Parietal Cortex

The Institute of Neuroscience of the Chinese Academy of Sciences has provided new insights; into the functional role of the PPC in decision-making. They report compelling evidence showing that the posterior parietal cortex (PPC) plays an essential role in decision-making; under critical conditions that largely ignored in previous studies.

Field of systems neuroscience

Recent studies showed a lack of behavioral effect following inactivation of the PPC; leading to widespread debate over its real function, and casting a shadow over decades of research on the neural mechanisms of decision-making based on correlations between PPC activity and behavior. It has, therefore, become an urgent concern in the field of systems neuroscience.

A novel behavioral technique was employ by researchers in a mouse experiment involving precise manipulation and monitoring of neuronal activity in the PPC using optogenetics; chemogenetics and in vivo two-photon imaging. The results showing that when neuronal activity in the PPC was temporarily inhibited; the animals’ ability to judge whether a new sensory stimulus belongs to one or another learned category was markedly impaired.

Behavioral effect following PPC

This may why many previous studies found no behavioral effect following PPC inactivation the sensory stimuli; used in those experiments used for task training, and the experimental animals had already learned how to respond to all the stimuli. To test this idea, the researchers decided to redesign the decision-making task by using laboratory mice to capture the critical elements of the decision-making process and to test the causal role of the PPC during the new behavioral task.
The results showing that PPC activity is indeed for decision-making; but only when the decisions made about newly presented tone stimuli. When the same new tone stimuli used to train the mice for two more days; PPC activity was no longer requiring for the animals to make correct choices.
The study provides evidence supporting the essential role of the PPC in decision-making and gives an explanation for the negative results in previous studies. Therefore, it may resolve the widespread debate about the PPC’s role in decision-making. In addition; it provides a new angle for studying the neural mechanisms underlying decision-making by underscoring its dynamic nature due to learning.