Both interface in V4 and both selectively shape networks in V4 (cf. Reynolds and Desimone, 2003 and Qiu et al., 2007). (Note that for the purposes of this review, although object “salience” may influence attention, we consider this part of the bottom-up process. Here, we use the term “attention” to refer to internally generated, top-down influences.) We frame our conception of V4 function in terms of “selection”. The visual attention literature commonly uses the term “select” to indicate either a region of space that is selected (spatial attention) or specific object features that are selected (feature http://www.selleckchem.com/products/Rapamycin.html attention). In the same vein,

objects in the visual scene “select” the neuronal networks in V4 that encode their features. We propose that these two “selection” processes share a common framework. More specifically, we propose that the functional architecture in V4 is the substrate through which both sets of influences are mediated and that, at the neural level, selective

modulation of networks in V4 may be fundamentally the same, albeit directed from different sources. Our perceptual system is continuously confronted with much more information than it can actively deal with. One way to reduce processing load is to select a fraction of the incoming visual information for scrutinized processing. Visual attention achieves this by focusing on a particular location in space (spatial attention) or on certain features of objects (feature attention). The ability to attend appropriately ATR inhibitor can be negatively affected by having other competing objects (distractors) in the visual field. In the biased competition model of visual attention (Bundesen, 1990, Desimone and Duncan, 1995 and Grossberg, 1980), attentional selection is achieved via a competition for neural resources; this competition can be biased in several ways. One source of this bias comes from involuntary, click here sensory-driven bottom-up mechanisms (e.g., salient attention-attracting stimuli). Another biasing mechanism is voluntary

attentional top-down feedback (e.g., internally generated goal-directed attention), which presumably originates in areas outside the visual cortex. The biased competition model states that only those stimuli that win the competition against surrounding distractor stimuli will have further access to higher order neural mechanisms linking percepts to mechanisms sustaining goal-directed actions including systems involved in memory, decision-making and generating motor plans (Desimone and Duncan, 1995, Luck et al., 1997 and Moran and Desimone, 1985). One goal of this review is to consider this integrative bottom-up and top-down view in the context of functional organization in V4. Spatial attention has often been characterized as a “spotlight” on a region in space where visual processes appear heightened (e.g., Posner, 1980).