The locus coeruleus (LC) is a small region of the brainstem that produces norepinephrine, a chemical with powerful effects on arousal and wakefulness which plays an important role in the body’s response to stress or panic. Recent research from the University of Chicago reveals that the LC also plays a specific role in visual sensory processing.
In a new study published in Neuron, neuroscientists artificially increased neuronal activity in the LC by briefly shining light on genetically modified neurons. They observed that this manipulation selectively enhanced performance in non-human primates performing a visual attention task, emphasizing the crucial role of attention in sensory perception.
“We want to understand what changes in your brain when you pay attention to something in the environment, because attention greatly affects your ability to discern stimuli,” said John Maunsell, PhD, the Albert D. Lasker Distinguished Service Professor of Neurobiology and Director of the Neuroscience Institute at the University of Chicago, and co-author of the study. “Now we have found a brain structure that has strong signals related to whether the subjects are paying attention to a stimulus or not, and we see big differences in how its neurons respond depending on where that attention is directed.”
Maunsell and co-author Supriya Ghosh, PhD, a postdoctoral researcher, focus on how neurons in different brain areas change to represent sensory input when a subject is paying attention to a stimulus or not. Previous studies have shown that LC activation, along with its norepinephrine production, may enhance performance on tasks requiring attention to differentiate between visual stimuli.
Ghosh, who specializes in subcortical brain structures, suggested that the LC could be a promising candidate for studying these effects. The team trained two monkeys to perform a visual task involving attention to the left or right side of a screen. They recorded neuron activity in the LC during the task and found that activity increased significantly only when the animal focused on the image appearing on the monitored side of the screen.
Using optogenetics, researchers artificially boosted LC activity while the animals performed the task to investigate the causal relationship between increased activity and performance. This artificial enhancement improved the animals’ ability to differentiate shapes on the corresponding half of the screen without affecting motor processing.
Distinguishing the effects of attention from other factors, such as decision-making or motor movements, is essential. Understanding how a relatively small brain structure like the LC influences such a critical function as attention is a step towards unraveling the complexities of the brain.
“Every time we gain more information about the likely contribution of a given brain structure, or how broad the range of functions of a given structure might be, that gives us much more power to understand the relationships among them,” Maunsell said. “No one part of the brain operates in isolation to produce complex behaviors.”
