This special collection emerged from a January 2025 workshop at the National Institute for Theory and Mathematics in Biology on “Biological systems that learn.” Living systems are composed of the same atoms and obey the same physical laws as nonliving matter, yet they routinely accomplish remarkable functions: proteins regulate catalytic activity with exceptional specificity and efficiency; cytoskeletal networks maintain strain memory and rigidity homeostasis while continuously disassembling and reassembling; sheets of originally homogenous cells develop into specialized organs; mammalian vascular networks distribute oxygen and nutrients throughout organisms; olfactory systems identify odors on top of strongly fluctuating backgrounds. The constituents—whether amino acids, cells or organisms themselves—perform their staggeringly intricate ballets reliably and without centralized control, even under challenging and changing conditions. Despite immense progress in identifying constituents and their interactions in biological systems, however, our understanding of how such behaviors emerge remains fragmentary at best.

In this special collection, we gather a number of papers to illustrate how physical matter–whether biological or non-biological–can be imbued with function. All of these systems can be described as tunable matter—physical matter with many adaptive degrees of freedom that are individually adjusted to satisfy design constraints as well as physical constraints to produce function. By tunable matter, we mean collectives of heterogeneous physical components whose effective interactions, coupled dynamics, or internal states (degrees of freedom) can be individually tuned to satisfy design and physical constraints required for collective function, much as weights are individually adjusted in artificial neural networks (ANN). Unlike ANNs, however, biological systems do not have access to central processors, so must either be tuned by mutation and selection, like the genome, or by a decentralized tuning process that requires only limited information accessible to the individual components, like the brain. The tunable matter paradigm generalizes this logic beyond the genome and brain, extending it to new classes of degrees of freedom, tuning processes, and biological functions. According to this approach, a useful route to understanding a given biological function is to identify the tunable degrees of freedom and tuning processes that lead to it. Many of the papers in this collection do precisely that–they show how interesting functions can emerge from degrees of freedom and tuning processes that are known to exist in biological systems.

By highlighting key mechanisms that allow living systems to learn and adapt, this special issue focuses attention on the tunable matter paradigm as an exciting avenue for future research. Papers in this collection take advantage of recent experience garnered from AI and non-biological systems that autonomously acquire desired function, highlighting that this is an opportune moment for progress. Just as frameworks for describing emergent behavior in non- tunable matter have driven key advances in condensed matter and materials science, we hope that this collection will ultimately inspire researchers to develop unifying frameworks for emergent collective function in living tunable matter that will drive paradigm shifts in the field of biology.

The Guest Editors

Sadjad Arzash, Syracuse University

Margaret Gardel, University of Chicago

Andrea Liu, University of Pennsylvania

Lisa Manning, Syracuse University

Ed Munro, University of Chicago

Haina Wang, University of Pennsylvania

Active persistent dynamics are shown to mimic some aspects of Hebbian unlearning — suggesting that nonequilibrium dynamics can provide an alternative way to improve associative recall in neural network models.

A cytoskeleton-inspired mechanical network with mechanosensitive proteins and motors performs contrastive learning from environmental cues via strain-rate dependent reactions and active forces, while maintaining learned responses despite continuous molecular turnover.

A study of bacterial movement across a range of both unconfined and highly confined environments establishes a quantitative link between behavioral rules and environmental context and reveals how E. coli can navigate complex habitats.

Resonant frequencies prioritize multi-looped structures or higher-level loops close to the driving source, while the network is prone to vessel shunting away from resonances — underscoring the importance of short-term pulsatility on long-term structures in adapting, periodically driven elastic flow networks like mammalian vasculature.

This study proposes that olfactory systems can adapt to rapidly fluctuating odor backgrounds using a manifold learning mechanism and demonstrates how this mechanism can outperform traditional predictive filtering methods.

This review article proposes that Marr’s three levels of analysis — the computational problem, the algorithms used, and their molecular implementation — can be a useful framework for studying developmental processes.

By examining collective patterning in a tractable model, this study reveals a trade-off between speed and accuracy and identifies counterintuitive properties of collective behavior, for instance optimized strategies do not always maximize information transfer.

A recurrent neural network model containing neurons with intrinsic plasticity measures how neuronal excitability varies with plasticity under different synaptic inputs — illuminating how these dynamics influence heterogeneity in neural responses.

This study details a data-driven implementation of Fisher’s geometric model — providing an empirically grounded approach for understanding evolutionary dynamics using deep learning methods.

Inspired by Crick’s molecular memory proposal, this study analyzes a nonequilibrium protein model and identifies molecular automata that can be exploited for computation, including in molecular stopwatches and error-tolerant memory.

An enhanced form of mechanical proofreading during dynamic cell-cell contact helps reconcile robust clonal selection with tunable specificity in adaptive immune responses.

E. coli integrate environmental history through scale-free memory, performing recurrent, neural-like computation to balance growth and survival in fluctuating nutrient conditions.

Experiments in a unicellular relative of animals validate the predictions of a model which treats organisms as Markovian Bayesian agents that learn from environmental states, providing insights into the link between within-lifetime learning and generational adaptation.

Mapping evolutionary dynamics to Bayesian learning shows that organismal complexity tends to match environmental complexity, but rapid environmental changes may favor simpler forms.

Using disordered solids as a model, this work demonstrates how cyclic environmental change can produce robust system memory.

A simulated cortical network rapidly establishes functional circuitry through autonomous learning from mechanically coupled sensors.

Tuning elastic networks for bidirectional allostery improves cooperative binding, while a modified tuning process ensures robustness against thermal fluctuations by raising the crossover temperature.

By mimicking biological brain noise, this work shows that activity-dependent fluctuations drive the emergence of modular architectures in artificial neural networks, improving robustness and generalization.

Sign In to Your Journals Account

Filter

Filter

Article Lookup

Enter a citation