Carina Marconi Germer

@article{pmid32120053,

title = {Reliable measurement of incisal bite force for understanding the control of masticatory muscles},

author = {Luciana S Moreira and Leonardo A Elias and Carina M Germer and Evanisi T Palomari},

doi = {10.1016/j.archoralbio.2020.104683},

issn = {1879-1506},

year  = {2020},

date = {2020-04-01},

urldate = {2020-04-01},

journal = {Arch Oral Biol},

volume = {112},

pages = {104683},

abstract = {OBJECTIVE: In the present study, we aimed at evaluating the steadiness of incisal bite force during isometric contractions of masticatory muscles.nnDESIGN: Two separate experiments were carried out in 11 healthy young women. A first experiment was performed to test the reliability of our protocol for measurement of incisal bite force steadiness. The second experiment aimed to evaluate the steadiness of incisal bite force at four submaximal (i.e., percentage of maximum voluntary contraction, MVC) levels (5 %MVC, 10 %MVC, 15 %MVC, and 20 %MVC), along with the bilateral myoelectric activity of two masticatory muscles (temporalis and masseter).nnRESULTS: The results from the first experiment showed that our protocol is substantially reliable (intraclass correlation coefficient, ICC > 0.80) for estimating force variability and moderate reliable (0.60 < ICC < 0.80) for estimating spectral properties of force signals. In the second experiment, we found that force standard deviation (SD) increased proportionally to the power of mean force, and coefficient of variation (CoV) was higher at low-intensity contractions and maintained at an approximately constant level for high-intensity contractions. The force-EMG relationships were linear for both muscles at the contraction intensities evaluated in the study (5 %MVC to 20 %MVC), and the median frequency did not change with contraction intensity.nnCONCLUSION: Therefore, we presented a reliable method to estimate the incisal bite force, along with additional data on force control and myoelectric activity of jaw elevator muscles during isometric steady contractions.},

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tppubtype = {article}

}

@article{pmid31791034,

title = {Neurophysiological correlates of force control improvement induced by sinusoidal vibrotactile stimulation},

author = {Carina Marconi Germer and Alessandro Del Vecchio and Francesco Negro and Dario Farina and Leonardo Abdala Elias},

doi = {10.1088/1741-2552/ab5e08},

issn = {1741-2552},

year  = {2020},

date = {2020-01-01},

journal = {J Neural Eng},

volume = {17},

number = {1},

pages = {016043},

abstract = {OBJECTIVE: An optimal level of vibrotactile stimulation has been shown to improve sensorimotor control in healthy and diseased individuals. However, the underlying neurophysiological mechanisms behind the enhanced motor performance caused by vibrotactile stimulation are yet to be fully understood. Therefore, here we aim to evaluate the effect of a cutaneous vibration on the firing behavior of motor units in a condition of improved force steadiness.nnAPPROACH: Participants performed a visuomotor task, which consisted of low-intensity isometric contractions of the first dorsal interosseous (FDI) muscle, while sinusoidal (175 Hz) vibrotactile stimuli with different intensities were applied to the index finger. High-density surface electromyogram was recorded from the FDI muscle, and a decomposition algorithm was used to extract the motor unit spike trains. Additionally, computer simulations were performed using a multiscale neuromuscular model to provide a potential explanation for the experimental findings.nnMAIN RESULTS: Experimental outcomes showed that an optimal level of vibration significantly improved force steadiness (estimated as the coefficient of variation of force). The decreased force variability was accompanied by a reduction in the variability of the smoothed cumulative spike train (as an estimation of the neural drive to the muscle), and the proportion of common inputs to the FDI motor nucleus. However, the interspike interval variability did not change significantly with the vibration. A mathematical approach, together with computer simulation results suggested that vibrotactile stimulation would reduce the variance of the common synaptic input to the motor neuron pool, thereby decreasing the low frequency fluctuations of the neural drive to the muscle and force steadiness.nnSIGNIFICANCE: Our results demonstrate that the decreased variability in common input accounts for the enhancement in force control induced by vibrotactile stimulation.},

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pubstate = {published},

tppubtype = {article}

}

@article{pmid31605381,

title = {The human central nervous system transmits common synaptic inputs to distinct motor neuron pools during non-synergistic digit actions},

author = {A Del Vecchio and C M Germer and L A Elias and Q Fu and J Fine and M Santello and D Farina},

doi = {10.1113/JP278623},

issn = {1469-7793},

year  = {2019},

date = {2019-12-01},

urldate = {2019-12-01},

journal = {J Physiol},

volume = {597},

number = {24},

pages = {5935--5948},

abstract = {KEY POINTS: Neural connectivity between distinct motor neuronal modules in the spinal cord is classically studied through electrical stimulation or multi-muscle EMG recordings. We quantified the strength of correlation in the activity of two distinct populations of motor neurons innervating the thenar and first dorsal interosseous muscles during tasks that required the two hand muscles to exert matched or un-matched forces in different directions. We show that when the two hand muscles are concurrently activated, synaptic input to the two motor neuron pools is shared across all frequency bandwidths (representing cortical and spinal input) associated with force control. The observed connectivity indicates that motor neuron pools receive common input even when digit actions do not belong to a common behavioural repertoire.nnABSTRACT: Neural connectivity between distinct motor neuronal modules in the spinal cord is classically studied through electrical stimulation or multi-muscle EMG recordings. Here we quantify the strength of correlation in the activity of two distinct populations of motor neurons innervating the thenar and first dorsal interosseous muscles in humans during voluntary contractions. To remove confounds associated with previous studies, we used a task that required the two hand muscles to exert matched or un-matched forces in different directions. Despite the force production task consisting of uncommon digit force coordination patterns, we found that synaptic input to motor neurons is shared across all frequency bands, reflecting cortical and spinal inputs associated with force control. The coherence between discharge timings of the two pools of motor neurons was significant at the delta (0-5 Hz), alpha (5-15 Hz) and beta (15-35 Hz) bands (P < 0.05). These results suggest that correlated input to motor neurons of two hand muscles can occur even during tasks not belonging to a common behavioural repertoire and despite lack of common innervation. Moreover, we show that the extraction of activity from motor neurons during voluntary force control removes cross-talk associated with global EMG recordings, thus allowing direct in vivo interrogation of spinal motor neuron activity.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid31197752,

title = {Sinusoidal vibrotactile stimulation differentially improves force steadiness depending on contraction intensity},

author = {Carina Marconi Germer and Luciana Sobral Moreira and Leonardo Abdala Elias},

doi = {10.1007/s11517-019-01999-8},

issn = {1741-0444},

year  = {2019},

date = {2019-08-01},

urldate = {2019-08-01},

journal = {Med Biol Eng Comput},

volume = {57},

number = {8},

pages = {1813--1822},

abstract = {Studies have reported the benefits of sensory noise in motor performance, but it is not clear if this phenomenon is influenced by muscle contraction intensity. Additionally, most of the studies investigated the role of a stochastic noise on the improvement of motor control and there is no evidence that a sinusoidal vibrotactile stimulation could also enhance motor performance. Eleven participants performed a sensorimotor task while sinusoidal vibrations were applied to the finger skin. The effects of an optimal vibration (OV) on force steadiness were evaluated in different contraction intensities. We assessed the standard deviation (SD) and coefficient of variation (CoV) of force signals. OV significantly decreased force SD irrespective of contraction intensity, but the decrease in force CoV was significantly higher for low-intensity contraction. To the best of our knowledge, our findings are the first evidence that sinusoidal vibrotactile stimulation can enhance force steadiness in a motor task. Also, the significant improvement caused by OV during low-intensity contractions is probably due to the higher sensitivity of the motor system to the synaptic noise. These results add to the current knowledge on the effects of vibrotactile stimulation in motor control and have potential implications for the development of wearable haptic devices. Graphical abstract In this work the effects of a sinusoidal vibrotactile stimulation on force steadiness was investigated. Index finger sensorimotor tasks were performed in three levels of isometric contraction of the FDI muscle: 5, 10 and 15 %MVC. An optimal level of vibration significantly improved force steadiness, but the decrease in force CoV caused by vibration was more pronounced in contractions at 5 %MVC.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{pmid25395252,

title = {Electrocardiogram, heart movement and heart rate in the awake gecko (Hemidactylus mabouia)},

author = {Carina M Germer and Juliana M Tomaz and Ana F Carvalho and Rosana A Bassani and José W M Bassani},

doi = {10.1007/s00360-014-0873-5},

issn = {1432-136X},

year  = {2015},

date = {2015-01-01},

journal = {J Comp Physiol B},

volume = {185},

number = {1},

pages = {111--118},

abstract = {The electrocardiogram (ECG) is the simplest and most effective non-invasive method to assess the electrical activity of the heart and to obtain information on the heart rate (HR) and rhythm. Because information on the HR of very small reptiles (body mass <10 g) is still scarce in the literature, in the present work we describe a procedure for recording the ECG in non-anesthetized geckos (Hemidactylus mabouia, Moreau de Jonnès, 1818) under different conditions, namely manual restraint (MR), spontaneous tonic immobility (TI), and in the non-restrained condition (NR). In the gecko ECG, the P, QRS and T waves were clearly distinguishable. The HR was 2.83 ± 0.02 Hz under MR, which was significantly greater (p < 0.001) than the HR under the TI (1.65 ± 0.09 Hz) and NR (1.60 ± 0.10 Hz) conditions. Spontaneously beating isolated gecko hearts contracted at 0.84 ± 0.03 Hz. The in vitro beating rate was affected in a concentration-dependent fashion by adrenoceptor stimulation with noradrenaline, as well as by the muscarinic cholinergic agonist carbachol, which produced significant positive and negative chronotropic effects, respectively (p < 0.001). To our knowledge, this is the first report on the ECG morphology and HR values in geckos, particularly under TI. The methodology and instrumentation developed here are useful for non-invasive in vivo physiological and pharmacological studies in small reptiles without the need of physical restraint or anesthesia.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}