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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.

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Similarity analysis between ipsilateral and contralateral finger representations. (A) Three hypothetical arrangements of finger patches: small regions of cortex that are preferentially activated for one of the contralateral (solid circles) or ipsilateral (dashed circles) fingers. Note that activation patches for individual fingers in M1 are highly overlapping; the distinct patches are for illustration only. Uncorrelated representations: patches for ipsi- and contralateral fingers are distinct and arranged in an interdigitated but uncorrelated fashion. Correlated representations: distinct patches, although patches responding to ipsilateral finger movements are always near patches responding to the corresponding contralateral fingers. Identical representations: ipsilateral movements activate the same patches as the corresponding contralateral finger. The latter 2 architectures would lead to a high spatial correlation of ipsilateral and contralateral patterns. (B) Percent signal change in the hand area of primary motor (averaged over hemispheres and individuals) for contra- and ipsilateral finger presses. Data are split into 5 groups of voxels according to the contralateral finger for which the voxels showed the maximal activation (left, highlighted diagonal in matrix). For ipsilateral actions (right), voxel groups tend to show the highest activation, below a global suppression, for movements of the mirror-symmetric ipsilateral finger. (C) Voxel-by-voxel correlation between the contralateral and ipsilateral finger patterns, corrected for overall noise and common activation patterns. The box plot extends from the 25th to the 75th percentile. Whiskers indicate the full range of the data. Outliers (indicated by circles) are data points that are more than 1.5 times the box length away from the median.
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BHS120F3: Similarity analysis between ipsilateral and contralateral finger representations. (A) Three hypothetical arrangements of finger patches: small regions of cortex that are preferentially activated for one of the contralateral (solid circles) or ipsilateral (dashed circles) fingers. Note that activation patches for individual fingers in M1 are highly overlapping; the distinct patches are for illustration only. Uncorrelated representations: patches for ipsi- and contralateral fingers are distinct and arranged in an interdigitated but uncorrelated fashion. Correlated representations: distinct patches, although patches responding to ipsilateral finger movements are always near patches responding to the corresponding contralateral fingers. Identical representations: ipsilateral movements activate the same patches as the corresponding contralateral finger. The latter 2 architectures would lead to a high spatial correlation of ipsilateral and contralateral patterns. (B) Percent signal change in the hand area of primary motor (averaged over hemispheres and individuals) for contra- and ipsilateral finger presses. Data are split into 5 groups of voxels according to the contralateral finger for which the voxels showed the maximal activation (left, highlighted diagonal in matrix). For ipsilateral actions (right), voxel groups tend to show the highest activation, below a global suppression, for movements of the mirror-symmetric ipsilateral finger. (C) Voxel-by-voxel correlation between the contralateral and ipsilateral finger patterns, corrected for overall noise and common activation patterns. The box plot extends from the 25th to the 75th percentile. Whiskers indicate the full range of the data. Outliers (indicated by circles) are data points that are more than 1.5 times the box length away from the median.

Mentions: Multivariate analysis methods. On the reconstructed cortical surface, a circular area (searchlight) was selected. The activation values for all corresponding voxels (activation patterns) were extracted for all trials. A cross-validated classification approach was used for each hand separately to determine whether activation patterns contained information about the finger pressed. In areas with information about both contra- and ipsilateral fingers, we used a similarity analysis (Fig. 3) to determine the relationship between representation of contra- and ipsilateral fingers.


Two distinct ipsilateral cortical representations for individuated finger movements.

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

Similarity analysis between ipsilateral and contralateral finger representations. (A) Three hypothetical arrangements of finger patches: small regions of cortex that are preferentially activated for one of the contralateral (solid circles) or ipsilateral (dashed circles) fingers. Note that activation patches for individual fingers in M1 are highly overlapping; the distinct patches are for illustration only. Uncorrelated representations: patches for ipsi- and contralateral fingers are distinct and arranged in an interdigitated but uncorrelated fashion. Correlated representations: distinct patches, although patches responding to ipsilateral finger movements are always near patches responding to the corresponding contralateral fingers. Identical representations: ipsilateral movements activate the same patches as the corresponding contralateral finger. The latter 2 architectures would lead to a high spatial correlation of ipsilateral and contralateral patterns. (B) Percent signal change in the hand area of primary motor (averaged over hemispheres and individuals) for contra- and ipsilateral finger presses. Data are split into 5 groups of voxels according to the contralateral finger for which the voxels showed the maximal activation (left, highlighted diagonal in matrix). For ipsilateral actions (right), voxel groups tend to show the highest activation, below a global suppression, for movements of the mirror-symmetric ipsilateral finger. (C) Voxel-by-voxel correlation between the contralateral and ipsilateral finger patterns, corrected for overall noise and common activation patterns. The box plot extends from the 25th to the 75th percentile. Whiskers indicate the full range of the data. Outliers (indicated by circles) are data points that are more than 1.5 times the box length away from the median.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

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

BHS120F3: Similarity analysis between ipsilateral and contralateral finger representations. (A) Three hypothetical arrangements of finger patches: small regions of cortex that are preferentially activated for one of the contralateral (solid circles) or ipsilateral (dashed circles) fingers. Note that activation patches for individual fingers in M1 are highly overlapping; the distinct patches are for illustration only. Uncorrelated representations: patches for ipsi- and contralateral fingers are distinct and arranged in an interdigitated but uncorrelated fashion. Correlated representations: distinct patches, although patches responding to ipsilateral finger movements are always near patches responding to the corresponding contralateral fingers. Identical representations: ipsilateral movements activate the same patches as the corresponding contralateral finger. The latter 2 architectures would lead to a high spatial correlation of ipsilateral and contralateral patterns. (B) Percent signal change in the hand area of primary motor (averaged over hemispheres and individuals) for contra- and ipsilateral finger presses. Data are split into 5 groups of voxels according to the contralateral finger for which the voxels showed the maximal activation (left, highlighted diagonal in matrix). For ipsilateral actions (right), voxel groups tend to show the highest activation, below a global suppression, for movements of the mirror-symmetric ipsilateral finger. (C) Voxel-by-voxel correlation between the contralateral and ipsilateral finger patterns, corrected for overall noise and common activation patterns. The box plot extends from the 25th to the 75th percentile. Whiskers indicate the full range of the data. Outliers (indicated by circles) are data points that are more than 1.5 times the box length away from the median.
Mentions: Multivariate analysis methods. On the reconstructed cortical surface, a circular area (searchlight) was selected. The activation values for all corresponding voxels (activation patterns) were extracted for all trials. A cross-validated classification approach was used for each hand separately to determine whether activation patterns contained information about the finger pressed. In areas with information about both contra- and ipsilateral fingers, we used a similarity analysis (Fig. 3) to determine the relationship between representation of contra- and ipsilateral fingers.

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