Critical times of involvement of areas important to working memory were examined both with pitch and audioverbal N-back tasks using single-pulse transcranial magnetic stimulation (TMS). TMS was administered to 12 healthy participants over dorsolateral prefrontal and inferior parietal regions in each hemisphere at four different times after stimulus onset (250, 450, 650, and 850 ms). For the pitch N-back task, interference with working memory, as evidenced by a significant increase in reaction time, was observed with TMS over the right hemisphere regions. In contrast, for the audioverbal N-back task, TMS resulted in significantly increased reaction time only for left inferior parietal TMS delivered 450 ms after stimulus onset. These results imply different hemispheric specializations for pitch and audioverbal working memory.
aDepartment of Diagnostic Radiology, Nuclear Medicine and Research Institute of Radiological Science
bDepartment of Psychiatry
cBrain Korea 21 Project for Medical Science, Yonsei University College of Medicine, Seoul
dDepartment of Psychology, Kangwon National University, Chuncheon
eDepartment of Psychiatry, Chonnam National University Medical School, Gwangju, Korea
Correspondence to Hae-Jeong Park, PhD, Assistant Professor, Department of Diagnostic Radiology, College of Medicine, Yonsei University, 134 Shinchon-dong, Seodaemun-gu, Seoul 120-749, Korea
Tel: +82 2 2228 2363; fax: +82 2 393 3035; e-mail: parkhj@yumc.yonsei.ac.kr
Received 11 October 2007; accepted 16 October 2007
