Does sensitivity in binary choice tasks depend on response modality?

Decision-making processes in perceptual learning depend on effectors

Visual perceptual learning is traditionally thought to arise in visual cortex. However, typical perceptual learning tasks also involve systematic mapping of visual information onto motor actions. Because the motor system contains both effector-specific and effector-unspecific representations, the question arises whether visual perceptual learning is effector-specific itself, or not. Here, we study this question in an orientation discrimination task. Subjects learn to indicate their choices either with joystick movements or with manual reaches. After training, we challenge them to perform the same task with eye movements. We dissect the decision-making process using the drift diffusion model. We find that learning effects on the rate of evidence accumulation depend on effectors, albeit not fully. This suggests that during perceptual learning, visual information is mapped onto effector-specific integrators. Overlap of the populations of neurons encoding motor plans for these effectors may explain partial generalization. Taken together, visual perceptual learning is not limited to visual cortex, but also affects sensorimotor mapping at the interface of visual processing and decision making.

Visual perceptual learning generalizes to untrained effectors

Visual perceptual learning (VPL) is an improvement in visual function following training. Although the practical utility of VPL was once thought to be limited by its specificity to the precise stimuli used during training, more recent work has shown that such specificity can be overcome with appropriate training protocols. In contrast, relatively little is known about the extent to which VPL exhibits motor specificity. Previous studies have yielded mixed results. In this work, we have examined the effector specificity of VPL by training observers on a motion discrimination task that maintains the same visual stimulus (drifting grating) and task structure, but that requires different effectors to indicate the response (saccade vs. button press). We find that, in these conditions, VPL transfers fully between a manual and an oculomotor response. These results are consistent with the idea that VPL entails the learning of a decision rule that can generalize across effectors.

Does the influence of near-threshold primes depend on the type of task?

Most studies investigating the influence of primes on the processing of subsequent targets involve a main task in which responses are made to the targets, and a task that tests prime awareness. If the participant is not aware of the prime location/identity but an influence of the prime is observed in the main task, researchers conclude that this influence can be ascribed to unconscious processing of the prime. This implies the assumption that the prime's influence is independent of task instructions: a prime consciously perceived in the prime task is consciously perceived in the main task. In the metacontrast-masking study, we compared motor- and attention-related electroencephalographic (EEG) components in three tasks with the same stimuli but different instructions and showed that early posterior contralateral negativities (PCNs) and lateralized readiness potentials (LRPs) were smaller when primes were task-relevant than when targets were task-relevant. This suggests that early components may depend on task instruction and are not purely prime-related.