Bridging the Species Divide: The Future of Neuroscience Depends on Cross-Species Collaboration

Neuroscience is experiencing an explosion of data, with researchers now capable of recording neural activity, behavior, and physiology across species at unprecedented scales. While laboratories can simultaneously monitor thousands of neurons in rodents and record deep brain structures in humans during real-world activities, a significant challenge persists: a deep-rooted fragmentation along species lines. This separation hinders the development of general principles of brain function and limits the field’s progress.

The Problem of Siloed Research

Historically, animal and human researchers have operated within distinct conceptual frameworks, attending separate conferences and developing theories that rarely intersect. This isn’t simply a matter of translation difficulties; the field has largely accepted this challenge instead of actively addressing it as a core scientific problem. Researchers often acknowledge species differences but rarely use them to refine or revise underlying theories. This fragmentation extends to the types of neural signals prioritized, with some focusing on single-unit activity (spikes) while others emphasize population-level signals like local field potentials.

Technological Convergence and Persistent Boundaries

Despite advancements that have blurred the lines between what’s possible in animal and human studies – such as the ability to record brain activity during natural behaviors in both – conceptual boundaries remain. For example, researchers studying the human brain now utilize both single-unit and local field potential recordings, recognizing the complementary strengths of each signal. High-density single-unit recordings in animal models are crucial for understanding the relationship between population-level signals and single-neuron activity, yet single-unit analyses often take precedence, limiting opportunities for cross-species connections.

The Case of Theta Oscillations

Brain rhythms, like theta oscillations (4-8 hertz), illustrate this fragmentation. In rodents, hippocampal theta activity during locomotion is typically continuous, influencing models of navigation and memory. However, in humans, theta activity is intermittent, linked to specific events rather than ongoing movement. This difference, replicated across laboratories and supported by findings in bats and nonhuman primates, initially faced skepticism. The dominant response wasn’t to explore the implications for theory, but to question the comparability of the signals. Even now, theories integrating these differing theta patterns remain scarce. Rodent-derived models continue to assume continuous oscillatory structure, treating the findings from other species as implementation details.

A Call for Integrated Frameworks

The field’s tendency to compartmentalize findings, rather than using differences to refine theory, is a broader issue. Intermittent hippocampal theta in humans suggests a different mode of neural coordination – one where rhythmic structure is recruited transiently to gate information or coordinate circuits. Ignoring these implications limits the scope and explanatory power of existing theories. A shift is needed towards frameworks designed to link signals across scales, leveraging the strengths of each system to overcome limitations.

Cultural Asymmetries and the Need for Change

Cultural factors within neuroscience likewise reinforce this divide. Human data aligning with animal models are often welcomed as validation, while discrepancies face higher evidentiary thresholds. This skepticism, sometimes justified by appeals to sample size, can insulate animal-derived theories from challenge. The field needs to value cross-species work and reward research that treats differences as opportunities for insight, not liabilities.

Moving Forward: A More Collaborative Future

Overcoming this fragmentation requires changes in training, conference structure, and academic culture. Theoretical frameworks must be explicitly tested and revised across species, and funding practices should prioritize work that embraces cross-species differences. If neuroscience is to build general principles of brain function, cross-species dialogue must become a core organizing principle, not an afterthought.