Transient Perceptual Neglect: Visual Working Memory Load Affects Conscious Object Processing Stephen M. Emrich 1 , Hana Burianová 2 , and Susanne Ferber 1,3 Abstract ■ Visual working memory ( VWM) is a capacity-limited cogni- tive resource that plays an important role in complex cognitive behaviors. Recent studies indicate that regions subserving VWM may play a role in the perception and recognition of visual ob- jects, suggesting that conscious object perception may depend on the same cognitive and neural architecture that supports the maintenance of visual object information. In the present study, we examined this question by testing object processing under a concurrent VWM load. Under a high VWM load, recognition was impaired for objects presented in the left visual field, in particular when two objects were presented simultaneously. Multivariate fMRI revealed that two independent but partially overlapping networks of brain regions contribute to object recog- nition. The first network consisted of regions involved in VWM encoding and maintenance. Importantly, these regions were also sensitive to object load. The second network comprised regions of the ventral temporal lobes traditionally associated with object recognition. Importantly, activation in both networks predicted object recognition performance. These results indicate that infor- mation processing in regions that mediate VWM may be critical to conscious visual perception. Moreover, the observation of a hemifield asymmetry in object recognition performance has important theoretical and clinical significance for the study of visual neglect. ■ INTRODUCTION Although our subjective experience of the visual world seems to be rich and detailed, in actuality our internal representations are quite sparse. A striking demonstration of our visual systemʼs processing limitations comes from the change detection task, in which observers first see a multi-item array and are asked to maintain as much in- formation as possible. The display is removed from view, and after a brief delay, a probe array appears to which observers report whether a change has occurred. Accord- ingly, observers have to hold information “on-line” after it has been removed from view, a cognitive faculty called visual working memory (VWM). Observers typically per- form well for arrays containing four items or less, but per- formance declines significantly beyond that limit (Cowan, 2001; Luck & Vogel, 1997). The neural substrate and electrophysiological signature of this processing bottleneck have been pinpointed to the posterior parietal cortex (in particular, the intraparietal sulcus, IPS) and lateral occipital areas, as activity in these regions increases concomitantly with an increase in work- ing memory (WM) load and plateaus at a given subjectʼs capacity (Robitaille, Grimault, & Jolicoeur, 2009; Xu & Chun, 2006; Todd & Marois, 2004, 2005). Although much has been discovered about the mechanisms of this capac- ity limit, it is unclear how VWM capacity relates to other aspects of conscious visual experience such as object rec- ognition. It has been argued that for an object percept to reach conscious awareness, it must be maintained in a capacity-limited global cognitive workspace as an episodic representation called an object file (Kahneman, Treisman, & Gibbs, 1992; Kahneman & Treisman, 1984; see also Baars & Franklin, 2003). Object files contain basic information about an objectʼs spatial and temporal coordinates and high-level information about its features such as shape, color, and texture. Recently, Hollingworth and Rasmussen (2010) demonstrated that VWM shares some properties with object files. Thus, interfering with VWM processes may affect the ability to create and sustain object files, thereby limiting their access to conscious awareness. Simi- larly, Xu and Chun (2009) have proposed a two-stage ob- ject file theory. In the first stage, objects are individuated, meaning that coarsely defined candidate objects are se- lected for representation based on their spatial locations (see also Pylyshyn, 1989). The neural substrate of this se- lection process has been pinpointed to the inferior IPS, in which activation levels are modulated by up to four separate spatial locations, but not by object complexity (Xu & Chun, 2006, 2007). In the second stage, these se- lected sparse representations are enhanced with more detailed information to allow for object identification. This process seems to be subserved by the superior IPS (sIPS) and the lateral occipital complex (LOC), an area associated with conscious object recognition (Grill-Spector, Kushnir, 1 University of Toronto, 2 Macquarie University, Sydney, Australia, 3 Rotman Research Institute, Toronto, Canada © 2011 Massachusetts Institute of Technology Journal of Cognitive Neuroscience 23:10, pp. 2968–2982