Neuro

J Physiol 589.1 (2011) pp 49–57

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TOPICAL REVIEW

The neural basis of visual attention
James W. Bisley
Department of Neurobiology and Jules Stein Eye Institute, David Geffen School of Medicine at UCLA, and Department of Psychology and the Brain Research Institute, UCLA, Los Angeles, CA 90095, USA

The Journal of Physiology

Visual attention is the mechanism the nervous system usesto highlight specific locations, objects or features within the visual field. This can be accomplished by making an eye movement to bring the object onto the fovea (overt attention) or by increased processing of visual information in neurons representing more peripheral regions of the visual field (covert attention). This review will examine two aspects of visual attention: the changes in neuralresponses within visual cortices due to the allocation of covert attention; and the neural activity in higher cortical areas involved in guiding the allocation of attention. The first section will highlight processes that occur during visual spatial attention and feature-based attention in cortical visual areas and several related models that have recently been proposed to explain this activity. Thesecond section will focus on the parietofrontal network thought to be involved in targeting eye movements and allocating covert attention. It will describe evidence that the lateral intraparietal area, frontal eye field and superior colliculus are involved in the guidance of visual attention, and describe the priority map model, which is thought to operate in at least several of these areas.(Received 5 May 2010; accepted after revision 27 August 2010; first published online 31 August 2010) Corresponding author J. Bisley: Department of Neurobiology, PO Box 951763, Los Angeles, CA 90095-1763, USA. Email: jbisley@mednet.ucla.edu

Visual attention

Although we are not always aware of it, visual attention is incredibly important for visual perception and for all the uses we put perception to,such as learning, memory and our interactions with the visual world. This is highlighted by behavioural protocols such as change blindness, which require subjects to identify changes in a scene, but remove the usual cues of these changes (such as movement or sudden onset) by having the entire display flash off and then on again at the time of the change (Rensink, 2000). Subjects are remarkablypoor at detecting these changes when broadly viewing the entire scene, but improve dramatically when their attention is allocated to the location of the change. In addition to these types of protocols, the importance of attention is highlighted in patients with parietal lesions who often show signs of attentional deficits as striking as the inability to notice anything in a particular region of space(Husain & Nachev, 2007; Adair & Barrett, 2008). Generally we think of focusing our attention onto objects or features in terms of making a rapid eye movement (a saccade) to bring the object of our attention to the centre of gaze. However, our visual system can also process information from selected peripheral regions of the retina. When this is done consciously, it is often
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described as‘looking out of the corner of your eye’. As the eyes do not move, this is referred to as covert attention (Posner, 1980). Both covert and overt attention can be allocated voluntarily (commonly referred to as top-down) or involuntarily (bottom-up). Classic examples of bottom-up attractors of attention are flashing or moving objects, such as the lights on top of emergency vehicles. In contrast, top-downattention can refer to any voluntary attention or attention that is driven by factors other than external stimuli.
The effects of attention on neurons in visual cortical areas

In the lab, covert attention provides a number of behavioural benefits. Subjects attending a particular
James Bisley is an Assistant Professor of Neurobiology at UCLA. In 1998 he received his PhD from the University of...