Bottom-up and top-down attention
As living beings, we are constantly bombarded with external stimuli. If your brain were to pay attention to every tiny sound in your surroundings or the dust motes floating through your peripheral vision, you’d never be able to focus on anything important. Focus can thus be defined as our ability to filter out unimportant information while leaving behind that which merits our attention.
Neuroscientists divide attention into two broad categories. Bottom-up attention occurs unconsciously, like how you automatically notice when your phone buzzes in your pocket. Top-down attention is under conscious control. It’s what you’re choosing to focus on, even if the subject isn’t inherently interesting, like an important school or work project.
These two types of attention utilize completely different circuits in your brain. The specific pathways depend on which sense you use to detect the stimulus. Let’s focus on visual stimuli here, since this form of attention is the most thoroughly studied.
The bottom-up attention pathway for visual stimuli begins in the primary visual cortex, located at the back of the brain. From there the signal splits into two pathways. The upper pathway decodes the object- and feature-level properties of the visual stimulus (what is it and what does it look like?), while the lower pathway decodes the spatial- and movement-level properties (where is it now and where is it going?). The two pathways reunite at the prefrontal cortex in the front of the brain, which ultimately controls our attention and decision-making processes.
While the signals travel from the back to the front of the brain, unconscious neural processes attempt to determine how much we ought to focus on this particular stimulus. Your brain takes into account the background signal, i.e., how much does this stimulus stand out in the current context? A brightly colored outfit would draw your attention more at a somber funeral than at a music festival.
Top-down attention is very different. Current evidence suggests that the signals for top-down attention do not original from external stimuli but from within our own brains, particularly the prefrontal cortex and the posterior parietal cortex. These two brain regions are where our more advanced neural processes, such as logic, planning, and emotional control, can have a say in where we direct our focus. Top-down attention is still poorly understood compared to bottom-up attention, due to its high level of complexity within the brain.
Neuroscientists divide attention into two broad categories. Bottom-up attention occurs unconsciously, like how you automatically notice when your phone buzzes in your pocket. Top-down attention is under conscious control. It’s what you’re choosing to focus on, even if the subject isn’t inherently interesting, like an important school or work project.
These two types of attention utilize completely different circuits in your brain. The specific pathways depend on which sense you use to detect the stimulus. Let’s focus on visual stimuli here, since this form of attention is the most thoroughly studied.
The bottom-up attention pathway for visual stimuli begins in the primary visual cortex, located at the back of the brain. From there the signal splits into two pathways. The upper pathway decodes the object- and feature-level properties of the visual stimulus (what is it and what does it look like?), while the lower pathway decodes the spatial- and movement-level properties (where is it now and where is it going?). The two pathways reunite at the prefrontal cortex in the front of the brain, which ultimately controls our attention and decision-making processes.
While the signals travel from the back to the front of the brain, unconscious neural processes attempt to determine how much we ought to focus on this particular stimulus. Your brain takes into account the background signal, i.e., how much does this stimulus stand out in the current context? A brightly colored outfit would draw your attention more at a somber funeral than at a music festival.
Top-down attention is very different. Current evidence suggests that the signals for top-down attention do not original from external stimuli but from within our own brains, particularly the prefrontal cortex and the posterior parietal cortex. These two brain regions are where our more advanced neural processes, such as logic, planning, and emotional control, can have a say in where we direct our focus. Top-down attention is still poorly understood compared to bottom-up attention, due to its high level of complexity within the brain.
Impact of sleep and stress on focus
Focus can be modulated by a variety of external factors. As we covered in a previous article, sleep is crucial for the health of our brains and bodies. Recent research has found that sleep also plays a huge role in attention. Study participants perform worse on attentional tasks the longer they go without sleep, and chronic sleep deprivation can have even worse effects. Studies report that the prefrontal cortex and posterior parietal cortex become less active with sleep deprivation, making it increasingly difficult to maintain top-down attention. Other studies have found that activity in the visual cortex is also reduced, suggesting impairment of bottom-up attention as well.
Sleep deprivation is also correlated with increased activity of the default mode network. This network becomes active when you are awake but not actively focused on anything, i.e., daydreaming. When you are sleep deprived, your brain’s ability to switch from the default mode network to attentional circuits becomes impaired, making it more difficult you to keep your mind from wandering.
Stress is another important factor that can impact our ability to focus. Short-term or acute stress generally seems to improve focus. One possible explanation is that a temporary increase in stress hormone levels could signal to your brain that this task particular is important and worthy of our limited attention. (It’s important to note that this may not be true for children, who show worsened focus when in acute stress.) In contrast, long-term or chronic stress has the opposite effect. People experiencing chronic stress have slower response times and worse accuracy on attentional tasks
Sleep deprivation is also correlated with increased activity of the default mode network. This network becomes active when you are awake but not actively focused on anything, i.e., daydreaming. When you are sleep deprived, your brain’s ability to switch from the default mode network to attentional circuits becomes impaired, making it more difficult you to keep your mind from wandering.
Stress is another important factor that can impact our ability to focus. Short-term or acute stress generally seems to improve focus. One possible explanation is that a temporary increase in stress hormone levels could signal to your brain that this task particular is important and worthy of our limited attention. (It’s important to note that this may not be true for children, who show worsened focus when in acute stress.) In contrast, long-term or chronic stress has the opposite effect. People experiencing chronic stress have slower response times and worse accuracy on attentional tasks