Summary: The brain constantly toggles between focusing on external sensory information and internal mental representations like memories, plans, and thoughts. This seamless switching is crucial for adaptive behavior, yet the underlying mechanisms remain poorly understood.
Recent research highlights both shared and distinct neural networks for external and internal attention, revealing costs and trade-offs when shifting between them. Understanding these processes could illuminate how attention operates in natural settings and how disruptions may contribute to cognitive or psychiatric disorders.
Key Facts:
- Shared Networks: Both external and internal attention recruit overlapping frontoparietal networks, but internal attention also engages medial and ventrolateral prefrontal regions.
- Switching Costs: Behavioral studies show measurable performance costs when shifting attention between external and internal domains compared to within a single domain.
- Open Questions: It remains unclear whether a superordinate control system coordinates these shifts or if they emerge from competitive dynamics within existing attention systems.
Source: Neuroscience News
Every day, your brain seamlessly balances between two worlds: the sights, sounds, and sensations streaming in from your surroundings, and the thoughts, memories, and plans you hold inside your mind.
This ability—to switch between focusing on what’s “out there” and what’s “in here”—is fundamental to how we adapt and function. Yet surprisingly, science has only recently begun to explore how the brain orchestrates this intricate dance.
New research sheds light on the neural mechanisms behind these shifts in attention, uncovering both striking similarities and critical differences between how the brain handles external and internal information.
By comparing how we direct focus toward the sensory environment versus mental representations, scientists hope to explain not only everyday behaviors—like remembering your grocery list while watching traffic—but also shed light on disorders where these systems may go awry.
Why Attention Is More Than Meets the Eye
For over a century, attention research focused primarily on the external world: how the brain selects and prioritizes sensory signals like sights and sounds. We now understand much about how frontal and parietal networks work together to amplify important signals, suppress distractions, and guide actions.
But even early theorists recognized that attention doesn’t stop at the senses—it also operates inside the mind. Internal attention allows you to focus on a memory, an idea, or a plan, sifting through mental contents to guide behavior.
Studies of internal attention gained momentum when scientists began to explore how cues can boost working memory performance by “retrofocusing” on specific stored items. These discoveries showed that internal attention can improve accuracy and even enhance the quality of memories being recalled.
Switching Between Two Domains
In everyday life, however, external and internal attention rarely operate in isolation. Whether driving, working, or chatting with a friend, we constantly shift back and forth—watching what’s happening, recalling what to do next, imagining possible outcomes.
This raises a fascinating question: how does the brain switch between these two domains?
Researchers are finding that while external and internal attention share many of the same brain networks—particularly the dorsal frontoparietal system—they also engage unique regions.
Internal attention seems to recruit medial and ventrolateral prefrontal areas, possibly because selecting among mental representations requires different computations than scanning the sensory world.
Behaviorally, switching between domains appears to incur a small but measurable cost: reaction times slow, and errors increase compared to switching between two tasks within the same domain.
Interestingly, this cost seems to be asymmetrical—switching from external to internal focus tends to take longer than the reverse, perhaps because the external world so readily captures our attention.
Rhythms and Competition
Some scientists suggest these shifts are not just deliberate but may also follow intrinsic rhythms. Attention appears to oscillate between external and internal focus on timescales from milliseconds to hours.
This rhythmic cycling could help the brain balance learning from the environment with consolidating internal models—ensuring neither domain dominates at the expense of the other.
Evidence also suggests that external and internal contents interact competitively within sensory areas. When working memory contents and incoming sensory signals share the same features, they can interfere with each other—though higher-order areas like the parietal cortex may help shield internal representations from disruption.
The Search for a “Switchboard”
What coordinates these shifts? Some hypotheses propose a superordinate control mechanism—a kind of neural “switchboard”—that determines when to prioritize external or internal information.
Candidates for this role include the hippocampus, which is known to alternate between encoding new sensory information and retrieving stored memories, and the anterior mid-dorsolateral prefrontal cortex, a region implicated in high-level control over competing cognitive demands.
Other theories suggest no dedicated switchboard is necessary; instead, shifts between domains may emerge from competitive dynamics within shared networks, where whichever domain has more salient or urgent information wins out.
Neuroimaging studies provide intriguing clues. Tasks that require switching between perceptual and memory-based decisions activate additional prefrontal and parietal regions compared to within-domain shifts.
Yet measures of spatial attention—like subtle eye movements and alpha-band brain oscillations—shift at the same speed whether the target is external or internal, suggesting the bottleneck may lie later in processing, perhaps at the level of decision-making or motor planning.
Why It Matters
Understanding how the brain shifts between external and internal attention is not just an academic exercise. These mechanisms are central to flexible, adaptive behavior—allowing us to plan, reflect, and act effectively in a dynamic world.
Disruptions to these systems could underlie symptoms of conditions like ADHD, schizophrenia, and depression, where individuals may become stuck in internal rumination or overly reactive to external stimuli.
By pinpointing the neural underpinnings of these shifts, researchers aim to develop interventions that help restore balance—whether through cognitive training, neuromodulation, or targeted therapies.
Open Questions and Future Directions
As the field moves forward, many exciting questions remain. Can the brain operate external and internal attention in parallel, or do they always compete? Which neural circuits resolve conflicts between the two? How do different types of internal contents—like imagination, long-term memories, or future plans—interact with sensory inputs?
Experimental designs that mimic real-life scenarios, like navigating virtual environments or multitasking under time pressure, will help capture the natural ebb and flow between external and internal focus. Animal models, advanced imaging techniques, and computational models will also be key to untangling the complex dynamics of this interplay.
Toward a Unified Understanding
The emerging view is that external and internal attention are not isolated systems but deeply intertwined aspects of a larger cognitive architecture. By understanding how the brain selects, prioritizes, and integrates information from both domains, we move closer to explaining how thoughts and perceptions come together to guide behavior.
Just as importantly, this line of research reminds us that much of what we experience as “being present” in the world depends on the seamless and often invisible work of attention.
The next time you catch yourself recalling a memory while glancing at a passing car—or planning your next move in a conversation while listening to someone speak—you’re witnessing your brain’s remarkable ability to bridge two worlds at once.
Funding: This work was supported by a Wellcome Trust Senior Investigator Award (ACN) 104571/Z/14/Z and by BrainWorks at the Center for Neurocognition and Behavior in the Wu Tsai Institute, Yale University (RRID: SCR_024556). Ideas for this perspective benefited greatly from collaborative work and scientific interactions with Sage Boettcher, Dejan Draschkow, Levi Kumle, and Freek van Ede.
About this perception and memory research news
Author: Neuroscience News Communications
Source: Neuroscience News
Contact: Neuroscience News Communications – Neuroscience News
Image: The image is credited to Neuroscience News
Original Research: Open access.
“How the brain shifts between external and internal attention” by Anna C. Nobre et al. Neuron
Abstract
How the brain shifts between external and internal attention
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.
