LAUSR

Vision is subserved by a hierarchical system, where increasingly complex representations are formed at each processing stage (Van Essen et al., 1992). This collection of interconnected brain regions is understood to work in concert to build a meaningful representation of our surroundings. Beginning with point-wise light detection by retinal ganglion cells, representations are pieced together in successive stages, forming scene segmentation and object representations. The earliest processing stages, involving the retina, lateral geniculate nucleus and early visual cortices, are thought to act as filters selective for various stimulus dimensions, giving rise to features such as orientation in areas LGN and V1 (Cheong et al., 2013; De Valois et al., 1982; Hubel & Wiesel, 1968). These early visual areas have been heavily studied and are understood to encode information about our surroundings in a retinotopic coordinate system, which preserves information in retinal coordinates centred on the focus of gaze. However, at some stage in the process, our visual system clearly must transition away from purely retinotopic frames of reference, to those which are of use in actually interacting with the objects around us—spatiotopic and bodycentred reference frames. That is, world coordinates, which do not necessarily match retinotopic ones. Higher visual areas, whose cells’ receptive fields can be so large as to cover the entire visual field, likely operate in such reference frames (Melcher & Morrone, 2015). How is the transition from retinotopic to world coordinates achieved? Perhaps we can draw from what we know about the formation of representations within the early visual system of neurotypical humans. Even within V1, we begin to see departures from the one-to-one correspondence of a strict retinotopic coordinate system. Indeed, one of the hallmark transformations within V1 is the transition from simple cells to complex cells, which goes from spatial phase-variant to phase-invariant selective preferences. In brief, simple cellsin V1 have defined, mutually antagonistic on/off sub–regions and respond to stimuli in a spatial–phase dependent manner, i.e., only when the light part of a preferentially oriented stimulus falls onto the excitatory “on” region and the dark part in the inhibitory, “off” region of the cell’sRF. Conversely, complex cells are not sensitive to spatial phase (the exact location of dark and light stimulus bands within the RF), so they respond to their preferred stimuli regardless of its position within the RF (Carandini, 2006; Hubel & Wiesel, 1962). This primitive conversion of spatial coordinate systems involves gains and losses in information. In V1, the gains are clear: complex, phaseinvariant representations endow these populations with the ability to encode motion direction and stereoscopic depth—both essential building blocks necessary in order to build an understanding of our environment. But, there is a loss in information with the construction of these representations, as well. In gaining the ability to process motion and depth, complex cells lose the ability to identify the precise spatial phase of visual stimulation. And yet, we are generally still able to consciously access that information when asked to identify the precise spatial phase of a visual stimulus, presumably by relying on information that resides within simple cells, or even