Decision making: subcortical neurons get into the act
When you are walking along a sidewalk or down a hall, your decision to go left, right or continue moving forward seems like a no-brainer. However, researchers at Baylor College of Medicine found that choice results from a complex relationship between neural activity and perceptual decisions--a relationship that may be important for unraveling mysteries regarding how sensory signals guide decision making.
In a study appearing in the current edition of Nature Neuroscience, Dr. Sheng Liu, assistant professor of neuroscience at BCM, and colleagues showed that this process might take place much earlier in the sensory pathways than previously thought. Researchers have generally assumed that signals related to decision making are only found in the cerebral cortex, but the team led by Liu found otherwise.
"We discovered robust neural activity related to decision making in subcortical regions that process sensory signals before they are transmitted to the cortex," said Liu, first author on the study and previously associated with the department of neurobiology at Washington University School of Medicine where this research was initiated.
In animal studies, Liu and his colleagues recorded brain activity as animals experienced movements in subtly different directions, and then reported their decision about which way they moved. Brain activity was analyzed to measure whether the activity of single neurons could predict the decisions that animals made (choice probabilities).
"We could predict the animal’s upcoming decision by looking at the activity of single neurons in the brainstem and cerebellum," Liu said. "The large choice probabilities show that neural activity in these lower-level subcortical brain areas is highly correlated with behavior."
He and his colleagues believe that choice-related signals first emerge in these areas because the neurons there convert raw sensory signals into a format more appropriate to drive perception.
"The choice probabilities appear to result from computations that are done in these subcortical areas to help the animal to avoid confusing its own self-motion with the forces that gravity exerts on the head," Liu said. "These results give us a better understanding of how sensory signals are processed and, in turn, will allow us to understand what is happening when this process goes wrong."
Others who took part in the study include: Yong Gu, professor with Institute of Neuroscience at Shanghai Institutes for Biological sciences, Chinese Academy of Sciences; Gregory C. DeAngelis, professor and chair of Brain and Cognitive Sciences at the University of Rochester; Dr. Dora Angelaki, professor and chair of neuroscience at Baylor College of Medicine and formerly a member of the department of neurobiology, Washington University School of Medicine.
Funding for this research is from National Institutes of Health grants EY12814, DC04260 and EY016178.