Cortical Mechanisms of Multisensory Linear Self-motion Perception / 神经科学通报·英文版

Accurate self-motion perception, which is critical for organisms to survive, is a process involving multiple sensory cues. The two most powerful cues are visual (optic flow) and vestibular (inertial motion). Psychophysical studies have indicated that humans and nonhuman primates integrate the two cues to improve the estimation of self-motion direction, often in a statistically Bayesian-optimal way. In the last decade, single-unit recordings in awake, behaving animals have provided valuable neurophysiological data with a high spatial and temporal resolution, giving insight into possible neural mechanisms underlying multisensory self-motion perception. Here, we review these findings, along with new evidence from the most recent studies focusing on the temporal dynamics of signals in different modalities. We show that, in light of new data, conventional thoughts about the cortical mechanisms underlying visuo-vestibular integration for linear self-motion are challenged. We propose that different temporal component signals may mediate different functions, a possibility that requires future studies.

Adaptabilidad perceptuo-motora como clave en la conducta motriz / Perceptuo-motor adaptability as a key in motor behavior

Este artículo propone una comprensión base de la adquisición de habilidades perceptuo-motoras en la vida diaria y deportiva desde la perspectiva de la teoría dinámica ecológica que se enfoca en la relación mutua del individuo y su medio-ambiente. En esta visión, los individuos son conceptualizados como sistemas neurobiológicos complejos en el cual la inherente autoorganización de sus sistemas respalda la formación de una conducta motora adaptativa dirigida a un objetivo bajo condicionantes de la tarea a ejecutar y el ambiente dinámico en el que se desenvuelve. Esta conducta motora por lo tanto, no sólo es consecuencia de cambios en la habilidad de coordinar nuestros movimientos, sino también de cambios en la habilidad de percibir variables esenciales del cuerpo, de la tarea y del ambiente, y afinar esta percepción con el movimiento, y viceversa. De estos conceptos emergen claves fundamentales en el rendimiento de una tarea, tal como es la habilidad de percibir propiedades claves para el objetivo propuesto, la habilidad de anticiparse a los eventos futuros del objeto, oponentes u ambientes con el cual se interactúa, y la habilidad de realizar un interjuego entre la estabilidad y flexibilidad de la coordinación motora, que surge del rol funcional de su inherente variabilidad. Autores de la dinámica ecológica, plantean modificar los paradigmas del aprendizaje motor, dirigido a buscar la adaptabilidad funcional de la conducta perceptuo-motora ante las distintas demandas que impone el propio cuerpo, la tarea y el ambiente, más que sólo buscar un patrón ideal de movimiento.

Aprendizagem motora baseada em demonstrações de movimento biológico / Motor learning based on biological motion demonstrations

O objetivo deste estudo foi avaliar o processo de aprendizagem motora de uma habilidade complexa da Ginástica Artística a partir da observação de demonstrações de modelos de pontos de luz e vídeo. Dezesseis participantes divididas em grupos dos respectivos modelos executaram um pré-teste, seguido de 100 tentativas de uma parada de mãos, igualmente distribuídas em blocos de 10 tentativas em dois dias, alternando períodos de demonstração e prática, com um teste de retenção após um dia. Cinemática de braço, tronco e perna das participantes possibilitaram análise da semelhança entre a coordenação de cada participante e do modelo e do tempo de movimento; a performance das participantes também foi avaliada por duas especialistas em Ginástica Artística. Ambas as análises indicaram que os grupos não diferiram. Os resultados são discutidos em termos da hipótese de suficiência de informação nos modelos de movimento biológico particularmente aplicada ao processo de aprendizagem de habilidades motoras complexas.

The aim of this study was to evaluate the motor learning process of a complex Artistic Gymnastics skill following demonstrations of point-light and video models. Sixteen participants divided into the respective model groups performed a pre-test and 100 trials of a handstand, equally distributed in blocks of 10 trials in two days, alternating periods of demonstration and practice, with retention test a day later. Participants' kinematics of arm, trunk, and leg was used to analyze the coordination similarities between each participant and the model and movement time; participants' performance was also evaluated by two Artistic Gymnastics experts. Both analyses revealed that the groups did not differ. Results are discussed in terms of the hypothesis of information sufficiency in biological motion models particularly applied to the learning process of complex motor skills.

Cat striate cortex: monocular and interocular comparisons of spatial-frequency selectivity

Spatial frequency and bandwith characteristics were determined for neurones in cat striate cortex. Responses to drifting sin-wave gratings, optimized for orientation, direction and velocity, were determined over a range of spatial frequencies. Comparative measurements of spatial frequency tuning at constant velocity and at constant temporal drift frequency revealed that, overall, tuning derived by either method was similar. Results were evaluated in relation to neuronal class (simple or complex); cell subclass (standard, intermediate or special), defined by length summation, directionality; and velocity selectivity. Distributions of optimal spatial frequency for simple and complex neurones were comparable. By contrast, bandwidths of simple neurones were markedly narrower than for complex neurones, Standard complex neurones, in turn, had narrower vandwidths than special or intermediate complex neurones. Optimal spaties frequency correlated inversely with optimal velocity, directly with orientation selectivity. Thus, neurones tuned to high spatial frequencies tended to respond optimally to low velocities, and were more sharply orientation selective, than neurones tuned to low spatial frequencies. In binocular nurones, spatial frequency tuning characteristics of the two monocular imputs were compared. For either eye, spatial frequency tuning curves were reproducible over time. In a minority of neurones, spatial frequency characteristics were matched for the two eyes . A Majority showed mismatch in spatial frequency characteristics between the eyes. Individual neurones were tuned to different bands of spatial frequencies through either eye; more sharply spatial-frequency selective through one eye than the other; or had both dissimilar bandwidth and spatial frequency. Changing imput spatial-frequency resulted in profound, systematic shifts in ocular dominance. These were progressive in the case of spatial-frequncy mismatch. In cases of bandwidth, or bandwidth an spatial-frequency mismatch, the eye associated with more sharply-tuned imput exerted relatively greater influence at centre frequencies, the other eye relatively greater influence at extreme frequencies...