Distinct decision processes for 3D and motion stimuli in both humans and monkeys revealed by computational modelling
Decision-making models distil principles of information processing that underlie a range of cognitive functions. For the cases of motion detection in random-dot kinematograms and decisions about the rotation of 3D structure-from-motion cylinders, contributing neural processes have been localized to specific circuits in extrastriate area V5/MT on the basis of both causal and correlative evidence, suggesting a common decision path. Here, we arranged for humans and rhesus monkeys to make perceptual choices about these two stimulus types, indicating their decision with either hand or eye movements. In both species, the parameter distributions of a hierarchical Drift Diffusion Model (DDM) revealed systematic differences for stimulus type but not the different modes of response. States in a hidden Markov model also indicated distinct decision strategies, again for the two stimulus types but not for response mode. Although physiological evidence points to area V5/MT as a vehicle for relevant perceptual signals for both stimulus types, computational modelling of the present results reveal distinct decision processes, therefore predicting that different neural processes underlie judgements about motion and 3D-depth, consistently for humans and monkeys.