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The Journal of Neuroscience, March 28, 2007, 27(13):3429-3438; doi:10.1523/JNEUROSCI.4273-06.2007
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Behavioral/Systems/Cognitive
Functional Coupling of Human Prefrontal and Premotor Areas during Cognitive Manipulation
Mitsunari Abe,1,3 Takashi Hanakawa,1,2 Yoshihiro Takayama,3 Chihiro Kuroki,4,5 Seiji Ogawa,4 andHidenao Fukuyama1 1Human Brain Research Center, Kyoto University Graduate School of Medicine, Kyoto 606-8507, Japan, 2Department of Cortical Function Disorders, National Center of Neurology and Psychiatry, Tokyo 187-8502, Japan, 3Department of Speech Physiology, Graduate School of Medicine, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan, 4Ogawa Laboratories for Brain Function Research, Hamano Life Science Research Foundation, Tokyo 160-0015, Japan, and 5Department of Brain and Nerve Science (Physiology), School of Medicine, Oita University Faculty of Medicine, Oita 879-5593, Japan
Correspondence should be addressed to Takashi Hanakawa, Department of Cortical Function Disorders, National Center of Neurology and Psychiatry, 4-1-1 Ogawahigashi, Kodaira, Tokyo 187-8502, Japan. Email: hanakawa{at}ncnp.go.jp
Evidence indicates the involvement of the rostral part of the dorsal premotor cortex (pre-PMd) in executive processes during working memory tasks. However, it remains unclear what the executive function of pre-PMd is in relation to that of the dorsolateral prefrontal cortex (DLPFC) and how these two areas interact. Using functional magnetic resonance imaging (fMRI), brain activity was examined during a delayed-encoding recognition task. Fifteen subjects had prelearned several four-code standard sequences and super sequences (SUPs) consisting of a train of two standard sequences to form "chunks" in long-term memory. During fMRI, subjects remembered eight-code encoding stimuli presented as an SUP or two unlinked standard sequences (2STs). A memory probe prompted the subjects to recognize codes across two chunks (ACROSS) or within a single chunk. A 2 x 2 factorial design was used to test two types of working memory manipulation: (1) a reductive operation selecting codes from chunks ("segmenting") and (2) a synthetic operation converting unlinked codes into a sequence ("binding"). Response time data supported the behavioral effects of each operation. Event-related fMRI showed that the "segmenting operation" activated the DLPFC bilaterally, whereas the "binding operation" enhanced the left pre-PMd activity. Activity in the ventrolateral prefrontal cortex suggested its involvement in the retrieval of task-relevant information from long-term memory. Furthermore, effective connectivity analysis indicated that the left pre-PMd and ipsilateral DLPFC interacted specifically during the ACROSS recognition of 2STs, the condition that involved both operations. We propose specific neural substrates for working memory manipulation: the DLPFC for segmenting/attentional selection and the pre-PMd for binding/sequencing. The functional coupling between the DLPFC and pre-PMd appears to play a role in combining these distinct operations.
Key words: chunk; memory; mental manipulation; dorsal premotor cortex; prefrontal cortex; fMRI
Received Sept. 30, 2006; revised Feb. 15, 2007; accepted Feb. 20, 2007.
Correspondence should be addressed to Takashi Hanakawa, Department of Cortical Function Disorders, National Center of Neurology and Psychiatry, 4-1-1 Ogawahigashi, Kodaira, Tokyo 187-8502, Japan. Email: hanakawa{at}ncnp.go.jp
This article has been cited by other articles:
T. Hanakawa, M. A. Dimyan, and M. Hallett
Motor Planning, Imagery, and Execution in the Distributed Motor Network: A Time-Course Study with Functional MRI
Cereb Cortex, March 20, 2008; (2008) bhn036v1.
[Abstract] [Full Text] [PDF]
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