RESEARCH ARTICLE Frederick J. P. Langheim Æ Alexander N. Merkle Arthur C. Leuthold Æ Scott M. Lewis Apostolos P. Georgopoulos Dipole analysis of magnetoencephalographic data during continuous shape copying Received: 4 February 2005 / Accepted: 26 September 2005 / Published online: 23 November 2005 Ó Springer-Verlag 2005 Abstract High density, whole head magnetoencepha- lography (MEG) was used to study ten healthy human subjects (five females and five males) participating in a continuous shape-copying task. The task was performed with eyes open and fixated. The three-part task began with 45 s of fixation on a blue dot, after which the dot turned red, and a pentagon was presented around it. Subjects continued to fixate on the red dot for 45 s, after which it turned green. The green dot instructed subjects to begin copying the shape continuously for 45 s, with- out visual feedback, using a joystick mounted at arm’s length. Data were collected at 1,017.25 Hz with a 248 sensor axial-gradiometer system. After cardiac artifact subtraction (Leuthold 2003), each corner was identified, and 1 s epochs (centered on each corner) were averaged and filtered from 1 to 44 Hz. Grand average flux maps demonstrated dipolar distributions identifying the most relevant sensors. With these sensors, which were located over flux extrema (Valaki et al. 2004), dipole models were used for source localization within subjects. Con- sistent dipole locations included the left motor cortex, bilateral parietal, frontal and temporal regions, and the occipital cortex. These results indicate that MEG source-localization may be derived from a limited number of trials of continuous data, and that visual cortex activity may be consistently present during con- tinuous motor activity despite the absence of novel vi- sual stimulation and eye-movements. Keywords Magnetoencephalography Æ MEG Æ Copying Æ Vision Æ Motor Introduction Traditional magnetoencephalography (MEG) source- localization paradigms involve the averaging of multiple short window stimulus response pairs. Because natural movements evolve in time, this experimental design could limit MEG studies of motor function. Therefore, we sought to explore the feasibility of using a continuous motor task for MEG source-localization. To that end, we chose to use a shape-copying task that has been extensively studied in our laboratory with single-unit recordings in monkeys (Averbeck et al. 2002, 2003) and fMRI in human subjects (Lewis et al. 2003). In this task, subjects were provided with a visual template that they copied using a joystick mounted outside their visual field. Subjects received no visual feedback of the joystick trajectory. In order to copy a figure, a subject must convert a visual display into a closely approximated motor pro- gram. Unlike tracing, in which the motor output cor- responds in space with the template, in copying subjects F. J. P. Langheim (&) Æ A. N. Merkle Æ A. C. Leuthold S. M. Lewis Æ A. P. Georgopoulos Brain Sciences Center, Veterans Affairs Medical Center, One Veterans Drive, Minneapolis, MN 55417, USA E-mail: frederick.langheim@gmail.com Tel.: +1-612-7252282 Fax: +1-612-7252291 F. J. P. Langheim Æ A. N. Merkle Æ A. C. Leuthold S. M. Lewis Æ A. P. Georgopoulos The Domenici Research Center for Mental Illness, Veterans Affairs Medical Center, Minneapolis, MN 55417, USA F. J. P. Langheim Æ A. C. Leuthold Æ A. P. Georgopoulos Department of Neuroscience, University of Minnesota Medical School, Minneapolis, MN 55455, USA F. J. P. Langheim Æ A. P. Georgopoulos MD/PhD Program, University of Minnesota Medical School, Minneapolis, MN 55455, USA S. M. Lewis Æ A. P. Georgopoulos Department of Neurology, University of Minnesota Medical School, Minneapolis, MN 55455, USA A. P. Georgopoulos Department of Psychiatry, University of Minnesota Medical School, Minneapolis, MN 55455, USA A. P. Georgopoulos Center for Cognitive Sciences, University of Minnesota, Minneapolis, MN 55455, USA Exp Brain Res (2006) 170: 513–521 DOI 10.1007/s00221-005-0234-4