A computational method for recording and analysis of mandibular movements

This study proposed the development of a new clinical tool capable of quantifying the movements of opening-closing, protrusion and laterotrusion of the mandible. These movements are important for the clinical evaluation of the temporomandibular function and muscles involved in mastication. Unlike current commercial systems, the proposed system employs a low-cost video camera and a computer program that is used for reconstructing the trajectory of a reflective marker that is fixed on the mandible. In order to illustrate the clinical application of this tool, a clinical experiment consisting on the evaluation of the mandibular movements of 12 subjects was conducted. The results of this study were compatible with those found in the literature with the advantage of using a low cost, simple, non-invasive, and flexible tool customized for the needs of the practical clinic

Study of age-related changes in postural control during quiet standing through Linear Discriminant Analysis

<p>Abstract</p> <p>Background</p> <p>The human body adopts a number of strategies to maintain an upright position. The analysis of the human balance allows for the understanding and identification of such strategies. The displacement of the centre of pressure (COP) is a measure that has been successfully employed in studies regarding the postural control. Most of these investigations are related to the analysis of individuals suffering from neuromuscular disorders. Recent studies have shown that the elderly population is growing very fast in many countries all over the world, and therefore, researches that try to understand changes in this group are required. In this context, this study proposes the analysis of the postural control, measured by the displacement of the COP, in groups of young and elderly adults.</p> <p>Methods</p> <p>In total 59 subjects participated of this study. They were divided into seven groups according to their age. The displacement of the COP was collected for each subject standing on a force plate. Two experimental conditions, of 30 seconds each, were investigated: opened eyes and closed eyes. Traditional and recent digital signal processing tools were employed for feature computation from the displacement of the COP. Statistical analyses were carried out in order to identify significant differences between the features computed from the distinct groups that could allow for their discrimination.</p> <p>Results</p> <p>Our results showed that Linear Discrimination Analysis (LDA), which is one of the most popular feature extraction and classifier design techniques, could be successfully employed as a linear transformation, based on the linear combination of standard features for COP analysis, capable of estimating a unique feature, so-called <it>LDA-value</it>, from which it was possible to discriminate the investigated groups and show a high correlation between this feature and age.</p> <p>Conclusion</p> <p>These results show that the analysis of features computed from the displacement of the COP are of great importance in studies trying to understand the ageing process. In particular, the <it>LDA-value </it>showed to be an adequate feature for assessment of changes in the postural control which can be related to functional changes that occur over the ageing.</p

Assessment of inter-examiner agreement and variability in the manual classification of auditory brainstem response

Abstract Background: The analysis of the Auditory Brainstem Response (ABR) is of fundamental importance to the investigation of the auditory system behaviour, though its interpretation has a subjective nature because of the manual process employed in its study and the clinical experience required for its analysis. When analysing the ABR, clinicians are often interested in the identification of ABR signal components referred to as Jewett waves. In particular, the detection and study of the time when these waves occur (i.e., the wave latency) is a practical tool for the diagnosis of disorders affecting the auditory system. Significant differences in inter-examiner results may lead to completely distinct clinical interpretations of the state of the auditory system. In this context, the aim of this research was to evaluate the inter-examiner agreement and variability in the manual classification of ABR. Methods: A total of 160 ABR data samples were collected, for four different stimulus intensity (80dBHL, 60dBHL, 40dBHL and 20dBHL), from 10 normal-hearing subjects (5 men and 5 women, from 20 to 52 years). Four examiners with expertise in the manual classification of ABR components participated in the study. The Bland-Altman statistical method was employed for the assessment of inter-examiner agreement and variability. The mean, standard deviation and error for the bias, which is the difference between examiners’ annotations, were estimated for each pair of examiners. Scatter plots and histograms were employed for data visualization and analysis. Results: In most comparisons the differences between examiner’s annotations were below 0.1 ms, which is clinically acceptable. In four cases, it was found a large error and standard deviation (>0.1 ms) that indicate the presence of outliers and thus, discrepancies between examiners. Conclusions: Our results quantify the inter-examiner agreement and variability of the manual analysis of ABR data, and they also allows for the determination of different patterns of manual ABR analysis

The approximate entropy of the electromyographic signals of tremor correlates with the osmotic fragility of human erythrocytes

<p>Abstract</p> <p>Background</p> <p>The main problem of tremor is the damage caused to the quality of the life of patients, especially those at more advanced ages. There is not a consensus yet about the origins of this disorder, but it can be examined in the correlations between the biological signs of aging and the tremor characteristics.</p> <p>Methods</p> <p>This work sought correlations between the osmotic fragility of erythrocytes and features extracted from electromyographic (EMG) activity resulting from physiological tremor in healthy patients (N = 44) at different ages (24-87 years). The osmotic fragility was spectrophotometrically evaluated by the dependence of hemolysis, provided by the absorbance in 540 nm (<it>A</it>_<it>54</it><it>o)</it>, on the concentration of NaCl. The data were adjusted to curves of sigmoidal regression and characterized by the half transition point (<it>H</it>_<it>50</it>), amplitude of lysis transition (<it>dx</it>) and values of <it>A</it>_{<it>540 </it>}in the curve regions that characterize the presence of lysed (<it>A</it>_<it>1</it>) and preserved erythrocytes (<it>A</it>_<it>2</it>). The approximate entropy was estimated from EMG signals detected from the extensor carpi ulnaris muscle during the movement of the hand of subjects holding up a laser pen towards an Archimedes spiral, fixed in a whiteboard. The evaluations were carried out with the laser pen at rest, at the center of the spiral, and in movement from the center to the outside and from outside to the center. The correlations among the parameters of osmotic fragility, tremor and age were tested.</p> <p>Results</p> <p>Negative correlations with age were found for <it>A</it>_{<it>1 </it>}and <it>dx</it>. With the hand at rest, a positive correlation with <it>H</it>_{<it>50 </it>}was found for the approximate entropy. Negative correlations with <it>H</it>_{<it>50 </it>}were found for the entropy with the hand in movement, as from the center to the outside or from the outside to the center of the spiral.</p> <p>Conclusion</p> <p>In healthy individuals, the increase in the erythrocyte osmotic fragility was associated with a decrease in the approximate entropy for rest tremor and with an increase of the entropy for movement tremor. This suggests that the neuromuscular degeneration associated with tremor entails also the mechanisms involved in the breakdown of structural homeostasis of the erythrocyte membrane.</p

Ergonomic assessment of an active orthosis for the rehabilitation of flexion and extension of Wrist

Muscular stiffness and limb rigidity are two main consequences of Parkinson’s disease. These motor symptoms may be present in distinct parts of the body, influencing functional tasks executed by hands. To aid people suffering from these motor symptoms, we developed an active wrist orthosis whose purpose is to enable increase the flexion and extension range of motion of the wrist joint. We identified five relevant ergonomic variables that should be considered when using the orthosis in the clinical practice: (i) device stability, (ii) forearm position; (iii) muscular strength; (iv) amplitude of motion; and (v) mass of the device. These variables were identified based on the observation of movements while users executed the flexion and extension of the wrist with and without the device. In this research, we present a description of the developed orthosis and an evaluation of the ergonomic variables (i), (ii) and (iii). An enhanced support structure has been used with the orthosis and shown to lead to a stability improvement. Electromyographic analysis showed that the use of the orthosis does not introduce undue muscular load on the user at distinct angular positions of the forearm

Rarity of monodominance in hyperdiverse Amazonian forests.

Tropical forests are known for their high diversity. Yet, forest patches do occur in the tropics where a single tree species is dominant. Such "monodominant" forests are known from all of the main tropical regions. For Amazonia, we sampled the occurrence of monodominance in a massive, basin-wide database of forest-inventory plots from the Amazon Tree Diversity Network (ATDN). Utilizing a simple defining metric of at least half of the trees ≥ 10 cm diameter belonging to one species, we found only a few occurrences of monodominance in Amazonia, and the phenomenon was not significantly linked to previously hypothesized life history traits such wood density, seed mass, ectomycorrhizal associations, or Rhizobium nodulation. In our analysis, coppicing (the formation of sprouts at the base of the tree or on roots) was the only trait significantly linked to monodominance. While at specific locales coppicing or ectomycorrhizal associations may confer a considerable advantage to a tree species and lead to its monodominance, very few species have these traits. Mining of the ATDN dataset suggests that monodominance is quite rare in Amazonia, and may be linked primarily to edaphic factors