Intra-cortical communication costs in visual coding of position

The visual cortex is thought to be hierarchically organised so that local features are processed in early areas with increasingly complex combinations of features represented at each subsequent level (Goodale & Milner, 1992; Ungerleider & Mishkin, 1982). Many of these early- to intermediate-stages contain a retinotopic representation of the visual field (Wandell, Dumoulin, & Brewer, 2009). Within the regions (e.g. V1) there are often populations of neurons which cluster together in terms of their tuning. When the system has to compare information from different populations of neurons (either those within a cortical region or those between regions) this may increase the chance of error affecting the precision of perceptual judgements. The current study investigated the precision of alignment discrimination between forms processed within common retinotopic maps, as well as forms thought to be processed in separate maps, and also between forms thought to be processed by separate populations of neurons within a map. It was proposed that in psychophysical judgements requiring relative localization between forms processed in separate maps there would be a cost to precision due to the cross-map comparison. The first part of the study examines whether localization between forms processed in separate cortical areas introduces a cost to precision.