Evidence of Perceptual History Propagation from Decoding of Visual Evoked Potentials

It is well known that recent sensory experience influences the perception of new stimuli. However, the underlying neural mechanisms mediating this influence are poorly understood. We measured ERP responses to pairs of stimuli presented randomly to the left or right hemifield. 17 participants judged whether the upper or lower half of the grating had higher spatial frequency, independently of its horizontal position. This design allowed us to trace the memory signal modulating the task, and also the implicit memory signal associated with hemispheric position. Using classification techniques, we decoded the position of the current and previous response based on voltage scalp distribution of the current trial. The representation of previous stimuli was not activated before onset of the current stimulus, and its classification reached full significance only 500 ms later, suggesting retrieval of an activity-silent memory trace both for the task relevant and the task-irrelevant characteristic of the stimuli. Overall, our data provide evidence for a framework wherein recent experience is reactivated concurrently with present neural activity to facilitate the enactment of serial integration.