Direction of Movement Is Encoded in the Human Primary Motor Cortex

Abstract

The present study investigated how direction of hand movement, which is a well-described parameter in cerebral organization of motor control, is incorporated in the somatotopic representation of the manual effector system in the human primary motor cortex (M1). Using functional magnetic resonance imaging (fMRI) and a manual step-tracking task we found that activation patterns related to movement in different directions were spatially disjoint within the representation area of the hand on M1. Foci of activation related to specific movement directions were segregated within the M1 hand area; activation related to direction 0° (right) was located most laterally/superficially, whereas directions 180° (left) and 270° (down) elicited activation more medially within the hand area. Activation related to direction 90° was located between the other directions. Moreover, by investigating differences between activations related to movement along the horizontal (0°+180°) and vertical (90°+270°) axis, we found that activation related to the horizontal axis was located more anterolaterally/dorsally in M1 than for the vertical axis, supporting that activations related to individual movement directions are direction- and not muscle related. Our results of spatially segregated direction-related activations in M1 are in accordance with findings of recent fMRI studies on neural encoding of direction in human M1. Our results thus provide further evidence for a direct link between direction as an organizational principle in sensorimotor transformation and movement execution coded by effector representations in M1.

Dissociable neural representations of wrist motor coordinate frames in human motor cortices

“…The results demonstrate that the intrinsic and extrinsic coordinate frames for motor control are distinctively represented in M1 and PM. Prior works have examined human premotor and motor area functions during motor control (Duque et al, 2012;Eisenberg et al, 2010Eisenberg et al, , 2011Sasaki et al, 2012;Stadler et al, 2012;Strother et al, 2012;Toxopeus et al, 2011). However, the current findings, to our knowledge, are the first to demonstrate the possibility of discriminating human brain areas for intrinsic and extrinsic coordinate frames using fMRI and machine learning.…”

“…Since M1 transmits output signals to the muscles through some layers, the selection of flexion or extension, which is associated with only internal body control, may be represented in M1. At the same time, the other layers of M1 receive input from PM, SMA, and the cingulate motor area, which may be the reason why direction of movement is encoded not only in PM regions but also in M1 to some degree (Eisenberg et al, 2010;Toxopeus et al, 2011). This in turn would explain why, in our analysis, M1 includes some voxels related to the extrinsic coordinate frame (Fig.…”

“…The present study specifically targeted PM (Georgopoulos et al, 1986;Kakei et al, -12 -2001;Stadler et al, 2012) and M1 (Kakei et al, 1999;Toxopeus et al, 2011) to examine final output of motor control. The ROI was defined based on the Wake Forest University PickAtlas Version 3.0 (Wake Forest University, Winston-Salem, NC; available at http://fmri.wfubmc.edu/software/PickAtlas; (Lancaster et al, 1997;Lancaster et al, 2000;Maldjian et al, 2004;Maldjian et al, 2003).…”

“…These observations are further extended by human functional magnetic resonance imaging (fMRI), transcranial magnetic stimulation (TMS), and positron emission tomography (PET) studies. M1 has been found to be involved in both the intrinsic and extrinsic coordinate frames (Alaerts et al, 2009;Eisenberg et al, 2010;Toxopeus et al, 2011). A TMS study showed that movement observation lead to highly muscle-specific resonating activity in M1, indicating representation of the intrinsic coordinate (Alaerts et al, 2009).…”

“…A TMS study showed that movement observation lead to highly muscle-specific resonating activity in M1, indicating representation of the intrinsic coordinate (Alaerts et al, 2009). Conversely, fMRI studies using a "center-out task" showed that M1 encodes direction of movement, i.e., the extrinsic coordinate frame (Eisenberg et al, 2010;Toxopeus et al, 2011). TMS studies have shown the involvement of PMd in motor preparation (Davare et al, 2006) and action prediction (Duque et al, 2012; -5 - Stadler et al, 2012), and TMS and PET studies have indicated a role for PMv in motor imagery, motor preparation, and grip force prediction (Dafotakis et al, 2008;Davare et al, 2009;Stephan et al, 1995).…”