The role of neural oscillations in coordinating competing cognitive processes

How does the human brain flexibly sample and prioritize incoming sensory information? Imagine a busy scene in Times Square in New York City on New Year’s Eve: towering skyscrapers, flashing lights, blaring music, swirling traffic, a colorful crowd of mingling people, the hubbub of multiple conversations, all while you are trying to listen to a friend talking with you on your cell phone.

Since our brain has limited sensory processing resources, we simply cannot fully process all of the surging flood of incoming sensory information arriving in this scene. So instead, we selectively focus our attention on the most behaviorally important information and events. The brain uses attentional filters to determine what should be prioritized, and these filters can boost relevant information.

For example, attention can selectively boost auditory processing of your friend’s voice, and enhance visual processing, focused on the street corner where you agreed to meet. Whereas previous research has sometimes described visual attention at a specific location (e.g., at a specific street corner) as a sustained spotlight that illuminates behaviorally important information, other recent investigations have instead shown that this attentional spotlight flickers at about four times per second.

That is, the strength of the attentional spotlight rhythmically increases and decreases over time. This rhythmic flickering of the spotlight suggests that the brain is “checking-in” or “updating” about four times per second to ensure that the present focus of the attentional spotlight is still the most important and relevant focus for the observer.

This rhythmic checking-in process creates time windows when it is easier to shift the attentional spotlight to a new location, potentially creating a critical balance between sampling and shifting behaviors. Rhythmic flickering of the attentional spotlight may have developed as a survival mechanism to help our ancestors (and other animals), for example, flexibly look for food while still keeping an eye out for predators.

This project investigates the neural origins and behavioral consequences of this rhythmic flickering of attention in normal human subjects. This research may also shed new light on brain disorders associated with abnormally limited attentional flexibility, such as attention deficit hyperactivity disorder (ADHD), in which individuals can become fixed in behavioral states associated with either high distractibility (i.e., shifting behaviors) or hyper-focus (i.e., sampling behaviors).

In order to investigate how and why the strength of the visual attentional spotlight rhythmically waxes and wanes about four times per second, this research uses eye tracking (a behavioral measure of eye position), and electroencephalography (EEG, a non-invasive, global measure of electrical activity in the brain) in humans. First, this research explores whether time periods associated with a weaker attentional spotlight are also associated with increased distractibility.

The results of these experiments will test the hypothesis that the brain is wired to be periodically distractible to enhance updating of selective attention. While this may be critical to performing everyday tasks that require both focus and preparedness for unexpected events, such as one may encounter while driving a car in busy rush-hour traffic, it is potentially problematic in our increasingly distracting modern environments (e.g., with a laptop open in front of us and a smart phone nearby).

Second, this project investigates whether rhythmic change in the strength of the attentional spotlight reflects a fundamental mechanism that the brain uses to mediate competing functions. Previous research has shown that the very same brain regions (such as the frontal eye fields in the cerebral cortex) that direct attention-related boosts in visual processing, also direct eye movements toward behaviorally important information.

This projects' experiments test whether these brain regions perform these potentially competing visual and motor (i.e., eye movements) functions by alternating between them over time, such that time periods associated with a weaker visual attentional spotlight are also associated with more eye movements. Finally, this project investigates whether the brain uses such rhythmic coordination of competing functions, not only in sensory processing, but as a more general mechanism for resolving sources of possible cognitive conflict, that might occur in a task where subjects are asked to simultaneously remember several similar items for a short period of time.

These experiments test whether the strength of representations for these to-be-remembered items rhythmically fluctuates over time (i.e., similar to the flickering strength of the attentional visual sensory spotlight). This research will increase understanding both of how the brain dynamically samples visual information from the environment and also how the brain continuously updates to maintain critical cognitive flexibility.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.