How The Brain Switches Between The External World And The Internal World

Your brain constantly switches between two worlds: what's around you (sounds, images, movements) and what's inside your mind (memories, thoughts, plans). This ability to focus sometimes on the external environment and sometimes on internal ideas is essential for making good daily decisions. Scientists are now beginning to understand how the brain performs this "scene switching" so quickly and automatically, and why it's so important for our attention, mental flexibility, and health.

Every day, our brain performs an extraordinary task: it switches focus between what's happening around us (such as sounds, images, and movements) and what's going on inside our mind (such as thoughts, memories, and plans). This balance between external and internal attention is essential for us to act, make decisions, and adapt to the world.

For a long time, scientists have primarily studied how we pay attention to the external environment, how we perceive sensory stimuli, such as images and sounds, and how the brain chooses what is most important to pay attention to. This has led to the discovery that certain areas of the brain, such as the frontal and parietal regions, work together to highlight relevant information and ignore distractions.

However, attention isn't limited to what we see and hear. We can also "turn our attention inward," that is, focusing on memories, ideas, or plans. This type of internal attention helps, for example, remember what we were going to say, plan our next steps, or solve problems mentally.

Recent studies have shown that we can even improve the quality of a memory simply by consciously focusing on it.

In real life, however, we rarely use just one type of attention at a time. Driving a car, talking to someone, or cooking requires the brain to constantly switch between what's in front of our eyes and what's in our mind.

It's as if the brain were a conductor, needing to conduct two different sets of instruments simultaneously, the external and the internal, keeping everything in harmony.

Current research shows that, despite using some brain areas in common, external and internal attention also activate different regions. For example, focusing on memory or ideas involves deeper areas of the brain, such as the medial prefrontal cortex.

Presumed superordinate control areas involved in switching between external and internal modes.

Furthermore, switching focus between these two modes can have a cost: we are generally slower and make more mistakes when switching from external to internal focus than vice versa. This is because the world around us is naturally more eye-catching and easily attracts our attention.

Functional magnetic resonance imaging (fMRI) results based on Wallis et al. Blue areas indicate activation during external attention, orange areas during internal attention, and green areas reflect regions activated during both. preSMA, presupplementary motor area; FEF, frontal eye field; MFG, middle frontal gyrus; IPS, intraparietal sulcus; fO, frontoinsular cortex; TPJ, temporoparietal junction; MTG, middle temporal gyrus; iFEF, inferior frontal eye field; SPL, superior parietal lobule.

Another interesting finding is that this switching between the two types of attention can follow its own rhythms. The brain appears to oscillate between external and internal focuses in cycles lasting from milliseconds to hours, which helps balance learning about the world and processing thoughts and memories.

There is still an unsolved mystery: what drives this shift in focus? Some researchers believe there's a kind of "control panel" in the brain, perhaps in the hippocampus or frontal areas, that decides where to pay attention. Others believe there's no single control center, and that switching occurs naturally, through competition between internal and external stimuli.

Understanding how this switching works is crucial. When this system fails, difficulties such as inattention, repetitive thoughts, or difficulty concentrating can arise, common symptoms in conditions like ADHD, depression, and schizophrenia.

Therefore, studying how the brain performs these transitions can help develop therapies, training, and even technological interventions to improve attention balance.

Modulation points during attention shifts between domains. (A) A superordinate control can govern shifts between external and internal attention. This controller can determine whether the external or internal attention network takes priority, with only the external or internal contents targeted by each network activated, respectively. (B) Such control functions can also influence any or all stages of attention modulation. (C) A superordinate control system for shifting attention between domains may not exist, and external and internal attention may directly compete for dominance. Note that showing the external and internal control networks as distinct in this figure does not imply their complete separation or anatomical independence. The differences may also simply reflect functional modes of operation.

In short, attention is not just a “flashlight” pointing at something. It is a complex and dynamic system that balances what we see with what we think, what we feel with what we remember. Learning more about this balance can help us better understand human behavior and find new ways to live with greater focus, clarity, and presence.

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How the brain shifts between external and internal attention

Anna C. Nobre, and Daniela Gresch

Neuron. July 16, 2025

DOI: 10.1016/j.neuron.2025.06.013

Abstract: 

Focusing on relevant contents to guide adaptive behavior is a core property of the brain. For decades, scientists have investigated mechanisms to anticipate, select, prioritize, and prepare sensory signals according to goals, memories, and salient events. More recently, researchers have considered how these attention functions operate within internal representations. However, neither external nor internal attention in isolation captures everyday behavior. The brain frequently and seamlessly shifts between contents from the sensory stream and those held in mind. In this perspective, we ask how the brain shifts between external and internal attention. We describe similarities and differences between selective external and internal attention, present competing hypotheses regarding the operating principles of between-domain shifts, and highlight putative brain areas and mechanisms. We discuss the scarce experimental forays comparing attention shifts between vs. within domains and contemplate how these constrain theoretical and computational models. We conclude by suggesting open questions to guide investigation.