Concurrence of form and function in developing networks and its role in synaptic pruning.

A fundamental question in neuroscience is how structure and function of neural systems are related. We study this interplay by combining a familiar auto-associative neural network with an evolving mechanism for the birth and death of synapses. A feedback loop then arises leading to two qualitatively different types of behaviour. In one, the network structure becomes heterogeneous and dissasortative, and the system displays good memory performance; furthermore, the structure is optimised for the particular memory patterns stored during the process. In the other, the structure remains homogeneous and incapable of pattern retrieval. These findings provide an inspiring picture of brain structure and dynamics that is compatible with experimental results on early brain development, and may help to explain synaptic pruning. Other evolving networks-such as those of protein interactions-might share the basic ingredients for this feedback loop and other questions, and indeed many of their structural features are as predicted by our model.

Undernutrition in the parental and first generation provokes an organ-specific response to oxidative stress on neonates of second filial generation of Wistar rats.

Undernutrition induces an increase of the oxidative stress that can predispose offspring to various diseases in adulthood through epigenetic reprogramming. The aim of this study was to evaluate the effects of intergenerational undernutrition on protein oxidation and antioxidant defence response on liver, heart and brain of the second-generation neonates (F2 ) of undernourished rats. For this purpose, both parents in parental (F0 ) and first generation (F1 ) were fed with a low-nutrient diet. Body mass and length decreased (p < 0.05) in F0 , F1 and F2 being the F1 males who exhibited a greater mass loss. A decrease in plasma albumin concentration was observed in F2 neonates (p < 0.05) and also a mass loss of liver, heart and brain (p < 0.05), although proportionally to body length reduction. Undernutrition increased levels of protein oxidation in liver and heart (p < 0.05) but not in brain (p > 0.05) while catalase activity increased only in brain (p < 0.05). In summary, intergenerational undernutrition modifies the antioxidant status through an organ-specific response, on F2 neonate rats, where the brain increased catalase activity to prevent a severe oxidative damage and support the vital functions of this key organ to maintain vital functions.

Emergence of low noise frustrated states in E/I balanced neural networks.

We study emerging phenomena in binary neural networks where, with a probability c synaptic intensities are chosen according with a Hebbian prescription, and with probability (1-c) there is an extra random contribution to synaptic weights. This new term, randomly taken from a Gaussian bimodal distribution, balances the synaptic population in the network so that one has 80%-20% relation in E/I population ratio, mimicking the balance observed in mammals cortex. For some regions of the relevant parameters, our system depicts standard memory (at low temperature) and non-memory attractors (at high temperature). However, as c decreases and the level of the underlying noise also decreases below a certain temperature Tt, a kind of memory-frustrated state, which resembles spin-glass behavior, sharply emerges. Contrary to what occurs in Hopfield-like neural networks, the frustrated state appears here even in the limit of the loading parameter α→0. Moreover, we observed that the frustrated state in fact corresponds to two states of non-vanishing activity uncorrelated with stored memories, associated, respectively, to a high activity or Up state and to a low activity or Down state. Using a linear stability analysis, we found regions in the space of relevant parameters for locally stable steady states and demonstrated that frustrated states coexist with memory attractors below Tt. Then, multistability between memory and frustrated states is present for relatively small c, and metastability of memory attractors can emerge as c decreases even more. We studied our system using standard mean-field techniques and with Monte Carlo simulations, obtaining a perfect agreement between theory and simulations. Our study can be useful to explain the role of synapse heterogeneity on the emergence of stable Up and Down states not associated to memory attractors, and to explore the conditions to induce transitions among them, as in sleep-wake transitions.

Isolated talonavicular joint arthrodesis through minimal incision surgery.

BACKGROUND: The purpose of this study was to analyze bony fusion and functional outcomes after talonavicular arthrodesis (TNA) using an original minimally invasive surgery (MIS). METHODS: There was a total of 11 feet in 11 patients who underwent TNA and were followed up for 47 months (range 40.8-53.1). Functional outcomes were measured by AOFAS and quality of life by eight sections of SF-36. RESULTS: Radiographic and clinical consolidation was achieved in 10 of 11 cases. In the AOFAS score, physical function improved a mean of 34.4 points (95% CI: 23.2-45.6; p<.0001) and pain improved a mean of 23.6 points (95% CI: 17.4-29.8; p<.0001). One osteoporotic and rheumatic patient had a non-union. No cases of early complications, such as wound infections, neurovascular damage or delayed wound healing, occurred. CONCLUSION: Isolated TNA by MIS could be an option for the treatment of TN arthritis, especially for patients at greater risk of wound healing complications. LEVEL OF EVIDENCE: Level IV, case series.

Effects of dynamic synapses on noise-delayed response latency of a single neuron.

The noise-delayed decay (NDD) phenomenon emerges when the first-spike latency of a periodically forced stochastic neuron exhibits a maximum for a particular range of noise intensity. Here, we investigate the latency response dynamics of a single Hodgkin-Huxley neuron that is subject to both a suprathreshold periodic stimulus and a background activity arriving through dynamic synapses. We study the first-spike latency response as a function of the presynaptic firing rate f. This constitutes a more realistic scenario than previous works, since f provides a suitable biophysically realistic parameter to control the level of activity in actual neural systems. We first report on the emergence of classical NDD behavior as a function of f for the limit of static synapses. Second, we show that when short-term depression and facilitation mechanisms are included at the synapses, different NDD features can be found due to their modulatory effect on synaptic current fluctuations. For example, an intriguing double NDD (DNDD) behavior occurs for different sets of relevant synaptic parameters. Moreover, depending on the balance between synaptic depression and synaptic facilitation, single NDD or DNDD can prevail, in such a way that synaptic facilitation favors the emergence of DNDD whereas synaptic depression favors the existence of single NDD. Here we report the existence of the DNDD effect in the response latency dynamics of a neuron.

Minimal incision surgery for tibiotalocalcaneal arthrodesis.

BACKGROUND: Tibiotalocalcaneal arthrodesis (TTCA) is a salvage procedure for severe diseases involving ankle and subtalar joints. However, this procedure is often associated with postoperative complications related to preoperative comorbidities. The purpose of this study was to present the clinical and functional outcomes of a consecutive series of TTCA using an original operative approach based on minimal incision surgery (MIS). METHODS: Forty patients were followed prospectively for a mean (SD) of 31 (12.5) months. Clinical data, which included x-rays, American Orthopaedic Foot and Ankle Society (AOFAS) ankle-hindfoot score, SF-36 scores, and a patient satisfaction survey, were collected. A further 25 patients were examined retrospectively. RESULTS: In the prospective group (n = 40), the mean AOFAS score improved by 44.8 points 1 year after the intervention (95% confidence interval [CI], 40.6-48.9), and the SF-36 improved by a mean of 17.5 points (95% CI, 1.4-20.9) in the mental component summary (MCS) score and 11.5 points (95% CI, 8.3-14.7) in the physical component summary (PCS) score. In the prospective group, postsurgical pain correlated with MCS score (r = 0.47, P < .001). In the entire group, bony union (defined as radiographic consolidation and absence of clinical symptoms) was observed in 86% of cases. Two deep infections, 2 nonunions in patients with preoperative persistent ulcers, and 7 delayed unions were the major complications observed in the entire group. One patient required amputation. No cases of superficial infection, wound dehiscence, or deep venous thrombosis were recorded. CONCLUSION: To our knowledge, the present series represents the largest study on TTCA using MIS. The data obtained in the present study showed clinical and functional improvement after surgery and similar bony union rates as previously reported in the literature but with fewer complications related to the surgical wounds. LEVEL OF EVIDENCE: Level IV, case series.

Plantar pressures in children with congenital talipes equino varus--a comparison between surgical management and the Ponseti technique.

The Ponseti technique for treatment for Congenital Talipes Equinovarus (CTEV) was introduced in the authors' institution in 2001, substituting a more traditional orthopaedic approach which involved surgery. There is currently limited published information regarding the differences in clinical outcomes between these two techniques, particularly in relation to plantar pressure analysis. This study aims to determine differences in pedobarographic outcome in children with CTEV, treated with either a surgical or Ponseti approach. A high resolution pedobarograph was used to record plantar pressure distribution in 52 children with CTEV and 26 children with typical development. Data were imported into Matlab where a custom programme was developed for processing and analysing pedobarographic recordings. There were significant differences in both treatment groups compared to the typically developed group (p<0.05) for most measurements. The most salient differences between treatment groups were (i) at the hind-foot where the Ponseti group had significantly lower maximum peak pressures (p<0.05); (ii) at the lateral mid-foot where children treated by the Ponseti approach showed significantly larger peak force (p<0.001), average peak pressure (p<0.001) and maximum peak pressure (p<0.01); (iii) at the lateral fore-foot where the surgical group showed lower average peak pressure (p<0.05); and (iv) in the medial/lateral fore-foot ratio where the Ponseti group showed significantly lower values (p<0.05). Plantar pressure analysis is a complementary measurement for the assessment of gait in children with CTEV. Data presented in this study showed that while there were deviations in children with CTEV, the differences observed between treatment groups suggest children in the Ponseti group have some level of under correction or recurrence.

Isolated subtalar arthrodesis through minimal incision surgery.

BACKGROUND: In recent years there has been an increase in the use of minimally invasive techniques, such as arthroscopy, percutaneous, and minimally invasive incisions, for foot and ankle surgery. The purpose of this study was to analyze the fusion rate and clinical results of isolated subtalar arthrodesis (ISA) using the novel and original technique of minimal incision surgery (MIS). METHODS: There were a total of 77 feet in 76 patients who underwent ISA and were followed for 50 months on average (range, 15-108). The first 30 cases were evaluated retrospectively, and 47 cases were evaluated prospectively. MIS without tourniquet was used in all cases and fusion was assessed radiographically and clinically. Clinical outcome measures used were the Angus and Cowell Scoring System, AOFAS Ankle-Hindfoot, the SF-36, and a patient satisfaction questionnaire 12 months after the intervention. RESULTS: Radiographic and clinical consolidation was achieved in 92% of cases. Main outcomes were "good" in 57 patients as determined by the Angus and Cowell criteria, with 13 "fair" and 7 "poor" results. In the prospective group, AOFAS scores improved by 47.6 points (95% CI: 50.7-42.5) 12 months after surgical intervention. SF-36 outcomes improved by 14.5 points (95% CI: 11.58-17.31) in the mental summary component and 4.2 points (95% CI: 2.2-6.1) in the physical summary component. We recorded no cases of early complications such as wound infections, neurovascular damage, or delayed wound healing. CONCLUSIONS: To our knowledge, the present series represents the largest study on subtalar arthrodesis using minimally invasive surgery. The data obtained showed a similar rate of bony union and clinical outcomes compared with the literature, but without early wound complications. ISA using the MIS technique was a good option for patients at greater risk of wound healing complications. LEVEL OF EVIDENCE: Level IV, case series.

[Anterolateral ankle pain: differential diagnosis and approach. A case report]. / Dolor anterolateral de tobillo, diagnóstico diferencial y abordaje. Presentación de un caso.

The ankle soft tissue pathology represents a very painful disorder for patients who, often times, are not precisely diagnosed. Anterolateral ankle impingement is a condition that occurs in young people and athletes due to a plantar flexion-inversion mechanism. We report a case of anterolateral ankle impingement describing the arthroscopic technique and making the differential diagnosis considering other conditions.

Pelvic kinematics and their relationship to gait type in hemiplegic cerebral palsy.

While there is general clinical consensus that children with Unilateral Spastic Cerebral Palsy (USCP) walk with an increased anterior pelvic tilt and the affected hemipelvis retracted, there is less agreement to observations in the coronal plane. Furthermore, the relationship of 3D pelvic kinematic parameters to the Winters, Gage and Hicks (WGH) hemiplegic gait classification has not been reported in the literature. Valid 3-D kinematic gait data were obtained in a representative population of 91 children with hemiplegia (56 M, mean age 10.8 yrs, age range 5-18 yrs; WGH classification Type I n=32, II n=5, III n=7, IV n=9, unclassified n=38). Deviations of symmetry and range of movement from our normative data set (n=48; 26F; mean age 9.9 yrs; age range 5-18 yrs) for mean tilt, tilt range, and difference between affected and unaffected sides for obliquity and rotation were defined as normal, mild, moderate or severe (<1 standard deviation (SD); >1<2 SD; >2<3 SD; >3 SD, respectively). Increased pelvic tilt range (>1 SD) was observed in 60.4% and pelvic retraction (>1 SD) was observed in 61.5% of USCP children in this study. Weak but significant correlations were found between WGH gait type and pelvic obliquity (ρ=0.29; p<0.01). No other correlations were found. Factors such as leg length discrepancy modify the functional leg length throughout the gait cycle contributing to the deviations observed. The evaluation of gait abnormalities in USCP should not be limited to the use of classifications based on sagittal plane kinematics but should seek to include 3D kinematics of the pelvis.

Anaerobic treatment of a medium strength industrial wastewater at low-temperature and short hydraulic retention time: a pilot-scale experience.

The aim of this work was to evaluate the performance of a pilot-scale upflow anaerobic sludge blanket (UASB) reactor during the treatment of cereal-processing industry wastewater under low-temperature conditions (17 degrees C) for more than 300 days. The applied organic loading rate (OLR(appl)) was gradually increased from 4 to 6 and 8 kg COD(sol)/m3d by increasing the influent soluble chemical oxygen demand (COD(sol)), while keeping the hydraulic retention time constant (5.2 h). The removal efficiency was high (82 to 92%) and slightly decreased after increasing the influent COD(sol) and the OLR(appl). The highest removed organic loading rate (OLR(rem)) was reached when the UASB reactor was operated at 8 kg COD(sol)/m3d and it was two times higher than that obtained for an OLR(appl) of 4 kg COD(sol)/m3d. Some disturbances were observed during the experimentation. The formation of biogas pockets in the sludge bed significantly complicated the biogas production quantification, but did not affect the reactor performance. The volatile fatty acids in the effluent were low, but increased as the OLR(appl) increased, which caused an increment of the effluent COD(sol). Anaerobic treatment at low temperature was a good option for the biological pre-treatment of cereal processing industry wastewater.

Dolor anterolateral de tobillo: diagnóstico diferencial y abordaje terapéutico / Anterolateral ankle pain: differential diagnosis and therapeutic approach

La patología de partes blandas del tobillo supone trastornos muy dolorosos para los pacientes que en muchas ocasiones carecen de diagnóstico preciso. El pinzamiento anterolateral de tobillo es una patología que aparece en gente joven y deportistas por mecanismo de flexión plantar-inversión. Se presenta un caso de pinzamiento anterolateral de tobillo, describiendo la técnica artroscópica y planteando el diagnóstico diferencial con otras patologías (AU)

Diseases of the ankle soft tissues are very painful disorders for patients for whom many times there is no accurate diagnosis. Anterolateral ankle impingement is a condition occurring in young people and athletes for plantar-inversion flexion mechanism. We report the case of anterolateral ankle impingement with a description of the arthroscopic technique and considering the differential diagnosis with other diseases (AU)

Unstable dynamics, nonequilibrium phases, and criticality in networked excitable media.

Excitable systems are of great theoretical and practical interest in mathematics, physics, chemistry, and biology. Here, we numerically study models of excitable media, namely, networks whose nodes may occasionally be dormant and the connection weights are allowed to vary with the system activity on a short-time scale, which is a convenient and realistic representation. The resulting global activity is quite sensitive to stimuli and eventually becomes unstable also in the absence of any stimuli. Outstanding consequences of such unstable dynamics are the spontaneous occurrence of various nonequilibrium phases--including associative-memory phases and one in which the global activity wanders irregularly, e.g., chaotically among all or part of the dynamic attractors--and 1/f noise as the system is driven into the phase region corresponding to the most irregular behavior. A net result is resilience which results in an efficient search in the model attractor space that can explain the origin of some observed behavior in neural, genetic, and ill-condensed matter systems. By extensive computer simulation we also address a previously conjectured relation between observed power-law distributions and the possible occurrence of a "critical state" during functionality of, e.g., cortical networks, and describe the precise nature of such criticality in the model which may serve to guide future experiments.

Instabilities in attractor networks with fast synaptic fluctuations and partial updating of the neurons activity.

We present and study a probabilistic neural automaton in which the fraction of simultaneously-updated neurons is a parameter, rhoin(0,1). For small rho, there is relaxation towards one of the attractors and a great sensibility to external stimuli and, for rho > or = rho(c), itinerancy among attractors. Tuning rho in this regime, oscillations may abruptly change from regular to chaotic and vice versa, which allows one to control the efficiency of the searching process. We argue on the similarity of the model behavior with recent observations, and on the possible role of chaos in neurobiology.

Competition between synaptic depression and facilitation in attractor neural networks.

We study the effect of competition between short-term synaptic depression and facilitation on the dynamic properties of attractor neural networks, using Monte Carlo simulation and a mean-field analysis. Depending on the balance of depression, facilitation, and the underlying noise, the network displays different behaviors, including associative memory and switching of activity between different attractors. We conclude that synaptic facilitation enhances the attractor instability in a way that (1) intensifies the system adaptability to external stimuli, which is in agreement with experiments, and (2) favors the retrieval of information with less error during short time intervals.

Amniotic membrane transplantation for conjunctival epithelization of exposed dermis-fat [corrected] graft.

We report the use of amniotic membrane over dermis-fat graft to improve conjunctival epithelization when fat is exposed. A 38-year-old male with previous history of orbital implant extrusion managed with a dermis-fat graft, presented with exposed fat secondary to dermis retraction in its central area. This caused difficulty with the conjunctival growth. Eighteen days after the amniotic membrane graft placement, a complete conjunctival reepithelization and an appropriate ocular prosthesis adaptation were achieved. Therefore, the amniotic membrane graft is a useful method to improve conjunctival growth in cases of dermis-fat grafts with fat exposure and limited conjunctiva, are present.

Control of neural chaos by synaptic noise.

We study neural automata - or neurobiologically inspired cellular automata - which exhibits chaotic itinerancy among the different stored patterns or memories. This is a consequence of activity-dependent synaptic fluctuations, which continuously destabilize the attractor and induce irregular hopping to other possible attractors. The nature of these irregularities depends on the dynamic details, namely, on the intensity of the synaptic noise and the number of sites of the network, which are synchronously updated at each time step. Varying these factors, different regimes occur, ranging from regular to chaotic dynamics. As a result, and in absence of external agents, the chaotic behavior may turn regular after tuning the noise intensity. It is argued that a similar mechanism might be on the basis of self-controlling chaos in natural systems.

Effects of fast presynaptic noise in attractor neural networks.

We study both analytically and numerically the effect of presynaptic noise on the transmission of information in attractor neural networks. The noise occurs on a very short timescale compared to that for the neuron dynamics and it produces short-time synaptic depression. This is inspired in recent neurobiological findings that show that synaptic strength may either increase or decrease on a short timescale depending on presynaptic activity. We thus describe a mechanism by which fast presynaptic noise enhances the neural network sensitivity to an external stimulus. The reason is that, in general, presynaptic noise induces nonequilibrium behavior and, consequently, the space of fixed points is qualitatively modified in such a way that the system can easily escape from the attractor. As a result, the model shows, in addition to pattern recognition, class identification and categorization, which may be relevant to the understanding of some of the brain complex tasks.

Biomechanical approaches applied to the lower and upper limb for the measurement of spasticity: a systematic review of the literature.

PURPOSE: To review and characterise biomechanical approaches for the measurement of spasticity as one component of the upper motor neurone syndrome. METHOD: Systematic literature searches based on defined constructs and a four-step review process of approaches used or described to measure spasticity, its association with function or associated phenomena. Most approaches were limited to individual joints and therefore, to reflect this trend, references were grouped according to which body joint(s) were investigated or whether it addressed a functional activity. For each joint, references were further sub-divided into the types of measurement method described. RESULTS: A database of 335 references was established for the review process. The knee, ankle and elbow joints were the most popular, perhaps reflecting the assumption that they are mono-planar in movement and therefore simpler to assess. Seven measurement methods were identified: five involving passive movement (manual, controlled displacement, controlled torque, gravitational and tendon tap) and two involving active movement (voluntary and functional). Generally, the equipment described was in an experimental stage and there was a lack of information on system properties, such as accuracy or reliability. Patient testing was either by cohort or case studies. The review also conveyed the myriad of interpretations of the concept of spasticity. CONCLUSIONS: Though biomechanical approaches provide quantitative data, the review highlighted several limitations that have prevented them being established as an appropriate method for clinical application to measure spasticity.