The role of the lateral intraparietal area in orienting attention and its implications for visual search.

Orienting visual attention is of fundamental importance when viewing a visual scene. One of the areas thought to play a role in the guidance of this process is the posterior parietal cortex. In this review, we will describe the way the lateral intraparietal area (LIP) of the posterior parietal cortex acts as a priority map to help guide the allocation of covert attention and eye movements (overt attention). We will explain the concept of a priority map and then show that LIP activity is biased by both bottom-up stimulus-driven factors and top-down cognitive influences, and that this activity can be used to predict the locus of covert attention and initial saccadic latencies in simple visual search tasks. We will then describe evidence for how this system acts during covert visual search and how its activity could be used to optimize overt visual search performance.

Mutation of the Drosophila vesicular GABA transporter disrupts visual figure detection.

The role of gamma amino butyric acid (GABA) release and inhibitory neurotransmission in regulating most behaviors remains unclear. The vesicular GABA transporter (VGAT) is required for the storage of GABA in synaptic vesicles and provides a potentially useful probe for inhibitory circuits. However, specific pharmacologic agents for VGAT are not available, and VGAT knockout mice are embryonically lethal, thus precluding behavioral studies. We have identified the Drosophila ortholog of the vesicular GABA transporter gene (which we refer to as dVGAT), immunocytologically mapped dVGAT protein expression in the larva and adult and characterized a dVGAT(minos) mutant allele. dVGAT is embryonically lethal and we do not detect residual dVGAT expression, suggesting that it is either a strong hypomorph or a null. To investigate the function of VGAT and GABA signaling in adult visual flight behavior, we have selectively rescued the dVGAT mutant during development. We show that reduced GABA release does not compromise the active optomotor control of wide-field pattern motion. Conversely, reduced dVGAT expression disrupts normal object tracking and figure-ground discrimination. These results demonstrate that visual behaviors are segregated by the level of GABA signaling in flies, and more generally establish dVGAT as a model to study the contribution of GABA release to other complex behaviors.