Benito de Celis Alonso

A multi-methodological MR resting state network analysis to assess the changes in brain physiology of children with ADHD

The purpose of this work was to highlight the neurological differences between the MR resting state networks of a group of children with ADHD (pre-treatment) and an age-matched healthy group. Results were obtained using different image analysis techniques. A sample of n = 46 children with ages between 6 and 12 years were included in this study (23 per cohort). Resting state image analysis was performed using ReHo, ALFF and ICA techniques. ReHo and ICA represent connectivity analyses calculated with different mathematical approaches. ALFF represents an indirect measurement of brain activity. The ReHo and ICA analyses suggested differences between the two groups, while the ALFF analysis did not. The ReHo and ALFF analyses presented differences with respect to the results previously reported in the literature. ICA analysis showed that the same resting state networks that appear in healthy volunteers of adult age were obtained for both groups. In contrast, these networks were not identical when comparing the healthy and ADHD groups. These differences affected areas for all the networks except the Right Memory Function network. All techniques employed in this study were used to monitor different cerebral regions which participate in the phenomenological characterization of ADHD patients when compared to healthy controls. Results from our three analyses indicated that the cerebellum and mid-frontal lobe bilaterally for ReHo, the executive function regions in ICA, and the precuneus, cuneus and the clacarine fissure for ALFF, were the “hubs” in which the main inter-group differences were found. These results do not just help to explain the physiology underlying the disorder but open the door to future uses of these methodologies to monitor and evaluate patients with ADHD.

On the use of α-chloralose for repeated BOLD fMRI measurements in rats

Most animal experiments in neurosciences require anesthesia of the experimental animal. For fMRI experiments most neuroscientist would prefer (I) a recoverable anesthesia that would (II) allow strong BOLD responses which are (III) reproducibly obtained for the same animal in repetitive experiments. Strong BOLD responses are particularly needed if weak physiological stimuli like whisker deflection are used. A-chloralose, in contrast to isoflurane, fulfils the need for strong activation but has been traditionally considered as a terminal drug due to its negative physiological side effects. Here it is demonstrated, that new commercial α-chloralose in a careful application scheme allows for repeated fMRI studies on the same animal with similar responses after whisker stimulation. Only minor effects on the normal behavior were observed between drugs. These include a longer time to return to baseline values of food ingestion and slower tail reaction for the α-chloralose experiments.

Magnetic Resonance Techniques Applied to the Diagnosis and Treatment of Parkinson's Disease.

Parkinson’s disease (PD) affects at least 10 million people worldwide. It is a neurodegenerative disease, which is currently diagnosed by neurological examination. No neuroimaging investigation or blood biomarker is available to aid diagnosis and prognosis. Most effort toward diagnosis using magnetic resonance (MR) has been focused on the use of structural/anatomical neuroimaging and diffusion tensor imaging (DTI). However, deep brain stimulation, a current strategy for treating PD, is guided by MR imaging (MRI). For clinical prognosis, diagnosis, and follow-up investigations, blood oxygen level-dependent MRI, DTI, spectroscopy, and transcranial magnetic stimulation have been used. These techniques represent the state of the art in the last 5 years. Here, we focus on MR techniques for the diagnosis and treatment of Parkinson’s disease.

Lateralization of responses to vibrissal stimulation: Connectivity and information integration in the rat sensory-motor cortex assessed with fMRI

Rats move their whiskers or vibrissae to gain sensory information about the world surrounding them. A single whisker can work as an independent detector but normal whisking involves the use of several vibrissae in a bilateral fashion. Here we used blood oxygen level dependent (BOLD) contrast to acquire functional magnetic resonance images (fMRI) of the rat brain activity during uni- and bilateral whisker stimulations with different timing schemes under Isoflurane anesthesia. Experiments were performed to assess the integration of bilateral information produced by normal whisking behavior. First, we showed that it was possible to obtain BOLD whisker activations using Isoflurane harmless for the animals and thus allowing for future repetitive/longitudinal studies. Second, we obtained different BOLD activation patterns depending on the number of stimulated whiskers and timing of the stimulation scheme. Third, we found lateralization of BOLD activations in the somatosensory-motor cortex. It manifested itself in considerably larger activations in the right hemisphere during equal bilateral whisker stimulation. Fourth, we found Granger Causality Analysis (GCA) to be a useful tool in information integration analysis, as it reproduced the stimulus specific Cross-correlation Analysis results. Both analyses showed that the amount of whiskers stimulated and the timing of stimulation lead to specific dynamic connectivity patterns. Finally, by adding directionality information GCA revealed meaningful lateralization of information processing in the rat whisker system consistent with the observed BOLD activation patterns.

A New Analysis of Resting State Connectivity and Graph Theory Reveals Distinctive Short-Term Modulations due to Whisker Stimulation in Rats

Resting state (RS) connectivity has been increasingly studied in healthy and diseased brains in humans and animals. This paper presents a new method to analyze RS data from fMRI that combines multiple seed correlation analysis with graph-theory (MSRA). We characterize and evaluate this new method in relation to two other graph-theoretical methods and ICA. The graph-theoretical methods calculate cross-correlations of regional average time-courses, one using seed regions of the same size (SRCC) and the other using whole brain structure regions (RCCA). We evaluated the reproducibility, power, and capacity of these methods to characterize short-term RS modulation to unilateral physiological whisker stimulation in rats. Graph-theoretical networks found with the MSRA approach were highly reproducible, and their communities showed large overlaps with ICA components. Additionally, MSRA was the only one of all tested methods that had the power to detect significant RS modulations induced by whisker stimulation that are controlled by family-wise error rate (FWE). Compared to the reduced resting state network connectivity during task performance, these modulations implied decreased connectivity strength in the bilateral sensorimotor and entorhinal cortex. Additionally, the contralateral ventromedial thalamus (part of the barrel field related lemniscal pathway) and the hypothalamus showed reduced connectivity. Enhanced connectivity was observed in the amygdala, especially the contralateral basolateral amygdala (involved in emotional learning processes). In conclusion, MSRA is a powerful analytical approach that can reliably detect tiny modulations of RS connectivity. It shows a great promise as a method for studying RS dynamics in healthy and pathological conditions.

Temperature measurements in healthy and diabetic foot

The diabetic foot (DF) is not one but a series of conditions that affect the good function of the nervous and circulatory system in low extremities of a patient. These problems may eventually lead to amputation if small infections in foot are not detected in their early stages. In this project the temperature of the right foot in healthy and diabetic patients was measured. The aim was set at finding physiological differences and having a basis for noninvasive diagnosis methodologies that can be developed to assess the degree of infection and other DF problems in patients.

Diagnosis of ADHD children by wavelet analysis

The aim of this study was to find a diagnostic method to distinguish children with attention deficit hyperactivity disorder (ADHD) from their healthy counterparts. The method presented here was based in the characterization of scalograms that result from applying a Continuous Wavelet Transform (CWT) to blood oxygen level dependent (BOLD) signals. This data was obtained from control and ADHD patients during resting state functional magnetic resonance imaging (fMRI) of the whole brain. Significant differences between the two study groups were obtained in regions known to be affected by ADHD as well as other less usual regions.

Functional MR imaging (BOLD and resting States). Clinical and research applications

Since the first experiments with the blood oxygen level contrast (BOLD) by Ogawa et al. in 1990 1, functional MRI has been a basic tool in the research environment and in the clinical world as well as. In this plenary lecture we will first give an introduction on the physics as well as the physiology behind the BOLD effect. Then we will explain how standard functional (fMRI) and resting states (RS) experiments are performed and data is analyzed. After, we will highlight the clinical as well as the research applications of these techniques. The function of a medical physicist in this environment will be then described and finally, we will present some examples of the research developed by our collaborators in Mexico.

Modeling the effects of magnetic fields on clinical brachytherapy with Monte Carlo methods

In this project, the dose distributions of a clinical Iridium-192 (192Ir) brachytherapy source in the presence and absence of a magnetic field (3T strength) was calculated using the TOPAS Monte Carlo tool. We wanted to verify the existence of a more contained deposition of dose because of the Lorentz force induced by the external magnetic field. Based on those findings we suggest which kinds of tumors would be suited for a treatment combining brachytherapy and magnetic fields.

Wavelet analysis on electroencephalographic time series to identify key patterns corresponding to arm movements for brain-computer interface

Electroencephalography (EEG) is the recording of electric potentials produced by neuronal activity within the cerebral cortex by placing electrodes on specific locations of the scalp. In our research, subjects performed real and imaginary movements of their right arm as EEG signals were recorded with a 32-electrode cap at a sampling rate of 1 kHz. Our experiment consisted of twelve 30-second tests, each composed of 5 repetitions of two opposite movements. Indications on timing, speed, and type of movement were provided by a computer program during the experiment. The 12 tests included two base lines with open and closed eyes, four tests covering all degrees of freedom of the shoulder and elbow, and one for hand movement, as well as imagination of all five movements. We used the Continuous Wavelet Transform, using the complex Morlet mother wavelet, to identify how characteristic frequencies change over time. We then developed a method for generating binary classifier functions capable of distinguishing bet...