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

Abstract

There is a growing interest in how the brain transforms body part positioning in the extrinsic environment into an intrinsic coordinate frame during motor control. To explore the human brain areas representing intrinsic and extrinsic coordinate frames, this fMRI study examined neural representation of motor cortices while human participants performed isometric wrist flexions and extensions in different forearm postures, thereby applying the same wrist actions (representing the intrinsic coordinate frame) to different movement directions (representing the extrinsic coordinate frame). Using sparse logistic regression, critical voxels involving pattern information that specifically discriminates wrist action (flexion vs. extension) and movement direction (upward vs. downward) were identified within the primary motor and premotor cortices. Analyses of classifier weights further identified contributions of the primary motor cortex to the intrinsic coordinate frame and the ventral and dorsal premotor cortex and supplementary motor area proper to the extrinsic coordinate frame. These results are consistent with existing findings using non-human primates and demonstrate the distributed representations of independent coordinate frames in the human brain.

Decoding finger movement in humans using synergy of EEG cortical current signals

“…4 ) showed that the hand knob and M1 were the main contributive areas for controlling finger movement in the intrinsic coordinate frame, while PMd and PMv were the main contributors for movement direction towards the target in the extrinsic coordinate frame, depending on their timing in transition from motor planning to execution. The differences in mapping were consistent with existing studies on non-human primates and humans 24 , 27 , 28 .…”

“…We compared topological maps for the Int-label and Ext-label decoders to determine if they used signals from areas physiologically relevant to the 8 intrinsic coordinate movements and 8 extrinsic coordinate movements for each motor control phase, motor planning and motor execution. Since we previously demonstrated neural representation of the two motor coordinate frames using fMRI 24 , and the results are consistent with existing findings using non-human primates 27 – 29 , 54 , 55 , the current study also targeted the same 5 ROIs: M1, PMd, PMv, SMA, and pre-SMA. The 5 ROIs were defined based on the Human Motor Area Template (HMAT) 56 .…”

“…The two types of labeling for target position and finger movement and mixing the two elbow angle data allowed us to extract critical and specific information on extrinsic and intrinsic coordination. Our previous work and prior studies have shown that direction of movement is mainly encoded in PMd and PMv, but also in M1 24 , 27 , 29 , and muscle and joint information are encoded mostly in M1 28 , 30 , 31 . Although there was no significant difference in the number of times CSs in M1 and PM were selected by the Int-label and Ext-label decoders using CS synergy, the hand-knob-dominant synergy selected by the Int-label decoder at 100 ms (left-most topological map in Fig.…”

“…and the other for finger movement (flexion, extension, etc.). In our previous work, we designed decoders for classifying motor activity during different postures according to their relation to extrinsic or intrinsic coordinate frames 24 . The extrinsic coordinate frame refers to movement with respect to the external environment, while the intrinsic coordinate frame refers to action with respect to the body.…”

“…We had participants perform the finger movement tasks in two different elbow angles to examine the effectiveness of brain activity synergy estimation. In our previous work using functional magnetic resonance imaging (fMRI), we found human neural representations of the intrinsic and extrinsic motor coordinate frames for the wrist 24 . So here we investigated whether similar results could be observed using EEG.…”