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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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Related in: MedlinePlus

Areas that show an effect of bimanual congruency (green) and bimanual finger encoding (blue) do not overlap. Green areas are activated more during asymmetric than during symmetric movements (threshold: 0.07% signal change), and blue areas show above-chance classification accuracy for the ipsilateral finger during bimanual actions (40% threshold). An effect of congruency was found in the depth of the IPS and superior frontal sulcus (SFS), whereas the encoding of bilateral finger movements is more closely located to the central sulcus (CS).
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BHS120F8: Areas that show an effect of bimanual congruency (green) and bimanual finger encoding (blue) do not overlap. Green areas are activated more during asymmetric than during symmetric movements (threshold: 0.07% signal change), and blue areas show above-chance classification accuracy for the ipsilateral finger during bimanual actions (40% threshold). An effect of congruency was found in the depth of the IPS and superior frontal sulcus (SFS), whereas the encoding of bilateral finger movements is more closely located to the central sulcus (CS).

Mentions: What is the source of this nonlinear encoding? First, we considered the possibility that the neural areas involved in producing bimanual actions were more activated during asymmetric actions (trials with different fingers) than during symmetric actions (trials with the same fingers). Such an effect would indeed lead to an interaction between the contra- and ipsilateral fingers. Many prior imaging studies have found more activity during asymmetric than during symmetric movements in the SMA, PM, and the SPL (Debaere et al. 2001; Ullen et al. 2003; Wenderoth et al. 2004, 2005; Diedrichsen et al. 2006). Consistent with these studies, we found areas in the superior frontal sulcus and along the IPS that were more activated during asymmetric actions (Fig. 8, green). This effect, however, was spatially completely separate from areas that encoded the bimanual action (Fig. 8, blue). Furthermore, in the bimanual (blue) regions, no difference between symmetric and asymmetric activity patterns could be found; the classifier could distinguish equally well between 2 patterns associated with asymmetric trials, as between symmetric and asymmetric patterns. Thus, the nonlinear encoding of bimanual finger combinations and the encoding of the congruency of bimanual actions were independent.Figure 8.


Two distinct ipsilateral cortical representations for individuated finger movements.

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

Areas that show an effect of bimanual congruency (green) and bimanual finger encoding (blue) do not overlap. Green areas are activated more during asymmetric than during symmetric movements (threshold: 0.07% signal change), and blue areas show above-chance classification accuracy for the ipsilateral finger during bimanual actions (40% threshold). An effect of congruency was found in the depth of the IPS and superior frontal sulcus (SFS), whereas the encoding of bilateral finger movements is more closely located to the central sulcus (CS).
© Copyright Policy - creative-commons
Related In: Results  -  Collection

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

BHS120F8: Areas that show an effect of bimanual congruency (green) and bimanual finger encoding (blue) do not overlap. Green areas are activated more during asymmetric than during symmetric movements (threshold: 0.07% signal change), and blue areas show above-chance classification accuracy for the ipsilateral finger during bimanual actions (40% threshold). An effect of congruency was found in the depth of the IPS and superior frontal sulcus (SFS), whereas the encoding of bilateral finger movements is more closely located to the central sulcus (CS).
Mentions: What is the source of this nonlinear encoding? First, we considered the possibility that the neural areas involved in producing bimanual actions were more activated during asymmetric actions (trials with different fingers) than during symmetric actions (trials with the same fingers). Such an effect would indeed lead to an interaction between the contra- and ipsilateral fingers. Many prior imaging studies have found more activity during asymmetric than during symmetric movements in the SMA, PM, and the SPL (Debaere et al. 2001; Ullen et al. 2003; Wenderoth et al. 2004, 2005; Diedrichsen et al. 2006). Consistent with these studies, we found areas in the superior frontal sulcus and along the IPS that were more activated during asymmetric actions (Fig. 8, green). This effect, however, was spatially completely separate from areas that encoded the bimanual action (Fig. 8, blue). Furthermore, in the bimanual (blue) regions, no difference between symmetric and asymmetric activity patterns could be found; the classifier could distinguish equally well between 2 patterns associated with asymmetric trials, as between symmetric and asymmetric patterns. Thus, the nonlinear encoding of bimanual finger combinations and the encoding of the congruency of bimanual actions were independent.Figure 8.

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