Limits...
Two distinct ipsilateral cortical representations for individuated finger movements.

Diedrichsen J, Wiestler T, Krakauer JW - Cereb. Cortex (2012)

Bottom Line: A second type of representation becomes evident in caudal premotor and anterior parietal cortices during bimanual actions.In these regions, ipsilateral actions are represented as nonlinear modulation of activity patterns related to contralateral actions, an encoding scheme that may provide the neural substrate for coordinating bimanual movements.We conclude that ipsilateral cortical representations change their informational content and functional role, depending on the behavioral context.

View Article: PubMed Central - PubMed

Affiliation: Institute of Cognitive Neuroscience, University College London, London, UK. j.diedrichsen@ucl.ac.uk

ABSTRACT
Movements of the upper limb are controlled mostly through the contralateral hemisphere. Although overall activity changes in the ipsilateral motor cortex have been reported, their functional significance remains unclear. Using human functional imaging, we analyzed neural finger representations by studying differences in fine-grained activation patterns for single isometric finger presses. We demonstrate that cortical motor areas encode ipsilateral movements in 2 fundamentally different ways. During unimanual ipsilateral finger presses, primary sensory and motor cortices show, underneath global suppression, finger-specific activity patterns that are nearly identical to those elicited by contralateral mirror-symmetric action. This component vanishes when both motor cortices are functionally engaged during bimanual actions. We suggest that the ipsilateral representation present during unimanual presses arises because otherwise functionally idle circuits are driven by input from the opposite hemisphere. A second type of representation becomes evident in caudal premotor and anterior parietal cortices during bimanual actions. In these regions, ipsilateral actions are represented as nonlinear modulation of activity patterns related to contralateral actions, an encoding scheme that may provide the neural substrate for coordinating bimanual movements. We conclude that ipsilateral cortical representations change their informational content and functional role, depending on the behavioral context.

Show MeSH

Related in: MedlinePlus

Representation of contra- and ipsilateral finger presses in the human neocortex. (A) Group-average percent signal change (threshold ±0.2%) averaged over all fingers and compared with rest. During ipsilateral actions, suppression can be observed in primary sensory and motor cortices. Positive activation during ipsilateral finger presses can be observed in the left hemisphere. (B) Classification accuracy, thresholded at >32%, Z > 1.97. Colored regions show local voxel patterns that significantly distinguish between different fingers. High classification accuracy for ipsilateral presses can be found in regions that are deactivated compared with the rest. (C) Mean signal change and classification accuracy for contralateral (red) and ipsilateral (blue) finger presses in the informative region within 5 anatomically defined ROIs of the left (L) and right hemispheres (R). Error bars indicate across-subject SE. (D) Overlap of classification accuracy (>32%) for contralateral (red) and ipsilateral (blue) fingers. Circles indicate the COG of classification accuracy for individual participants for precentral and postcentral ROIs. CS, central sulcus; SFS, superior frontal sulcus.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3643717&req=5

BHS120F2: Representation of contra- and ipsilateral finger presses in the human neocortex. (A) Group-average percent signal change (threshold ±0.2%) averaged over all fingers and compared with rest. During ipsilateral actions, suppression can be observed in primary sensory and motor cortices. Positive activation during ipsilateral finger presses can be observed in the left hemisphere. (B) Classification accuracy, thresholded at >32%, Z > 1.97. Colored regions show local voxel patterns that significantly distinguish between different fingers. High classification accuracy for ipsilateral presses can be found in regions that are deactivated compared with the rest. (C) Mean signal change and classification accuracy for contralateral (red) and ipsilateral (blue) finger presses in the informative region within 5 anatomically defined ROIs of the left (L) and right hemispheres (R). Error bars indicate across-subject SE. (D) Overlap of classification accuracy (>32%) for contralateral (red) and ipsilateral (blue) fingers. Circles indicate the COG of classification accuracy for individual participants for precentral and postcentral ROIs. CS, central sulcus; SFS, superior frontal sulcus.

Mentions: We first determined the changes in the overall blood-oxygenation level-dependent (BOLD) response during contra- and ipsilateral finger presses. Figure 2A shows activation averaged over all fingers of each hand compared with the rest. For contralateral finger presses, we found activation in a set of regions including the hand area of primary motor cortex (M1), primary sensory cortex (S1), PM, the SMA, and SPL.Figure 2.


Two distinct ipsilateral cortical representations for individuated finger movements.

Diedrichsen J, Wiestler T, Krakauer JW - Cereb. Cortex (2012)

Representation of contra- and ipsilateral finger presses in the human neocortex. (A) Group-average percent signal change (threshold ±0.2%) averaged over all fingers and compared with rest. During ipsilateral actions, suppression can be observed in primary sensory and motor cortices. Positive activation during ipsilateral finger presses can be observed in the left hemisphere. (B) Classification accuracy, thresholded at >32%, Z > 1.97. Colored regions show local voxel patterns that significantly distinguish between different fingers. High classification accuracy for ipsilateral presses can be found in regions that are deactivated compared with the rest. (C) Mean signal change and classification accuracy for contralateral (red) and ipsilateral (blue) finger presses in the informative region within 5 anatomically defined ROIs of the left (L) and right hemispheres (R). Error bars indicate across-subject SE. (D) Overlap of classification accuracy (>32%) for contralateral (red) and ipsilateral (blue) fingers. Circles indicate the COG of classification accuracy for individual participants for precentral and postcentral ROIs. CS, central sulcus; SFS, superior frontal sulcus.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3643717&req=5

BHS120F2: Representation of contra- and ipsilateral finger presses in the human neocortex. (A) Group-average percent signal change (threshold ±0.2%) averaged over all fingers and compared with rest. During ipsilateral actions, suppression can be observed in primary sensory and motor cortices. Positive activation during ipsilateral finger presses can be observed in the left hemisphere. (B) Classification accuracy, thresholded at >32%, Z > 1.97. Colored regions show local voxel patterns that significantly distinguish between different fingers. High classification accuracy for ipsilateral presses can be found in regions that are deactivated compared with the rest. (C) Mean signal change and classification accuracy for contralateral (red) and ipsilateral (blue) finger presses in the informative region within 5 anatomically defined ROIs of the left (L) and right hemispheres (R). Error bars indicate across-subject SE. (D) Overlap of classification accuracy (>32%) for contralateral (red) and ipsilateral (blue) fingers. Circles indicate the COG of classification accuracy for individual participants for precentral and postcentral ROIs. CS, central sulcus; SFS, superior frontal sulcus.
Mentions: We first determined the changes in the overall blood-oxygenation level-dependent (BOLD) response during contra- and ipsilateral finger presses. Figure 2A shows activation averaged over all fingers of each hand compared with the rest. For contralateral finger presses, we found activation in a set of regions including the hand area of primary motor cortex (M1), primary sensory cortex (S1), PM, the SMA, and SPL.Figure 2.

Bottom Line: A second type of representation becomes evident in caudal premotor and anterior parietal cortices during bimanual actions.In these regions, ipsilateral actions are represented as nonlinear modulation of activity patterns related to contralateral actions, an encoding scheme that may provide the neural substrate for coordinating bimanual movements.We conclude that ipsilateral cortical representations change their informational content and functional role, depending on the behavioral context.

View Article: PubMed Central - PubMed

Affiliation: Institute of Cognitive Neuroscience, University College London, London, UK. j.diedrichsen@ucl.ac.uk

ABSTRACT
Movements of the upper limb are controlled mostly through the contralateral hemisphere. Although overall activity changes in the ipsilateral motor cortex have been reported, their functional significance remains unclear. Using human functional imaging, we analyzed neural finger representations by studying differences in fine-grained activation patterns for single isometric finger presses. We demonstrate that cortical motor areas encode ipsilateral movements in 2 fundamentally different ways. During unimanual ipsilateral finger presses, primary sensory and motor cortices show, underneath global suppression, finger-specific activity patterns that are nearly identical to those elicited by contralateral mirror-symmetric action. This component vanishes when both motor cortices are functionally engaged during bimanual actions. We suggest that the ipsilateral representation present during unimanual presses arises because otherwise functionally idle circuits are driven by input from the opposite hemisphere. A second type of representation becomes evident in caudal premotor and anterior parietal cortices during bimanual actions. In these regions, ipsilateral actions are represented as nonlinear modulation of activity patterns related to contralateral actions, an encoding scheme that may provide the neural substrate for coordinating bimanual movements. We conclude that ipsilateral cortical representations change their informational content and functional role, depending on the behavioral context.

Show MeSH
Related in: MedlinePlus