Funciones ejecutivas: una revisión de su fundamentación teórica / Executive functions: a review of their theoretical basis

El presente artículo busca establecer los fundamentos de las funciones ejecutivas (FE) a nivel conceptual, para lo cual se plantea el seguimiento de los siguientes elementos: a) definición de las funciones cerebrales inferiores y superiores; b) relación entre FE y estructura anatomo-funcional; y c) confluencia final de las FE en un modelo integrador. a) Las funciones cerebrales inferiores están ligadas a los procesos más primitivos del ser humano. Permiten la satisfacción de necesidades básicas para la supervivencia; por tanto, se refieren a las capacidades adquiridas genéticamente sin que para su ejecución medie ningún proceso de aprendizaje. Por su parte, las funciones cerebrales superio-res se emparentan con los procesos neuropsicológicos bajo los cuales se sustenta la capacidad de modificar el ambiente y las circunstancias. Lo anterior ocurre gracias a: memoria, atención, lenguaje, razonamiento abstracto, actos gestuales y funciones ejecutivas (Rodríguez et al., 2006). Estas funciones cerebrales son el fundamento de las FE. b) Frente a su localización anatómica y funcional, Goldberg (2001) determina los lóbulos frontales como principal sustrato, por cuanto representan el centro ejecutivo del cerebro y la porción cerebral con mayor evolución de la corteza. Estos son los en-cargados de recibir la información de los estímulos y de la totalidad de las modalidades sensoriales. c) La anterior conceptualización permite definir las FE como un conjunto de capacidades referidas a la formulación de metas, planificación para el logro de dichas metas y la ejecución de la conducta de manera eficaz (Lezak, 1982).

This article seeks to establish the foundations of executive functions (EF) at a conceptual level, for which the following elements are proposed: a) definition of lower and higher brain functions; b) relationship between EF and anatomical-functional structure; and c) final confluence of EF in an integrative model. a) Lower brain functions are linked to the most primitive processes of the human being. They allow the satisfaction of basic needs for survival; therefore, they refer to genetically acquired capacities without any learning process for their execution. On the other hand, higher brain functions are related to the neuropsychological processes under which the capacity to modify the environment and circumstances is sustained. This occurs thanks to: memory, attention, language, abstract reasoning, gestural acts and executive functions (Rodriguez et al., 2006). These brain functions are the foundation of EF. b) Regarding its anatomical and functional location, Goldberg (2001) determines the frontal lobes as the main substrate, since they represent the executive center of the brain and the cerebral portion with the highest evolution of the cortex. These are responsible for receiving information from stimuli and from the totality of sensory modalities. c) The above conceptualization allows defining EF as a set of capacities referred to the formulation of goals, planning for the achievement of these goals and the execution of behavior in an effective manner (Lezak, 1982).

Cortical Brain Functions ­ The Brodmann Legacy in the 21st Century

In 1909, Korbinian Brodmann described 52 functional brain areas, 43 of them found in the human brain. More than a century later, his devoted functional map was incremented by Glasser et al in 2016, using functional nuclear magnetic resonance imaging techniques to propose the existence of 180 functional areas in each hemisphere, based on their cortical thickness, degree of myelination (cortical myelin content), neuronal interconnection, topographic organization, multitask answers, and assessment in their resting state. This opens a huge possibility, through functional neuroanatomy, to understand a little more about normal brain function and its functional impairment in the presence of a disease.

Optogenetic Glia Manipulation: Possibilities and Future Prospects

Our brains are composed of two distinct cell types: neurons and glia. Emerging data from recent investigations show that glial cells, especially astrocytes and microglia, are able to regulate synaptic transmission and thus brain information processing. This suggests that, not only neuronal activity, but communication between neurons and glia also plays a key role in brain function. Thus, it is currently well known that the physiology and pathophysiology of brain function can only be completely understood by considering the interplay between neurons and glia. However, it has not yet been possible to dissect glial cell type-specific roles in higher brain functions in vivo. Meanwhile, the recent development of optogenetics techniques has allowed investigators to manipulate neural activity with unprecedented temporal and spatial precision. Recently, a series of studies suggested the possibility of applying this cutting-edge technique to manipulate glial cell activity. This review briefly discusses the feasibility of optogenetic glia manipulation, which may provide a technical innovation in elucidating the in vivo role of glial cells in complex higher brain functions.

Neuropsicología y la localización de las funciones cerebrales superiores en estudios de resonancia magnética funcional con tareas / Neuropsychology and the localization of superior brain functions in fMRI with task studies

El objetivo es destacar la capacidad de la resonancia magnética funcional con tareas para evaluar diversas funciones cerebrales superiores, mediante la ejecución de paradigmas que producen activación cerebral de las regiones involucradas. Resaltar la importancia del neuropsicólogo en la creación de paradigmas y en la interpretación de los resultados. Se realizó una revisión no sistemática de la literatura científica recogida en las bases de datos de: Rev Neurol, Neurology, Radiología, Neuroimage, J Neuroimaging, Science, Brain, Neuroscience and biobehavioral reviews, journal of neuroscience, Eur J Radiol, Magnetic resonance in medicine, Neurosurgery, Neuroimagingclin, Neuropsidologia latinoamericana, International journal of neuroscience, Science, Biol Psychiatry, Psychol Med, Arch Gen Psychiatry, Psychiatry Res Neuroimaging, Neuro Report, Neuron, J ClinExpNeuropsychol, Proc Natl Acad Sci U S A, Ann Neurol Neurobiol Aging, Neurosci Lett, Journal of Neuroscience. Los descriptores utilizados fueron "Resonancia magnética funcional", "Paradigmas" y "Neuropsicología". Se seleccionaron los artículos científicos de cualquier tipo y en español e inglés; desde el inicio de la indización de la fuente primaria hasta noviembre de 2014. Se recuperaron 42 artículos. Se analizaron todos los conceptos sobre resonancia magnética funcional, neuropsicología, funciones cerebrales superiores, áreas cerebrales activadas, paradigmas. Los mapas de activación neuronal confirman la participación simultánea de diferentes áreas cerebrales, incluso distantes, durante la ejecución de paradigmas. La participación del neuropsicólogo dentro del grupo multidisciplinario es muy importante por su conocimiento profundo de los factores involucrados en el desempeño de las diferentes tareas cognitivas potencialmente evaluables por resonancia magnética funcional.

To highlight the capacity of functional magnetic resonance imaging (fMRI) with tasks in order to measure different higher brain functions by running paradigms that produce brain activation in the regions involved. Highlighting the importance of the neuropsychologist in creating paradigms and interpreting results. A non-systematic review of the scientific literature contained in the databases was conducted: Rev Neurol, Neurology, Radiología, Neuroimage, J Neuroimaging, Science, Brain, Neuroscience and biobehavioral reviews, journal of neuroscience, Eur J Radiol, Magnetic Resonance in Medicine, Neurosurgery, Neuroimagingclin, Neuropsicologia Latinoamericana, International Journal of Neuroscience, Biol Psychiatry, Psychol Med, Arch Gen Psychiatry, Psychiatry Res Neuroimaging, Neuro Report, Neuron, J ClinExpNeuropsychol , Proc Natl Acad Sci U S A, Ann Neurol Neurobiol Aging, Neurosci Lett, Journal of Neuroscience. The descriptors used were: "functional MRI", "Paradigms" and "Neuropsychology". Papers in Spanish and English of any kind were selected since the start of indexing the primary source until November 2014. 42 articles were retrieved. The following concepts were analyzed: functional magnetic resonance imaging, neuropsychology, higher brain functions, activated brain areas paradigms. The neural activation maps confirm the simultaneous involvement of different brain areas, even distant ones, during the execution of paradigms. Neuropsychologist participation within the multidisciplinary team is very important for its deep understanding of the factors involved in the performance of different cognitive tasks potentially assessable by fMRI.

Electroencephalographic attributes of goats under conscious state.

Electroencephalographic studies were undertaken in goats to correlate with normal behavioral states and physiological conditions. Duplicate EEG records from 4 adult female goats (8–12 months, 10±2 kg body wt), using bipolar scalp electrodes placed in occipital region, were obtained to evaluate electrical responses of brain during different postures and states of alertness. EEG recordings were obtained under comfortable conditions and after adequate training of animals. EEG frequency (Hz) during lying down posture was significantly (P<0.05) lower compared to standing posture (32.63±1.34 Vs 38.63±1.03), the individual values ranging between 29 to 42 Hz. EEG amplitudes however varied non significantly between two states with respective values of 5.75±0.25 and 6.11±0.26 μV. During light and deep drowsiness, the frequencies recorded were 21.63±0.94 and 13.00±0.68 Hz, whereas amplitudes were 12.45±0.55 and 19.96±0.68 μV, respectively and the differences being statistically significant (P<0.05). Mean EEG frequencies of the order of 7.13±1.14 and 3.25±0.49 Hz and amplitudes of 16.59±2.55 and 19.86±3.19 μV were recorded during light and deep sleep, respectively. General trend indicated that frequency decreased and amplitudes increased with onset of drowsiness and these changes were proportional to the state of consciousness.

Application of Functional MRI in the Field of Rehabilitation Medicine

The higher cognitive functions of human brain are hypothesized to be selectively distributed across large-scale neural networks interconnected cortical and subcortical areas. Recently, advances in functional imaging made it possible to visualize the brain areas activated by certain cognitive function in vivo. Out of several technologies currently available for brain activation study, functional magnetic resonance imaging (fMRI) is increasingly being used because of its superior time resolution and finer spatial resolution. The technique is non-invasive without radiation hazard, which allow to take repeated multiple scans within the same individual. The most common approach to fMRI of brain is the one using 'blood-oxygen level dependent (BOLD)' contrast, which based on the localized hemodynamic changes following neural activities in the certain areas of brain. With functional imaging techniques including fMRI, neural networks subserving for higher cognitive functions such as language, memory, attention, and visuospatial functions could be visualized. Neural substrates of human emotion and motivation behaviors also begin to be unveiled. Brain mapping with functional imaging is a very useful method for detecting eloquent areas in a neurosurgical setting to prevent the residual disabilities. One of the issues recently having attention in the field of functional imaging is the reorganization of neural network following brain injuries. Much research results using fMRI identified intra- and/or interhemispheric reorganization of neural networks accompanied with functional recovery after brain injury. Effects of learning and rehabilitation on the extent and pattern of neural reorganization was also delineated. fMRI will be a very useful tool for developing of various rehabilitation treatments, which promote successful functional recovery by maximizing the plasticity of brain.