We present computer simulations of a model of the brain mechanisms operating in short-term memory tasks that are consistent with the anatomy and physiology of prefrontal cortex and associated subcortical structures. These simulations include dynamical processes in thalamocortical loops which are used to generate short-term persistent responses in prefrontal cortex. We discuss this model in terms of the representation of input stimuli in cortical association areas and prefrontal short-term memory areas. We report on interference phenomena that result from the interaction of these dynamical processes and lateral projections within cortical columns. These interference phenomena can be used to elucidate the representational organization of short-term memory.