scholarly journals Cortical entrainment of human hypoglossal motor unit activities

2012 ◽  
Vol 107 (1) ◽  
pp. 493-499 ◽  
Author(s):  
Christopher M. Laine ◽  
Laura A. Nickerson ◽  
E. Fiona Bailey
Keyword(s):  
Motor Unit ◽  
Primary Motor Cortex ◽  
Spike Timing ◽  
Emg Activity ◽  
Motor Nucleus ◽  
Frequency Range ◽  
Population Activity ◽  
Single Motor Unit ◽  
Cortical Entrainment

Output from the primary motor cortex contains oscillations that can have frequency-specific effects on the firing of motoneurons (MNs). Whereas much is known about the effects of oscillatory cortical drive on the output of spinal MN pools, considerably less is known about the effects on cranial motor nuclei, which govern speech/oromotor control. Here, we investigated cortical input to one such motor pool, the hypoglossal motor nucleus (HMN), which controls muscles of the tongue. We recorded intramuscular genioglossus electromyogram (EMG) and scalp EEG from healthy adult subjects performing a tongue protrusion task. Cortical entrainment of HMN population activity was assessed by measuring coherence between EEG and multiunit EMG activity. In addition, cortical entrainment of individual MN firing activity was assessed by measuring phase locking between single motor unit (SMU) action potentials and EEG oscillations. We found that cortical entrainment of multiunit activity was detectable within the 15- to 40-Hz frequency range but was inconsistent across recordings. By comparison, cortical entrainment of SMU spike timing was reliable within the same frequency range. Furthermore, this effect was found to be intermittent over time. Our study represents an important step in understanding corticomuscular synchronization in the context of human oromotor control and is the first study to document SMU entrainment by cortical oscillations in vivo.

EMG Changes in Human Thenar Motor Units With Force Potentiation and Fatigue

2006 ◽  
Vol 95 (3) ◽  
pp. 1518-1526 ◽  
Author(s):  
C. K. Thomas ◽  
R. S. Johansson ◽  
B. Bigland-Ritchie
Keyword(s):  
Motor Unit ◽  
Motor Units ◽  
Emg Activity ◽  
Single Motor Unit ◽  
Tetanic Force ◽  
Twitch Force ◽  
Emg Amplitude ◽  
Before And After ◽  
Induced Changes ◽  
Motor Unit Emg

Few studies have analyzed activity-induced changes in EMG activity in individual human motor units. We studied the changes in human thenar motor unit EMG that accompany the potentiation of twitch force and fatigue of tetanic force. Single motor unit EMG and force were recorded in healthy subjects in response to selective stimulation of their motor axons within the median nerve just above the elbow. Twitches were recorded before and after a series of pulse trains delivered at frequencies that varied between 5 and 100 Hz. This stimulation induced significant increases in EMG amplitude, duration, and area. However, in relative terms, all of these EMG changes were substantially smaller than the potentiation of twitch force. Another 2 min of stimulation (13 pulses at 40 Hz each second) induced additional potentiation of EMG amplitude, duration, and area, but the tetanic force from every unit declined. Thus activity-induced changes in human thenar motor unit EMG do not indicate the alterations in force or vice versa. These data suggest that different processes underlie the changes in EMG and force that occur during human thenar motor unit activity.

The motor-unit population of the cat tenuissimus muscle

1988 ◽  
Vol 59 (4) ◽  
pp. 1128-1142 ◽  
Author(s):  
A. Lev-Tov ◽  
C. A. Pratt ◽  
R. E. Burke
Keyword(s):  
Motor Unit ◽  
Motor Units ◽  
Retrograde Transport ◽  
Length Change ◽  
Single Type ◽  
Motor Nucleus ◽  
Single Motor Unit ◽  
Hindlimb Muscles ◽  
Typical Type ◽  
Fast Twitch

1. We studied the organization of motor units in the tenuissimus (TEN) muscle of pentobarbital-anesthetized cats. The cat TEN is a long, delicate straplike muscle that spans hip and knee, which has a very flat length-tension curve through 22 mm of length change. 2. The TEN motor nucleus, labeled by retrograde transport of several forms of horseradish peroxidase, was composed of 8-31 cells in different cats, of which about half were, on average, in the size range of alpha-motoneurons. TEN motoneurons were scattered through the ventrolateral portion of lamina IX, over a rostrocaudal distance of up to 6.5 mm, making it relatively easy to isolate individual TEN motor axons for single motor-unit stimulation. 3. Individual TEN muscle units were classified into four groups [fast-twitch, fatigable (FF), intermediate, fatigue-resistant (Fint), fast-twitch, fatigue-resistant (FR), and slow-twitch, fatigue resistant (S)] on the basis of "sag" and fatigue index mechanical properties, as in other cat hindlimb muscles. There was a relatively large proportion of Fint units (28%) in the TEN sample, and the range of tetanic tension (approximately 19-fold) was much smaller than found in other cat hindlimb muscles. 4. A majority of TEN muscle fibers could be classified into the three major histochemical types (IIB, IIA, and I) found in other cat muscles, but a substantial minority remained "unclassified." A single type Fint muscle unit was successfully depleted of glycogen for histochemical study. It exhibited a typical type IIB histochemical profile. 5. Despite its unusual morphology, the cat TEN contains the same types of motor units found in larger, more "typical" limb muscles.

Motor Unit Territories in the Human Perioral Musculature

1994 ◽  
Vol 37 (5) ◽  
pp. 975-984 ◽  
Author(s):  
Lisa Goffman ◽  
Anne Smith
Keyword(s):  
Motor Unit ◽  
Cross Correlation ◽  
Coherence Function ◽  
Broad Band ◽  
Motor Units ◽  
Oscillatory Activity ◽  
Frequency Range ◽  
Motor Tasks ◽  
Single Motor Unit ◽  
Lower Lip

The perioral region was divided into four quadrants, and electromyograms (EMGs) were recorded from each area. The coherence function (i.e., the squared cross correlation between two signals computed at each frequency in the spectrum) was used to determine aspects of the organization of motor unit territories and to examine potential higher level sources of input in speech and nonspeech tasks. Coherence functions were computed between pairs of EMGs and were examined for significant values in the range of 20–240 Hz. When two pairs of electrodes were intentionally placed to record the activity from a common subset of motor units in a single quadrant of the lower lip, all subjects exhibited significant broad-band coherence in every frequency in all experimental tasks. Thus, the presence of such a pattern of broad-band significant coherence for EMG pairs recorded from different quadrants would indicate that single motor unit territories extended across perioral quadrants. When separate EMG recordings were obtained from the four quadrants of the lips, coherence functions computed between EMG pairs were typically zero across the entire frequency range. These findings suggest that perioral motor unit territories are organized into nonoverlapping quadrants. Further, the present analyses suggest that, unlike bilateral pairs of jaw-closing muscles during chewing, these motor units are not driven by any correlated oscillatory activity in chewing or other oral motor tasks.

scholarly journals Syngap1 Dynamically Regulates the Fine-Scale Reorganization of Cortical Circuits in Response to Sensory Experience

2020 ◽  
Author(s):  
Nerea Llamosas ◽  
Thomas Vaissiere ◽  
Camilo Rojas ◽  
Sheldon Michaelson ◽  
Courtney A. Miller ◽  
...  
Keyword(s):  
Neurodevelopmental Disorders ◽  
Cortical Plasticity ◽  
Neurodevelopmental Disorder ◽  
Spike Timing ◽  
Sensory Cortex ◽  
Fine Scale ◽  
Cortical Circuits ◽  
Population Activity ◽  
Cellular Processes

AbstractExperience induces complex, neuron-specific changes in population activity within sensory cortex circuits. However, the mechanisms that enable neuron-specific changes within cortical populations remain unclear. To explore the idea that synapse strengthening is involved, we studied fine-scale cortical plasticity in Syngap1 mice, a neurodevelopmental disorder model useful for linking synapse biology to circuit functions. Repeated functional imaging of the same L2/3 somatosensory cortex neurons during single whisker experience revealed that Syngap1 selectively regulated the plasticity of a low-active, or “silent”, neuronal subpopulation. Syngap1 also regulated spike-timing-dependent synaptic potentiation and experience-mediated in vivo synapse bouton formation, but not synaptic depression or bouton elimination in L2/3. Adult re-expression of Syngap1 restored plasticity of “silent” neurons, demonstrating that this gene controls dynamic cellular processes required for population-specific changes to cortical circuits during experience. These findings suggest that abnormal experience-dependent redistribution of cortical population activity may contribute to the etiology of neurodevelopmental disorders.

scholarly journals Reversed timing-dependent associative plasticity in the human brain through interhemispheric interactions

2013 ◽  
Vol 109 (9) ◽  
pp. 2260-2271 ◽  
Author(s):  
Virginia Conde ◽  
Henning Vollmann ◽  
Marco Taubert ◽  
Bernhard Sehm ◽  
Leonardo G. Cohen ◽  
...  
Keyword(s):  
Motor Cortex ◽  
Human Brain ◽  
Primary Motor Cortex ◽  
Long Term Potentiation ◽  
Spike Timing ◽  
In Vivo Model ◽  
Sensorimotor Network ◽  
Median Nerve Stimulation

Spike timing-dependent plasticity (STDP) has been proposed as one of the key mechanisms underlying learning and memory. Repetitive median nerve stimulation, followed by transcranial magnetic stimulation (TMS) of the contralateral primary motor cortex (M1), defined as paired-associative stimulation (PAS), has been used as an in vivo model of STDP in humans. PAS-induced excitability changes in M1 have been repeatedly shown to be time-dependent in a STDP-like fashion, since synchronous arrival of inputs within M1 induces long-term potentiation-like effects, whereas an asynchronous arrival induces long-term depression (LTD)-like effects. Here, we show that interhemispheric inhibition of the sensorimotor network during PAS, with the peripheral stimulation over the hand ipsilateral to the motor cortex receiving TMS, results in a LTD-like effect, as opposed to the standard STDP-like effect seen for contralateral PAS. Furthermore, we could show that this reversed-associative plasticity critically depends on the timing interval between afferent and cortical stimulation. These results indicate that the outcome of associative stimulation in the human brain depends on functional network interactions (inhibition or facilitation) at a systems level and can either follow standard or reversed STDP-like mechanisms.

scholarly journals Uncovering Network Architecture Using an Exact Statistical Input-Output Relation of a Neuron Model

2018 ◽  
Author(s):  
Safura Rashid Shomali ◽  
Majid Nili Ahmadabadi ◽  
Seyyed Nader Rasuli ◽  
Hideaki Shimazaki
Keyword(s):  
Network Architecture ◽  
Background Activity ◽  
Spike Timing ◽  
Input Output ◽  
Unified Framework ◽  
Population Activity ◽  
Visual Neurons ◽  
V1 Neurons ◽  
Integrate And Fire

SummaryAn appealing challenge in Neuroscience is to identify network architecture from neural activity. A key requirement is the knowledge of statistical input-output relation of single neurons in vivo. Using a recent exact solution of spike-timing for leaky integrate-and-fire neurons under noisy inputs balanced near threshold, we construct a unified framework that links synaptic inputs, spiking nonlinearity, and network architecture, with statistics of population activity. The framework predicts structured higher-order interactions of neurons receiving common inputs under different architectures: It unveils two network motifs behind sparse activity reported in visual neurons. Comparing model’s prediction with monkey’s V1 neurons, we found excitatory inputs to pairs explain the sparse activity characterized by negative triple-wise interactions, ruling out shared inhibition. While the model predicts variation in the structured activity according to local circuitries, we show strong negative interactions are in general a signature of excitatory inputs to neuron pairs, whenever background activity is sparse.

scholarly journals Development of Tonic Firing Behavior in Rat Soleus Muscle

2008 ◽  
Vol 99 (4) ◽  
pp. 1899-1905 ◽  
Author(s):  
Torsten Eken ◽  
Geoffrey C. B. Elder ◽  
Terje Lømo
Keyword(s):  
Motor Unit ◽  
Soleus Muscle ◽  
Firing Frequency ◽  
Lumbar Spinal Cord ◽  
Emg Activity ◽  
Adult Rats ◽  
Tonic Firing ◽  
Single Motor Unit ◽  
Firing Behavior ◽  
Lumbar Spinal

Tonic firing behavior in soleus muscle of unrestrained rats aged 7 to ≥100 days was studied by chronic single-motor-unit and gross-electromyographic (EMG) recordings. Median motor-unit firing frequency at 10 days was 19–26 Hz and did not change appreciably after this time, whereas interval-to-interval firing variability was reduced with age. Two units with median frequencies 40 and 59 Hz were encountered in one 7-day-old rat. Integrated rectified gross EMG developed from being phasic only to predominantly tonic during the second and third postnatal week. From the end of the third week, rather short tonic periods with irregular amplitude were replaced by longer lasting constant-amplitude periods. Quantitatively, median duration of gross-EMG activity episodes more than doubled, while 90th-percentile values for episode duration increased 19-fold, from 7.4 s at 7 days to 140 s in adults. The main part of this increase took place after 22 days. Previous work in adult rats has indicated that descending monoaminergic innervation is essential for maintained tonic motoneuron activity, which probably is caused by depolarizing plateau potentials. Such innervation of the lumbar spinal cord matures gradually to an adult pattern and density ∼3–4 wk after birth. The present results, describing a concurrent considerable development of tonic firing behavior, support and extend these findings.

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