Perfil cognitivo en el Mareo Perceptual Postural Persistente: Implicancias sobre su fisiopatología como disfunción cognitiva viso-vestibular superior / Cognitive profile in Persistent Postural Perceptual Dizziness: Implications on its pathophysiology as a superior visio-vestibular cognitive dysfunction

Introducción: El mareo perceptual postural persistente (MPPP) es, probablemente, la causa más prevalente de mareo crónico. Sin embargo, su fisiopatología es aún motivo de duda y debate. En el presente artículo, proponemos que el MPPP se caracteriza por disfunciones cognitivas de orden superior, al punto de diferenciarse en estas dimensiones de controles sanos y pacientes con patologías vestibulares no-MPPP. Objetivo: Determinar si pacientes con MPPP presentan alteraciones discriminantes respecto a grupos controles, en ámbitos de atención, memoria de trabajo visoespacial, planificación espacial, funciones ejecutivas y rendimiento cognitivo global. Material y Método: Estudio descriptivo transversal con sujetos de entre 18 y 65 años, reclutados de una unidad de otoneurología ambulatoria. Se aplicaron pruebas Montreal Cognitive Assessment (MoCA), tarea de retención de dígitos, Trail Making Test, Corsi Block-Tapping Task y Torre de Londres. Resultados: 30 pacientes fueron categorizados en tres grupos: grupo MPPP (n = 14), grupo vestibular no-MPPP (n = 11) y grupo control (n = 5). El grupo MPPP exhibió un rendimiento significativamente inferior en pruebas de planificación, velocidad de procesamiento y funciones ejecutivas en ámbitos visoespaciales, mientras que en atención y memoria visoespacial no hubo diferencias entre grupos. Conclusión: El MPPP podría caracterizarse por una disfunción de procesos cognitivos superiores de construcción espacial de mayor complejidad, respetando funciones visoespaciales de menor orden como la memoria de trabajo. Estos hallazgos ofrecen nuevas luces para comprender la fisiopatología del MPPP y sus implicancias clínicas.

Introduction: Persistent postural-perceptual dizziness (PPPD) is probably the most prevalent cause of chronic dizziness. However, its pathophysiology is still a matter of uncertainty and debate. In this article, we propose that PPPD is characterized by higher-order cognitive dysfunctions, to the point of differentiating it from healthy controls and patients with non-PPPD vestibular pathologies. Aim: To determine whether patients with PPPD exhibit discriminant alterations compared to control groups in the areas of attention, visuospatial working memory, spatial planning, executive functions, and global cognitive performance. Materials and Methods: A cross-sectional descriptive study was conducted with subjects between the ages of 18 and 65 years, recruited from an outpatient otoneurology unit. Tests included the Montreal Cognitive Assessment (MoCA), digit retention task, Trail Making Test, Corsi Block-Tapping Task, and the Tower of London. Results: 30 patients were categorized into three groups: PPPD group (n = 14), non-PPPD vestibular group (n = 11), and control group (n = 5). The PPPD group showed significantly lower performance on tests of planning, processing speed, and executive function in visuospatial domains, while there were no differences between groups in attention and visuospatial memory. Conclusion: PPPD may be characterized by dysfunction of higher-order cognitive processes related to spatial construction of greater complexity, while sparing lower-order visuospatial functions such as working memory. These findings offer new insights into the pathophysiology of PPPD and its clinical implications.

Neural Correlates of Spatial Navigation in Primate Hippocampus / 神经科学通报·英文版

The hippocampus has been extensively implicated in spatial navigation in rodents and more recently in bats. Numerous studies have revealed that various kinds of spatial information are encoded across hippocampal regions. In contrast, investigations of spatial behavioral correlates in the primate hippocampus are scarce and have been mostly limited to head-restrained subjects during virtual navigation. However, recent advances made in freely-moving primates suggest marked differences in spatial representations from rodents, albeit some similarities. Here, we review empirical studies examining the neural correlates of spatial navigation in the primate (including human) hippocampus at the levels of local field potentials and single units. The lower frequency theta oscillations are often intermittent. Single neuron responses are highly mixed and task-dependent. We also discuss neuronal selectivity in the eye and head coordinates. Finally, we propose that future studies should focus on investigating both intrinsic and extrinsic population activity and examining spatial coding properties in large-scale hippocampal-neocortical networks across tasks.

Egocentric and allocentric spatial memory in healthy aging: performance on real-world tasks

Although normal aging has been related to several cognitive difficulties, other processes have been studied less, such as spatial memory. Our aim was to compare egocentric and allocentric memory in an elderly population using ecological tasks. Twenty-eight cognitively unimpaired participants performed Egocentric and Allocentric Spatial Memory Tasks, as well as Spatial Span from CANTAB, Benton's Judge of Line Orientation test (JoLO), and Montreal Cognitive Assessment test (MoCA). The results revealed that younger participants showed better performance than older participants on both the Egocentric and Allocentric Spatial Memory Tasks, although only the Egocentric test was able to discriminate between younger, middle, and older elderly participants. Learning effect was found in Allocentric Spatial Memory Task in younger and older groups, but not in the middle group. Allocentric and egocentric performance was not related to other visuospatial neuropsychological scores and gender did not influence performance in any task. Egocentric and Allocentric Spatial Memory Tasks may be useful tools in early screening for cognitive decline, as they are able to detect age differences in the cognitive unimpaired elderly population.

Microglia and neurons in the hippocampus of migratory sandpipers

The semipalmated sandpiper Calidris pusilla and the spotted sandpiper Actitis macularia are long- and short-distance migrants, respectively. C. pusilla breeds in the sub-arctic and mid-arctic tundra of Canada and Alaska and winters on the north and east coasts of South America. A. macularia breeds in a broad distribution across most of North America from the treeline to the southern United States. It winters in the southern United States, and Central and South America. The autumn migration route of C. pusilla includes a non-stop flight over the Atlantic Ocean, whereas autumn route of A. macularia is largely over land. Because of this difference in their migratory paths and the visuo-spatial recognition tasks involved, we hypothesized that hippocampal volume and neuronal and glial numbers would differ between these two species. A. macularia did not differ from C. pusilla in the total number of hippocampal neurons, but the species had a larger hippocampal formation and more hippocampal microglia. It remains to be investigated whether these differences indicate interspecies differences or neural specializations associated with different strategies of orientation and navigation.