Electrical synapses are key to decision-making in animal brains

In the intricate networks of human and animal brains, decision-making is a highly complex process. While chemical synapses often take center stage, it appears they’re not the only stars of the show.

Recent research from scientists at Yale and the University of Connecticut has revealed the significant role of electrical synapses in shaping our decisions.

The study was led by Dr. Daniel Colon-Ramos, a professor of neuroscience and cell biology at Yale School of Medicine.

How brains make decisions

Animal brains are like supercomputers that handle endless streams of information from the world around them – what they see, hear, smell, and sense. But not all of this information is important.

To make sense of it all, brains use a system to filter out irrelevant details (like background noise or unimportant sights) and focus only on the most critical information for the moment.

For example, a rabbit in a field might hear the wind rustling the grass (irrelevant) but will quickly focus on the sound of a predator approaching (critical). This ability to tune in to the most important details and act accordingly is what scientists call “action selection.” 

It’s the brain’s way of deciding what to pay attention to and how to respond, helping animals survive and thrive in their environments.

“For animals, filtering sensory input is not about blocking noise but prioritizing context-relevant signals,” explained Daniel Colón-Ramos, Yale neuroscientist and senior author of the study.

Adjusting behavior based on context

The study centered on a tiny worm called C. elegans, which might seem simple but offers powerful insights into how brains work. Despite its small size and basic nervous system, C. elegans shows surprisingly advanced behavior, such as choosing and sticking to its preferred temperature.

When placed in an environment with varying temperatures, these worms navigate toward their “ideal” temperature zone. They first use a strategy called gradient migration, moving across the temperature gradient until they get closer to their preferred range.

Once they arrive near their target temperature, the worms switch to a different strategy known as isothermal tracking. In this phase, they fine-tune their movements to stay within the ideal temperature zone, ensuring that they remain comfortable.

These two strategies highlight how even simple creatures can adjust their behavior based on context, making C. elegans an excellent model for studying decision-making and neural processes.

But how do they determine which behavior fits the context?

Role of electrical synapses

The researchers identified electrical synapses, mediated by a protein called INX-1, as key players. These synapses connect two neurons (AIY neurons) responsible for locomotion decisions.

Unlike chemical synapses, electrical synapses act as filters, dampening weak signals and prioritizing significant sensory input.

“Altering this electrical conduit in a single pair of cells can change what the animal chooses to do,” Colón-Ramos said.

In worms with normal INX-1 function, the electrical synapses reduce sensitivity to minor temperature changes, allowing the worms to navigate efficiently. However, worms lacking INX-1 show hypersensitivity to small fluctuations, causing them to get “stuck” in less favorable conditions.

“It’s like watching a confused bird flying with its legs extended,” Colón-Ramos noted. “Birds normally extend their legs to land, but doing so mid-flight disrupts their goals.”

Implications for broader neuroscience

Electrical synapses exist across many species, including humans, suggesting the findings have far-reaching implications.

For example, similar configurations of electrical synapses in amacrine cells help regulate visual sensitivity in human retinas.

“These findings allow scientists to explore how single-neuron relationships influence perception and behavior,” said Colón-Ramos. “The principles of action selection may vary, but the role of electrical synapses in shaping sensory responses could be widespread.”

Electrical synapses guide decision-making

The study FROM Yale and University of Connecticut highlights the critical role of electrical synapses in guiding decision-making by filtering sensory information.

By unraveling this mechanism in worms, scientists gain insights into broader principles of neuroscience, with potential applications in understanding human cognition and behavior.

This work was supported by major institutions, including the National Institutes of Health (NIH) and the National Science Foundation (NSF).

The study is published in the journal Cell.

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