Pedro Antonio Valdés-Hernández

Cuban Neurosciences Center | CNEURO · Neuroimaging Department

Electrophysiological Source Imaging (ESI) is hampered by lack of “gold standards” for model validation. Concurrent electroencephalography (EEG) and electrocorticography (ECoG) experiments (EECoG) are useful for this purpose, especially primate models due to their flexibility and translational value for human research. Unfortunately, there is only o...

Concurrent electroencephalography (EEG) and electrocorticography (ECoG) recordings (namely EECoG) constitutes a thorough gold standard to validating EEG generative models and developing EEG source imaging (ESI) methods. Primate models have the unique advantages of both flexibility and translational value in human research. However, the complexity o...

In this paper, we describe a novel methodology, BC-VARETA, for estimating the Inverse Solution (sources activity) and its Precision Matrix (connectivity parameters) in the frequency domain representation of Stationary Time Series. The aims of this method are three. First: Joint estimation of Source Activity and Connectivity as a frequency domain li...

Current clinical practice in focal epilepsy involves brain source imaging (BSI) to localize brain areas where from interictal epileptiform discharges (IEDs) emerge. These areas, named irritative zones, have been useful to define candidate seizures-onset zones during pre-surgical workup. Since human histological data are mostly available from final...

Illustration of the M2 region for Wistar rats (green-left and red-right). Note that it distributes along the rostral-caudal direction. The irritative zone in M2-right was located on its caudal aspect (Bregma = -0.63 mm), while the one in M2-left was located more rostral (Bregma = +4.45 mm).

Introduction Concurrent EEG/ECoG recordings are crucial in providing a gold standard to develop EEG models, especially using primate models. These could be crucial for selecting methods for determining valid brain connectivity measures. Two essential points are to eliminate the unavoidable artifacts that contaminate such types of recordings as well...

Electrocorticography (ECoG) is an electrophysiological technique that records brain activity directly from the cortical surface with high temporal (ms) and spatial (mm) resolution. Its major limitations are in the high invasiveness and in the restricted field-of-view of the electrode grid, which partially covers the cortex. To infer brain activity...

The estimation of EEG generating sources constitutes an Inverse Problem (IP) in Neuroscience. This is an ill-posed problem due to the non-uniqueness of the solution and regularization or prior information is needed to undertake Electrophysiology Source Imaging. Structured Sparsity priors can be attained through combinations of (L1 norm-based) and (...

In spite of the large amount of existing neural models in the literature, there is a lack of a systematic review of the possible effect of choosing different initial conditions on the dynamic evolution of neural systems. In this short review we intend to give insights into this topic by discussing some published examples. First, we briefly introduc...

The curtain of technical limitations impeding rat multichannel non-invasive electroencephalography (EEG) has risen. Given the importance of this preclinical model, development and validation of EEG source imaging (ESI) is essential. We investigate the validity of well-known human ESI methodologies in rats which individual tissue geometries have bee...

Current high-throughput data acquisition technologies probe dynamical systems with different imaging modalities, generating massive data sets at different spatial and temporal resolutions posing challenging problems in multimodal data fusion. A case in point is the attempt to parse out the brain structures and networks that underpin human cognitive...

Evidence about high global and local parallel information processing between brain gray matter regions has being previously reported for different mammalian species (e.g. cat, monkey and humans). Here our goal is to study these characteristics but this time in mouse looking for other different mammalian species that shares this trait, which should...

Over the last decade, several papers have focused on the construction of highly detailed mouse high field magnetic resonance image (MRI) templates via non-linear registration to unbiased reference spaces, allowing for a variety of neuroimaging applications such as robust morphometric analyses. However, work in rats has only provided medium field MR...

Pearson correlations values between the six topological measures obtained for brain anatomical networks of mice subjects: clustering (C), characteristic path length (L), modularity (Q), global efficiency (Eglob), local efficiency (Eloc) and small-worldness (). For the sake of simplicity, here we present correlations only trough measures (i.e. witho...

Prediction accuracies (%) obtained for control and shiverer mice subjects according to results of each fiber tracking algorithm and the combination of all them, with regard clustering (C), characteristic path length (L), modularity (Q), global efficiency (Eglob), local efficiency (Eloc) or/and small-worldness (σ) brain anatomical network measures....

Individual conditioned probabilities of being a control subject with regard clustering (C), characteristic path length (L), modularity (Q), global efficiency (Eglob), local efficiency (Eloc) or small-worldness () measures obtained for the brain anatomical networks (estimated in individual native spaces) of control and shiverer mice subjects (preced...

Mouse considered regions for each brain hemisphere (modified WHS parcellation scheme). (DOC)

Gamma () and lambda () parameters obtained for the brain anatomical networks of control and shiverer mice groups. For each measure and fiber tracking algorithm, mean values are reported with their corresponding standard errors (i.e. the uncertainty of how the sample mean represents the underlying population mean). For each measure, the multivariate...

Individual conditioned probabilities of being a control subject with regard clustering (C), characteristic path length (L), modularity (Q), global efficiency (Eglob), local efficiency (Eloc) or small-worldness () measures obtained for the brain anatomical networks (using mean FA as an indicator of each fiber path's integrity) of control and shivere...

Individual conditioned probabilities of being a control subject with regard clustering (C), characteristic path length (L), modularity (Q), global efficiency (Eglob), local efficiency (Eloc) or small-worldness () measures obtained for the brain anatomical networks (with arc weights between nodes [regions] defined only as the number of connecting fi...

Neuroimaging classification procedures between normal and pathological subjects are sparse and highly dependent of an expert's clinical criterion. Here, we aimed to investigate whether possible brain structural network differences in the shiverer mouse mutant, a relevant animal model of myelin related diseases, can reflect intrinsic individual brai...

Patients with prosopagnosia are unable to recognize faces consciously, but when tested indirectly they can reveal residual identification abilities. The neural circuitry underlying this covert recognition is still unknown. One candidate for this function is the partial survival of a pathway linking the fusiform face area (FFA) and anterior-inferior...

In studies of EEG/MEG problems involving cortical sources, the cortex may be modeled by a 2-D manifold inside the brain. In such cases the primary or impressed current density over this manifold is usually approximated by a set of dipolar sources located at the vertices of the cortical surface tessellation. In this study, we analyze the different e...

There are few studies on the neuroanatomical determinants of EEG spectral properties that would explain its substantial inter-individual variability in spite of decades of biophysical modeling that predicts this type of relationship. An exception is the negative relation between head size and the spectral position of the alpha peak (P(alpha)) repor...

We examine the performance of approximate models (AM) of the head in solving the EEG inverse problem. The AM are needed when the individual's MRI is not available. We simulate the electric potential distribution generated by cortical sources for a large sample of 305 subjects, and solve the inverse problem with AM. Statistical comparisons are carri...

On March 8, 2008 in Havana, the Latin American Network for Brain Mapping (LABMAN) was created with participants from Argentina, Brazil, Colombia, Cuba and Mexico. The focus of LABMAN is to promote neuroimaging and systems neuroscience in the region through the implementation of training and exchange programs, and to increase public awareness of the...

In this paper we introduce a new method to characterize the intravoxel anisotropy based on diffusion-weighted imaging (DWI). The proposed solution, under a fully Bayesian formalism, deals with the problem of joint Bayesian Model selection and parameter estimation to reconstruct the principal diffusion profiles or primary fiber orientations in a vox...

A new methodology based on Diffusion Weighted Magnetic Resonance Imaging (DW-MRI) and Graph Theory is presented for characterizing the anatomical connections between brain gray matter areas. In a first step, brain voxels are modeled as nodes of a non-directed graph in which the weight of an arc linking two neighbor nodes is assumed to be proportion...

This work presents a new method to characterize anisotropy in a voxel in High Angular Resolution Diffusion Weighted Imaging (DWI). DWI is a MRI technique that measures locally the water diffusion in vivo in animal and human brains. Several papers have proposed anisotropy descriptions based on this neuroimaging tecnique by different ways (Tuch et. a...