Transcranial magnetic stimulation of left prefrontal cortex impairs working memory

Objectives: Several lines of evidence suggest that the prefrontal cortex is involved in working whether transient functional disruption of the dorsola teral prefrontal cortex (DLPFC) would impair performance in a sequential-le tter working memory task. Methods: Subjects were shown sequences of letters and asked to state whethe r the letter just displayed was the same as the one presented 3-back. Singl e-pulse transcranial magnetic stimulation (TMS) was applied over the DLPFC between letter presentations. Results: TMS applied over the left DLPFC resulted in increased errors relat ive to no TMS controls. TMS over the right DLPFC did not alter working memo ry performance. Conclusion: Our results indicate that the left prefrontal cortex has a cruc ial role in at least one type of working memory. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.