Figure 1. The effects of spatial attention on region-level priority maps.
Spatial attention might act via one of several mechanisms to change the spatial representation of a stimulus within a putative priority map.(a) The hypothetical spatial representation carried across an entire region in response to an unattended circular stimulus. (b) Under one hypothetical scenario, attention might enhance the spatial representation of the same stimulus by amplifying the gain of the spatial representation (i.e. multiplying the representation by a constant greater than 1). (c) Alternatively, attention might act via a combination of multiple mechanisms such as increasing the gain, decreasing the size, and increasing the baseline activity of the entire region (i.e. adding a constant to the response across all areas of the priority map). (d) Cross-sections of panels a–c. Note that this is not meant as an exhaustive description of different attentional modulations. (e) These different types of attentional modulation can give rise to identical responses when the mean BOLD response is measured across the entire expanse of a priority map. Note that simple Cartesian representations, such as those shown in a–c, may be visualized in early visual areas where retinotopy is well-defined at the spatial resolution of the BOLD response. However, later areas might still encode precise spatial representations of a stimulus even when clear retinotopic organization is not evident, so using alternative methods for reconstructing stimulus representations, such as the approach described in Figure 3, is necessary to evaluate the fidelity of information encoded in putative attentional priority maps.