Summary: A new study reveals how electrical synapses help animals, including worms, filter sensory inputs and make context-appropriate decisions. Researchers found that these synapses, mediated by the protein INX-1, connect specific neurons in worms, dampening irrelevant signals and prioritizing essential ones.
This mechanism enables worms to navigate temperature gradients effectively, avoiding distractions. In worms without functioning INX-1, hypersensitivity to minor temperature changes disrupts their ability to choose context-appropriate behaviors.
Since electrical synapses exist in many animals, including humans, the findings may offer insights into how brains process sensory information for decision-making. The research highlights a universal principle: precise neural connections are key to filtering sensory inputs and guiding behavior.
Key Facts
- Neural Filtering: Electrical synapses dampen weak signals, allowing worms to prioritize relevant sensory inputs for efficient navigation.
- Protein INX-1 Role: INX-1-mediated electrical synapses in AIY neurons enable context-specific behavior in worms.
- Broader Implications: Similar mechanisms may regulate sensory processing in other animals, including humans, influencing decision-making and perception.
Source: Yale
Scientists at Yale and the University of Connecticut have taken a major step in understanding how animal brains make decisions, revealing a crucial role for electrical synapses in “filtering” sensory information.
The new research, published in the journal Cell, demonstrates how a specific configuration of electrical synapses enables animals to make context-appropriate choices, even when faced with similar sensory inputs.
Animal brains are constantly bombarded with sensory information — sights, sounds, smells, and more. Making sense of this information, scientists say, requires a sophisticated filtering system that focuses on relevant details and enables an animal to act accordingly.
Such a filtering system doesn’t simply block out “noise” — it actively prioritizes information depending on the situation. Focusing on certain sensory information and deploying a context-specific behavior is known as “action selection.”
The Yale-led study focused on a worm, C. elegans, which, surprisingly, provides a powerful model for understanding the neural mechanisms of action selection. C. elegans can learn to prefer specific temperatures; when in a temperature gradient, it uses a simple, yet effective strategy to navigate towards its preferred temperature.
Worms first move across the gradient towards their preferred temperature (a behavior called “gradient migration”) — and once they have identified temperature conditions more to their liking, they track that temperature, which allows them to stay within their preferred range (a behavior called “isothermal tracking”).
Worms also can perform these behaviors in context-specific manners, deploying gradient migration when they are far away from their preferred temperature, and isothermal tracking when they are near a preferred temperature.
But how are they able to perform the correct behavior in the correct context?
For the new study, the researchers investigated a specific type of connection between neuronal cells, called electrical synapses, which differs from the more widely studied chemical synapses.
They found that these electrical synapses, mediated by a protein called INX-1, connect a specific pair of neurons (AIY neurons) which are responsible for controlling locomotion decisions in the worm.
“Altering this electrical conduit in a single pair of cells can change what the animal chooses to do,” said Daniel Colón-Ramos, the Dorys McConnell Duberg Professor of Neuroscience and Cell Biology at Yale School of Medicine and corresponding author of the study.
The team found that these electrical synapses don’t simply transmit signals, they also act as a “filter.” In worms with normal INX-1 function, the electrical connection effectively dampens signals from the thermosensory neurons, allowing the worm to ignore weak temperature variations and focus on the larger changes experienced in the temperature gradient.
This ensures that the worms move efficiently across the gradient and toward their preferred temperature without getting distracted by context-irrelevant signals, like those experienced in isothermal tracks which present throughout the gradient but are not at the preferred temperatures.
However, in worms lacking INX-1, the AIY neurons become hypersensitive, responding much more strongly to minor temperature fluctuations. This hypersensitivity causes the worms to react to these small signals, trapping the animals in isotherms that are not their preferred temperature.
Such abnormal tracking of isotherms within incorrect contexts adversely affects the worms’ ability to move across the temperature gradient towards their preferred temperature.
“It would be like watching a confused bird flying with its legs extended,” Colón-Ramos said. “Birds normally extend their legs prior to landing but were a bird to extend its legs in the incorrect context it would be detrimental to its normal behavior and goals.”
Since electrical synapses are found throughout the nervous systems of many animals, from worms to humans, the findings have significant implications beyond the behavior of worms.
“Scientists will be able to use this information to examine how relationships in single neurons can change how an animal perceives its environment and responds to it,” Colón-Ramos said.
“While the specific details of action selection will likely vary, the underlying principle of the role of electrical synapses in coupling neurons to alter responses to sensory information could be widespread.
“For example, in our retina, a group of neurons called ‘amacrine cells’ uses a similar configuration of electrical synapses to regulate visual sensitivity when our eyes adapt to light changes.”
Synaptic configurations are central to the way animals process sensory information and then react, and the results uncovered in the new study suggest that configurations of electrical synapses play a crucial role in modulating how nervous systems process context-specific sensory information to guide perception and behavior in animals.
Colón-Ramos is also associate director of Yale’s Wu Tsai Institute, which is devoted to the study of cognition.
The study’s co-lead authors are Agustin Almoril-Porras and Ana Calvo from Yale. Co-authors are Jonathan Beagan, Malcom Díaz Garcia, Josh Hawk, Ahmad Aljobeh, Elias Wisdom, and Ivy Ren, all of Yale; and Longgang Niu and Zhao-Wen Wang of the University of Connecticut.
Funding: The work was supported by the National Institutes of Health, the National Science Foundation, and a Howard Hughes Medical Institute Scholar Award.
About this neuroscience research news
Author: Bess Connolly
Source: Yale
Contact: Bess Connolly – Yale
Image: The image is credited to Neuroscience News
Original Research: Open access.
“Configuration of electrical synapses filters sensory information to drive behavioral choices” by Daniel Colón-Ramos et al. Cell
Abstract
Configuration of electrical synapses filters sensory information to drive behavioral choices
Synaptic configurations underpin how the nervous system processes sensory information to produce a behavioral response.
This is best understood for chemical synapses, and we know far less about how electrical synaptic configurations modulate sensory information processing and context-specific behaviors.
We discovered that innexin 1 (INX-1), a gap junction protein that forms electrical synapses, is required to deploy context-specific behavioral strategies underlying thermotaxis behavior in C. elegans.
Within this well-defined circuit, INX-1 couples two bilaterally symmetric interneurons to integrate sensory information during migratory behavior across temperature gradients.
In inx-1 mutants, uncoupled interneurons display increased excitability and responses to subthreshold sensory stimuli due to increased membrane resistance and reduced membrane capacitance, resulting in abnormal responses that extend run durations and trap the animals in context-irrelevant tracking of isotherms.
Thus, a conserved configuration of electrical synapses enables differential processing of sensory information to deploy context-specific behavioral strategies.
