Neural dynamics underlying perceptual decision-making: An eeg study using biological motion direction discrimination task

Perceptual decisions constitute the core of most interactions with the environment and are modeled with the basic assumption that noisy evidence is accumulated over time until a certain bound is reached. The centro-parietal positivity (CPP), has been shown to reflect accumulation-to-bound dynamics in human EEG studies. Although CPP has been validated in various tasks, biological motion perception has not been investigated thoroughly in the context of perceptual decision-making. Here we employed a design similar to widely employed random-dot motion tasks, where the stimuli were presented in a continuous visual stream. In particular, scrambled motion control stimuli were transitioned into target point-light displays of human walkers in a two-alternative forced choice task of reporting walking direction. It has been shown that CPP displays characteristics expected by the hidden decision variable occurring through evidence accumulation dynamics, including a build-up rate scaling with the evidence strength and reaching a common level near decision reports. Moreover, CPP differentiates between correct and invalidly responded trials, shows predictive qualities for reaction times, and covaries with the drift rate parameter estimates after drift-diffusion model fitting. In addition, investigation of the pre-stimulus attention levels and biological-motion specific signals revealed that pre-target attention might exert its influence on the decision-making process with the enhanced quality of higher-level visual encoding following the target stimulus. As a result, our study extended the previous findings on CPP into the biological motion literature and provided an overview of the neural dynamics for perceptual decisions.