Intermuscular coherence

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Intermuscular Coherence is a measure to quantify correlations between the activity of two muscles, which is often assessed using electromyography. The correlations in muscle activity are quantified in frequency domain, [1] and therefore referred to as intermuscular coherence. [2]

Muscle contractile soft tissue of mammals

Muscle is a soft tissue found in most animals. Muscle cells contain protein filaments of actin and myosin that slide past one another, producing a contraction that changes both the length and the shape of the cell. Muscles function to produce force and motion. They are primarily responsible for maintaining and changing posture, locomotion, as well as movement of internal organs, such as the contraction of the heart and the movement of food through the digestive system via peristalsis.

Electromyography

Electromyography (EMG) is an electrodiagnostic medicine technique for evaluating and recording the electrical activity produced by skeletal muscles. EMG is performed using an instrument called an electromyograph to produce a record called an electromyogram. An electromyograph detects the electric potential generated by muscle cells when these cells are electrically or neurologically activated. The signals can be analyzed to detect medical abnormalities, activation level, or recruitment order, or to analyze the biomechanics of human or animal movement.

Frequency domain signal representation

In electronics, control systems engineering, and statistics, the frequency domain refers to the analysis of mathematical functions or signals with respect to frequency, rather than time. Put simply, a time-domain graph shows how a signal changes over time, whereas a frequency-domain graph shows how much of the signal lies within each given frequency band over a range of frequencies. A frequency-domain representation can also include information on the phase shift that must be applied to each sinusoid in order to be able to recombine the frequency components to recover the original time signal.

Contents

History

The synchronisation of motor units of a single muscle in animals and humans are known for decades. The early studies that investigated the relationship of EMG activity used time-domain cross-correlation to quantify common input. [3] [4] The explicit notion of presence of synchrony between motor units of two different muscles was reported at a later time. [5] In the 1990s, coherence analysis was introduced to examine in frequency content of common input. [2]

Neural oscillation Brainwaves are repetitive patterns of neural activity in the central nervous system

Neural oscillations, or brainwaves, are rhythmic or repetitive patterns of neural activity in the central nervous system. Neural tissue can generate oscillatory activity in many ways, driven either by mechanisms within individual neurons or by interactions between neurons. In individual neurons, oscillations can appear either as oscillations in membrane potential or as rhythmic patterns of action potentials, which then produce oscillatory activation of post-synaptic neurons. At the level of neural ensembles, synchronized activity of large numbers of neurons can give rise to macroscopic oscillations, which can be observed in an electroencephalogram. Oscillatory activity in groups of neurons generally arises from feedback connections between the neurons that result in the synchronization of their firing patterns. The interaction between neurons can give rise to oscillations at a different frequency than the firing frequency of individual neurons. A well-known example of macroscopic neural oscillations is alpha activity.

A motor unit is made up of a motor neuron and the skeletal muscle fibers innervated by that motor neuron's axonal terminals. Groups of motor units often work together to coordinate the contractions of a single muscle; all of the motor units within a muscle are considered a motor pool. The concept was proposed by Charles Scott Sherrington.

Physiology

Intermuscular coherence can be used to investigate the neural circuitry involved in motor control. Correlated muscle activity indicates common input to the motor unit pools of both muscles [6] [7] and reflects shared neural pathways (including cortical, subcortical and spinal) that contribute to muscle activity and movement. [8] The strength of intermuscular coherence is dependent on the relationship between muscles and is generally stronger between muscle pairs that are anatomically and functionally closely related. [9] [10] Intermuscular coherence can therefore be used to identify impairments in motor pathways. [11] [12]

See also

Corticomuscular Coherence relates to the synchrony in the neural activity of brain's cortical areas and muscle. The neural activities are picked up by electrophysiological recordings from the brain and muscle (EMG). It is a method to study the neural control of movement.

Corticocortical coherence is referred to the synchrony in the neural activity of different cortical brain areas. The neural activities are picked up by electrophysiological recordings from the brain. It is a method to study the brain's neural communication and function at rest or during functional tasks.

Related Research Articles

Nervous system the entire nerve apparatus of the body

The nervous system is a highly complex part of an animal that coordinates its actions and sensory information by transmitting signals to and from different parts of its body. The nervous system detects environmental changes that impact the body, then works in tandem with the endocrine system to respond to such events. Nervous tissue first arose in wormlike organisms about 550 to 600 million years ago. In vertebrates it consists of two main parts, the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS consists of the brain and spinal cord. The PNS consists mainly of nerves, which are enclosed bundles of the long fibers or axons, that connect the CNS to every other part of the body. Nerves that transmit signals from the brain are called motor or efferent nerves, while those nerves that transmit information from the body to the CNS are called sensory or afferent. Spinal nerves serve both functions and are called mixed nerves. The PNS is divided into three separate subsystems, the somatic, autonomic, and enteric nervous systems. Somatic nerves mediate voluntary movement. The autonomic nervous system is further subdivided into the sympathetic and the parasympathetic nervous systems. The sympathetic nervous system is activated in cases of emergencies to mobilize energy, while the parasympathetic nervous system is activated when organisms are in a relaxed state. The enteric nervous system functions to control the gastrointestinal system. Both autonomic and enteric nervous systems function involuntarily. Nerves that exit from the cranium are called cranial nerves while those exiting from the spinal cord are called spinal nerves.

Muscle spindle Innervated muscle structure involved in reflex actions and proprioception

Muscle spindles are stretch receptors within the body of a muscle that primarily detect changes in the length of the muscle. They convey length information to the central nervous system via afferent nerve fibers. This information can be processed by the brain as proprioception. The responses of muscle spindles to changes in length also play an important role in regulating the contraction of muscles, for example, by activating motor neurons via the stretch reflex to resist muscle stretch.

Grey column

The grey column refers to a somewhat ridge-shaped mass of grey matter in the spinal cord. This presents as three columns: the anterior grey column, the posterior grey column, and the lateral grey column, all of which are visible in cross-section of the spinal cord.

Rodolfo Llinás Colombian neuroscientist

Rodolfo Llinás Riascos is a Colombian neuroscientist. He is currently the Thomas and Suzanne Murphy Professor of Neuroscience and Chairman Emeritus of the department of Physiology & Neuroscience at the NYU School of Medicine. Llinás has published over 800 scientific articles.

Central pattern generators (CPGs) are biological neural circuits that produce rhythmic outputs in the absence of rhythmic input. They are the source of the tightly-coupled patterns of neural activity that drive rhythmic motions like walking, breathing, or chewing. The ability to function without input from higher brain areas still requires modulatory inputs, and their outputs are not fixed. Flexibility in response to sensory input is a fundamental quality of CPG-driven behavior. To be classified as a rhythmic generator, a CPG requires:

  1. "two or more processes that interact such that each process sequentially increases and decreases, and
  2. that, as a result of this interaction, the system repeatedly returns to its starting condition."
Scratch reflex

The scratch reflex is a response to activation of sensory neurons whose peripheral terminals are located on the surface of the body. Some sensory neurons can be activated by stimulation with an external object such as a parasite on the body surface. Alternatively, some sensory neurons can respond to a chemical stimulus that produces an itch sensation. During a scratch reflex, a nearby limb reaches toward and rubs against the site on the body surface that has been stimulated. The scratch reflex has been extensively studied to understand the functioning of neural networks in vertebrates. Despite decades of research, key aspects of the scratch reflex are still unknown, such as the neural mechanisms by which the reflex is terminated.

From the ancient Egyptian mummifications to 18th century scientific research on "globules" and neurons, there is evidence of neuroscience practice throughout the early periods of history. The early civilizations lacked adequate means to obtain knowledge about the human brain. Their assumptions about the inner workings of the mind, therefore, were not accurate. Early views on the function of the brain regarded it to be a form of "cranial stuffing" of sorts. In ancient Egypt, from the late Middle Kingdom onwards, in preparation for mummification, the brain was regularly removed, for it was the heart that was assumed to be the seat of intelligence. According to Herodotus, during the first step of mummification: "The most perfect practice is to extract as much of the brain as possible with an iron hook, and what the hook cannot reach is mixed with drugs." Over the next five thousand years, this view came to be reversed; the brain is now known to be the seat of intelligence, although colloquial variations of the former remain as in "memorizing something by heart".

Mesencephalic nucleus of trigeminal nerve

The mesencephalic nucleus is involved with reflex proprioception of the periodontium and of the muscles of mastication in the jaw that functions to prevent biting down hard enough to lose a tooth. To subserve this reflex protective function, mechanoreceptive nerves in the periodontal ligament sense tooth movement and project to the mesencephalic nucleus. Likewise, afferent fibers from muscle spindles, the sensory organs of skeletal muscle, are stimulated by the stretch of hard contraction of jaw muscles. The temporomandibular joints and the Golgi tendon organs of the jaw muscles do not project to the mesencephalic nucleus. The mesencephalic nucleus is one of four trigeminal nerve nuclei, three sensory and one motor. The other two sensory nuclei are the chief sensory nucleus mediating conscious facial touch and the spinal trigeminal nucleus, mediating pain in the head, and is of importance in headache. The trigeminal motor nucleus innervates the muscles of mastication.

Low-threshold spikes (LTS) refer to membrane depolarizations by the T-type calcium channel. LTS occur at low, negative, membrane depolarizations. They often follow a membrane hyperpolarization, which can be the result of decreased excitability or increased inhibition. LTS result in the neuron reaching the threshold for an action potential. LTS is a large depolarization due to an increase in Ca2+ conductance, so LTS is mediated by calcium (Ca2+) conductance. The spike is typically crowned by a burst of two to seven action potentials, which is known as a low-threshold burst. LTS are voltage dependent and are inactivated if the cell's resting membrane potential is more depolarized than −60mV. LTS are deinactivated, or recover from inactivation, if the cell is hyperpolarized and can be activated by depolarizing inputs, such as excitatory postsynaptic potentials (EPSP). LTS were discovered by Rodolfo Llinás and coworkers in 1980s.

In mammals, the Bötzinger complex (BötC) is a group of neurons located in the rostral ventrolateral medulla, and ventral respiratory column. In the medulla, this group is located caudally to the facial nucleus and ventral to nucleus ambiguus.

Proprioception Sense of the relative position of ones own body parts and strength of effort employed in movement

Proprioception, also referred to as kinaesthesia, is the sense of self-movement and body position. It is sometimes described as the "sixth sense".

The neuroscience of rhythm refers to the various forms of rhythm generated by the central nervous system (CNS). Nerve cells, also known as neurons in the human brain are capable of firing in specific patterns which cause oscillations. The brain possesses many different types of oscillators with different periods. Oscillators are simultaneously outputting frequencies from .02 Hz to 600 Hz. It is now well known that a computer is capable of running thousands of processes with just one high frequency clock. Humans have many different clocks as a result of evolution. Prior organisms had no need for a fast responding oscillator. This multi-clock system permits quick response to constantly changing sensory input while still maintaining the autonomic processes that sustain life. This method modulates and controls a great deal of bodily functions.

Neural accommodation or neuronal accommodation occurs when a neuron or muscle cell is depolarised by slowly rising current in vitro. The Hodgkin–Huxley model also shows accommodation. Sudden depolarisation of a nerve evokes propagated action potential by activating voltage-gated fast sodium channels incorporated in the cell membrane if the depolarisation is strong enough to reach threshold. The open sodium channels allow more sodium ions to flow into the cell and resulting in further depolarisation, which will subsequently open even more sodium channels. At a certain moment this process becomes regenerative and results in the rapid ascending phase of action potential. In parallel with the depolarisation and sodium channel activation, the inactivation process of the sodium channels is also driven by depolarisation. Since the inactivation is much slower than the activation process, during the regenerative phase of action potential, inactivation is unable to prevent the "chain reaction"-like rapid increase in the membrane voltage.

Krešimir Krnjević is a Canadian-British neurophysiologist.

Classification of peripheral nerves

The classification of peripheral nerves in the peripheral nervous system (PNS) groups the nerves into two main groups, the somatic and the autonomic nervous systems. Together, these two systems provide information regarding the location and status of the limbs, organs, and the remainder of the body to the central nervous system (CNS) via nerves and ganglia present outside of the spinal cord and brain. The somatic nervous system directs all voluntary movements of the skeletal muscles, and can be sub-divided into afferent and efferent neuronal flow. The autonomic nervous system is divided primarily into the sympathetic and parasympathetic nervous systems with a third system, the enteric nervous system, receiving less recognition.

Brain-body interactions are patterns of neural activity in the central nervous system to coordinate the activity between the brain and body. The nervous system consists of central and peripheral nervous systems and coordinates the actions of an animal by transmitting signals to and from different parts of its body. The brain and spinal cord are interwoven with the body and interact with other organ systems through the somatic, autonomic and enteric nervous systems. Neural pathways regulate brain-body interactions and allow to sense and control its body and interact with the environment.

References

  1. ↑ Rosenberg, J. R., Amjad, A. M., Breeze, P., Brillinger, D. R., & Halliday, D. M. (1989). The Fourier approach to the identification of functional coupling between neuronal spike trains. Progress in Biophysics and Molecular Biology, 53(1), 1–31.
  2. 1 2 Farmer, S. F., Bremner, F. D., Halliday, D. M., Rosenberg, J. R., & Stephens, J. A. (1993). The frequency content of common synaptic inputs to motoneurones studied during voluntary isometric contraction in man. The Journal of Physiology, 470(1), 127–155
  3. ↑ Person, R. S.; Kudina, L. P. (1968). "Cross-correlation of electromyograms showing interference patterns". Electroencephalography and Clinical Neurophysiology. 25 (1): 58–68. doi:10.1016/0013-4694(68)90087-4. ISSN   0013-4694. PMID   4174784.
  4. ↑ Kirkwood, P. A.; Sears, T. A. (1978). "The synaptic connexions to intercostal motoneurones as revealed by the average common excitation potential". The Journal of Physiology. 275: 103–134. doi:10.1113/jphysiol.1978.sp012180. ISSN   0022-3751. PMC   1282535 . PMID   633094.
  5. ↑ Bremner, F. D., Baker, J. R., & Stephens, J. A. (1991). Correlation between the discharges of motor units recorded from the same and from different finger muscles in man. The Journal of Physiology, 432(1), 355–380. http://doi.org/10.1113/jphysiol.1991.sp018389
  6. ↑ Negro, Francesco; Farina, Dario (2011-01-28). "Linear transmission of cortical oscillations to the neural drive to muscles is mediated by common projections to populations of motoneurons in humans". The Journal of Physiology. 589 (3): 629–637. doi:10.1113/jphysiol.2010.202473. ISSN   0022-3751. PMC   3055547 . PMID   21135042.
  7. ↑ Boonstra, Tjeerd W.; Breakspear, Michael (2012). "Neural mechanisms of intermuscular coherence: implications for the rectification of surface electromyography". Journal of Neurophysiology. 107 (3): 796–807. doi:10.1152/jn.00066.2011. ISSN   1522-1598. PMID   22072508.
  8. ↑ Boonstra, Tjeerd W.; Farmer, Simon F.; Breakspear, Michael (2016). "Using Computational Neuroscience to Define Common Input to Spinal Motor Neurons". Frontiers in Human Neuroscience. 10: 313. doi:10.3389/fnhum.2016.00313. ISSN   1662-5161. PMC   4914567 . PMID   27445753.
  9. ↑ Gibbs, J.; Harrison, L. M.; Stephens, J. A. (1995-05-15). "Organization of inputs to motoneurone pools in man". The Journal of Physiology. 485 ( Pt 1): 245–256. doi:10.1113/jphysiol.1995.sp020727. ISSN   0022-3751. PMC   1157987 . PMID   7658378.
  10. ↑ Kerkman, Jennifer N.; Daffertshofer, Andreas; Gollo, Leonardo L.; Breakspear, Michael; Boonstra, Tjeerd W. (2018). "Network structure of the human musculoskeletal system shapes neural interactions on multiple time scales". Science Advances. 4 (6): eaat0497. Bibcode:2018SciA....4..497K. doi:10.1126/sciadv.aat0497. ISSN   2375-2548. PMC   6021138 . PMID   29963631.
  11. ↑ Nishimura, Yukio; Morichika, Yosuke; Isa, Tadashi (2009-03-01). "A subcortical oscillatory network contributes to recovery of hand dexterity after spinal cord injury". Brain. 132 (3): 709–721. doi:10.1093/brain/awn338. ISSN   0006-8950. PMC   2664448 . PMID   19155271.
  12. ↑ Fisher, Karen M.; Zaaimi, Boubker; Williams, Timothy L.; Baker, Stuart N.; Baker, Mark R. (2012-09-01). "Beta-band intermuscular coherence: a novel biomarker of upper motor neuron dysfunction in motor neuron disease". Brain. 135 (9): 2849–2864. doi:10.1093/brain/aws150. ISSN   0006-8950. PMC   3437020 . PMID   22734124.


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