Ever find yourself pausing in the middle of doing work to look out the window while thoughts about the weather or plans for the weekend fill your head? And then, just as quickly, a colleague calls your name and you’re right back to the task at hand? It’s normal for attention to ebb and flow, drifting off for periods of time then returning with ease. How does this happen? One recent study out of the Max Planck Institute for Human Development and the University of Southern California helps to better understand how we shift from a state of inattentiveness to one of focused attention.
During states of inattentiveness, our brains are governed by slow, rhythmic fluctuations of neural activity. These slow neural rhythms are called alpha oscillations, and they block sensory input during inattentiveness. “While the link between the waxing and waning of alpha oscillations and attention has been established for some time, less is known about what makes these rhythmic firing patterns come and go,” says Markus Werkle-Bergner, a senior scientist with the Center for Lifespan Psychology at the Max Planck Institute, in a statement.
To learn more about these waves and their connection to attention, scientists focus on a tiny, overlooked part of the brain called the locus coeruleus (LC). This tiny cell structure is referred to as the “blue spot.” It’s located in the brainstem, and is only about 15mm in size. The LC is hidden deep under the cortex, and is the primary source of the neuromodulator norepinephrine (NE) in the brain. It receives input from widespread brain regions, and projects throughout the forebrain, brainstem, cerebellum, and spinal cord.
“Due to its small size and its location deep in the brainstem, it was previously almost impossible to investigate the noradrenergic nucleus non-invasively in living humans,” explains says Mara Mather, professor of Gerontology at the University of Southern California. “Fortunately, over the past years, animal research has revealed that fluctuations in pupil size are linked to the activity of the blue spot. Thus, our eyes can be regarded as a window to a brain region that long seemed inaccessible.”
To study whether the blue spot’s noradrenaline could be one factor regulating alpha oscillations, the researchers combined recordings of pupil size and neural oscillations while participants solved a demanding attention task. As expected, during moments of larger pupil size alpha oscillations disappeared. Moreover, participants who showed stronger pupil and alpha responses were better at solving the attention task.
The scientists additionally turned to previous animal research that recorded neural activity directly from the thalamus, a region in the middle of the brain that functions as a pacemaker of the alpha rhythm. Importantly, the rhythmic flow from the thalamus causes the alpha oscillations seen during states of inattentiveness. However, adding noradrenaline to these neurons stills these rhythms.
It is suggested that the blue spot’s noradrenaline regulates our brain’s sensitivity to process information by suppressing alpha generators in the thalamus. Thus, during situations requiring a sudden shift in attention, a surge of noradrenaline helps us refocus—and quickly get back to work.
Further long-term studies that assess both the locus coeruleus and thalamus in the same participants may be able to shed new light on the neural mechanisms of attention and its decline in aging and disease.
The report is published in the journal Trends in Cognitive Sciences.
Article written by Rhonda Errabelli