Neuroscientists Have Vastly Underestimated Brain Cells’ Computing Power

One of nan cardinal mysteries of nan encephalon is really it achieves truthful overmuch pinch truthful little. At immoderate fixed moment, it processes an entire world of input, pilots a assemblage and generates conscious experience—all pinch comparatively humble power demands. Traditionally, nan brain’s 86 cardinal neurons are each assumed to beryllium a azygous “processor,” operating arsenic 1 computational unit. But for nan past fewer decades, neuroscientists person suspected that a neuron mightiness really location galore processors, making it acold much powerful. Now researchers person recovered nan first nonstop grounds of this successful animals, showing that neurons’ galore branches, called dendrites, tin compute accusation independently of nan compartment body.

The study, published successful July successful Science, shows that dendrites “dramatically expand” nan computational capacity of individual neurons and, consequently, of nan encephalon arsenic a whole, says elder writer Attila Losonczy, a neuroscientist astatine nan University of Texas Southwestern Medical Center. Neurons successful textbook diagrams look deceptively simple, pinch only a fistful of dendrites extending from nan compartment body. In reality, they sprawl wildly into elaborate treelike arbors, allowing a azygous neuron to person input from thousands of its neighbors. Scientists erstwhile thought these dendrites were small much than “boring cables” that simply passed incoming signals to nan compartment assemblage for processing, Losonczy says. If this were true, each neuron would fundamentally beryllium 1 computational unit.

But dendrites’ sprawling architecture hints astatine a deeper purpose. “Nature puts a batch of effort and power to support those branched structures,” Losonczy says. For nan past 30 years, experiments connected lab-grown neurons and excised encephalon insubstantial person suggested that dendrites could compute accusation connected their own. To trial nan thought successful surviving animals, Losonczy’s squad utilized caller voltage-imaging exertion to grounds activity from parts of individual neurons successful mice’s hippocampi, a encephalon region progressive successful representation and navigation. While moving connected miniature wheels, nan mice navigated virtual environments successful hunt of rewards.

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In acquainted environments, activity successful nan dendrites mostly matched that of nan compartment body. And erstwhile nan researchers moved nan reward astir wrong nan acquainted surroundings, nan compartment assemblage adjusted quickly, while definite dendrites retained remnants of nan earlier activity. But successful an wholly caller environment, immoderate dendrites changed their activity to correspond nan caller location before the compartment body, which caught up only aft repeated exploration. This suggests that nan dendrites were computing accusation connected their own, while their expertise to sphere traces of nan past aliases get up of nan compartment assemblage raises nan anticipation that they service arsenic section “memory devices,” Losonczy says.

The findings uncover really overmuch computation mightiness beryllium happening wrong a azygous neuron of a surviving being. “Perhaps nan champion affinity is that a neuron itself is already a neural network,” says Antonio Fernandez-Ruiz, a neuroscientist astatine Cornell University, who was not progressive successful nan caller work. Losonczy besides suspects that nan “nice hierarchical organization” of nan dendritic branches mightiness springiness nan encephalon moreover much computational powerfulness than simply having much neurons acting arsenic azygous processors.

Beverley Clark, a neuroscientist astatine University College London, who besides wasn’t progressive successful nan caller research, thinks that dendrites computing independently allows each neuron to beryllium “super flexible.” For her, location is much to nan computational powerfulness of nan encephalon than what we presently understand. What’s happening successful nan compartment assemblage captures only 1 portion of nan brain’s power. “It’s what you spot crossed nan dendritic character that’s really important,” Clark says.