The existence of dedicated neuronal modules such as those organized in the cerebral cortex, thalamus, basal ganglia, cerebellum, or spinal cord raises the question of how these functional modules are coordinated for appropriate motor behavior. Study of human locomotion offers an interesting field for addressing this central question. The coordination of the elevation of the 3 leg segments under a planar covariation rule (Borghese et al., 1996) was recently modeled (Barliya et al., 2009) by phase-adjusted simple oscillators shedding new light on the understanding of the central pattern generator (CPG) processing relevant oscillation signals. We describe the use of a dynamic recurrent neural network (DRNN) mimicking the natural oscillatory behavior of human locomotion for reproducing the planar covariation rule in both legs at different walking speeds. Neural network learning was based on sinusoid signals integrating frequency and amplitude features of the first three harmonics of the sagittal elevation angles of the thigh, shank, and foot of each lower limb. We verified the biological plausibility of the neural networks. Best results were obtained with oscillations extracted from the first three harmonics in comparison to oscillations outside the harmonic frequency peaks. Physiological replication steadily increased with the number of neuronal units from 1 to 80, where similarity index reached 0.99. Analysis of synaptic weighting showed that the proportion of inhibitory connections consistently increased with the number of neuronal units in the DRNN. This emerging property in the artificial neural networks resonates with recent advances in neurophysiology of inhibitory neurons that are involved in central nervous system oscillatory activities. The main message of this study is that this type of DRNN may offer a useful model of physiological central pattern generator for gaining insights in basic research and developing clinical applications.

EEG-based systems have been the most widely used in the field of Brain-Computer Interfaces (BCI) for two decades. Plenty of applications have been proposed from games to rehabilitation systems. Until recently, EEG recording devices were too expensive for an end-user. Today, several low-cost alternatives have appeared on the market. The most sophisticated of these low-cost devices is the Emotiv Epoc headset. Some studies reported that this device is suitable for customers in terms of performance. However, none of the previous studies reported to what extent the Emotiv headset is working well compared to a medical system. The aim of this paper is thus to scientifically compare a medical system and the Emotiv Epoc headset by determining their respective performances in the context of a P300 BCI paradigm. In this study, seven healthy subjects performed P300 experiments and two different conditions were studied: sitting on a chair and walking on a treadmill at constant speed. Results show that the Emotiv headset, although able to record EEG data and not only artifacts, is sometimes significantly worse than a medical system. Those results suggest that the design of a specific low-cost EEG recording systems for rehabilitation purposes at a low price is still required.

This paper presents MINDWALKER, which is an ambitious EC funded research project coordinated by Space Applications Services aiming at the development of novel Brain Neural Computer Interfaces (BNCI) and robotics technologies, with the goal of obtaining a crutch-less assistive lower limbs exoskeleton, with non-invasive brain control approach as main strategy. Complementary BNCI control approaches such as arms electromyograms (EMG) are also researched. In the last phase of the project, the developed system should undergo a clinical evaluation with Spinal Cord Injured (SCI) subjects at the Fondazione Santa Lucia, Italy.

Success in locomotor rehabilitation programs can be improved with the use of brain-computer interfaces (BCIs). Although a wealth of research has demonstrated that locomotion is largely controlled by spinal mechanisms, the brain is of utmost importance in monitoring locomotor patterns and therefore contains information regarding central pattern generation functioning. In addition, there is also a tight coordination between the upper and lower limbs, which can also be useful in controlling locomotion. The current paper critically investigates different approaches that are applicable to this field: the use of electroencephalogram (EEG), upper limb electromyogram (EMG), or a hybrid of the two neurophysiological signals to control assistive exoskeletons used in locomotion based on programmable central pattern generators (PCPGs) or dynamic recurrent neural networks (DRNNs). Plantar surface tactile stimulation devices combined with virtual reality may provide the sensation of walking while in a supine position for use of training brain signals generated during locomotion. These methods may exploit mechanisms of brain plasticity and assist in the neurorehabilitation of gait in a variety of clinical conditions, including stroke, spinal trauma, multiple sclerosis, and cerebral palsy.

In this paper we detail a phase lagging model of brain response to external stimuli. The model is derived using the basic laws of physics like conservation of energy law. This model eliminates the paradox of instantaneous propagation of the action potential in the brain. The solution of this model is then presented. The model is further applied in the case of a single neuron and is verified by simulating a single action potential. The results of this modeling are useful not only for the fundamental understanding of single action potential generation, but also they can be applied in case of neuronal interactions, where the results can be verified against the real EEG signal.

Recent research has shown that a P300 system can be used while walking without requiring any specific gait-related artifact removal techniques. Also, standard EEG-based Brain-Computer Interfaces (BCI) have not been really assessed for lower limb rehabilitation/prosthesis. Therefore, this paper gives a first baseline estimation (for future BCI comparisons) of the subjective and objective performances of a four-state P300 BCI plus a non-control state for lower-limb rehabilitation purposes. To assess usability and workload, the System Usability Scale and the NASA Task Load Index questionnaires were administered to five healthy subjects after performing a real-time treadmill speed control. Results show that the P300 BCI approach could suit fitness and rehabilitation applications, whereas prosthesis control, which suffers from a low reactivity, appears too sensitive for risky and crowded areas.

usefulness in the field of motor control as diagnostic tools and potential prosthetic controllers.

Brain-computer interfaces (BCIs) enable their users to interact with their surrounding environment using the activity of their brain only, without activating any muscle. This technology provides severely disabled people with an alternative mean to communicate or control any electric device. On the other hand, BCI applications are more and more dedicated to healthier people, with the aim of giving them access to augmented reality or new rehabilitation tools. As it is noninvasive, light and relatively cheap, electroencephalography (EEG) is the most used acquisition technique to record cerebral activity of the BCI users. However, when using such type of BCI, user movements are likely to provoke motions of the measuring electrodes which can severely damage the EEG quality. Thus, current BCI technology requires that the user sits and performs as little movements as possible. This is of course a strong limitation of BCI for use in ordinary life. Very recently, preliminary studies have been published in the literature and suggest that BCI applications can be realized even in the physically moving context. In this paper, we thoroughly investigate the possibility to develop a P300-based BCI system in ambulatory condition. The study is based on experimental data recorded with seven subjects executing a visual P300 speller-like discrimination task while simultaneously walking at different speeds on a treadmill. It is demonstrated that a P300-based BCI is definitely feasible in such conditions. Different artifact correction methods are described and discussed in detail. To conclude, a recommended approach is given for the development of a real-time application.

No adequate mathematical model of the brain activity exists until today.This is due to the fact that the brain is an extremely complex non-linear system.This research work presents a novel mathematical model of the human brain response to external stimuli.Using the basic laws of physics: the conservation of energy principle, the second law of thermodynamics and the least action principle, a phase-lagging diffusion model of a single neuron action potential has been proposed with validation.This model overcomes the paradox of instantaneous propagation in the classical diffusion equation by introducing a time lag.Applying the external stimuli, simulated as a series of Gaussian energy pulses, to this model has generated fractal time series similar to EEG.Various functions describing concepts of the importance of information, relevance of information and information gain have been introduced.Measures like the Hurst exponent and the Jeffreys measure have been proposed to quantify the stimulus and its effects.Software has been developed to analyse the captured EEG signals from subjects and compute fractal measures of the signals.Analysis of the effects of different auditory, visual and olfactory stimuli on different subjects is performed and results have been provided with applications to real life.

The present paper discusses a novel technique - dynamic analysis of multi-fractal time series - that may become a useful tool for improving the understanding of transition from laminar to turbulent flow regimes. It is proposed to view records of velocity and temperature fluctuations as fractal time series, whose measures, such as fractal dimensions, the Jeffreys divergence measure, and the Hurst exponent, themselves vary in time. The validation tests show that the variations of the fractal measures may be used for quantifying the transition between the flow regimes.