Summary: A new study identified an evolutionarily ancient neural circuit within the brainstem that acts as a fundamental “attentional selection engine.” For decades, scientific consensus held that selective spatial attention, the capacity to prioritize relevant visual inputs while filtering out noise, was primarily governed by the highly evolved prefrontal cortex of primates and humans. However, this classical model failed to explain how lower vertebrates like fish, birds, and reptiles successfully navigate distractions.
By testing mice on human-like visual attention tasks, the team discovered that a specific circuit of inhibitory brainstem neurons dictates distractibility. Silencing these neurons rendered the animals hyper-distractible to even faint peripheral stimuli without impairing their vision or motor control, while reactivating them completely restored their ability to ignore strong distractions.
Key Facts
- The Brainstem Engine: The study isolated a foundational circuit of inhibitory neurons in the brainstem that actively evaluates competing environmental inputs to determine which stimulus commands immediate focus.
- Evolutionary Conservation: This mechanism predates the prefrontal cortex by hundreds of millions of years, explaining why primitive vertebrates can exhibit high levels of spatial focus.
- Reversible Hyper-Distractibility: Temporarily deactivating these specific brainstem neurons instantly induced behavioral symptoms mirroring a hallmark trait of ADHD, which was fully corrected the next day by turning the neurons back on.
- Pure Attentional Deficit: Rigorous control testing proved that the performance drop upon circuit silencing was not caused by visual degradation or motor clumsiness; the impairment was strictly limited to competitive information processing.
- Clinical Implications for ADHD & Autism: Because this ancestral architecture is conserved in humans, researchers hypothesize that functional deficits within this brainstem engine may underlie conditions like ADHD and autism, opening pathways for highly targeted, non-stimulant pharmacological treatments.
Source: JHU
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.
Key Questions Answered:
A: For decades, neuroscience textbooks taught that complex attention and focus were almost exclusively managed by the prefrontal cortex, a brain region that is only highly developed in humans and advanced primates. This discovery completely turns that assumption upside down. By identifying this core inhibitory circuit in the ancient brainstem, the researchers proved that basic spatial attention is actually a primitive, deeply embedded survival tool that evolved hundreds of millions of years ago, allowing animals without complex cortexes to focus on prey and avoid predators.
A: When the brainstem circuit was disabled, the mice became acutely hyper-distractable. During a visual attention task where they normally excelled at tracking a central target, they completely lost their focus the moment any minor, irrelevant distraction flashed on the periphery of the screen. Remarkably, this effect was completely reversible: when the team reactivated the neurons the following day, the very same mice could once again ignore even incredibly bright and intense distractions seamlessly.
A: Currently, most attention deficit treatments target dopamine and norepinephrine pathways widely across the prefrontal cortex, which can cause broad side effects. Because all evolutionary evidence indicates that humans possess this exact same ancient brainstem architecture, scientists can now investigate whether structural or functional abnormalities in this specific midbrain circuit are driving ADHD and autism symptoms. If true, it could pave the way for a whole new generation of highly localized, precision drugs that treat attention disorders at their evolutionary source.
Editorial Notes:
- This article was edited by a Neuroscience News editor.
- Journal paper reviewed in full.
- Additional context added by our staff.
About this neuroscience and ADHD research news
Author: Jill Rosen
Source: JHU
Contact: Jill Rosen – JHU
Image: The image is credited to Neuroscience News
Original Research: Open access.
“Evolutionarily old brainstem neurons are required for the control of selective spatial attentionh” by Ninad B. Kothari, Arunima Banerjee, Qingcheng Zhang, Wen-Kai You & Shreesh P. Mysore. Nature Communications
DOI:10.1038/s41467-026-72340-9
Abstract
Evolutionarily old brainstem neurons are required for the control of selective spatial attention
To behave adaptively in complex environments, animals must selectively process the most important information in space while ignoring distractors.
Here, we report that an evolutionarily ancient group of brainstem inhibitory neurons, called PLTi, is surprisingly critical for this function of selective spatial attention. In freely behaving mice performing a human-like spatial attention task, we found that bilateral silencing of PLTi severely disrupted target selection without causing perceptual or task-relevant motor impairments.
PLTi’s effects depended necessarily on goal-relevant, rather than just physical salience-based signals, together revealing it as a specialized site for priority-driven attentional target selection. PLTi’s core contribution was in controlling accuracy and categorical precision of the decision boundary separating the target from lower-priority distractors.
PLTi’s control of neural representations of competing stimuli in the superior colliculus, an established attentional hub, revealed a potential mechanistic pathway. PLTi may, therefore, be a conserved brainstem site across vertebrates for winner-take-all-like spatial decisions.
