Perceptual learning of motion direction discrimination transfers to an opposite direction with TPE training

Motion direction learning is known to be specific to the trained direction. However, in this study we used our recently developed TPE (training-plus-exposure) method to demonstrate that motion direction learning can transfer to an opposite direction. Specifically, we first replicated the strict direction specificity of motion direction learning with a group of moving dots. However, when the participants were exposed to the opposite direction in an irrelevant dot number discrimination task, either simultaneously with motion direction training or at a later time, but not in a reversed order, motion direction learning transferred to the opposite direction significantly and sometimes completely. These results suggest that motion direction learning may be a high-level process in which the brain learns the potentially transferrable rules of reweighting the motion direction inputs. However, we speculate that high-level learning may not functionally connect to sensory neurons that are tuned to other directions but are not stimulated during training, which leads to direction specificity. It is the stimulus exposure in TPE training that connects high-level learning to the exposed opposite direction to enable learning transfer.