Scientists from the Salk Institute have determined that brain waves in the visual cortex serve as a computational engine, allowing the brain to construct internal representations of the external world that enhance prediction, reconstruction, and perception capabilities.

While the scientists behind the new study focused their work on the visual cortex, they suspect that similar brain waves washing over other areas of the brain’s surface likely serve a similar role for other sensory systems.

Unraveling the Role of Traveling Brain Waves in the Visual Cortex

The human brain uses electricity to communicate between synapses. Research has shown that this electrical activity can travel in waves across the brain’s surface. Called neural traveling waves, the phenomenon’s role in brain function and consciousness is not completely understood.

Previous studies have established that traveling brain waves play a significant role in behavior and attention. In 2020, Salk neuroscientist John Reynolds, PhD, successfully identified traveling brain waves in the visual systems of animals during a wakeful state.

According to a statement from Reynolds, the senior and co-corresponding author on the new paper, and colleagues, the 2020 research effort also found a direct correlation between traveling brain waves in the visual cortex and an animal’s ability to perceive objects directly in front of them. The authors suggest this discovery explained the “classic conundrum” of searching for something like a pair of keys or a phone that was right in front of you the whole time.

Although the connection between traveling brain waves and an awake animal’s ability to perceive objects seemed solid, Reynolds said he was left wondering why. 

Process is Analogous to LLM’s Like ChatGPT

In their newly proposed theory, Reynolds and colleagues suggest that traveling brain waves are not simply “electrical noise” resulting from the brain’s normal relaying of signals. Instead, the Salk Institute team proposes that the neural connections responsible for the generation of traveling brain waves change their physiological structure, or “synaptic weights,” to more accurately reflect the outside world.

“Each sight, smell, sound, and action of an animal alters the connections that generate these waves, building the neural circuitry that the brain uses to construct an internal representation of the external world,” the team’s statement explains.

In the visual cortex, the part of the brain responsible for receiving and processing visual information, the team proposed that traveling brain waves perform four distinct functions. These include modulating visual perception from moment to moment and turning recent visual sensory inputs into “internal representations” of objects, people, and surroundings.

The team proposes that traveling brain waves also help humans generate short-term predictions about their surroundings, and “store and replay patterns that represent memories of events unfolding in time.” Reynolds said the process laid out by his team is analogous to how ChatGPT and other LLMs translate and interpret data.

“They learn statistical structure from language and use that knowledge to generate meaningful and appropriately structured text that reflects the patterns of language,” the researcher explained. “The brain may be doing something functionally similar—a biological generative model built from the ground up by experience.”

“One Step Closer” to Understanding How Our Brains Compute the World

When detailing the potential impact of their proposed role for traveling brain waves in the visual cortex, the team highlights the contrast between a rich and complex world and its general predictability.

“Objects around you exist in 3D space, you see the world in retinal images that change with your eye and body movements, and the laws of physics and physiology overlay this all,” they explain.

Reynold’s team says that traveling brain waves are merely the brain’s way of internalizing these predictable “regularities” and encoding them in its synapse network. If correct, they said that this encoding would allow the brain to “infer the likely causes of sensory input and construct an internal model of the world.”

“This framing brings us one step closer to understanding how our brains compute the busy, messy world around us, turning a complicated sensory onslaught into behaviors and experiences,” they conclude.

The study “Neural traveling waves in cortex: network mechanisms and potential roles in neural computation” was published in Neuron.

Christopher Plain is a Science Fiction and Fantasy novelist and has spent the last six years as Associate News Editor and Head Science Writer at The Debrief. Follow and connect with him on X, learn about his books at plainfiction.com, or email him at christopher@thedebrief.org

New blood vessels flood the developing brain, then must be sculpted into a functional network. In the cortex, this pruning depends on selective elimination of redundant connections, but the cellular command center behind vascular refinement has remained only partly understood. A new study now points to microglia—the brain’s immune sentinels—as active architects of cerebrovascular pruning during postnatal development.

Using live visualization in the frontal cortex of postnatal day 11 mice, researchers tracked how microglia behave around forming blood vessels. They observed that microglia do not merely associate with vasculature; instead, they progressively migrate toward vessels as development proceeds. As vessel remodeling advances, microglia become enriched at sites where pruning occurs, suggesting a causal role rather than passive surveillance.

To test function, the team manipulated microglia–vessel interactions and assessed vascular outcomes. Intervening in microglial activity altered the extent of vessel elimination, consistent with the idea that microglia mediate pruning to refine the emerging vascular map. The results connect microglial behavior directly to the efficiency and organization of the developing cortical circulation.

Central to the mechanism is an immune signaling pathway previously linked to neuronal synaptic refinement: PD-L1 and its receptor PD-1. The study identifies PD-L1–PD-1 signaling as a regulator of microglia-driven vascular pruning. When this axis was disrupted, pruning was impaired, indicating that immune checkpoint-like communication can shape vascular architecture in the developing brain.

The authors further implicate a specific molecular source from microglia. They report that microglial CD5L secretion promotes the PD-1–dependent pruning program. In other words, microglia release CD5L, engage PD-1 signaling through PD-L1 interactions, and thereby influence which vessels persist and which are eliminated.

Collectively, the work reframes cerebrovascular pruning as a neuroimmune-guided developmental process. By showing that microglia actively target redundant vasculature and by defining a PD-L1–PD-1/CD5L pathway, the study provides mechanistic evidence for how immune cells can tune vascular networks to match developing brain circuitry.

Beyond development, the findings raise broader questions about whether similar immune checkpoint signaling contributes to abnormal vascular remodeling in disease, where pruning can be either excessive or insufficient. For now, the study delivers a clear developmental role: microglia help determine what the brain keeps growing and what it discards.

DOI: https://doi.org/10.1038/s41593-026-02378-x

Article Title: Microglia prune developing cortical blood vessels through PD-1 signaling.

Article References: Zhang, M., Wang, Y., Yang, R. et al. Microglia prune developing cortical blood vessels through PD-1 signaling. Nat Neurosci (2026). https://doi.org/10.1038/s41593-026-02378-x

Image Credits: AI Generated