Despite the subjective experience of a continuous and coherent external world, we will argue that the perception and categorisation of visual space is constrained by the spatial resolution of the sensory systems but also and above all, by the pre-reflective representations of the body in action. Recent empirical data in cognitive neurosciences will be presented that suggest that multidimensional categorisation of perceptual space depends on body representations at both an experiential and a functional level. Results will also be resumed that (...) show that representations of the body in action are pre-reflective in nature as only some aspects of the pre-reflective states can be consciously experienced. Finally, a neuro-cognitive model based on the integration of afferent and efferent information will be described, which suggests that action simulation and associated predicted sensory consequences may represent the underlying principle that enables pre-reflective representations of the body for space categorisation and selection for action. (shrink)

Philosophical considerations as well as several recent studies from neurophysiology, neuropsychology, and psychophysics converged in showing that the peripersonal space is structured in a body-centred manner and represented through integrated sensory inputs. Multisensory representations may deserve the function of coding peripersonal space for avoiding or interacting with objects. Neuropsychological evidence is reviewed for dynamic interactions between space representations and action execution, as revealed by the behavioural effects that the use of a tool, as a physical extension of the reachable space, (...) produces on visual–tactile extinction. In particular, tool-use transiently modifies action space representation in a functionally effective way. The possibility is discussed that the investigation of multisensory space representations for action provides an empirical way to consider in its specificity pre-reflexive self-consciousness by considering the intertwining of self-relatedness and object-directness of spatial experience shaped by multisensory and sensorimotor integrations. (shrink)

Evidence for a dichotomy between the planning of an action and its on-line control in humans is reviewed. This evidence suggests that planning and control each serve a specialized purpose utilizing distinct visual representations. Evidence from behavioral studies suggests that planning is influenced by a large array of visual and cognitive information, whereas control is influenced solely by the spatial characteristics of the target, including such things as its size, shape, orientation, and so forth. Evidence from brain imaging and neuropsychology (...) suggests that planning and control are subserved by separate visual centers in the posterior parietal lobes, each constituting part of a larger network for planning and control. Planning appears to rely on phylogenetically newer regions in the inferior parietal lobe, along with the frontal lobes and basal ganglia, whereas control appears to rely on older regions in the superior parietal lobe, along with the cerebellum. Key Words: action; apraxia; control; illusions; optic ataxia; PET; planning; reaching;. (shrink)

The control of action has traditionally been described as "automatic". In particular, movement control may occur without conscious awareness, in contrast to normal visual perception. Studies on rapid visuomotor adjustment of reaching movements following a target shift have played a large part in introducing such distinctions. We suggest that previous studies of the relation between motor performance and perceptual awareness have confounded two separate dissociations. These are: (a) the distinction between motoric and perceptual representations, and (b) an orthogonal distinction between (...) conscious and unconscious processes. To articulate these differences more clearly, we propose a new measure of motor awareness, based on subjects' ability to reproduce the spatial details of reaching movements they have just made. Here we focus on the dissociation between motor awareness and perceptual awareness that may occur when subjects make rapid visuomotor adjustments to reaching movements following a target shift. In experiment 1, motor awareness was dissociated from perceptual awareness of a target shift during reaching movement. Participants' reproduction of movement endpoints following visuomotor adjustment was independent of whether they saw the target shift or not. Experiment 2 replicated this result, and further showed that neither motor awareness nor motor performance were disrupted by TMS over the parietal cortex. The neural mechanisms underlying motor awareness, and the implications for theories of consciousness, are discussed. (shrink)