Summary: New research shows individual neurons in the hippocampus can track slow theta and fast gamma brain rhythms at the same time by switching their firing patterns. This phenomenon, called interleaved resonance, enables single cells to carry layered information: bursts of spikes align with theta-frequency inputs, while isolated spikes resonate with gamma-frequency inputs.
These results deepen our understanding of how the hippocampus organizes spatial navigation and memory processing, and they could help explain how rhythm disturbances contribute to neurological disorders such as Alzheimer’s disease, epilepsy, and schizophrenia.
Key facts:
- Dual coding: CA1 pyramidal neurons can encode both theta and gamma rhythms simultaneously by using distinct firing modes.
- Flexible firing modes: Neurons switch between bursts and single spikes depending on intrinsic ion conductances and recent activity.
- Clinical relevance: Loss of this tuning or flexibility may underlie cognitive and memory impairments in several brain disorders.
Source: FAU
The brain continuously maps the environment like a living GPS, using tiny electrical signals exchanged among neurons—specialized cells that enable thinking, movement, memory and perception.
Those electrical signals often organize into rhythms or brain waves, notably slower theta oscillations and faster gamma oscillations. How single neurons respond to and integrate these rhythms is crucial for understanding real-time navigation and memory formation.
A collaborative study led by Florida Atlantic University, with partners at Erasmus Medical Center and the University of Amsterdam, reports that CA1 pyramidal neurons in the hippocampus can simultaneously process inputs at multiple frequencies. Published in PLOS Computational Biology, the work combines computational modeling with advanced voltage imaging to explain how one neuron can alternate between single spikes and rapid bursts depending on internal dynamics and ongoing network activity.
The researchers describe this behavior as “interleaved resonance”: a single neuron can act like a multi-band receiver, responding to theta inputs with bursting activity while locking single spikes to gamma inputs. This layered encoding allows one cell to convey different types of information concurrently within the same electrical trace.
Rodrigo Pena, Ph.D., senior author and assistant professor of biological sciences at FAU’s Charles E. Schmidt College of Science, explains that this flexibility expands the computational power of individual neurons beyond what was previously appreciated.
The study identifies three ionic conductances that shape a neuron’s resonance and firing mode: the persistent sodium current (INaP), the delayed rectifier potassium current (IKDR), and the hyperpolarization-activated current (Ih). By tuning the levels of these currents, neurons shift their preference for theta- or gamma-frequency inputs and transition between burst and single-spike firing.
Timing also matters: long silent periods increase the likelihood of burst firing, adding a temporal dependency to how information is encoded. In sum, the interplay of intrinsic ionic properties and the temporal pattern of inputs enables neurons to adapt their response dynamically to behavioral demands.
These findings offer a new mechanistic view of how the hippocampus forms spatial memory and sequences of activity as animals move through environments. Prior studies linked theta and gamma rhythms to navigation and memory, but this work shows neurons are not locked into a single operating mode—instead, they can mix firing patterns to convey multiple information streams simultaneously.
Pena notes that when neurons lose the ability to switch appropriately between bursting and single spiking, cognitive functions such as memory encoding and attention could be impaired. Understanding interleaved resonance may therefore suggest strategies to restore healthy rhythmic coordination in neurological diseases where brain oscillations are disrupted.
Co-authors include César C. Ceballos, Ph.D. (first author, postdoctoral fellow, FAU), Nourdin Chadly, Ph.D. (Erasmus Medical Center and University of Amsterdam), and Erik Lowet, Ph.D. (assistant professor, Neuroscience Department, Erasmus Medical Center).
About this neuroscience research news
Author: Gisele Galoustian
Source: FAU
Contact: Gisele Galoustian – FAU
Image: The image is credited to Neuroscience News
Original Research: Open access. “Interleaved single and bursting spiking resonance in neurons” by Rodrigo Pena et al., PLOS Computational Biology
Abstract
Interleaved single and bursting spiking resonance in neurons
Under in vivo conditions, CA1 pyramidal neurons in the hippocampus transition between isolated spikes and burst firing. Down-states and up-states—subthreshold hyperpolarized and depolarized membrane states—contribute significantly to these transitions, but linking subthreshold dynamics to spiking patterns has long been challenged by technical limits of electrophysiology and imaging.
Recent voltage-imaging advances using genetically encoded indicators, together with computational modeling, have enabled more direct correlations between subthreshold activity and spiking modes. Using a detailed computational model of a CA1 pyramidal cell, this study examined how intrinsic conductances and oscillatory drive generate down- and up-states and modulate the switch from single spiking to bursting.
The analysis revealed distinct spiking resonances associated with single-spike and burst modes that can coexist in the same voltage trace when the neuron receives theta- or gamma-frequency inputs—hence the term interleaved resonance. These resonances differ in frequency and amplitude, offering flexible processing options for neural circuits.
The model focused on three critical conductances: persistent sodium (GNaP), delayed rectifier potassium (GKDR), and hyperpolarization-activated (Gh). Intermediate values of GNaP and GKDR supported resonance at gamma frequencies for single spiking, while low GNaP with high GKDR favored burst locking to theta frequencies. The duration of silent intervals also strongly influenced the probability of transitioning into either mode. These features match observations in previously recorded in vivo voltage-imaging datasets.
Understanding how ionic currents and oscillatory inputs combine to shape interleaved resonance gives important insight into the mechanisms of neuronal excitability and the hippocampus’s role in spatial memory and information encoding under natural conditions.