Nuestros investigadores

Maite Aznárez Sanado


Publicaciones científicas más recientes (desde 2010)

Autores: Eudave Ramos, Luis Humberto; Aznárez Sanado, Maite; Luis García, Elkin Oswaldo; et al.
ISSN 1931-7557  Vol. 11  Nº 4  2017  págs. 986 - 997
Previous research on motor sequence learning (MSL) in the elderly has focused mainly on unilateral tasks, even though bilateral coordination might be impaired in this age group. In this fMRI study, 28 right-handed elderly subjects were recruited. The paradigm consisted of a Novel and a simple Control sequence executed with the right (R), left (L) and both hands (B). Behavioral performance (Accuracy[AC], Inter-tap Interval[ITI]) and associated brain activity were assessed during early learning. Behavioral performance in the Novel task was similar between unilateral conditions whereas in the bimanual condition more errors and slower motor execution were observed. Brain activity increases during learning showed differences between Conditions: R showed increased activity in pre-SMA, basal ganglia and left hippocampus while B showed activity increments mainly in posterior parietal cortex and cerebellum. L did not show any activity modulation during learning. Performance correlates for AC (related to spatial success) and ITI (related to accurate timing) shared a cortico-basal-cerebellar network. However, it was found that the ITI regressor presented additional significant correlations with activity in SMA and basal ganglia in R. The AC regressor showed additional significant correlations with activity in more extended thalamic and cerebellar areas in B. The present findings suggest that, behaviorally, the spatial and temporal components of MSL are impaired in elderly subjects when using both hands. Additionally, differential brain activity patterns were found across hand modalities. The results obtained reveal the existence of a highly specialized network in the dominant hand and identify areas specifically involved in bimanual coordination.
Autores: Ruiz-Goikoetxea, M., ; Cortese, S., ; Aznárez Sanado, Maite; et al.
Revista: BMJ OPEN
ISSN 2044-6055  Vol. 7  Nº 9  2017  págs. e018027
Attention-deficit hyperactivity disorder (ADHD) has been related to increased rates of unintentional injuries. However, the magnitude of the effect and to which extent variables such as sex, age or comorbidity can influence this relationship is unknown. Additionally, and importantly, it is unclear if, and to which degree, ADHD medications can decrease the number of unintentional injuries. Due to the amount of economic and social resources invested in the treatment of injuries, filling these gaps in the literature is highly relevant from a public health standpoint. Here, we present a protocol for a systematic review and meta-analysis to estimate the relationship between ADHD and unintentional injuries and assess the impact of pharmacological treatment for ADHD METHODS AND ANALYSIS: We will combine results from 114 bibliographic databases for studies relating ADHD and risk of injuries. Bibliographic searches and data extraction will be carried out independently by two researchers. The studies' risk of bias will be assessed using the Newcastle-Ottawa Scale. Articles reporting ORs or HRs of suffering an injury in ADHD compared with controls (or enough data to calculate them) will be combined using Robust Variance Estimation, a method that permits to include multiple non-independent outcomes in the analysis. All analyses will be carried out in Stata. Age, sex and comorbid conduct disorders will be considered as potential causes of variance and their effect analysed through meta-re
Autores: Ibarrola García, Sara; Iriarte Redín, María Concepción; Aznárez Sanado, Maite
ISSN 1696-2095  Vol. 15  Nº 1  2017  págs. 75-104
Autores: Aznárez Sanado, Nerea; Aznárez Sanado, Maite; Sierrasesúmaga Ariznavarreta, Luis; et al.
ISSN 1137-6627  Vol. 40  Nº 1  2017  págs. 85 - 92
Fundamento. Los pacientes afectos de osteosarcoma reciben tratamiento con quimioterapia administrada por vía intraarterial (QTia)3 directamente al tumor y son expuestos a radiación ionizante durante el mismo. Los pacientes pediátricos son especialmente vulnerables a esta exposición. Material y métodos. Se registró la cantidad de radiación ionizante recibida por 16 pacientes pediátricos afectos de osteosarcoma durante la administración de QTia en la Clínica Universidad de Navarra. Resultados. La mediana de radiación total recibida fue de 33,4 Gy·cm2 (IQR 43,33 Gy·cm2) y la mediana de número de pruebas por paciente de 10 (IQR: 6.5). Conclusión. El estudio resalta la importancia de cuantificar la radiación recibida por un grupo de niños y adolescentes afectos de osteosarcoma durante el tratamiento con QTia ya que no conviene olvidar los potenciales efectos adversos a largo plazo de esta exposición. Actualmente, no existen estudios previos que aporten datos acerca de la cantidad de radiación ionizante recibida a través de este procedimiento.
Autores: Aznárez Sanado, Nerea; Aznárez Sanado, Maite; Sierrasesúmaga Ariznavarreta, Luis; et al.
ISSN 1137-6627  Vol. 40  Nº 1  2017  págs. 85 - 92
Background. Osteosarcoma paediatric patients are usually treated with intra-arterial chemotherapy (QTia) which is administered directly to the tumour. This procedure exposes patients to ionizing radiation. Paediatric patients are especially sensitive to this exposure. Methods. The total amount of ionizing radiation received from QTia administration was quantified in a group of 16 osteosarcoma paediatric patients from the Clinica Universidad de Navarra. Results. The median of the total radiation received per patient was 33.4 (IQR: 43.33, and the median number of procedures performed per subject was 10 (IQR: 6.5). Conclusions. The study highlights the importance of quantifying the radiation received by a group of children and adolescents affected by osteosarcoma during treatment with QTia. Long-term side effects of this radiation should be considered in paediatric patients. Currently, there are no previous studies that provide data of the amount of ionizing radiation received through this procedure.
Autores: Arrondo Ostiz, Gonzalo; Aznárez Sanado, Maite; Fernández Seara, María Asunción; et al.
ISSN 0924-977X  Vol. 25  Nº 6  2015  págs. 817 - 827
Studies on animals and humans have demonstrated the importance of dopamine in modulating decision-making processes. In this work, we have tested dopaminergic modulation of economic decision-making and its neural correlates by administering either placebo or metoclopramide, a dopamine D2-receptor antagonist, to healthy subjects, during a functional MRI study. The decision-making task combined probability and time delay with a fixed monetary reward. For individual behavioral characterization, we used the Probability Time Trade-off (PTT) economic model, which integrates the traditional trade-offs of reward magnitude-time and reward magnitude-probability into a single measurement, thereby quantifying the subjective value of a delayed and probabilistic outcome. A regression analysis between BOLD signal and the PTT model index permitted to identify the neural substrate encoding the subjective reward-value. Behaviorally, medication reduced the rate of temporal discounting over probability, reflected in medicated subjects being more prone to postpone the reward in order to increase the outcome probability. In addition, medicated subjects showed less activity during the task in the postcentral gyrus as well as frontomedian areas, whereas there were no differences in the ventromedial orbitofrontal cortex (VMOFC) between groups when coding the subjective value. The present study demonstrates by means of behavior and imaging that dopamine modulation alters the probability-time trade-off in human economic decision-making.
Autores: Goñi Cortés, Joaquín; Sporns, O., ; Cheng, H., ; et al.
ISSN 1053-8119  Vol. 83  2013  págs. 646 - 657
High-resolution isotropic three-dimensional reconstructions of human brain gray and white matter structures can be characterized to quantify aspects of their shape, volume and topological complexity. In particular, methods based on fractal analysis have been applied in neuroimaging studies to quantify the structural complexity of the brain in both healthy and impaired conditions. The usefulness of such measures for characterizing individual differences in brain structure critically depends on their within-subject reproducibility in order to allow the robust detection of between-subject differences. This study analyzes key analytic parameters of three fractal-based methods that rely on the box-counting algorithm with the aim to maximize within-subject reproducibility of the fractal characterizations of different brain objects, including the pial surface, the cortical ribbon volume, the white matter volume and the gray matter/white matter boundary. Two separate datasets originating from different imaging centers were analyzed, comprising 50 subjects with three and 24 subjects with four successive scanning sessions per subject, respectively. The reproducibility of fractal measures was statistically assessed by computing their intra-class correlations. Results reveal differences between different fractal estimators and allow the identification of several parameters that are critical for high reproducibility. Highest reproducibility with intra-class correlations in the range of 0.9-0.95 is achieved with the correlation dimension. Further analyses of the fractal dimensions of parcellated cortical and subcortical gray matter regions suggest robustly estimated and region-specific patterns of individual variability. These results are valuable for defining appropriate parameter configurations when studying changes in fractal descriptors of human brain structure, for instance in studies of neurological diseases that do not allow repeated measurements or for disease-course longitudinal studies.
Autores: Aznárez Sanado, Maite; Fernández Seara, María Asunción; Loayza Paredes, Francis Roderich; et al.
ISSN 1053-1807  Vol. 37  Nº 3  2013  págs. 619-631
Purpose: To elucidate differences in activity and connectivity during early learning due to the performing hand. Materials and Methods: Twenty right-handed subjects were recruited. The neural correlates of explicit visuospatial learning executed with the right, the left hand, and bimanually were investigated using functional magnetic resonance imaging. Connectivity analyses were carried out using the psychophysiological interactions model, considering right and left anterior putamen as index regions. Results: A common neural network was found for the three tasks during learning. Main activity increases were located in posterior cingulate cortex, supplementary motor area, parietal cortex, anterior putamen, and cerebellum (IVV), whereas activity decrements were observed in prefrontal regions. However, the left hand task showed a greater recruitment of left hippocampal areas when compared with the other tasks. In addition, enhanced connectivity between the right anterior putamen and motor cortical and cerebellar regions was found for the left hand when compared with the right hand task. Conclusion: An additional recruitment of brain regions and increased striato-cortical and striato-cerebellar functional connections is needed when early learning is performed with the nondominant hand. In addition, access to brain resources during learning may be directed by the dominant hand in the bimanual task. J. Magn. Reson. Imaging 2013;37:619631. (c) 2012 Wiley Periodicals, Inc.
Autores: Fernández Seara, María Asunción; Mengual Poza, Elisa; Vidorreta Díaz de Cerio, Marta; et al.
ISSN 1053-8119  Vol. 59  Nº 3  2012  págs. 2743-2750
Alterations in cerebral perfusion and metabolism in Parkinson's disease have been assessed in several studies, using nuclear imaging techniques and more recently magnetic resonance imaging. However, to date there is no consensus in the literature regarding the extent and the magnitude of these alterations. In this work, arterial spin labeled perfusion MRI was employed to quantify absolute cerebral blood flow in a group of early-to-moderate Parkinson's disease patients and age-matched healthy controls. Perfusion comparisons between the two groups showed that Parkinson's disease is characterized by wide-spread cortical hypoperfusion. Subcortically, hypoperfusion was also found in the caudate nucleus. This pattern of hypoperfusion could be related to cognitive dysfunctions that have been previously observed even at the disease early stages. The present results were obtained by means of whole brain voxel-wise comparisons of absolute perfusion values, using statistical parametric mapping, thus avoiding the potentially biased global mean normalization procedure. In addition, this work demonstrates that between-group comparison of relative perfusion values after global mean normalization, introduced artifactual relative perfusion increases, where absolute perfusion was in fact preserved. This has implications for perfusion studies of other brain disorders. (C) 2011 Elsevier Inc. All rights reserved.
Autores: Goñi Cortés, Joaquín; Aznárez Sanado, Maite; Arrondo Ostiz, Gonzalo; et al.
Revista: PLOS ONE
ISSN 1932-6203  Vol. 6   Nº 3  2011  págs. e17408
Decision making can be regarded as the outcome of cognitive processes leading to the selection of a course of action among several alternatives. Borrowing a central measurement from information theory, Shannon entropy, we quantified the uncertainties produced by decisions of participants within an economic decision task under different configurations of reward probability and time. These descriptors were used to obtain blood oxygen level-dependent (BOLD) signal correlates of uncertainty and two clusters codifying the Shannon entropy of task configurations were identified: a large cluster including parts of the right middle cingulate cortex (MCC) and left and right pre-supplementary motor areas (pre-SMA) and a small cluster at the left anterior thalamus. Subsequent functional connectivity analyses using the psycho-physiological interactions model identified areas involved in the functional integration of uncertainty. Results indicate that clusters mostly located at frontal and temporal cortices experienced an increased connectivity with the right MCC and left and right pre-SMA as the uncertainty was higher. Furthermore, pre-SMA was also functionally connected to a rich set of areas, most of them associative areas located at occipital and parietal lobes. This study provides a map of the human brain segregation and integration (i.e., neural substrate and functional connectivity respectively) of the uncertainty associated to an economic decision making paradigm.
Autores: Fernández Seara, María Asunción; Aznárez Sanado, Maite; Mengual Poza, Elisa; et al.
Revista: British Journal of Pharmacology
ISSN 0007-1188  Vol. 163   Nº 8  2011  págs. 1639 - 1652
Autores: Loayza Paredes, Francis Roderich; Fernández Seara, María Asunción; Aznárez Sanado, Maite; et al.
ISSN 1053-8119  Vol. 55  Nº 2  2011  págs. 635 - 643
Egocentric tactile perception is crucial for skilled hand motor control. In order to better understand the brain functional underpinnings related to this basic sensorial perception, we performed a tactile perception functional magnetic resonance imaging (fMRI) experiment with two aims. The first aim consisted of characterizing the neural substrate of two types of egocentric tactile discrimination: the spatial localization (SLD) and simultaneity succession discrimination (SSD) in both hands to define hemispheric dominance for these tasks. The second goal consisted of characterizing the brain activation related to the spatial attentional load, the functional changes and their connectivity patterns induced by the psychometric performance (PP) during SLD. We used fMRI in 25 right-handed volunteers, applying pairs of sinusoidal vibratory stimuli on eight different positions in the palmar surface of both hands. Subjects were required either to identify the stimulus location with respect to an imaginary midline (SLD), to discriminate the simultaneity or succession of a stimuli pair (SSD) or to simply respond to stimulus detection. We found a fronto-parietal network for SLD and frontal network for SSD. During SLD we identified right hemispheric dominance with increased BOLD activation and functional interaction of the right supramarginal gyrus with contralateral intra-parietal sulcus for right and left hand independently. Brain activity correlated to spatial attentional load was found in bilateral structures of intra-parietal sulcus, precuneus extended to superior parietal lobule, pre-supplementary motor area, frontal eye fields and anterior insulae for both hands. We suggest that the right supramarginal gyrus and its interaction with intra-parietal lobule may play a pivotal role in the phenomenon of tactile neglect in right fronto-parietal lesions.