Spatial Statistical Models: an overview under the Bayesian Approach

Spatial documentation is exponentially increasing given the availability of Big IoT Data, enabled by the devices miniaturization and data storage capacity. Bayesian spatial statistics is a useful statistical tool to determine the dependence structure and hidden patterns over space through prior knowledge and data likelihood. Nevertheless, this modeling class is not well explored as the classification and regression machine learning models given their simplicity and often weak (data) independence supposition. In this manner, this systematic review aimed to unravel the main models presented in the literature in the past 20 years, identify gaps, and research opportunities. Elements such as random fields, spatial domains, prior specification, covariance function, and numerical approximations were discussed. This work explored the two subclasses of spatial smoothing global and local.Comment: 33 pages, 6 figure

Multi-scale and cross-dimensional TMS mapping: A proof of principle in patients with Parkinson’s disease and deep brain stimulation

IntroductionTranscranial magnetic stimulation (TMS) mapping has become a critical tool for exploratory studies of the human corticomotor (M1) organization. Here, we propose to gather existing cutting-edge TMS-EMG and TMS-EEG approaches into a combined multi-dimensional TMS mapping that considers local and whole-brain excitability changes as well as state and time-specific changes in cortical activity. We applied this multi-dimensional TMS mapping approach to patients with Parkinson’s disease (PD) with Deep brain stimulation (DBS) of the sub-thalamic nucleus (STN) ON and OFF. Our goal was to identifying one or several TMS mapping-derived markers that could provide unprecedent new insights onto the mechanisms of DBS in movement disorders.MethodsSix PD patients (1 female, mean age: 62.5 yo [59–65]) implanted with DBS-STN for 1 year, underwent a robotized sulcus-shaped TMS motor mapping to measure changes in muscle-specific corticomotor representations and a movement initiation task to probe state-dependent modulations of corticospinal excitability in the ON (using clinically relevant DBS parameters) and OFF DBS states. Cortical excitability and evoked dynamics of three cortical areas involved in the neural control of voluntary movements (M1, pre-supplementary motor area – preSMA and inferior frontal gyrus – IFG) were then mapped using TMS-EEG coupling in the ON and OFF state. Lastly, we investigated the timing and nature of the STN-to-M1 inputs using a paired pulse DBS-TMS-EEG protocol.ResultsIn our sample of patients, DBS appeared to induce fast within-area somatotopic re-arrangements of motor finger representations in M1, as revealed by mediolateral shifts of corticomuscle representations. STN-DBS improved reaction times while up-regulating corticospinal excitability, especially during endogenous motor preparation. Evoked dynamics revealed marked increases in inhibitory circuits in the IFG and M1 with DBS ON. Finally, inhibitory conditioning effects of STN single pulses on corticomotor activity were found at timings relevant for the activation of inhibitory GABAergic receptors (4 and 20 ms).ConclusionTaken together, these results suggest a predominant role of some markers in explaining beneficial DBS effects, such as a context-dependent modulation of corticospinal excitability and the recruitment of distinct inhibitory circuits, involving long-range projections from higher level motor centers and local GABAergic neuronal populations. These combined measures might help to identify discriminative features of DBS mechanisms towards deep clinical phenotyping of DBS effects in Parkinson’s Disease and in other pathological conditions

Automatized set-up procedure for transcranial magnetic stimulation protocols

International audienceTranscranial Magnetic Stimulation (TMS) established itself as a powerful technique for probing and treating the human brain. Major technological evolutions, such as neuronavigation and robotized systems, have continuously increased the spatial reliability and reproducibility of TMS, by minimizing the influence of human and experimental factors. However, there is still a lack of efficient setup procedure, which prevents the automation of TMS protocols. For example, the setup procedure for defining the stimulation intensity specific to each subject is classically done manually by experienced practitioners, by assessing the motor cortical excitability level over the motor hotspot (HS) of a targeted muscle. This is time-consuming and introduces experimental variability. Therefore, we developed a probabilistic Bayesian model (AutoHS) that automatically identifies the HS position. Using virtual and real experiments, we compared the efficacy of the manual and automated procedures. AutoHS appeared to be more reproducible, faster, and at least as reliable as classical manual procedures. By combining AutoHS with robotized TMS and automated motor threshold estimation methods, our approach constitutes the first fully automated setup procedure for TMS protocols. The use of this procedure decreases inter-experimenter variability while facilitating the handling of TMS protocols used for research and clinical routine. Highlights • Automatized setup procedures would facilitate TMS experiments and increase reproducibility • We developed a Bayesian model aiming at automatically finding the motor hotspot • Implementation of this model in a robotized TMS system allows the automatic search for the motor hotspo

A study on the tolerance of intermittent hypoxia training and its effect on sensory and motor spinal pathways

Intermittent hypoxia is defined as brief exposures of low oxygen concentration. It is commonly associated with a disease state known as obstructive sleep apnoea, however, a mild to moderate form can benefit patients with spinal cord injury. Studies have shown that a single exposure of intermittent hypoxia enhances the excitability of spinal connections spared following a cord injury. The enhanced excitability may last for more than an hour and during this time medical professionals can use conventional rehabilitation therapies and offer a heighten rehabilitation outcome and perhaps even speed up recovery. Nevertheless, there is a limited understanding in the tolerance of the intermittent hypoxia protocol given to spinal cord injury patients and its effects on spinal pathways. The purpose of this thesis was to go back to the basics and study intermittent hypoxia on healthy volunteers. To examine the tolerance, and to also find an appropriate IHT intervention that challenged the homeostasis of healthy volunteers, measurements of heart rate, saturation of oxygen in the blood, and blood pressure were taken. To analyse the response of the autonomic nervous system, heart rate variability was analysed. Regarding the investigation on spinal pathways, the effect on the sensory and motor pathways was examined by recording somatosensory evoked potentials and motor evoked potentials. These measurements were taken prior, during and up to 30 minutes following the IHT intervention. Results showed that a single exposure of IHT given to healthy young volunteers was well tolerated and its effects were long lasting and localised on the corticospinal tract following a stimulus on the motor cortex. Yet, to know the true potential of its ability to alter corticospinal excitability it is also essential to study its effect on skeletal muscle metabolism and as a result on force.Intermittent hypoxia is defined as brief exposures of low oxygen concentration. It is commonly associated with a disease state known as obstructive sleep apnoea, however, a mild to moderate form can benefit patients with spinal cord injury. Studies have shown that a single exposure of intermittent hypoxia enhances the excitability of spinal connections spared following a cord injury. The enhanced excitability may last for more than an hour and during this time medical professionals can use conventional rehabilitation therapies and offer a heighten rehabilitation outcome and perhaps even speed up recovery. Nevertheless, there is a limited understanding in the tolerance of the intermittent hypoxia protocol given to spinal cord injury patients and its effects on spinal pathways. The purpose of this thesis was to go back to the basics and study intermittent hypoxia on healthy volunteers. To examine the tolerance, and to also find an appropriate IHT intervention that challenged the homeostasis of healthy volunteers, measurements of heart rate, saturation of oxygen in the blood, and blood pressure were taken. To analyse the response of the autonomic nervous system, heart rate variability was analysed. Regarding the investigation on spinal pathways, the effect on the sensory and motor pathways was examined by recording somatosensory evoked potentials and motor evoked potentials. These measurements were taken prior, during and up to 30 minutes following the IHT intervention. Results showed that a single exposure of IHT given to healthy young volunteers was well tolerated and its effects were long lasting and localised on the corticospinal tract following a stimulus on the motor cortex. Yet, to know the true potential of its ability to alter corticospinal excitability it is also essential to study its effect on skeletal muscle metabolism and as a result on force