The empirical study of visual space has centered on determining its geometry, whether it is a perspective projection, flat or curved, Euclidean or non-Euclidean, whereas the topology of space consists of those properties that remain invariant under stretching but not tearing. For that reason distance is a property not preserved in topological space whereas the property of spatial order is preserved. Specifically the topological properties of dimensionality, orientability, continuity, and connectivity define “real” space as studied by physics and are the (...) spatial properties that characterize the physical universe as being an integral whole. By contrast the geometrical analysis of VS has taken little cognizance of its topology. Instead such properties have been presupposed a priori rather than being established a posteriori by empirical means, perhaps because these properties are self-evident. Applying the method of coordinative definition expounded by Hans Reichenbach for determining geometrical and topological properties of physical space, it can be shown that VS fulfills the topological criteria of being a “real” space sui generis. Though theorized to be produced by the brain, the topology of VS is not topologically equivalent with the structure and activity of the brain because, as will be shown, the topology of VS cannot be formed from the topology of the brain without tearing and/or cutting and pasting. (shrink)

Two theses appear to be central to Reid’s view of the visual field. By sight, we do not originally perceive depth or linear distance from the eye. By sight, we originally perceive the position that points on the surface of objects have with regard to the centre of the eye. In different terms, by sight, we originally perceive the compass direction and degree of elevation of points on the surface of objects with reference to the centre of the eye. I (...) consider various problems about distance perception and perception of position with regard to the centre of the eye raised by Reid’s texts. These questions are relevant to Reid’s description of the geometry of visibles as the “intrinsic” geometry of the surface of the sphere. (shrink)

This review addresses the role of early sensory areas in the awareness of tactile information in humans. The results of recent studies dealing with this important topic are critically discussed: In particular, we report on evidence from neuropsychology, neurophysiology, neuroimaging, and behavioral experiments that have highlighted the crucial role played by the primary somatosensory cortex in mediating our awareness of tactile information. Phenomena, such as tactile hallucinations, tactile illusions, the perception of supernumerary limbs, and synaesthesia are also discussed. The research (...) reviewed here clearly shows that the activation of SI is necessary, but not sufficient, for the awareness of touch. On the basis of the evidence outlined here, we propose a neurocognitive model that provides a conceptual framework in which to interpret the results of the literature regarding tactile consciousness. (shrink)