The relationship between resting potentials and EEG (electroencephalogram) signals highlights the fundamental role of neuronal electrical activity. Here's a breakdown:
Resting Potential
- The resting membrane potential is the baseline electrical charge across a neuron's membrane, typically around -70mV inside the cell relative to the outside.
- This potential is maintained by the sodium-potassium pump and leak channels:
- Pumps 3 Na⁺ ions out and 2 K⁺ ions in, creating an imbalance in ion distribution.
- K⁺ leaks out through passive channels, further contributing to the negative charge inside the neuron.
Resting Potential and EEG
- EEG Measures Extracellular Activity:
EEG does not measure the resting potential of individual neurons directly. It detects summed extracellular electrical activity generated by many neurons, particularly during depolarization and hyperpolarization events.
- Neuronal Resting Potential Sets the Stage:
The resting potential is critical for neurons to respond to stimuli and generate action potentials. Large-scale shifts in electrical activity, such as during synchronized depolarization of neuron populations, create the voltage fluctuations observed in EEG.
- Role in EEG Oscillations:
Resting potentials contribute to the stability and readiness of neurons to participate in oscillatory networks. EEG rhythms (e.g., alpha, beta waves) emerge from the collective behavior of neurons cycling between depolarized and hyperpolarized states.
- Perturbations in Resting Potential:
Changes in resting potential due to pathological conditions (e.g., epilepsy, ischemia) can affect EEG patterns. A disrupted resting potential might lead to abnormal EEG signatures like sharp waves or spike-and-wave discharges.
In summary, while the resting potential itself is not directly observed in EEG, it underpins the neuronal activity that generates the electrical fields measurable by EEG.