The Representation of Visual and Motor Aspects of Reaching Movements in the Human Motor Cortex

Abstract

The human primary motor cortex (M1) is robustly activated during visually guided hand movements. M1 multivoxel patterns of functional MRI activation are more correlated during repeated hand movements to the same targets than to greatly differing ones, and therefore potentially contain information about movement direction. It is unclear, however, whether direction specificity is due to the motor command, as implicitly assumed, or to the visual aspects of the task, such as the target location and the direction of the cursor's trajectory. To disambiguate the visual and motor components, different visual-to-motor transformations were applied during an fMRI scan, in which participants made visually guided hand movements in various directions. The first run was the "baseline" (i.e., visual and motor mappings were matched); in the second run ("rotation"), the cursor movement was rotated by 45°with respect to the joystick movement. As expected, positive correlations were seen between the M1 multivoxel patterns evoked by the baseline run and by the rotation run, when the two movements were matched in their movement direction but the visual aspects differed. Importantly, similar correlations were observed when the visual elements were matched but the direction of hand movement differed. This indicates that M1 is sensitive to both motor and visual components of the task. However, repeated observation of the cursor movement without concurrent joystick control did not elicit significant activation in M1 or any correlated patterns of activation. Thus, visual aspects of movement are encoded in M1 only when they are coupled with motor consequences.

Visuomotor Representations within the Human Primary Motor Cortex: The Elusive Markers of Visuomotor Associative Learning

“…In particular, it remained unclear whether human M1 is sensitive to visual information such as the position of a movement's target. Eisenberg et al (2011) addressed this question in a recent study published in The Journal of Neuroscience. Eisenberg et al (2011) used multivoxel pattern analysis to dissociate, within M1, visual and motor aspects of a visually guided motor task.…”

“…Eisenberg et al (2011) addressed this question in a recent study published in The Journal of Neuroscience. Eisenberg et al (2011) used multivoxel pattern analysis to dissociate, within M1, visual and motor aspects of a visually guided motor task. In multi-voxel pattern analysis, spatial patterns of blood-oxygen level-dependent (BOLD) signals within a specific region are computed separately under two conditions, and then the patterns are correlated to determine how much of an overlap occurs under the two conditions.…”

“…In multi-voxel pattern analysis, spatial patterns of blood-oxygen level-dependent (BOLD) signals within a specific region are computed separately under two conditions, and then the patterns are correlated to determine how much of an overlap occurs under the two conditions. In their experiment, Eisenberg et al (2011) recorded fMRI data while participants used a joystick to move a cursor on a computer screen toward a target that appeared at five predetermined positions, In the baseline condition, the cursor moved in the same direction as the joystick. In the subsequent rotation condition, participants performed a similar task, but this time a 45°rotation was introduced between the direction of joystick movement and that of the cursor movement.…”

“…It is therefore possible that in the Eisenberg et al (2011) study, subjects may have learned to associate the position of a visual target with the need to execute a specific motor command. This would mean that activity in M1 did not reflect the visual aspects of the task, but rather, aspects of the motor commands the visual cues were paired with.…”

“…The visuomotor associative learning task used by Eisenberg et al (2011) is very similar to ones used in action observation research. Interestingly, recent results in this field suggested that visuomotor associative learning might originate in the premotor region and influence M1 excitability via strong corticocortical connections (Catmur et al, 2008(Catmur et al, , 2011.…”