When we perform complex tasks, such as cooking, it is necessary to maintain task rules and update and select information one after another. These functions are called executive functions and located in the frontal cortex. In our laboratory, using visual search and n-back tasks which require short-term memory and information updating in monkeys, we study neural activity in the frontal association cortex and the effects of drug administration. For example, during the n-back task, in which the monkeys must remember the latest location of visual stimuli that appear in sequence, the prefrontal neuron in the right figure show increased its activity when erasing of past information. We have also previously revealed neural activity in the prefrontal cortex during the continuous focus of attention on one of multiple objects moving around in space.