Perspectives on classical controversies about the motor cortex

Omrani, Mohsen; Kaufman, Matthew T.; Hatsopoulos, Nicholas G.; Cheney, Paul D.

doi:10.1152/jn.00795.2016

Cited by 110 publications

(104 citation statements)

References 248 publications

(267 reference statements)

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“…More recently, Dietrichsen et al also found fMRI evidence, which confirms that large portions of the motor cortex represent complex muscle synergies in humans too (Ejaz 2015). These findings are in agreement with the functioning of so called corticomotoneuronal cells that have connections to multiple muscle groups to facilitate represent complex movement actions (Omrani 2017). These corticomotoneuronal cells are, however, confined to the evolutionary younger subdivision of M1, the Brodmann area BA4p which is the inferior portion of M1 on the pre-central bank of the central sulcus Strick 2006, 2009;Lemon 2008).…”

Section: Introductionsupporting

confidence: 68%

“…The current state of consensus in the field is nicely summarized by Paul Cheney in (Omrani 2017; see also references therein); Overall, corticomotoneuronal cells in the primary motor encode muscle-related parameters of movement such as muscle activity and muscle force. Although some corticomotoneuronal cells in the primary motor cortex (particularly those involved with finger movements) have their terminations confined to motoneurons of single muscles, a large amount of corticomotoneuronal cells are not rigidly coupled to the activity of its target muscles but show specialization for particular movements or categories of muscle activity.…”

Section: Discussionmentioning

confidence: 99%

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Sub-millimeter fMRI reveals multiple topographical digit representations that form action maps in human motor cortex

Huber¹,

Finn²,

Handwerker³

et al. 2018

Preprint

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The human brain coordinates a wide variety of motor activities. On a large scale, the cortical motor system is topographically organized such that neighboring body parts are represented by neighboring brain areas. This homunculus-like somatotopic organization along the central sulcus has been observed using neuroimaging for large body parts such as the face, hands and feet. However, on a finer scale, invasive electrical stimulation studies show deviations from this somatotopic organization that suggest an organizing principle based on motor actions rather than body part moved. It has not been clear how the action-map organization principle of the motor cortex in the mesoscopic (sub-millimeter) regime integrates into a body map organization principle on a macroscopic scale (cm). Here we developed and applied advanced mesoscopic (sub-millimeter) fMRI and analysis methodology to non-invasively investigate the functional organization topography across columnar and laminar structures in humans. We find that individual fingers have multiple mirrored representations in the primary motor cortex depending on the movements they are involved in. We find that individual digits have cortical representations up to 3 mm apart from each other arranged in a column-like fashion. These representations are differentially engaged depending on whether the digits' muscles are used for different motor actions such as flexion movements like grasping a ball or retraction movements like releasing a ball. This research provides a starting point for noninvasive investigation of mesoscale topography across layers and columns of the human cortex and bridges the gap between invasive electrophysiological investigations and large coverage noninvasive neuroimaging. high-resolution fMRI | motor cortex | cortical layers | cortical columns | VASO

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Section: Introductionsupporting

confidence: 68%

Section: Discussionmentioning

confidence: 99%

Sub-millimeter fMRI reveals multiple topographical digit representations that form action maps in human motor cortex

Huber¹,

Finn²,

Handwerker³

et al. 2018

Preprint

View full text Add to dashboard Cite

show abstract

“…The relevant time scale for temporal coding by spike timing in the somatosensory cortex seems to be within tens of milliseconds from the stimulus, and the analysis requires extremely precise information about stimulus onset time 46,51,52 , which is not available in our naturalistic experimental paradigm. More generally, structured population dynamics in vibrissa motor cortex aligns well with other observations of population coding in motor cortex, where the population activity vector of both preparatory 53 and movementrelated activity 54,55 correlates with movement features [56][57][58] .…”

Section: Population Patterns In Cortical Networksupporting

confidence: 85%

Subject sex and partner sex modulate social touch responses across multiple cortical areas

Ebbesen

Bobrov

Rao

et al. 2019

Preprint

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Touch is a fundamental aspect of social, parental and sexual behavior. Despite our detailed knowledge about cortical processing of non-social touch, we still know little about how social touch cortical circuits. We investigated neural activity across five frontal, motor and sensory cortical areas in rats engaging in naturalistic social facial touch. Information about social touch and the sex of the interaction partner (a biologically significant feature) is a major determinant of cortical activity. 25.3% of units were modulated during social touch and 8.3% of units displayed 'sex-touch' responses (responded differently, depending on the sex of the interaction partner). Single-unit responses were part of a structured, partner-sex-and, in some cases, subject-sex-dependent population response. Simulations suggest that a change in inhibitory drive might underlie these population dynamics. Our observations suggest that socio-sexual characteristics of touch (subject and partner sex) widely modulate cortical activity and need to be investigated with cellular resolution. Single cortical neurons signal social touch and partner sex= 1 = −1 Figure 1 | Diverse cortical responses and variable behavioral timing during social facial touch. (a) The social gap paradigm 27 . Rats separated on two platforms will reach across the gap to engage in social facial touch. In social facial touch, rats align their snouts and whisk to palpate each other's face with their mystacial vibrissae. We recorded the behavior of male and female rats by videography from above in visual darkness under infrared illumination 29,33,34 . (b) Anatomical location of vibrissa motor cortex ('VMC'the primary motor representation of the mystacial vibrissae), cingulate cortex ('ACC'a putative homolog of human/primate anterior cingulate cortex), prelimbic cortex ('PrL'a putative homolog of human/primate medial prefrontal cortex), barrel cortex ('S1'the primary somatosensory representation of the mystacial vibrissae) and auditory cortex ('A1'). (c) Example peri-stimulus time histograms (PSTHs) of touch-activated single neurons (Wilcoxon signed-rank test), aligned to the first whisker-to-whisker touch in each social touch episode. Raster plot above shows single trials, black dots indicate single spikes and vertical line indicates beginning of social facial touch. Black line below indicates mean firing rate, smoothed with an Alpha kernel ( = 75 ms), shaded area indicates s.e.m. (d) Example PSTHs of touch-suppressed single neurons (Wilcoxon signed-rank test), aligned to the first whisker-to-whisker touch in each social touch episode. Same plotting convention as in (c). (e) Top: Histograms of touch duration (red) and inter-touch-time (blue) of social facial touch episodes. The time axes of both plots are clipped at 10 s. Below: Probability distributions of touch duration (red) and inter-touch-interval (blue) of social touch episodes, plotted on a logarithmic time scale. The two distributions span multiple orders of magnitude and strongly overlap.

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“…It is unclear whether this finding affects our chosen ROIs. Some studies have reported widespread correlations with force across motor areas (Dai, Liu, Saghal, Brown, & Yue, ; Omrani, Kaufman, Hatsopoulos, & Cheney, ), while in other cases, the only reported region that overlapped with our ROIs was M1 (Ward & Frackowiak, ; Ward, Swayne, & Newton, ). To our knowledge, no study thus far has considered the effect of force of movement on effective connectivity within the cortical motor network.…”

Section: Resultsmentioning

confidence: 68%

Dopaminergic modulation of motor network compensatory mechanisms in Parkinson's disease

Jastrzębowska

Marquis

Melie‐García

et al. 2019

Human Brain Mapping

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The dopaminergic system has a unique gating function in the initiation and execution of movements. When the interhemispheric imbalance of dopamine inherent to the healthy brain is disrupted, as in Parkinson's disease (PD), compensatory mechanisms act to stave off behavioral changes. It has been proposed that two such compensatory mechanisms may be (a) a decrease in motor lateralization, observed in drug‐naïve PD patients and (b) reduced inhibition ‐ increased facilitation. Seeking to investigate the differential effect of dopamine depletion and subsequent substitution on compensatory mechanisms in non‐drug‐naïve PD, we studied 10 PD patients and 16 healthy controls, with patients undergoing two test sessions — “ON” and “OFF” medication. Using a simple visually‐cued motor response task and fMRI, we investigated cortical motor activation — in terms of laterality, contra‐ and ipsilateral percent BOLD signal change and effective connectivity in the parametric empirical Bayes framework. We found that decreased motor lateralization persists in non‐drug‐naïve PD and is concurrent with decreased contralateral activation in the cortical motor network. Normal lateralization is not reinstated by dopamine substitution. In terms of effective connectivity, disease‐related changes primarily affect ipsilaterally‐lateralized homotopic cortical motor connections, while medication‐related changes affect contralaterally‐lateralized homotopic connections. Our findings suggest that, in non‐drug‐naïve PD, decreased lateralization is no longer an adaptive cortical mechanism, but rather the result of maladaptive changes, related to disease progression and long‐term dopamine replacement. These findings highlight the need for the development of noninvasive therapies, which would promote the adaptive mechanisms of the PD brain.

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Perspectives on classical controversies about the motor cortex

Cited by 110 publications

References 248 publications

Sub-millimeter fMRI reveals multiple topographical digit representations that form action maps in human motor cortex

Sub-millimeter fMRI reveals multiple topographical digit representations that form action maps in human motor cortex

Subject sex and partner sex modulate social touch responses across multiple cortical areas

Dopaminergic modulation of motor network compensatory mechanisms in Parkinson's disease

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