”
The team found that attention in mice is controlled also within the brainstem, by a circuit of inhibitory neurons that all vertebrates have, including birds and fish. The impetus to identify these neurons in mice and to investigate their function in mammals stems from earlier studies of birds, frogs and turtles by Mysore and other scientists.
The team had mice perform a human-like attention task. Mice had to focus on visual information presented directly ahead on a screen, while ignoring distracting information to the side. Mice earned rewards if they touched the screen with their nose at a location signaled by the information ahead of them, rather than at the location signaled by the distracting information. The mice were very good at it, until the team temporarily disabled the brainstem neurons.
“When we inactivate these neurons, the mice become hyper distractable,” Kothari said.
The team tested further to rule out that it wasn’t any sort of impairment in motor movements or in the animal’s ability to see objects that was keeping the mouse from being successful at the task upon silencing these neurons.
“The only thing impaired was their ability to take the competing pieces of information, compare them, and pay attention to the location with the most important information, Mysore said. “This part of the brain is like an attentional selection engine. It helps solve the question: “What is most important information I should pay attention to right now?”
Next the team would like to figure out how these neurons are controlling spatial attention in vertebrates, and ultimately, to what degree they are involved in human attention.
“All the evidence to date suggests that these neurons exist in humans too,” said Mysore. “But are they responsible for selective spatial attention in humans? An exciting hypothesis is that they play a crucial role.”
They’d like to measure the activity of these neurons in people with ADHD and autism, and if their function is indeed affected, it could lead to more targeted drugs and treatments.
Authors include Arunima Banerjee, Qingcheng (Jessica) Zhang and Wen-Kai You, all of Johns Hopkins.
Journal
Nature Communications