Investigators have discovered that activity in two widely distributed brain networks previously considered separate are actually correlated with each other and together play a key role in recognition memory, according to Northwestern Medicine study published in Cell Reports.
Rodrigo Braga, PhD, assistant professor in the Ken and Ruth Davee Department of Neurology’s Division of Epilepsy and Clinical Neurophysiology, was senior author of the study.
As the human brain has evolved, the cerebral cortex – the outermost layer of the brain – expanded. The most-expanded areas, according to Braga, are organized into large-scale networks that support different cognitive functions. An intriguing feature is that these networks are organized into sequences of parallel networks, where the same sequence of networks can be observed in multiple parts of the brain.
Two of these networks, however, have historically strayed away from this sequence: the parietal memory network – located in the posterior parts of the brain and associated with recognition – and the salience network – located in the anterior parts of the brain and associated with detecting important stimuli.
“We asked why do these two networks look different, when all the other networks have a similar distributed architecture?” Braga said.
In the study, the scientists mapped the parietal memory network and salience network in the brains of six participants using high-resolution functional MRI imaging and found that these networks are strongly correlated with each other, suggesting that they form a unified network. To replicate their results, the scientists also collected neuroimaging data from study participants enrolled at Northwestern’s Center for Translational Imaging.
“We observed that the two networks are really correlated with each other to the point where you can logically say they’re the same network. Prior approaches have tended to divide those into two different parts, but our data don’t support that: they are really closely linked,” Braga said. “Importantly, when these networks are considered unified, their organization matches the distributed architecture that is shared by the other networks, suggesting that previous studies have been over-splitting this larger network into posterior and anterior parts.”
The findings may have implications for widening treatment options for neurocognitive disorders such as major depressive disorder, which previous work has shown can be treated by targeting stimulation to the salience network.
“Our work suggests that neuromodulation could be applied to other parts of this unified network to theoretically to achieve therapeutic effects,” Braga said.
Young Hye Kwon, PhD, a postdoctoral fellow in the Braga laboratory, was lead author of the study.
Co-authors include Joseph Salvo, Donnisa Edmonds and Ania Holubecki, students in the Northwestern University Interdepartmental Neuroscience (NUIN) program; Nathan Anderson, PhD, a postdoctoral fellow in the Braga laboratory; and Kendrick Kay, PhD, assistant professor of Radiology at the University of Minnesota.
This work was supported in part by National Institute of Mental Health grant R00 MH117226; an Alzheimer’s Disease Core Center grant P30 AG013854 from the National Institute on Aging; training award T32 NS047987; the William Orr Dingwall Foundations of Language Fellowship; National Institutes of Health R01 MH118370 and National Science Foundation award NSFCAREER 2305698; and National Institutes of Health grant R01EY034118.
