Attention and the representation of objects in space.

Visual information is processed by the brain in a large number of functional sites across a network of anatomically separate areas. In order to guide coherent behaviour, visual attention is required to select and integrate information regarding the spatial and perceptual attributes of separate objects from the numerous areas involved in their representation. The empirical work reported in this thesis investigates the role of spatial information in guiding this process and considers the different types of representation that may be involved. Using an experimental paradigm designed to disambiguate priming in egocentric and allocentric coordinates, the thesis contrasts the predictions of location and object-based models of attention across a series of experiments that manipulate the way attention is oriented to the location or identity of objects in the visual scene. Initial chapters investigate the distinction between exogenous and endogenous attention and its implication for the coordinate frame in which selection occurs. Subsequent chapters investigate the role of non-spatial attributes such as colour differentiation and grouping in determining the nature of spatial representation underlying shifts of attention as well as spatial-temporal constraints on object-based priming. The results across the thesis are inconsistent with the distinction imposed by space and object-based models of attention and instead support a more flexible account in which attentional mechanisms activate representations that combine non-spatial and spatial information about localised objects at a number of levels of spatial description