Neurons Encode Complex Information Through Dual Brain Wave Responses

Summary

A new study reveals that individual neurons in the hippocampus can simultaneously respond to both slow theta and fast gamma brain waves by switching between distinct firing modes. This process, termed interleaved resonance, enables neurons to encode complex information using bursts for theta waves and single spikes for gamma waves. These findings enhance our understanding of how the brain organizes navigation and memory-related thoughts and may have significant implications for neurological disorders such as Alzheimer’s, epilepsy, and schizophrenia.

Key Facts

• Dual Coding Mechanism: Neurons can process theta and gamma waves concurrently using different firing modes.
• Flexible Firing: Neurons switch between bursts and single spikes based on internal ion currents and timing.
• Clinical Implications: Disruptions in this tuning system may contribute to cognitive deficits in neurological diseases.

The brain continuously maps the external world, functioning like a GPS even without conscious awareness. This process relies on tiny electrical signals transmitted between neurons, specialized cells that facilitate thinking, movement, memory, and emotion. These signals often form rhythmic patterns known as brain waves, including slower theta waves and faster gamma waves, which help structure how the brain processes information. Understanding how individual neurons respond to these rhythms is crucial for deciphering brain functions related to real-time navigation and how these processes may falter in disease.

A recent study by Florida Atlantic University, in collaboration with Erasmus Medical Center and the University of Amsterdam, has uncovered a remarkable capability of hippocampal neurons to process and encode information from multiple brain rhythms simultaneously. Published in PLOS Computational Biology, the research introduces a phenomenon called “interleaved resonance,” where a single neuron switches between firing single spikes and rapid bursts based on its internal properties and the brain’s ongoing electrical activity.

The study focused on CA1 pyramidal neurons, critical for memory formation and spatial navigation—essential for determining location and movement. These neurons communicate through electrical impulses, firing either isolated single spikes or rapid bursts, each mode conveying distinct information tied to specific behavioral contexts. Previously, the factors driving these mode switches were not well understood.

Using advanced computational modeling and voltage imaging of real brain activity, researchers demonstrated that neurons can respond to both theta and gamma wave inputs concurrently but in different ways. This results in a dual-coding system where neurons use bursts to align with theta waves and single spikes for gamma waves, both embedded within the same electrical signal.

“Our models reveal that a single neuron can act like a multi-band radio, tuning into different frequencies and adjusting its behavior accordingly,” said Rodrigo Pena, Ph.D., senior author and assistant professor at FAU’s Charles E. Schmidt College of Science. “This system is far more flexible and powerful than previously thought.”

The researchers found that this behavior depends on the neuron’s internal settings, specifically three ion-driven currents: persistent sodium, delayed rectifier potassium, and hyperpolarization-activated current. By modulating these currents, neurons can shift their resonance between theta and gamma waves and between burst and single-spike firing. Neurons were also more likely to fire bursts after extended silent periods, adding a time-dependent aspect to information encoding.

“This dual-coding ability provides a new perspective on how the brain organizes and transfers information,” Pena noted. “Disruptions in neurons’ ability to switch between spikes and bursts could impair memory formation or attention, offering insights into conditions where brain rhythms are disrupted.”

The findings address longstanding neuroscience questions, such as how spatial memory forms in the hippocampus, and highlight the brain’s complexity and adaptability. Prior research showed that theta and gamma rhythms influence neuronal firing during spatial movement. This study reveals that neurons are not confined to a single firing mode but can dynamically adjust based on external inputs and their internal electrical environment, enabling them to carry multiple layers of information.

“The brain’s building blocks are far more dynamic than previously thought,” said Pena. “A neuron can follow different rhythms, adapting its firing patterns to meet the moment’s needs. This discovery advances our understanding of brain function and could guide future treatments for restoring healthy neural activity in neurological disorders.”

Study co-authors include César C. Ceballos, Ph.D., first author and postdoctoral fellow at FAU; Nourdin Chadly, Ph.D., from Erasmus Medical Center and the University of Amsterdam; and Erik Lowet, Ph.D., assistant professor at Erasmus Medical Center.

Source: Florida Atlantic University
Original Research: “Interleaved single and bursting spiking resonance in neurons” by Rodrigo Pena et al., PLOS Computational Biology

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