The effect of tDCS on task relevant and irrelevant perceptual learning of complex objects

Abstract

During perceptual learning the visual representations in the brain are altered, but the causal role of these changes has not yet been fully characterized. Here we investigated the effect of tDCS delivered on the lateral occipital (LO) cortex on task-relevant and task-irrelevant learning of complex objects. Participants completed three training sessions and one test session on separate days. They were trained in two tasks: one relevant to object recognition (object naming in a backward masking paradigm) and one where objects were presented in the background but not relevant for the task (orientation judgment). Visual input was equated as much as possible between the tasks: an object and an oriented red line were presented in each trial in both tasks. The only crucial difference between the tasks was the relevance of the stimuli: the object was relevant for the object naming task, while the oriented red line but not the object was relevant for the orientation judgment task. During training, half of the participants received anodal tDCS stimulation on LO. In the test session, participants were tested on their ability to name the trained objects, the irrelevant objects presented during the orientation judgment task, and a new set of objects they were not exposed to during training. Participants stimulated with anodal tDCS during training showed a larger improvement of performance for the trained objects compared to participants in the sham condition. No learning effect was found for the irrelevant objects or the new objects. To conclude, this study suggests that LO plays a causal role in relevant object learning. Mere exposure is not sufficient to train object recognition in our paradigm. Meeting abstract presented at VSS 2016