scholarly journals Challenges and perspectives of quantitative functional sodium imaging (fNaI)

2018 ◽  
Author(s):  
Claudia AM Gandini Wheeler-Kingshott ◽  
Frank Reimer ◽  
Fulvia Palesi ◽  
Antonio Ricciardi ◽  
Gloria Castellazzi ◽  
...  
Keyword(s):  
Motor Cortex ◽  
Neuronal Activity ◽  
Primary Motor Cortex ◽  
Signal Transmission ◽  
Blood Oxygenation ◽  
Intracellular Space ◽  
Sodium Imaging ◽  
Concentration Changes

AbstractBrain function has been investigated via the blood oxygenation level dependent (BOLD) effect using magnetic resonance imaging (MRI) for the past decades. Advances in sodium imaging offer the unique chance to access signal changes directly linked to sodium ions (23Na) flux across the cell membrane, which generates action potentials, hence signal transmission in the brain. During this process 23Na transiently accumulates in the intracellular space. Here we show that quantitative functional sodium imaging (fNaI) at 3T is potentially sensitive to 23Na concentration changes during finger tapping, which can be quantified in grey and white matter regions key to motor function. For the first time, we measured a 23Na concentration change of 0.54 mmol/l in the ipsilateral cerebellum, 0.46 mmol/l in the contralateral primary motor cortex, 0.27 mmol/l in the corpus callosum and −11 mmol/l in the ipsilateral primary motor cortex, suggesting that fNaI is sensitive to distributed functional alterations. Open issues persist on the role of the glymphatic system in maintaining 23Na homeostasis, the role of excitation and inhibition as well as volume distributions during neuronal activity. Hemodynamic and physiological signal recordings coupled to realistic models of tissue function will be critical to understand the mechanisms of such changes and contribute to meeting the overarching challenge of measuring neuronal activity in vivo.

scholarly journals Role of cutaneous and proprioceptive inputs in sensorimotor integration and plasticity occurring in the facial primary motor cortex

2020 ◽  
Vol 598 (4) ◽  
pp. 839-851 ◽  
Author(s):  
Giovanna Pilurzi ◽  
Francesca Ginatempo ◽  
Beniamina Mercante ◽  
Luigi Cattaneo ◽  
Giovanni Pavesi ◽  
...  
Keyword(s):  
Motor Cortex ◽  
Sensorimotor Integration ◽  
Primary Motor Cortex ◽  
Proprioceptive Inputs

scholarly journals Cortical circuit alterations precede disease onset in Huntington’s disease mice

2018 ◽  
Author(s):  
Johanna Neuner ◽  
Elena Katharina Schulz-Trieglaff ◽  
Sara Gutiérrez-Ángel ◽  
Fabian Hosp ◽  
Matthias Mann ◽  
...  
Keyword(s):  
Motor Cortex ◽  
Huntington's Disease ◽  
Huntington’S Disease ◽  
Primary Motor Cortex ◽  
Disease Onset ◽  
Single Neurons ◽  
Two Photon ◽  
Layer 2 ◽  
Cortical Circuit

AbstractHuntington’s disease (HD) is a devastating hereditary movement disorder, characterized by degeneration of neurons in the striatum and cortex. Studies in human patients and mouse HD models suggest that disturbances of neuronal function in the neocortex play an important role in the disease onset and progression. However, the precise nature and time course of cortical alterations in HD have remained elusive. Here, we use chronicin vivotwo-photon calcium imaging to monitor the activity of single neurons in layer 2/3 of the primary motor cortex in awake, behaving R6/2 transgenic HD mice and wildtype littermates. R6/2 mice show age-dependent changes in neuronal activity with a clear increase in activity at the age of 8.5 weeks, preceding the onset of motor and neurological symptoms. Furthermore, quantitative proteomics demonstrate a pronounced downregulation of synaptic proteins in the cortex, and histological analyses in R6/2 mice and HD patient samples reveal reduced inputs from parvalbumin-positive interneurons onto layer 2/3 pyramidal cells. Thus, our study provides a time-resolved description as well as mechanistic details of cortical circuit dysfunction in HD.Significance statementFuntional alterations in the cortex are believed to play an important role in the pathogenesis of Huntington’s disease (HD). However, studies monitoring cortical activity in HD modelsin vivoat a single-cell resultion are still lacking. We have used chronic two-photon imaging to investigate changes in the activity of single neurons in the primary motor cortex of awake presymptomatic HD mice. We show that neuronal activity increases before the mice develop disease symptoms. Our histological analyses in mice and in human HD autopsy cases furthermore demonstrate a loss inhibitory synaptic terminals from parvalbimun-positive interneurons, revealing a potential mechanism of cortical circuit impairment in HD.

Role of Voluntary Drive in Encoding an Elementary Motor Memory

2005 ◽  
Vol 93 (2) ◽  
pp. 1099-1103 ◽  
Author(s):  
Alain Kaelin-Lang ◽  
Lumy Sawaki ◽  
Leonardo G. Cohen
Keyword(s):  
Motor Cortex ◽  
Primary Motor Cortex ◽  
Motor Memory ◽  
Motor Drive ◽  
Motor Training ◽  
Corticomotor Excitability ◽  
Proprioceptive Input ◽  
Active Training ◽  
Passive Movements

Motor training consisting of repetitive thumb movements results in encoding of motor memories in the primary motor cortex. It is not known if proprioceptive input originating in the training movements is sufficient to produce this effect. In this study, we compared the ability of training consisting of voluntary (active) and passively-elicited (passive) movements to induce this form of plasticity. Active training led to successful encoding accompanied by characteristic changes in corticomotor excitability, while passive training did not. These results support a pivotal role for voluntary motor drive in coding motor memories in the primary motor cortex.

scholarly journals The Role of Human Primary Motor Cortex in the Production of Skilled Finger Sequences

2018 ◽  
Vol 38 (6) ◽  
pp. 1430-1442 ◽  
Author(s):  
Atsushi Yokoi ◽  
Spencer A. Arbuckle ◽  
Jörn Diedrichsen
Keyword(s):  
Motor Cortex ◽  
Primary Motor Cortex

scholarly journals Dexterous Object Manipulation Requires Context-Dependent Sensorimotor Cortical Interactions in Humans

2019 ◽  
Vol 30 (5) ◽  
pp. 3087-3101 ◽  
Author(s):  
Pranav J Parikh ◽  
Justin M Fine ◽  
Marco Santello
Keyword(s):  
Motor Cortex ◽  
Primary Motor Cortex ◽  
Object Manipulation ◽  
Storage And Retrieval ◽  
Relative Contribution ◽  
Contact Points ◽  
Behavioral Studies ◽  
Online Feedback ◽  
Digit Position

Abstract Dexterous object manipulation is a hallmark of human evolution and a critical skill for everyday activities. A previous work has used a grasping context that predominantly elicits memory-based control of digit forces by constraining where the object should be grasped. For this “constrained” grasping context, the primary motor cortex (M1) is involved in storage and retrieval of digit forces used in previous manipulations. In contrast, when choice of digit contact points is allowed (“unconstrained” grasping), behavioral studies revealed that forces are adjusted, on a trial-to-trial basis, as a function of digit position. This suggests a role of online feedback of digit position for force control. However, despite the ubiquitous nature of unconstrained hand–object interactions in activities of daily living, the underlying neural mechanisms are unknown. Using noninvasive brain stimulation, we found the role of primary motor cortex (M1) and somatosensory cortex (S1) to be sensitive to grasping context. In constrained grasping, M1 but not S1 is involved in storing and retrieving learned digit forces and position. In contrast, in unconstrained grasping, M1 and S1 are involved in modulating digit forces to position. Our findings suggest that the relative contribution of memory and online feedback modulates sensorimotor cortical interactions for dexterous manipulation.

Interhemispheric Inhibition in Distal and Proximal Arm Representations in the Primary Motor Cortex

2007 ◽  
Vol 97 (3) ◽  
pp. 2511-2515 ◽  
Author(s):  
Michelle L. Harris-Love ◽  
Monica A. Perez ◽  
Robert Chen ◽  
Leonardo G. Cohen
Keyword(s):  
Motor Cortex ◽  
Primary Motor Cortex ◽  
Biceps Brachii ◽  
Conditioning Stimulus ◽  
Motor Evoked Potential ◽  
Triceps Brachii ◽  
Functional Movement ◽  
Resting Motor Threshold ◽  
Inhibitory Interactions

Interhemispheric inhibitory interactions (IHI) operate between homologous distal hand representations in primary motor cortex (M1). It is not known whether proximal arm representations exhibit comparable effects on their homologous counterparts. We studied IHI in different arm representations, targeting triceps brachii (TB, n = 13), first dorsal interosseous (FDI, n = 13), and biceps brachii (BB, n = 7) muscles in healthy volunteers. Transcranial magnetic stimulation test stimuli (TS) were delivered to M1 contralateral to the target muscle preceded 10 ms by a conditioning stimulus (CS) to the opposite M1 at 110–150% resting motor threshold (RMT). IHI was calculated as the ratio between motor-evoked potential (MEP) amplitudes in conditioned relative to unconditioned trials. Mean RMTs were 38.9, 46.9, and 46.0% of stimulator output in FDI, TB, and BB muscles, respectively. IHI was 0.45 ± 0.41 (FDI), 0.78 ± 0.38 (TB), and 0.52 ± 0.32 (BB, P < 0.01) when test MEP amplitudes were matched and 0.28 ± 0.17 (FDI) and 0.85 ± 0.31 (TB, P < 0.05) when TS intensities expressed as percentage RMT were matched. Significant IHI ( P < 0.05) was identified with minimal CS intensities (expressed as percentage stimulator output) in the 30 s for FDI, 60 s for TB, and 40 s for BB. Additionally, a CS of roughly 120% RMT suppressed the test MEP but not a test H-reflex in BB, suggesting IHI observed in BB is likely mediated by a supraspinal mechanism. We conclude that IHI differs between different arm muscle representations, comparable between BB and FDI but lesser for TB. This finding suggests the amount of IHI between different arm representations does not strictly follow a proximal-to-distal gradient, but may be related to the role of each muscle in functional movement synergies.

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