Serial biases in parametric responses during visuospatial delayed reponses tasks provide the opportunity to study the mechanisms of different memory processes, at different temporal scales. We addressed the neural basis of interference between successive trials by analyzing behavioral and electrophysiological data from monkeys and humans performing visuospatial delayed response tasks. Our analyses show that brain signals represent memorized stimuli robustly during memory delays, but not in the inter-trial periods. However, stimulus representations reemerge in electrophysiological activity just prior to the new trial, suggesting the interaction between electrically active and inactive representations of memorized information. We specified this hypothesis mechanistically in a bump-attractor computational model that included short-term synaptic plasticity. The model matched the physiology and psychophysics and derived predictions that we validated in monkey physiology. Finally, I will present results from a behavioral study in anti-NMDAR encephalitis patients that supports a role of synaptic mechanisms in the generation of serial biases in working memory.