This study will use a within subject design in which each participant will perform a working memory task combined with Transcranial Magnetic Stimulation. TMS will be applied in three possible procedures, 1) Online TMS, 2) Offline TMS and 3) Sham TMS. All subjects will be given two trials within their one session, one of which will be sham TMS for all subjects and another of which will be randomly assigned to either Online or Offline TMS. Trials order will be randomly counterbalanced across subjects, who will be blind to the treatment of frontal vs. sham TMS (independent variable). Participants will be randomized into either the online or offline groups by computer generated lists to ensure equal numbers of participants in each condition. Half of the subjects will receive online TMS (online group) and half will receive offline TMS (offline group). Subjects will be randomly assigned to one of the two groups. The dependent variables will be performance accuracy and reaction time on the working memory task. By utilizing online and offline TMS, investigators will be able to explore whether frontal cortex is involved transiently in visual working memory or persistently throughout the task.