A research team led by faculty members at Wayne State University has found that communication between two key memory regions in the brain determines how what we experience becomes part of what we remember, and how As these regions mature, the precise ways in which they interact make us better at forming lasting memories.
The study, “Dissociable Oscillatory Theta Signatures from Memory Formation in the Developing Brain,” was published in the February 15 issue of Current biology.
According to the researchers, it has long been suspected that interactions between the medial temporal lobe (MTL) and the prefrontal cortex (PFC), two regions of the brain that play a key role in supporting memory formation, are responsible for the robust increase in memory. abilities between childhood and adulthood. To understand the nature of these interactions, they examined rare electrocorticographic (ECoG) data recorded simultaneously from MTLs and PFCs in child and adult neurosurgical patients who were attempting to memorize scene images. With these unique data, the researchers examined how MTL-PFC interactions support memory development.
“We started by identifying two distinct brain signals – oscillations that can be thought of as fluctuations in coordinated electrical brain activity, both in theta frequency, a slower theta (~3 Hz) and a higher fast (~7 Hz) – that underlie memory formation in MTL. We then continued to isolate the unique effects that these fast and slow theta oscillations play in MTL-PFC interactions,” said Noa Ofen, Ph.D., an associate professor of psychology in the College of Liberal Arts and Sciences and a faculty member of the Institute of Gerontology, the Merrill Palmer Skillman Institute, and the Translational Neuroscience Program at Wayne State. both oscillations emphasized MTL-PFC interactions, but in unique and complementary ways, and we were excited to also find that these distinct signatures of interactions between memory regions dictai ent if a memory was successfully formed.”
The team then asked whether these signatures of MTL-PFC interactions directly explained better memory in older people compared to younger people, and indeed they found that MTL-PFC interactions immediately preceding the onset of the stage differentiate high-performing adolescents from low-performing adolescents and children, showing direct relationships with memory development.
Another finding from the study is that there appear to be age differences in fast and slow theta oscillations – the slow theta frequency slows down with age and the fast rate quickens. This is a critical new finding that has potentially broad implications for understanding brain development and understanding age-related differences in recognition performance.
Curious about the underlying anatomical infrastructure that gives rise to the interactions that support memory, the team paired their findings with diffusion-weighted MRI data from a subset of subjects. They found that the neurophysiological signatures of memory development were linked to the structural maturation of a specific white matter tract – the cingulum.
“Putting the pieces together, this research reveals that key regions of memory interact via two increasingly dissociable mechanisms as memory improves with age,” said Elizabeth Johnson, Ph.D., professor Associate of Medical Social Sciences and Pediatrics at Northwestern University.
“The results suggest that the development of memory is rooted in the development of the brain’s ability to multitask – here, coordinating distinct slow and fast theta networks along the same tract. This tells us something fundamental about the how memory becomes what it is.”
The study’s lead authors are Elizabeth L. Johnson, Ph.D., former Wayne State postdoctoral fellow and assistant professor of medical social sciences and pediatrics at Northwestern University and Noa Ofen, Ph.D., professor Fellow in Psychology and Faculty Member of the Institute of Gerontology, Merrill Palmer Skillman Institute, and Translational Neuroscience Program, Wayne State University. Other co-authors are Wayne State University graduate students Qin Yin and Nolan O’Hara; Dr. Lingfei Tang, postdoctoral student at Wayne State University; and Dr. Eishi Asano and Dr. Justin Jeong, Departments of Pediatrics and Neurology, Wayne State University School of Medicine and Michigan Children’s Hospital.
This research was supported by grants from the National Institutes of Health (NIMH R01MH107512, NINDS R00NS115918, NINDS R01NS64033, and NINDS R01089659.