Wayne State develops better understanding of memory retrieval between children and adults

DETROIT — Neuroscientists from Wayne State University and the Massachusetts Institute of Technology (MIT) are taking a deeper look into how the brain mechanisms for memory retrieval differ between adults and children. While the memory systems are the same in many ways, the researchers have learned that crucial functions with relevance to learning and education differ. The team's findings were published on July 17, 2012, in the Journal of Neuroscience. According to lead author Noa Ofen, Ph.D., assistant professor in WSU's Institute of Gerontology and Department of Pediatrics, cognitive ability, including the ability to learn and remember new information, dramatically changes between childhood and adulthood. This ability parallels with dramatic changes that occur in the structure and function of the brain during these periods. In the study, "The Development of Brain Systems Associated with Successful Memory Retrieval of Scenes," Ofen and her collaborative team tested the development of neural underpinnings of memory from childhood to young adulthood. The team of researchers exposed participants to pictures of scenes and then showed them the same scenes mixed with new ones and asked them to judge whether each picture was presented earlier. Participants made retrieval judgments while researchers collected images of their brains with magnetic resonance imaging (MRI). Using this method, the researchers were able to see how the brain remembers. "Our results suggest that cortical regions related to attentional or strategic control show the greatest developmental changes for memory retrieval," said Ofen. The researchers said that older participants used the cortical regions more than younger participants when correctly retrieving past experiences. "We were interested to see whether there are changes in the connectivity of regions in the brain that support memory retrieval," Ofen added. "We found changes in connectivity of memory-related regions. In particular, the developmental change in connectivity between regions was profound even without a developmental change in the recruitment of those regions, suggesting that functional brain connectivity is an important aspect of developmental changes in the brain." This study marks the first time that the development of connectivity within memory systems in the brain has been tested, and the results suggest that the brain continues to rearrange connections to achieve adult-like performance during development. Ofen and her research team plan to continue research in this area, focused on modeling brain network connectivity, and applying these methods to study abnormal brain development continuing education for mfts ### This research was funded by the National Institute of Mental Health of the National Institutes of Health; grant number R01-MH-080344. Wayne State University is one of the nation's pre-eminent public research institutions in an urban setting. Through its multidisciplinary approach to research and education, and its ongoing collaboration with government, industry and other institutions, the university seeks to enhance economic growth and improve the quality of life in the city of Detroit, state of Michigan and throughout the world. For more information about research at Wayne State University, visit http://www.research.wayne.edu.

Linked Brain Centers Mature in Sync

Imaging Reveals Underlying Unity Between Brain Structure and Development

Long-term neuroimaging studies show for the first time that areas of the brain that are wired together structurally and functionally also tend to mature in tandem over the course of development. The finding adds a new dimension to a picture that is emerging of how structure, function, and development of the brain are intertwined ceus for mfts

Background

Studies of brain development have shown that growth across the brain is not steady and uniform; some areas mature more quickly than others. These studies to date have not, however, examined whether areas of the brain that are linked functionally also develop in a coordinated way. It’s a challenging question because the developmental changes in brain anatomy that can be detected by neuroimaging unfold very slowly. Also, tempos of anatomical change differ from person to person, so comparing brain dimensions in different individuals at the same age can be misleading. The only way to approach this question is to track patterns of growth in the same individuals over many years.

This Study

To address this question, Armin Raznahan and colleagues at NIMH took advantage of a dataset that is unique in the world, consisting of records of brain growth measured by magnetic resonance imaging (MRI) of individuals from childhood to young adulthood. They studied changes in thickness of the outer layer of the brain, the cortex. In order to look for correlated anatomical change in connected parts of the brain, these investigators used records of cortical thickness from 108 individuals from ages 9 to 22. They focused on a well-defined and documented brain circuit: the default mode network or DMN. The DMN, a network identified by functional brain imaging, consists of nodes, or centers, in the brain that are active when someone’s mind is at rest, but quiet when the mind is focused on a task. In addition to tracking growth in the DMN, the NIMH investigators also looked at patterns of growth on the right and left side of the brain. There are extensive neuronal connections between the right and left hemispheres of the brain. Activation tends to be symmetrical and simultaneous within analogous parts on either side of the brain.

Results showed that there was a marked correlation in the rates of cortical thickness change between different points within the DMN when compared with the average correlation among thousands of other points across the brain. A similar pattern was seen among points in a second “task positive” network that is active while someone is carrying out goal-directed tasks; rates of change in cortical thickness within this second network also showed a pattern of coordinated maturing. Parts of the cortex involved in the integration and processing of incoming information and responses—the association cortex—were most likely to show correlated anatomical change with broad areas of the cortex. Similar correlations in change were not seen among parts of the cortex involved primarily in sensory input.

Correlations in anatomical change were also apparent between analogous centers on the right and left side of the brain, paralleling the symmetry in activation of these areas. Finally, the investigators looked at an area of the cortex (the frontopolar cortex) for which previous work had shown differences in the rate of maturation between males and females. This study found the same difference between males and females in maturation rate in this area. In addition, there were differences between the sexes in the degree to which thickness change in this area showed coordination with that of other areas of the cortex.

The coloring in this MRI scan reflects the extent to which changes in various areas of the maturing cortex correlate with similar changes over time in the default mode network, a network in the brain that is active when a person is at rest. Red indicates the highest degree of correlation—blue is the lowest. (Colors indicate correlation with one “node” within the default mode network, indicated by a circle in the image.)

Source: Armin Raznahan, Child Psychiatry Branch, National Institute of Mental Health


Significance

Neuroscientists are increasingly viewing the brain in terms of the development and function of neural circuits. According to Dr. Raznahan, this approach represents a sea change compared to the earlier emphasis on studying individual brain areas. In addition to the work reported here, recent studies of gene expression (activity) patterns in the brain suggest that genes that have roles in laying down connections between functionally related areas are also especially active during development.

In a high percentage of cases of mental disorders, the first symptoms emerge during youth; this is one piece of evidence that mental illnesses are disorders of development. Research on the relationships between brain connectedness and structural maturation can help provide a basis for future studies of how disruptions in the laying down of neural circuits in the brain during development can shape the structure and function of the adult brain and set the stage for mental illness. The authors point out in their paper that disorders that disrupt functional connections might also alter structural brain development. Comparing how development unfolds in individuals with and without disorders of mental health can offer clues to causes and targets for therapies. Finally, the findings on sex differences reported here can lend insight into the types of behavior seen during adolescence, especially risk-taking.

Reference

Raznahan, A., Lerch, J.P., Lee, N., Greenstein, D., Wallace, G., Stockman, M., Clasen, L., Shaw, P., and Giedd, J. Patterns of coordinated anatomical change in human cortical development: a longitudinal neuroimaging study of maturational coupling. Neuron. 2011 Dec 8;72(5):873-84.