A new pathway by which several brain areas communicate within the brain’s striatum has been identified by Carnegie Mellon University neuroscientists.
The findings demonstrate structural and functional connections that let the brain use reinforcement learning to make spatial decisions, such as the dorsolateral prefrontal (DLPFC), orbitofrontal cortex (OFC) and posterior parietal cortex (PPC).
Communication between these regions is important for abilities like how a golfer is able to estimate where to swing his club or how a person finds a face in a large crowd filled with similar faces.
Knowing how these specific pathways work together provides crucial insight into how learning occurs. It also could lead to improved treatments for Parkinson’s disease.
Timothy Verstynen, assistant professor of psychology in CMU’s Dietrich College of Humanities and Social Sciences said:
“By understanding precisely how these systems communicate together, we can come up with a better understanding for how these systems operate in the healthy brain, but also start to understand how in Parkinson’s disease different types of systems ‘cascade,’ or start with one symptom like motor dysfunction and move to another like memory or decision-making problems."
The hope is that more knowledge of how the connectivity is related to behavior will help scientists develop therapeutic interventions that focus on strengthening potentially weakened or damaged pathways.
Diffusion Spectrum Imaging
For the study, Verstynen and Kevin Jarbo, a Ph.D. student in psychology, used diffusion spectrum imaging and fiber technology to analyze brain images collected from 60 healthy adults. The advanced imaging techniques allowed Verstynen and Jarbo to visualize the white matter pathways from the DLPFC, OFC and PPC.
They found that the pathways from all three areas projected to similar areas within a forebrain region called the striatum, a part of the basal ganglia pathways that are most commonly associated with Parkinson’s disease. The patterns were consistent across all participants.
The researchers followed the structural connectivity analysis with a functional connectivity analysis by using resting state fMRI images.
The results showed that the convergence zones were not only structurally connected but functionally connected as well. More importantly, the areas at the surface of the brain in all three cortical areas showed a high overlap of structure and functional connectivity.
“Our findings suggest that there may be a structural and functional network in the brain that allows us to integrate information about where we are focusing our attention in our visuospatial environment with reward and punishment signals associated with our past action choices in order to learn how to update, and hopefully improve, our future action decisions,” Jarbo said.
An additional implication for this study is a deeper understanding of how reinforcement learning occurs.
“A lot of models of the reinforcement learning process assume that reward signals from the orbitofrontal cortex converge with information from other areas. These have been shown to be true for other regions of the prefrontal cortex. We are the first to show that spatial attention information from the parietal cortex may also contribute to this process,” Verstynen said.
Kevin Jarbo and Timothy D. Verstynen Converging Structural and Functional Connectivity of Orbitofrontal, Dorsolateral Prefrontal, and Posterior Parietal Cortex in the Human Striatum The Journal of Neuroscience, 4 March 2015, 35(9): 3865-3878; doi: 10.1523/JNEUROSCI.2636-14.2015