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Study shows the brain’s building blocks are highly specialized
By Emily Leighton
The findings could reshape how scientists understand intelligence, aging and brain disease
By Emily Leighton
For decades, neuroscientists have approached the brain like a subway map, focusing on the connections between stations. The prevailing view was that the stations themselves were largely interchangeable, and that intelligence emerged from the complexity of the network linking them together.
A new study published in Nature Communications suggests the system is far more specialized.
“Union Station in downtown Toronto is very different from a small suburban stop,” explained Dr. Julio Martinez-Trujillo, associate professor in physiology and pharmacology and one of the study’s senior authors. “It handles more traffic, more connections and more complexity. We think the brain works in a similar way.”
Researchers from Western University and international collaborators have shown that neurons in different regions of the primate brain are specialized – structurally and electrically tailored for the distinct jobs they perform.
The findings suggest the brain’s hardware may matter more than previously thought.
We thought much of the brain's complexity came from connectivity, or how neurons talk to one another. But what we're showing is that the neurons themselves are different.
Senior Author; Associate Professor, Department of Physiology and Pharmacology
The research focused on two different parts of the primate brain – the primary visual cortex, which rapidly processes incoming visual information, and the lateral prefrontal cortex, associated with cognition, working memory and attention.
To investigate, the team analyzed hundreds of neurons, measuring their electrical activity and reconstructing their anatomy. Using machine learning, the researchers then classified the cells into major neuronal types.
Neurons in the primary visual cortex behaved like high-speed relays – fast and responsive to rapid changes in environment. By contrast, neurons in the lateral prefrontal cortex were slower and more stable, better suited for sustaining information over time.
“One system is designed to constantly detect changes, while the other is built to maintain a stable model of the world,” said Martinez-Trujillo.
The study also found that prefrontal neurons tend to have larger and more elaborate branching structures, which may allow the brain to integrate more complex information from multiple sources simultaneously.
It's an evolutionary upgrade that may also come at a cost. The same features that support advanced cognition could also create vulnerabilities linked to aging and disease.
Researchers say the larger, more complex neurons found in the lateral prefrontal cortex may be more susceptible to stresses associated with conditions like Alzheimer’s disease, where cognitive regions of the brain are often affected before sensory areas.
"The regions that support higher cognition are often the ones that deteriorate first,” said Martinez-Trujillo.
The findings may also have implications for neurodevelopmental conditions like schizophrenia and autism, which involve disruptions in how the brain develops and organizes itself over time.
Martinez-Trujillo says the work could help explain why many neurological and psychiatric disorders remain difficult to model in mice, whose brains do not undergo the same prolonged developmental expansion seen in primates, including humans.
“The brain is not simply a network of repeated parts,” he said. “Its intelligence may depend on cells that evolved to become fundamentally different from one another.”