Functional organization of the primary motor cortex characterized by event-related fMRI during movement preparation and execution Yufeng Zang a,b , Fucang Jia a , Xuchu Weng a, * , Enzhong Li c , Shengzhong Cui a , Yufeng Wang b , Eliot Hazeltine d , Richard Ivry d a LaboratoryforHigherBrainFunction,InstituteofPsychology,ChineseAcademyofSciences,Beijing100101,China b InstituteofMentalHealth,PekingUniversity,Beijing100083,China c DepartmentofMRI,ShougangGeneralHospital,Beijing100041,China d DepartmentofPsychology,UniversityofCaliforniaBerkeley,CA94720,USA Received 6 June 2002; received in revised form 17 October 2002; accepted 21 October 2002 Abstract Neuronal recording and neuroimaging studies have shown that the primary motor area (M1) not only participates in motor execution, but is also engaged during movement preparation. The purpose of the present study was to map the distribution of the preparation- and execution-related activity within the contralateral M1 using functional magnetic resonance imaging. Eleven subjects performed a delayed sequential finger movement task, in which a CUE signal indicated a movement sequence in advance of an imperative GO signal. The hemodynamic response related to the CUE and GO signals decreased in a linear fashion across the central sulcus, with activity greater along the lateral extent compared to the medial extent. This decrease was especially evident in the epoch following the CUE. Our data reveal a pattern of functional organization within M1 related to the preparation and execution of movement sequences. q 2002 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Primary motor cortex; Supplementary motor area; Preparation; Execution; Sequential movement; Functional magnetic resonance imaging; Event-related procedure Neuronal recording in non-human primates and neuroi- maging studies in the humans suggest a hierarchical orga- nization across the cortical areas involved in motor control. The primary motor area (M1) is thought to constitute one of the lower levels of the hierarchy, primarily involved in the initiation and execution of movements that follows proces- sing in higher cortical areas related to response selection and preparation. This simple model has undergone refinement and revision over the years [18]. Preparation-related activity can be observed in motor neurons within M1 of the monkey [1,5], although the majority of M1 neurons are not influ- enced by the behavioral context [15]. Moreover, some func- tional neuroimaging studies in humans have indicated that M1 participates in motor preparation as well as execution [6,11,16], although other studies have failed to detect preparation-related activity in M1 [13,19]. Using event-related functional magnetic resonance imaging (fMRI), we have recently reported that the hemo- dynamic response in M1 increases, albeit weakly, during an extended preparatory interval prior to the production of sequential finger movements [4]. To extend this finding, the present study was designed, to replicate the involvement of M1 in sequence preparation and to map hemodynamic changes over the course of movement preparation and execution. We used event-related fMRI to explore M1 while subjects performed a delayed sequential movement task. Eleven right-handed volunteers (six male and five female, aged 20–30) participated in the experiment. None reported significant neurological or psychiatric disorders. Informed written consent was obtained from all subjects and approved by the Institutional Review Board at the Institute of Psychology, Chinese Academy of Sciences. The methods were similar to those reported in our previous study [4]. During scanning, subjects performed a delayed sequential finger movement task with the right hand. The stimuli were presented on a rear-projection screen. Initially, a row of four vertical gray rectangle boxes was illuminated (Fig. 1a). The boxes, from left to Neuroscience Letters 337 (2003) 69–72 0304-3940/02/$ - see front matter q 2002 Elsevier Science Ireland Ltd. All rights reserved. doi:10.1016/S0304-3940(02)01236-3 www.elsevier.com/locate/neulet * Corresponding author. Tel.: 186-10-6485-4476; fax: 186-10- 6487-2070. E-mailaddress: wengxc@psych.ac.cn (X. Weng).