Spatial Representations and Sensorimotor Transformations

Abstract

Each year, the Centre de recherche en sciences neurologiques of the Université de Montréal organizes a symposium on a topic in the neurosciences. For the IXth International Symposium, the theme chosen was "Spatial Representations and Sensorimotor Transformations."Many of the diverse functions performed by the central nervous system have an important spatial component in common. For instance, there are neural mechanisms for the analysis and perception of the three-dimensional structure of visual space, such as the location, form, and movement of objects in the visual environment. There exist processes to determine the spatial location of auditory stimuli. One can also regard the body as an "internal" space for which mechanisms have evolved for the kinesthetic perception of the position and movement of body parts relative to one another, and for the position and orientation of the body within its immediate external environment. Motor control also requires spatial information, since many movements of the eyes, head, and limbs follow specific paths or are aimed at the specific spatial location of an object as signalled by sensory processes.One can argue, therefore, that a major aspect of the functioning of the brain involves the generation of many different spatial representations, and the exchange of information among them. Each of these neural representations provides a spatial coordinate framework whose coordinate axes are based on certain types of information. For instance, movement of the limb toward an object can be described equally well in several different coordinate systems, such as those based on its spatial path, its dynamics (the direction and level of forces, torques, and external loads), or the muscle activity by which it is achieved. A better understanding of the coordinates in which the CNS codes these various types of information will provide a better appreciation of the neural mechanisms generating the spatial representations. It will also provide a clearer understanding of the transformations that must occur to relay information between sensory and motor representations, which permit an animal to interact successfully with its environment.The participants at this Symposium were invited to examine some of these issues as they pertain to the somatic and visual systems.