The spread of attention across features of a surface.

Contrasting theories of visual attention have emphasized selection by spatial location, individual features, and whole objects. We used functional magnetic resonance imaging to ask whether and how attention to one feature of an object spreads to other features of the same object. Subjects viewed two spatially superimposed surfaces of random dots that were segregated by distinct color-motion conjunctions.

Dividing attention between two transparent motion surfaces results in a failure of selective attention.

In object-based attention, it is easier to divide attention between features within a single object than between features across objects. In this study we test the prediction of several capacity models in order to best characterize the cost to dividing attention between objects. Here we studied behavioral performance on a divided attention task in which subjects attended to the motion and luminance of overlapping random dot kinemategrams, specifically red upward moving dots superimposed with green downward moving dots.

Disinhibition combines with excitation to extend the operating range of the OFF visual pathway in daylight.

Cone signals divide into parallel ON and OFF bipolar cell pathways, which respond to objects brighter or darker than the background and release glutamate onto the corresponding type of ganglion cell. It is assumed that ganglion cell excitatory responses are driven by these bipolar cell synapses. Here, we report an additional mechanism: OFF ganglion cells were driven in part by the removal of synaptic inhibition (disinhibition).