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Subthreshold membrane resonance in neocortical neurons
B Hutcheon1, R M Miura, E Puil
1Department of Pharmacology and Therapeutics, Faculty of Medicine, University of British Columbia, Vancouver, Canada.
Journal of Neurophysiology
|August 1, 1996
Summary
Neurons in rat sensorimotor cortex exhibit frequency-selective firing due to membrane resonance, particularly the hyperpolarization-activated cation current (IH). This resonance influences synchronized brain activity.
Area of Science:
- Neuroscience
- Computational Neuroscience
- Cellular Electrophysiology
Background:
- Neurons in the sensorimotor cortex exhibit diverse firing patterns, including regular spiking (RS), intrinsic bursting (IB), and fast spiking (FS).
- Understanding subthreshold voltage responses to oscillatory inputs is crucial for comprehending neural circuit dynamics and synchronized brain activity.
Purpose of the Study:
- To investigate subthreshold and suprathreshold voltage responses to oscillatory current inputs in sensorimotor cortex neurons.
- To classify neurons based on firing patterns and analyze their frequency response curves (FRCs).
- To identify the ionic currents responsible for low-frequency membrane resonance and their role in frequency-selective firing.
Main Methods:
- Whole-cell recording techniques were used to study voltage responses in juvenile rat sensorimotor cortex neurons.
- Neurons were classified as RS, IB, and FS based on firing patterns.
- Frequency response curves (FRCs) were determined using swept-sine-wave (ZAP) current inputs.
- Voltage-clamp experiments identified the roles of hyperpolarization-activated cation current (IH), inwardly rectifying K+ current (IIR), and persistent Na+ current (INaP).
Main Results:
- RS and IB neurons showed rectifying voltage-current relationships, while FS neurons were nearly ohmic.
- Approximately 60% of RS and IB neurons exhibited membrane resonance at their resting potential (0.7–2.5 Hz), which was voltage-dependent.
- Resonant neurons selectively fired action potentials near their resonant frequency at rest, but this selectivity diminished upon depolarization.
- The hyperpolarization-activated cation current (IH) was identified as a key contributor to subthreshold resonance, while persistent Na+ current (INaP) amplified resonance at depolarized potentials, and inwardly rectifying K+ current (IIR) attenuated it.
Conclusions:
- The frequency selectivity of sensorimotor cortex neurons, mediated by currents like IH, may play a role in synchronized brain activity.
- Voltage-dependent modulation of frequency-selective firing provides a potential mechanism for controlling low-frequency synchronized activity in the neocortex.