Abstract
The activity of a border ownership selective (BOS) neuron indicates where a foreground object is located relative to its (classical) receptive field (RF). A population of BOS neurons thus provides an important component of perceptual grouping, the organization of the visual scene into objects. In previous theoretical work, it has been suggested that this grouping mechanism is implemented by a population of dedicated grouping (“G”) cells that integrate the activity of the distributed feature cells representing an object and, by feedback, modulate the same cells, thus making them border ownership selective. The feedback modulation by G cells is thought to also provide the mechanism for object-based attention. A recent modeling study showed that modulatory common feedback, implemented by synapses with N-methyl-D-aspartate (NMDA)-type glutamate receptors, accounts for the experimentally observed synchrony in spike trains of BOS neurons and the shape of cross-correlations between them, including its dependence on the attentional state. However, that study was limited to pairs of BOS neurons with consistent border ownership preferences, defined as two neurons tuned to respond to the same visual object, in which attention decreases synchrony. But attention has also been shown to increase synchrony in neurons with inconsistent border ownership selectivity. Here we extend the computational model from the previous study to fully understand these effects of attention. We postulate the existence of a second type of G-cell that represents spatial attention by modulating the activity of all BOS cells in a spatially defined area. Simulations of this model show that a combination of spatial and object-based mechanisms fully accounts for the observed pattern of synchrony between BOS neurons. Our results suggest that modulatory feedback from G-cells may underlie both spatial and object-based attention.
Highlights
In this study, we focus on the interplay of two features of intermediate vision
Our results suggest that modulatory feedback from grouping cells (G-cells) may underlie both spatial and object-based attention
We showed in our previous study [41] the non-monotonic effect of G-cell firing rates on synchrony between border ownership selective (BOS) cells
Summary
We focus on the interplay of two features of intermediate vision. The first is selective attention which enhances perception of particular sensory stimuli [1,2,3,4,5]. Top-down visual attention can be categorized into at least three distinct types: spatial, feature-based, and objectbased attention [6,7,8]. We focus on spatial and object-based attention. It has been suggested that these types of attention rely on distinct cortical pathways [9] for enhancing the related neural responses and for improving the discriminability of visual stimuli [10,11,12]. The second feature is figure-ground segregation, the integration of visual features into objects and the segmentation between different objects and the background. This is an important step in understanding complex scenes, with images of many objects projected simultaneously onto the retinae. This has been called border ownership since the foreground object, which is closer to the observer, determines the fate of the border (e.g. when the object is moving) and “owns” it [13,14,15]
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