Dynamics of visual perceptual decision-making in freely behaving mice

ABSTRACT

Studying the temporal dynamics of visual perceptual decision-making can offer key insights into cognitive processes contributing to it. Here, we investigated the time course as well as fundamental psychophysical constants governing visual perceptual decision-making in freely behaving mice performing 2-AFC orientation discrimination tasks. We did so by analyzing response accuracy against reaction time (i.e., conditional accuracy), and using drift diffusion modeling, in a series of experiments in which we varied target size, contrast, duration, and presence of a foil. Our results revealed two distinct stages in the time course of mouse visual decision-making - a ‘sensory encoding’ stage, in which conditional accuracy exhibits a classic tradeoff with response speed before asymptoting at a peak level, and a subsequent ‘short term memory-dependent’ stage exhibiting a classic asymptotic decay of performance following stimulus offset. We estimated the duration of visual sensory encoding as ~300 ms across tasks, the lower bound of the duration of short-term memory as ~1700 ms, the briefest duration of visual stimulus input that is informative as ~40 ms, and the longest duration that benefits overall decision accuracy as 1000 ms. Separately, by varying stimulus onset delay, we demonstrated that the conditional accuracy function and RT distribution, the two components of overall accuracy, can be independently modulated, and also estimated impulsivity of mice via an ‘impulsivity index’. Our results reveal shared stages in mouse and human visual decision dynamics and establish a quantitative foundation for investigating the underlying neural circuit bases in mice.