ScienceDaily reports (here) on a paper by Niebergall, Khayat, Treue and Martinez-Trujillo, Multifocal Attention Filters Targets from Distracters within and beyond MT Neurons’ Receptive Field Boundaries.
What they show is the ability to split the ‘attentional spotlight’ in order to attend to multiple visual object without processing other objects between the objects of interest.
When we pay attention to an object, neurons responsible for this location in our field of view are more active then when they process unattended objects. But quite often we want to pay attention to multiple objects in different spatial positions, with interspersed irrelevant objects.
There are three theories of how this is done: either the focus is ‘zoomed out’ to cover all relevant objects even if this includes irrelevant ones; or, the focus is split into more than one focus; or, the focus switches back and forth between relevant objects.
In order to explain how such a complex ability is achieved, the neuroscientists measured the activity of individual neurons in areas of the brain involved in vision. They studied two rhesus macaques, which were trained in a visual attention task. The monkeys had learned to pay attention to two relevant objects on a screen, with an irrelevant object between them. The experiment showed, that the macaques’ neurons responded strongly to the two attended objects with only a weak response to the irrelevant stimulus in the middle. So the brain is able to spatially split visual attention and ignore the areas in between.
Here is the paper’s abstract:
Visual attention has been classically described as a spotlight that enhances the processing of a behaviorally relevant object. However, in many situations, humans and animals must simultaneously attend to several relevant objects separated by distracters. To account for this ability, various models of attention have been proposed including splitting of the attentional spotlight into multiple foci, zooming of the spotlight over a region of space, and switching of the spotlight among objects. We investigated this controversial issue by recording neuronal activity in visual area MT of two macaques while they attended to two translating objects that circumvented a third distracter object located inside the neurons’ receptive field. We found that when the attended objects passed through or nearby the receptive field, neuronal responses to the distracter were either decreased or remained unaltered. These results demonstrate that attention can split into multiple spotlights corresponding to relevant objects while filtering out interspersed distracters.