Abstract
The Where’s Waldo problem concerns how individuals can rapidly learn to search a scene to detect, attend, recognize, and look at a valued target object in it. This article develops the ARTSCAN Search neural model to clarify how brain mechanisms across the What and Where cortical streams are coordinated to solve the Where’s Waldo problem. The What stream learns positionally-invariant object representations, whereas the Where stream controls positionally-selective spatial and action representations. The model overcomes deficiencies of these computationally complementary properties through What and Where stream interactions. Where stream processes of spatial attention and predictive eye movement control modulate What stream processes whereby multiple view- and positionally-specific object categories are learned and associatively linked to view- and positionally-invariant object categories through bottom-up and attentive top-down interactions. Gain fields control the coordinate transformations that enable spatial attention and predictive eye movements to carry out this role. What stream cognitive-emotional learning processes enable the focusing of motivated attention upon the invariant object categories of desired objects. What stream cognitive names or motivational drives can prime a view- and positionally-invariant object category of a desired target object. A volitional signal can convert these primes into top-down activations that can, in turn, prime What stream view- and positionally-specific categories. When it also receives bottom-up activation from a target, such a positionally-specific category can cause an attentional shift in the Where stream to the positional representation of the target, and an eye movement can then be elicited to foveate it. These processes describe interactions among brain regions that include visual cortex, parietal cortex, inferotemporal cortex, prefrontal cortex (PFC), amygdala, basal ganglia (BG), and superior colliculus (SC).
Highlights
This paper develops a neural model, called the ARTSCAN Search model (Figure 1), to explain how the brain solves the Where’s Waldo problem; in particular, how individuals can rapidly search a scene to detect, attend, recognize and look at a target object in it
The ventral What stream is associated with object learning, recognition, and prediction, whereas the dorsal Where stream carries out processes such as object localization, spatial attention, and eye movement control (Ungerleider and Mishkin, 1982; Mishkin et al, 1983; Goodale and Milner, 1992)
MODELS The ARTSCAN Search model builds upon the ARTSCAN model (Fazl et al, 2009) and its further development in pARTSCAN to enable both view- and positionally-invariant object categories to be learned (Cao et al, 2011)
Summary
This paper develops a neural model, called the ARTSCAN Search model (Figure 1), to explain how the brain solves the Where’s Waldo problem; in particular, how individuals can rapidly search a scene to detect, attend, recognize and look at a target object in it. Name or motivational primes can supplemented by a volitional signal, activate an object-value category and, from there, an object category that has view- and positionally-invariant properties Such cognitive-emotional and motivated attention processes are modeled in the CogEM model, which is joined with pARTSCAN to enable motivationally-primed searches in the ARTSCAN Search model. When one of the primed positionally-selective categories is activated bottom-up by the sought-after object, that category can fire, and can thereby activate the corresponding positional representation in PPC (Figures 1B,C) This What-to-Where stream interaction can draw spatial attention to the position of the desired target, which in turn can activate an eye movement to foveate the target before further engaging it. The Appendix summarizes the model’s mathematical equations and parameters
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