Funciones cognitivas del cerebelo: implicación en las funciones ejecutivas / Cognitive function of cerebellum: implications in executive functions

Las funciones ejecutivas han sido tradicionalmente relacionadas con estructuras cerebrales corticales, específicamente con la corteza prefrontal y de manera secundaria se han relacionado a otras estructuras corticales debido a la vasta conectividad que establece la corteza prefrontal a lo largo de la corteza cerebral, por otro lado la implicación de estructuras subcorticales en las funciones cognitivas es un campo en estudio, el cual apenas se está desarrollando. Recientes investigaciones con neuroimagen funcional y los estudios Neuropsicológicos de pacientes con alteraciones en el cerebelo han mostrado la posible participación activa de esta estructura. El objetivo general de este trabajo fue realizar una revisión y posterior análisis de la evidencia empírica y teórica (clínica, neuroimageneológica y experimental) que pusiera en evidencia las implicaciones funcionales del cerebelo en las funciones ejecutivas. Se discutieron las aportaciones funcionales del cerebelo a las funciones ejecutivas a través de sus correlatos y circuitos neuroanatómicos, y se analizaron las descripciones de casos clínicos de pacientes con afectación de algún tipo de función ejecutiva como consecuencia de una alteración del cerebelo. Frente a los hallazgos se encuentran resultados divergentes, por un lado frente a la evidencia neuroanatómica entre las dos estructuras (CPF-Cerebelo) se genera una conectividad indudable. Frente a la evidencia neuropsicológica, no hay un consenso, aunque mucha de la evidencia afirma una indudable participación del cerebelo a las funciones ejecutivas.

Executive functions have been traditionally associated with cortical brain structures, specifically the prefrontal cortex and secondarily other structure have been implicated because of the extensive cortical connectivity that establishes the prefrontal cortex throughout the cerebral cortex, on the other hand the involvement of subcortical structures in cognitive functions is a field study, which is only just developing. Recent research with functional neuroimaging and neuropsychological studies of patients with alterations in the cerebellum have shown the possible involvement of this structure. The overall objective of this study was to review and subsequent analysis of empirical and theoretical evidence (clinical, neuroimaging and experimental) to put in evidence the functional implications of the cerebellum in executive functions. Discussed the functional input of the cerebellum to executive functions through their circuits and neuroanatomical correlates, and analyzed the descriptions of clinical cases of patients with involvement of some kind of executive function as a result of an alteration of the cerebellum. Against the findings are divergent results, first neuroanatomical evidence against the two structures (CPF)Cerebellum) is generated undoubtedly connectivity. Faced with the neuropsychological evidence, there is no consensus, although much of the evidence says a definite involvement of the cerebellum to executive functions.

Lateral interactions in visual perception of temporal signals: cortical and subcortical components

The aim of this work was to isolate and investigate subcortical and cortical lateral interactions involved in flicker perception. We quantified the perceived flicker strength (PFS) in the center of a test stimulus which was simultaneously modulated with a surround stimulus (50 percent Michelson contrast in both stimuli). Subjects were requested to adjust the modulation depth of a separate matching stimulus that was physically identical to the center of the test stimulus but without the surround. Using LCD goggles, synchronized to the frame rate of a CRT screen, the center and surround could be presented monoptically or dichoptically. In the monoptic condition, center-surround interactions can have both subcortical and cortical origins. In the dichoptic condition, center-surround interactions cannot occur in the retina and the LGN, therefore isolating a cortical mechanism. Results revealed both a strong monoptic (subcortical plus cortical) lateral interaction and a weaker dichoptic (cortical) lateral interaction. Subtraction of the dichoptic from the monoptic data revealed a subcortical mechanism of the lateral interaction. While the modulation of the cortical PFS component showed a low-pass temporal-frequency tuning, the modulation of the subcortical PFS component was maximal at 6 Hz. These findings are consistent with two separate temporal channels influencing the monoptic PFS, each with distinct lateral interactions strength and frequency tuning characteristics. We conclude that both subcortical and cortical lateral interactions modulate flicker perception.