Relating dynamic cognitive variables to neural population activity

Millions of neurons work together to produce perceptions, thoughts, and actions, but exactly how this happens remains a mystery. Recent advances in technology that can record the activity of many neurons at once have led to breakthroughs in understanding how populations of neurons behave. However, relating so-called population behavior to cognitive processes such as decision-making has proved a challenge. We have made significant progress toward bridging this gap by developing a new method for tracking an important aspect of decision-making. In our experimental approach, subjects are engaged in a two-alternative decision-making task. They are presented with randomly-timed pulses of evidence in favor of one alternative or another, then, at the end of the task, each subject must decide which of the two alternatives had the greater number of pulses. We found that both rodent and human subjects used a decision-making strategy called “accumulation of evidence,” which tracks how sensory evidence accumulates for or against different choices during the formation of a decision. Having identified the decision-making strategy, we next plan to incorporate simultaneous electrode recordings of many neurons to relate population activity to the accumulation of evidence in decisions. Because such an accumulation of evidence strategy is thought to be a core component of perceptual, social, and even economic decisions, our method provides a unique opportunity to relate neural activity to a wide variety of cognitive processes.