Contribution of intrinsic properties and synaptic inputs to motoneuron discharge patterns: a simulation study

Powers, Randall K.; Elbasiouny, Sherif M.; Rymer, William Z.; Heckman, C. J.

doi:10.1152/jn.00510.2011

Cited by 90 publications

(131 citation statements)

References 65 publications

Supporting

Mentioning

114

Contrasting

Unclassified

Order By: Relevance

“…When applying "proportional inhibition" (an inhibitory input that rose and fell in parallel with the excitatory input; also referred to as "balanced inhibition"; Berg et al 2007), with the inhibitory conductance applied uniformly across the soma and dendrites ( Fig. 7 panel 2, in Powers et al 2012), the low-rate modulation observed closely resembles that which we have observed in the spastic-paretic limb of stroke survivors (Figs. 1 and 4).…”

Section: Pic-based Mechanisms For Saturation In Motor Unit Firing Ratsupporting

confidence: 55%

“…This mechanism would produce saturation at a relatively low firing rate. In animal preparations, however (Lee and Heckman 1998;Powers et al 2012), PIC activation alone does not produce the strong saturation seen in the present results, as demonstrated by the observed prolonged period of flat or even negative firing rate modulation.…”

Section: Pic-based Mechanisms For Saturation In Motor Unit Firing Ratcontrasting

confidence: 50%

“…The PIC, however, is also known to be highly sensitive to inhibitory synaptic input (Bui et al 2008a(Bui et al , 2008bHounsgaard et al 1988;Kuo et al 2003). In fact, Powers et al (2012) suggested that the contribution of PICs to rate modulation is likely to depend on a mixture of excitatory and inhibitory synaptic currents contributing to the net synaptic drive to the motoneuron pool. To examine the potential contributions of PIC activation and synaptic input patterns to motor unit rate modulation, Powers and colleagues examined the responses of a set of cable motoneuron models to different patterns of excitatory and inhibitory inputs.…”

Section: Pic-based Mechanisms For Saturation In Motor Unit Firing Ratmentioning

confidence: 99%

“…The rate saturations may result from limitations in descending voluntary excitatory drive, changes in intrinsic motoneuron properties [such as persistent inward currents (PICs)], or both. In fact, recent evidence from simulations in motoneuron models suggest that a mixture of excitation and inhibition can result in saturation in firing rates (Powers et al 2012) that closely resemble the firing profiles observed in stroke survivors during voluntary increases in force (Mottram et al 2009). Thus, in contrast to the spontaneous firing of motor units observed in the muscles of stroke survivors while at rest (Mottram et al 2010), firing rates are abnormally low during purposeful activation of the muscle (Gemperline et al 1995).…”

mentioning

confidence: 92%

See 3 more Smart Citations

Disturbances of motor unit rate modulation are prevalent in muscles of spastic-paretic stroke survivors

Mottram

Heckman

Powers

et al. 2014

Journal of Neurophysiology

Self Cite

View full text Add to dashboard Cite

Mottram CJ, Heckman CJ, Powers RK, Rymer WZ, Suresh NL. Disturbances of motor unit rate modulation are prevalent in muscles of spastic-paretic stroke survivors. J Neurophysiol 111: 2017-2028, 2014. First published February 26, 2014 doi:10.1152/jn.00389.2013.-Stroke survivors often exhibit abnormally low motor unit firing rates during voluntary muscle activation. Our purpose was to assess the prevalence of saturation in motor unit firing rates in the spastic-paretic biceps brachii muscle of stroke survivors. To achieve this objective, we recorded the incidence and duration of impaired lower-and higherthreshold motor unit firing rate modulation in spastic-paretic, contralateral, and healthy control muscle during increases in isometric force generated by the elbow flexor muscles. Impaired firing was considered to have occurred when firing rate became constant (i.e., saturated), despite increasing force. The duration of impaired firing rate modulation in the lower-threshold unit was longer for spasticparetic (3.9 Ϯ 2.2 s) than for contralateral (1.4 Ϯ 0.9 s; P Ͻ 0.001) and control (1.1 Ϯ 1.0 s; P ϭ 0.005) muscles. The duration of impaired firing rate modulation in the higher-threshold unit was also longer for the spastic-paretic (1.7 Ϯ 1.6 s) than contralateral (0.3 Ϯ 0.3 s; P ϭ 0.007) and control (0.1 Ϯ 0.2 s; P ϭ 0.009) muscles. This impaired firing rate of the lower-threshold unit arose, despite an increase in the overall descending command, as shown by the recruitment of the higher-threshold unit during the time that the lower-threshold unit was saturating, and by the continuous increase in averages of the rectified EMG of the biceps brachii muscle throughout the rising phase of the contraction. These results suggest that impairments in firing rate modulation are prevalent in motor units of spastic-paretic muscle, even when the overall descending command to the muscle is increasing.

show abstract

Section: Pic-based Mechanisms For Saturation In Motor Unit Firing Ratsupporting

confidence: 55%

Section: Pic-based Mechanisms For Saturation In Motor Unit Firing Ratcontrasting

confidence: 50%

Section: Pic-based Mechanisms For Saturation In Motor Unit Firing Ratmentioning

confidence: 99%

mentioning

confidence: 92%

See 2 more Smart Citations

Disturbances of motor unit rate modulation are prevalent in muscles of spastic-paretic stroke survivors

Mottram

Heckman

Powers

et al. 2014

Journal of Neurophysiology

Self Cite

View full text Add to dashboard Cite

show abstract

“…In vertebrate smooth muscle, neuromodulators act directly on the muscle (Burnstock 1985). In skeletal muscle, persistent inward currents in motor neuronal dendrites are modulated by serotonin and norepinephrine (Heckman et al 2008) and, given appropriate excitatory and inhibitory synaptic input, regulate motor output (Powers et al 2012).…”

Section: Variability In Animals and Responses And Its Reduction By Nomentioning

confidence: 99%

Motor neuronal activity varies least among individuals when it matters most for behavior

Cullins

Shaw

Gill

et al. 2015

Journal of Neurophysiology

View full text Add to dashboard Cite

How does motor neuronal variability affect behavior? To explore this question, we quantified activity of multiple individual identified motor neurons mediating biting and swallowing in intact, behaving Aplysia californica by recording from the protractor muscle and the three nerves containing the majority of motor neurons controlling the feeding musculature. We measured multiple motor components: duration of the activity of identified motor neurons as well as their relative timing. At the same time, we measured behavioral efficacy: amplitude of grasping movement during biting and amplitude of net inward food movement during swallowing. We observed that the total duration of the behaviors varied: Within animals, biting duration shortened from the first to the second and third bites; between animals, biting and swallowing durations varied. To study other sources of variation, motor components were divided by behavior duration (i.e., normalized). Even after normalization, distributions of motor component durations could distinguish animals as unique individuals. However, the degree to which a motor component varied among individuals depended on the role of that motor component in a behavior. Motor neuronal activity that was essential for the expression of biting or swallowing was similar among animals, whereas motor neuronal activity that was not essential for that behavior varied more from individual to individual. These results suggest that motor neuronal activity that matters most for the expression of a particular behavior may vary least from individual to individual. Shaping individual variability to ensure behavioral efficacy may be a general principle for the operation of motor systems.

show abstract

Muscle, Biomechanics, and Implications for Neural Control

Ting

Chiel

2017

Neurobiology of Motor Control

View full text Add to dashboard Cite

Contribution of intrinsic properties and synaptic inputs to motoneuron discharge patterns: a simulation study

Abstract: Powers RK, ElBasiouny SM, Rymer WZ, Heckman CJ. Contribution of intrinsic properties and synaptic inputs to motoneuron discharge patterns: a simulation study.

Cited by 90 publications

References 65 publications

Disturbances of motor unit rate modulation are prevalent in muscles of spastic-paretic stroke survivors

Disturbances of motor unit rate modulation are prevalent in muscles of spastic-paretic stroke survivors

Motor neuronal activity varies least among individuals when it matters most for behavior

Muscle, Biomechanics, and Implications for Neural Control

Contact Info

Product

Resources

About