The brain rhythms of focused attention and… is that my phone?

In a large bowl, dissolve yeast and one tablespoon of sugar into lukewarm water. Whisk in the oil, and then add four eggs one at a time. Now gradually add eight cups of flour: One…two…three…was that three? Four… five… a sudden BUZZ-BUZZ from my apron pocket interrupts my counting. I’ve been expecting a phone call sometime today from my boss. Could this be her calling now with important news, or is it just my friend wanting to chat again? My brain is faced with a dilemma – keep going on the flour so I don’t lose my place, or switch my attention to my phone?

Our brains are highly adept at directing attention toward our goals, even with distractions all around. Generations of women before me have made the same challah bread recipe in spite of cranky children, bodily discomfort, and the sometimes uncontrollable desire to chit-chat while baking. The tricky part is that the brain must be able to maintain focus to accomplish complex tasks like counting cups of flour or weaving bread, but equally critical is the ability to monitor our surroundings so we can switch attention to important information when it appears unexpectedly. In other words, I want to focus on my bread-making to avoid taste- and texture-altering mistakes, but I also don’t want to be so hyper-focused on counting flour that I miss an important phone call. How do our brains give us moments of intense focus while at the same time monitoring our surroundings for new information that might be even more critical?

Discovering the rhythms of attention

This delicate balance of sharp focus and broad awareness is accomplished by the incredible flexibility of the human brain. Neuroscientists like myself are fascinated with one method by which the brain achieves dynamism known as oscillations. Oscillations occur when groups of neurons in a particular brain area vary their electrical activity (which they use to send signals to one another) up and down together as a group, like a crowd in a baseball stadium doing the wave. To listen in on brain oscillations, researchers must pick up these electrical signals from thousands of neurons at a time using electrodes.

Figure 1: Attention Game Involving Sharp Focus and Broad Awareness. To play this game, a player fixes their eyes on the square in the center of the screen, and is given a “spatial cue” signaling where a target (a dim light) is likely to appear (one of the four corners of the screen). The cue then disappears, and players focus their attention on the cued area in anticipation of the dim light target. When the target appears, players press a button to indicate that they detected it. Once in a while, the cue will incorrectly indicate the wrong area, and the dim light will appear in one of the other four corners, so players must balance sharp focus with broad awareness to play this game well. (adapted from Fiebelkorn, 2018)

Recently, a group of researchers at Princeton University discovered a link between these ups-and-downs of neural activity and the back-and-forth shifts of attentional focus. In order to detect oscillations that support attention, these researchers decided to teach non-human primates to play a computer game requiring both focused and broad attention (Figure 1). The monkeys’ goal was to signal as fast as possible that a dim light had appeared on their screen. First, the monkeys received a cue signal indicating that they should pay attention to one of four possible locations on the screen, where the dim light was likely to appear. Cleverly, these researchers built some uncertainty into this game: sometimes the cue lied, and the dim light appeared unexpectedly at a different one of the four locations. This meant that players had to both focus their attention sharply on the cued location as well as be open to occasional attention-switches to the other three corners.

Like humans, monkeys have attentional lapses sometimes: in this challenging computer game, sometimes the monkeys would miss the dim light completely. However, the scientists noticed a curious and consistent pattern in when these lapses occurred. After the cue was given, a varying amount of time passed before the target dim light appeared, and depending on exactly when it appeared the participants were more or less likely to detect it (Figure 2). In other words, attention seemed to flicker in and out rhythmically on a steady beat, around 5 switches per second. If the target dim light appeared when attention was at its peak, the monkey detected it accurately, but if it appeared just a fraction of a second later, then the monkey would miss the dim light more often than not. This suggested to the researchers that attention had a distinct rhythm to it, waning and waxing very quickly like a light-bulb flickering on and off. This pattern seemed a lot like the oscillations of crowds of neurons. But are these two rhythms, attentional and neural, actually related?

Are attention rhythms and brain rhythms alike?

Figure 2: Attention Fluctuates Between Focused and Unfocused States. As players attempted to balance sharp focus and broad awareness in the game described in Figure 1, researchers noticed attention fluctuated between focused states (where the target dim light was detected) and unfocused states (where the target was missed, also known as a “lapse” of attention). Depending on when the target appeared relative to the cue, players were more or less likely to detect it. (adapted from Fiebelkorn, 2018)

This link was discovered only when the researchers recorded electrical activity from a specific set of interconnected brain regions often referred to as the “attention network” while the monkeys were playing this attention game. This network stretches across the length of the brain from the front (“frontal”) to the back (“parietal”), and helps guide attention toward relevant information. This group of researchers looked at neural activity coming from the two ends of the network. They found that neural oscillations in both frontal and parietal areas kept the same pace as the attentional rhythms, at around 5 switches per second. This meant that as attention shifted between focused and distracted states, brain activity fluctuated between high and low states as well!

So we now know that the brain rhythms and the attention rhythms match up, fluctuating between a state of focused attention and one of broad awareness that gives our brains the opportunity to switch attention to new things if necessary. But do these matching rhythms have anything to do with how the brain functions? Knowing that fast signaling from neuron to neuron (known as the gamma rhythm) occurs when the brain is engaged in complex tasks like memory games, we might guess that the focused attention state would have more gamma rhythms than the broad-awareness state. Indeed, these same researchers found that during the focused attention state there were more gamma rhythms detected from the electrodes, indicating high speed neuronal communication. This fast signaling was much less frequent during the broad-awareness state; instead, the brain tended to signal more slowly. These two “states” of attention, each with their own characteristic neural rhythms (fast during attention and slow during broad awareness), reveals that the brain uses multiple coordinated rhythms of activity to bring us in and out of focus.

The advantage of fast switching

Why would our brains switch back and forth between focused and unfocused states many times per second? Anyone who has experienced a long work-day knows that attention fluctuates in and out over the course of hours, often dipping toward midday and peaking again after lunch. What would be the advantage of also having attention fluctuate so rapidly that we don’t even notice it? It may be the case that our subjective experience of “multi-tasking” or having two concurrent processing streams, is really more like a super-fast spotlight of attention moving back and forth rapidly. In our uncertain world, we can never perfectly predict when something might change that requires us to switch our attention to something new. This research suggests that fast rhythms in the brain may allow us frequent opportunities to switch attention just in case, even if we don’t always choose to. It’s as though our brains are giving us a chance five times every second to scan the environment and evaluate new information  — is that my boss calling? — without losing track of our baking ingredients.

Edited by Isabel Low

References:

Fiebelkorn, I.C, Pinsk, M.A, Kastner, S. “A Dynamic Interplay within the Frontoparietal Network Underlies Rhythmic Spatial Attention” (2018). Neuron, Volume 99, Issue 4, 842 - 853.e8