Desarrollo de la inhibición: comparación de medidas neuropsicológicas y de seguimiento de ojos

Inhibition is the ability to stop an automatic response when a stimulus is presented. It is one main component of executive function models. Few studies have evaluated the development of this ability’s in children between five and eight years of age using eye tracking measures. The first objective of this exploratory study is to evaluate the performance difference of younger compared to older children. The second objective is to evaluate if inhibition assessed via three different neuropsychological tests develops at a similar rate as inhibition assessed via two eye tracking tasks. Forty-six children aged 5.7 to 8.4 years completed both types of tests. Results show that one neuropsychological test was sensitive to the children’ increasing inhibition ability, while both eye tracking tests were. Additionally, scores from one eye tracking task correlated with scores from one neuropsychological test. Possible explanations of moderate relations between tasks are discussed.La inhibición es la capacidad de detener una respuesta automática. Es una de las funciones ejecutivas principales. Pocos estudios han evaluado su desarrollo en niños de cinco a ocho años utilizando pruebas de seguimiento de ojos. Este estudio exploratorio tiene, como primer objetivo, evaluar la diferencia de rendimiento entre los más jóvenes y los mayores. El segundo objetivo es evaluar si la inhibición se desarrolla a un ritmo similar en tres pruebas neuropsicológicas y dos pruebas de seguimiento de ojos. Cuarenta y seis niños, de 5 años y 8 meses a 8 años y 5 meses, realizaron ambos tipos de pruebas. Los resultados muestran que una de las pruebas neuropsicológicas y ambas pruebas de seguimiento de ojos fueron sensibles a la mejora de la inhibición. Además, resultados de una prueba de seguimiento de ojos y de una prueba neuropsicológica estaban correlacionados. Se discuten las explicaciones posibles de las relaciones entre las tareas

Efficient procedure to remove ECG from sEMG with limited deteriorations: Extraction, quasi-periodic detection and cancellation

An efficient method is presented to remove ECG from EMG with limited deterioration. The ECG pulses are first localized and then remove only where they have been detected. A combination of ICA and DWT is first used to extract ECG information. Then, the pulses positions are detected with an original algorithm based on FFT which takes advantage of the quasi-periodic nature of the ECG. The proposed method accurately detects pulses positions and efficiently removes the ECG from EMG signals even when both signals are strongly overlapped. The interpretations of the surface electromyography (sEMG) signals from the trunk region are strongly distorted by the heart activity (ECG), especially in case of low-amplitude EMG responses analyses. Many methods have been investigated to resolve this nontrivial problem, by using advanced data processing on the overall sEMG recorded signal. However, if they reduce ECG artifacts, those cancellation methods also deteriorate noiseless parts of the signal. This work proposes an original ECG cancellation method designed to limit the deterioration of sEMG information. To do that, the proposed techniques does not directly attempt to remove the ECG, but is based on two main steps: the localization of ECG and the cancellation of ECG but only where heart pulses have been detected. The phase of localization efficiently extracts the ECG contribution by combining the discrete wavelet transforms (DWT) and the method of independent component analysis (ICA). And finally, this phase takes advantage of quasi-periodic properties of ECG signals to accurately detect pulses localization with an original algorithm based on the fast Fourier transform (FFT). Intensive simulations were achieved in terms of relative errors, coherence and accuracy for different levels of ECG interference. And the correlation coefficients computed from the paraspinal muscles EMG signals of 12 healthy participants were also used to evaluate the developed method. The results from simulation and real data demonstrate that the proposed method accurately detects pulses positions and efficiently removes the ECG from EMG signals, even when both signals are strongly overlapped, and greatly limits the deterioration of the EMG

Muscle Activity Adaptations to Spinal Tissue Creep in the Presence of Muscle Fatigue

Aim The aim of this study was to identify adaptations in muscle activity distribution to spinal tissue creep in presence of muscle fatigue. Methods Twenty-three healthy participants performed a fatigue task before and after 30 minutes of passive spinal tissue deformation in flexion. Right and left erector spinae activity was recorded using large-arrays surface electromyography (EMG). To characterize muscle activity distribution, dispersion was used. During the fatigue task, EMG amplitude root mean square (RMS), median frequency and dispersion in x- and y-axis were compared before and after spinal creep. Results Important fatigue-related changes in EMG median frequency were observed during muscle fatigue. Median frequency values showed a significant main creep effect, with lower median frequency values on the left side under the creep condition (p[less than or equal to]0.0001). A significant main creep effect on RMS values was also observed as RMS values were higher after creep deformation on the right side (p = 0.014) a similar tendency, although not significant, was observed on the left side (p = 0.06). A significant creep effects for x-axis dispersion values was observed, with higher dispersion values following the deformation protocol on the left side (p[less than or equal to]0.001). Regarding y-axis dispersion values, a significant creep x fatigue interaction effect was observed on the left side (p = 0.016) a similar tendency, although not significant, was observed on the right side (p = 0.08). Conclusion Combined muscle fatigue and creep deformation of spinal tissues led to changes in muscle activity amplitude, frequency domain and distribution

Detection method of flexion relaxation phenomenon based on wavelets for patients with low back pain

The flexion relaxation phenomenon (FRP) can be defined as a reduction or silence of myoelectric activity of the lumbar erector spinae muscle during full trunk flexion. It is typically absent in patients with chronic low back pain (LBP). Before any broad clinical utilization of this neuromuscular response can be made, effective, standardized, and accurate methods of identifying FRP limits are needed. However, this phenomenon is clearly more difficult to detect for LBP patients than for healthy patients. The main goal of this study is to develop an automated method based on wavelet transformation that would improve time point limits detection of surface electromyography signals of the FRP in case of LBP patients. Conventional visual identification and proposed automated methods of time point limits detection of relaxation phase were compared on experimental data using criteria of accuracy and repeatability based on physiological properties. The evaluation demonstrates that the use of wavelet transform (WT) yields better results than methods without wavelet decomposition. Furthermore, methods based on wavelet per packet transform are more effective than algorithms employing discrete WT. Compared to visual detection, in addition to demonstrating an obvious saving of time, the use of wavelet per packet transform improves the accuracy and repeatability in the detection of the FRP limits. These results clearly highlight the value of the proposed technique in identifying onset and offset of the flexion relaxation response in LBP subjects

The effect of spinal manipulation impulse duration on spine neuromechanical responses

INTRODUCTION: Spinal manipulation therapy (SMT) is characterized by specific kinetic and kinematic parameters that can be modulated. The purpose of this study is to investigate fundamental aspects of SMT dose-physiological response relation in humans by varying SMT impulse duration. METHODS: Twenty healthy adults were subjected to four different SMT force-time profiles delivered by a servo-controlled linear actuator motor and differing in their impulse duration. EMG responses of the left and right thoracic paraspinal muscles (T6 and T8 levels) and vertebral displacements of T7 and T8 were evaluated for all SMT phases. RESULTS: Significant differences in paraspinal EMG were observed during the “Thrust phase” and immediately after (“Post-SMT1”) (all T8 ps < 0.01 and T6 during the thrust ps < 0.05). Sagittal vertebral displacements were similar across all conditions (p > 0.05). CONCLUSION: Decreasing SMT impulse duration leads to a linear increase in EMG response of thoracic paraspinal during and following the SMT thrust

Neuromechanical response to spinal manipulation therapy: effects of a constant rate of force application

Background Neuromechanical responses to spinal manipulation therapy (SMT) have been shown to be modulated through the variation of SMT biomechanical parameters: peak force, time to peak force, and preload force. Although rate of force application was modulated by the variation of these parameters, the assumption that neuromuscular responses are modulated by the rate of force application remains to be confirmed. Therefore, the purpose of the present study was to evaluate the effect of a constant rate of force application in neuromechanical responses to SMT in healthy adults. Methods Four SMT force-time profiles presenting different time to peak force and peak force, but with a constant rate of force application were applied on 25 healthy participants' T7 transverse processes. Muscular responses were recorded through surface electromyography electrodes (T6 and T8 levels), while vertebral displacements were assessed through pasted kinematic markers on T6 to T8 spinous processes. Effects of SMT force-time profiles on neuromechanical responses were assessed using repeated-measures ANOVAs. Results There was no main effect of SMT force-time profile modulation on muscular responses (ps > .05) except for the left T8 (F (3, 72) = 3.23, p = .03) and left T6 (F (3, 72) = 2.94, p = .04). Muscular responses were significantly lower for the lowest peak force condition than the highest (for T8) or second highest (for T6). Analysis showed that increasing the SMT peak force (and concomitantly time to peak force) led to a significant vertebral displacement increase for the contacted vertebra (F T7 (1, 17) = 354.80, p < .001) and both adjacent vertebras (F T6 (1, 12) = 104.71, p < .001 and F T8 (1, 19) = 468.68, p < .001). Conclusion This study showed that peak force modulation using constant rate of force application leads to similar neuromuscular responses. Coupled with previous investigations of SMT peak force and duration effects, the results suggest that neuromuscular responses to SMT are mostly influenced by the rate of force application, while peak force modulation yields changes in the vertebral displacement. Rate of force application should therefore be defined in future studies. Clinical implications of various SMT dosages in patients with spine related pain should also be investigated