Untangling target match signals. Left, Previous results suggest that during visual target search, visual and working memory signals are combined within or before IT along the ventral visual pathway in a nonlinearly separable or tangled fashion, followed by computations in PRH that untangle target match information such that it is more accessible to a linear population readout. Right, Each point depicts a hypothetical population response, consisting of a vector of the spike count responses to a single condition on a single trial. Clouds of points depict the predicted dispersion across repeated presentations of the same condition due to trial-by-trial variability. The different shapes depict the hypothetical responses to different images and the two shades (black, gray) depict the hypothetical responses to target matches and distractors, respectively. A target-switching task (such as the delayed-match-to-sample task, Fig. 2) requires discriminating the same objects presented as target matches and as distractors. In a tangled representation (bottom), a nonlinear decision boundary (corresponding to a nonlinear population readout) is required to separate these two groups whereas an untangled representation (top) can be read out with a linear decision boundary (corresponding to a linear population readout). As reported by Pagan et al. (2013), target match signals are more tangled in IT and more untangled in PRH.