Evidence accumulation occurs locally in the parietal cortex

The source of the evidence accumulation signal widely observed in the brain during decision making is unknown. Here, the authors used a two-stage decision task to show that the accumulation signal in the posterior parietal cortex arises locally. Decision making often entails evidence accumulation, a process that is represented by neural activities in a network of multiple brain areas. Yet, it has not been identified where exactly the accumulation originates. We reason that a candidate brain area should both represent evidence accumulation and information that is used to compute evidence. Therefore, we designed a two-stage probabilistic reasoning task in which the evidence for accumulation had to be first determined from sensory signals orthogonal to decisions. With a linear encoding model, we decomposed the responses of posterior parietal neurons to each stimulus into an early and a late component that represented two dissociable stages of decision making. The former reflected the transformation from sensory inputs to accumulable evidence, and the latter reflected the accumulation of evidence and the formation of decisions. The presence of both computational stages indicates that evidence accumulation signal in the parietal cortex is computed locally.

Automated summary

The study demonstrates that the accumulation signal in the posterior parietal cortex during decision making is generated locally, providing important insights into the neural mechanisms underlying the decision-making process.