UNM-led study finds that when it comes to networks, nature has an edge

Networks exist in both nature - such as biological systems like food webs and gene regulatory networks - and in engineered systems as seen in power grids. Though natural and engineered systems share an overarching goal - providing a mechanism for interacting components to transmit information - one system appears have a clear advantage, according to findings published recently by a University of New Mexico-led team.

In this case, the team found that nature does is best when it comes to networks.

"The Frequency Response of Networks as Open Systems," published in Nature Communications, was authored by former UNM graduate student Amirhossein Nazerian, now at Colorado State University; Malbor Asilani, Florida State University; Melvyn Tyloo, University of Exeter; Wai Lim Ku, Howard University; and Francesco Sorrentino, a professor of mechanical engineering at UNM.

Sorrentino said that a central question that motivated this research is whether the structure of a network itself influences how signals move through it. In other words, are some networks naturally better at transmitting signals while others tend to suppress them?

To find the answer to that question, Sorrentino and team developed a mathematical framework that allowed them to quantify how much a signal entering a network is amplified or attenuated as it propagates through the system.

"This allowed us to systematically compare many different real-world networks and investigate how their structure shapes the way they respond to external inputs," he said.

The findings were clear-cut, finding that nature-made systems have some clear advantages.

"Our study reveals a striking difference between natural and engineered networks," Sorrentino said.

He said that the finding, while new and noteworthy, is a logical one.

"Many biological systems are structured in ways that facilitate the transmission of signals, which makes sense because these systems rely on the efficient flow of information, energy or regulatory activity to function properly."

In contrast, engineered systems, such as power grids, tend to be designed to suppress the amplification of signals and disturbances.

"In these systems, uncontrolled signal propagation could lead to instability or failure," Sorrentino said. "Identifying this fundamental distinction helps us better understand how different types of networks are shaped either by evolutionary pressures in nature or by stability requirements in engineering design."

He said one of the most surprising findings was that many biological networks share a structural feature that naturally promotes signal transmission.

He explained that biological networks are often organized in ways that are close to directed acyclic structures, which means that signals tend to flow in a preferred direction without strong feedback loops. This architecture naturally favors the propagation of signals through the system.

"What makes this particularly striking is that such structures appear across many different biological contexts - from ecological food webs to cellular regulatory networks," Sorrentino said. "This suggests that evolution may favor network architectures that efficiently transmit signals across different scales of biological organization."

He noted that one interesting aspect of the study is that the team characterized the Bode plots of networks, which describe how a linear system responds to incoming signals with different frequencies and are regularly taught in the undergraduate mechanical engineering curriculum at UNM.

"What makes this particularly striking is that such structures appear across many different biological contexts - from ecological food webs to cellular regulatory networks. This suggests that evolution may favor network architectures that efficiently transmit signals across different scales of biological organization."

- Professor Francesco Sorrentino

This study looking at understanding how networks pass or block signals has several real-world applications. For example, in power grids, engineers want to prevent disturbances from spreading across the network and causing large-scale failures.

"Our framework helps identify structural features that suppress signal amplification and could inform future grid design and resilience strategies," he said.

In biological systems, the ability to transmit signals efficiently is often essential.

"For instance, gene regulatory networks must relay regulatory information between genes, while food webs transmit energy and biomass through ecosystems," Sorrentino said. "By identifying structural patterns that promote or inhibit signal propagation, our work provides a new way to understand how these complex systems function."

Sorrentino, whose career has focused on various aspects and applications of control theory and how network systems work (he was the recipient of the National Institutes of Health Trailblazer Award in 2020 for a project involving drug delivery), said this current study opens several exciting directions for future research.

He said one important next step is to study how signal propagation changes when networks evolve over time or when their connections adapt dynamically.

"Many real-world systems - from brain networks to infrastructure systems - continuously change their connectivity, and understanding how this affects signal transmission is an important challenge," Sorrentino said.

This study was supported by grants from the Air Force Office of Scientific Research, Oak Ridge National Laboratory and the National Institutes of Health.