La especialización hemisférica y la regulación de la conducta motora desde la perspectiva de la neurociencia cognitiva / Hemispheric specialization and regulation of motor behavior on a perspective of cognitive neuroscience

Introducción Nuestra comprensión de la organización funcional del cerebro se debe a los avances en las técnicas de neuroimagen y a una intensa investigación clínica. Recientemente, la ciencia cognitiva (neurociencia cognitiva) en combinación con los avances tecnológicos han cambiado nuestra comprensión sobre la relación cerebro-conducta. Esta relación simbiótica ha permitido una mejor caracterización del sitio de la lesión en pacientes con trastornos cerebrales y de los patrones de activación en sujetos sanos. Objetivo En el presente artículo se discute la contribución del hemisferio izquierdo y la participación del hemisferio derecho en la regulación de la conducta motora; esto nos permitirá comprender mejor la lateralización de las funciones motoras. Desarrollo Los resultados apoyan la visión de un predominio del hemisferio izquierdo para el lenguaje y el control motor, y un predominio del hemisferio derecho para las funciones espaciales y la atención. Las áreas especializadas son probablemente predeterminadas y ciertas funciones están lateralizadas a uno u otro hemisferio, esto debido a la eficiente organización y procesamiento de la información en el cerebro. Conclusión En los estudios revisados, se observaron funciones específicas para cada hemisferio, lo que sugiere la existencia de una compleja organización que recluta a varias áreas del Sistema Nervioso para el adecuado desempeño de una tarea.

Introduction Our understanding of functional brain organization is due to advances in neuroimaging technologies and intensive clinical research. Recently, cognitive science (cognitive neuroscience), combined with advances in technology, have changed our understanding of brain-behavior relationship. This symbiotic relationship has allowed a better characterization of the lesion site in patients with brain disorders and patterns of activation in healthy subjects. Objective In this article we discuss the contribution of the left hemisphere and right hemisphere involvement in the regulation of motor behavior; this will allow us to better understand the lateralization of motor functions. Development The results support the view of a left hemisphere dominance for language and motor control, and a right hemisphere dominance for spatial functions and attention. Specialized areas are probably predetermined and certain functions are lateralized to one or other hemisphere due to the efficient organization and information processing in the brain. Conclusion In the studies reviewed, specific functions for each hemisphere were observed, suggesting the existence of a complex organization that recruits several areas of the Nervous System for proper task performance.

Cognitive mechanisms and motor control during a saccadic eye movement task: evidence from quantitative electroencephalography / Mecanismos cognitivos e controle motor durante uma tarefa de movimento sacádico dos olhos: evidências de eletroencefalografia quantitativa

The saccadic movement is an important behavioral measure used to investigate several cognitive processes, including attention and sensorimotor integration. The present study aimed at investigating changes in beta coherence over frontal, motor, occipital, and parietal cortices during the performance of two different conditions of a prosacadic paradigm. The conditions involved a different pattern of stimulus presentation: a fixed and random stimulus presentation. Twelve healthy volunteers (three male, mean age of 26.25 (SD=4.13) performed the task, while their brain activity pattern was recorded using quantitative electroencephalography. The results showed an interaction between factors condition and moment for the pair of electrode C3/C4. We observed a main effect for moment to CZ/C4, FZ/F3, and P3/PZ. We also found a main effect for condition to FZ/F4, P3/P4, and O1/O2. Our results demonstrated an important role of the inter-connection of the two hemispheres in visual search and movement preparation. The study demonstrates an automation of action and reduction of the focus of attention during the task. We also found that the inter-hemispheric beta coherence plays an important role in the differentiation of the two conditions, and that beta in the right frontal cortex is able to differentiate the conditions, demonstrating a greater involvement of procedural memory in fixed condition. Our results suggest a neuronal specialization in the execution of prosacadic paradigm involving motor task sequence.

O movimento sacádico é uma importante medida de comportamento usada para investigar vários processos cognitivos, incluindo atenção e integração sensório-motora. O presente estudo teve como objetivo investigar as mudanças na coerência em beta nos córtices frontal, motor, parietal e occipital durante a realização de duas condições diferentes de um paradigma do movimento sacádico. As condições envolveram um padrão diferente de apresentação do estímulo: a apresentação do estímulo fixo e do aleatório. Doze voluntários saudáveis ​​(três do sexo masculino, com idade média de 26,25; DP=4,13) realizaram a tarefa, enquanto o seu padrão de atividade cerebral era monitorado, usando eletroencefalografia quantitativa. Os resultados mostraram uma interação entre condição dos fatores e momento para o par de eletrodos C3/C4. Observou-se um efeito principal ao momento para CZ/C4, FZ/F3 e P3/PZ. Encontrou-se também um efeito principal à condição para FZ/F4, P3/P4 e O1/O2. Os resultados demonstram um importante papel da ligação interconexão entre os dois hemisférios, em busca visual e preparação do movimento. O estudo demonstra uma automatização da ação e uma redução do foco de atenção durante a tarefa. Identificou-se também que a coerência em beta entre regiões inter-hemisféricas desempenha um papel importante na diferenciação entre as duas condições. Ainda, beta no córtex frontal direito é capaz de diferenciar as condições, demonstrando-se um maior envolvimento da memória de procedimento em condição fixa. Sendo assim, os presentes resultados sugerem especialização neuronal na execução do paradigma prossacádico envolvendo sequência de tarefa motora.

Sistema hipocretinérgico y narcolepsia / Hypocretin system and narcolepsy

Narcolepsy is a sleep disorder characterized by excessive daytime sleepiness, cataplexy, hypnagogic hallucinations, and sleep-onset rapid eye movement (REM) sleep periods. It is now identified as a neurodegenerative disease because there is a massive loss of specific neurons in the brain. These neurons contain the neuropeptides hypocretin-1 and hypocretin-2, which are also known as orexin-A and orexin-B. Cerebrospinal fluid hypocretin-1 measurements are diagnostic for primary narcolepsy. The cause of neural loss could be autoinmune since most patients have the HLA DQB1*0602 alíele that predisposes to the disorders. The discovery of hypocretin deficiency is redefining the clinical entity of narcolepsy and offering novel diagnostic procedures. This article reviews the current understanding of narcolepsy and discusses the implications of hypocretin discovery (Rev Méd Chile 2009; 137:1209-16).

Hipocretinas, péptidos relacionados con la narcolepsia / Hypocretins, peptides associated with narcolepsy

La narcolepsia es un trastorno del sueño caracterizado por excesiva somnolencia diurna, transiciones prematuras de la vigila al sueño de movimientos oculares rápidos, alucinaciones hipnagógicas y cataplexia. Evidencias experimentales indican que la narcolepsia en humanos es una enfermedad neurodegenerativa asociada con la pérdida de neuronas hipocretinérgicas localizadas en el hipotálamo lateral. Además, se sabe que los pacientes narcolépticos presentan reducción significativa en la concentración de hipocretinas (HCRT) en el líquido cefalorraquídeo. Nuestro laboratorio ha generado un nuevo modelo experimental de narcolepsia en rata, que nos permite estudiar la enfermedad desde un enfoque histológico y neuroquímico. Hemos demostrado que la toxina hipocretina 2/saporina destruye selectivamente las neuronas hipocretinérgicas. Además, la pérdida de estas neuronas induce un cuadro conductual similar al observado en otros modelos experimentales o narcolepsia en humanos. En la presente revisión abordamos aspectos generales de la narcolepsia, del sistema hipocretinérgico, así como de los modelos experimentales de narcolepsia y el uso de los transplantes como alternativa para tratar la enfermedad.

Narcolepsy is a chronic disease characterized by excessive somnolence, abrupt transitions from wakefulness to rapid eye movement sleep stage and cataplexy. Experimental evidence show that narcolepsy in humans is a neurodegenerative disease associated with the lost of hypocretin (HCRT) neurons in the lateral hypothalamus. Narcoleptic patients also display a significant diminution in HCRT contents of cerebrospinal fluid. In order to study narcolepsy, several experimental models have been developed. Murine and canine models currently allow us to study this disease. Our laboratory has developed a new experimental rat model of narcolepsy. This model allows us to study the disease from a histological and neurochemical perspective. Elsewhere we have reported that the use of the toxin hypocretin2/saporine (HCRT2/ SAP) selectively destroys hypocretinergic neurons. The loss of these neurons induces a similar behavioural profile as the one observed in other experimental models of narcolepsy. In the present review we describe an overview on narcolepsy, the hypocretinergic system, experimental models in narcolepsy and the use of transplants as an alternative therapeutic tool.