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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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Methods for Experiment 2. (A) In the unimanual condition, we tested 3 fingers for each hand. Separate classifiers were used to detect representations of contra- and ipsilateral fingers. (B) In the bimanual condition, all 9 combinations of the left and right fingers were tested. A single bimanual classifier was trained to distinguish between these 9 combinations. By comparing the true bimanual combination with the classifier's prediction, we could then determine whether the fingers of the contra- and/or ipsilateral hand were decoded correctly.
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BHS120F4: Methods for Experiment 2. (A) In the unimanual condition, we tested 3 fingers for each hand. Separate classifiers were used to detect representations of contra- and ipsilateral fingers. (B) In the bimanual condition, all 9 combinations of the left and right fingers were tested. A single bimanual classifier was trained to distinguish between these 9 combinations. By comparing the true bimanual combination with the classifier's prediction, we could then determine whether the fingers of the contra- and/or ipsilateral hand were decoded correctly.

Mentions: Participants were instructed to make unimanual or bimanual finger presses. In the unimanual condition, participants had to press 1 of 3 the fingers (digit 1, 3, or 5) of the left or right hand (Fig. 4A). In the bimanual condition, all 9 possible combinations of these fingers were tested (Fig. 4B). We then used 3 separate classifiers to identify regions that showed finger-specific patterns: 1 for left unimanual actions, 1 for right unimanual actions, and 1 for bimanual actions. The latter classifier was trained to distinguish between the 9 unique combinations of bimanual finger presses, independent of the fingers involved in the combination.Figure 4.


Two distinct ipsilateral cortical representations for individuated finger movements.

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

Methods for Experiment 2. (A) In the unimanual condition, we tested 3 fingers for each hand. Separate classifiers were used to detect representations of contra- and ipsilateral fingers. (B) In the bimanual condition, all 9 combinations of the left and right fingers were tested. A single bimanual classifier was trained to distinguish between these 9 combinations. By comparing the true bimanual combination with the classifier's prediction, we could then determine whether the fingers of the contra- and/or ipsilateral hand were decoded correctly.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

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

BHS120F4: Methods for Experiment 2. (A) In the unimanual condition, we tested 3 fingers for each hand. Separate classifiers were used to detect representations of contra- and ipsilateral fingers. (B) In the bimanual condition, all 9 combinations of the left and right fingers were tested. A single bimanual classifier was trained to distinguish between these 9 combinations. By comparing the true bimanual combination with the classifier's prediction, we could then determine whether the fingers of the contra- and/or ipsilateral hand were decoded correctly.
Mentions: Participants were instructed to make unimanual or bimanual finger presses. In the unimanual condition, participants had to press 1 of 3 the fingers (digit 1, 3, or 5) of the left or right hand (Fig. 4A). In the bimanual condition, all 9 possible combinations of these fingers were tested (Fig. 4B). We then used 3 separate classifiers to identify regions that showed finger-specific patterns: 1 for left unimanual actions, 1 for right unimanual actions, and 1 for bimanual actions. The latter classifier was trained to distinguish between the 9 unique combinations of bimanual finger presses, independent of the fingers involved in the combination.Figure 4.

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