The superior colliculus, a brain structure which helps control eye and head movements, is linked to people's attention to their surroundings, a new study has found.
Lead author Lee Lovejoy of the study from the Salk Institute for Biological Studies, said: "Our ability to survive in the world depends critically on our ability to respond to relevant pieces of information and ignore others. Our work shows that the superior colliculus is involved in the selection of things we will respond to, either by looking at them or by thinking about them."
Richard Krauzlis, Ph.D., an associate professor in the Salk's Systems Neurobiology Laboratory, added: "We often look directly at attended objects and the superior colliculus is a major component of the motor circuits that control how we orient our eyes and head toward something seen or heard."
In their current study, the Salk researchers specifically asked whether the superior colliculus is necessary for covert attention. To tease out the superior colliculus' role in covert attention, they designed a motion discrimination task that distinguished between control of gaze and control of attention.
The superior colliculus contains a topographic map of the visual space around us, just as conventional maps mirror geographical areas. Lovejoy and Krauzlis exploited this property to temporarily inactivate the part of the superior colliculus corresponding to the location of the cued stimulus on the computer screen. No longer aware of the relevant information right in front of them the subjects instead based all of their decision about the stimulus' movement on irrelevant information found elsewhere on the screen.
Lovejoy explained: "The result is very similar to what happens in patients with neglect syndrome. Up to a half of acute right-hemisphere stroke patients demonstrate signs of spatial neglect, failing to be aware of objects or people to their left in extra-personal space."
Krauzlis concluded: "Our results show that deciding what to attend to and what to ignore is not just accomplished with the neocortex and thalamus, but also depends on phylogenetically older structures in the brainstem.
"Understanding how these newer and older parts of the circuit interact may be crucial for understanding what goes wrong in disorders of attention."
The study has been published in the Dec. 20, 2009, issue of the journal Nature Neuroscience.