Single-Unit Activity (SUA)
Action potentials from individual neurons.
Single-unit activity (SUA) refers to action potentials (spikes) recorded from individual neurons. This is the gold standard for understanding how single neurons encode information, respond to stimuli, and participate in neural computations.
Why it matters: Single-unit recordings provide the highest temporal precision (sub-millisecond) and allow tracking individual neurons across time. This enables analysis of spike timing, firing rates, and single-cell responses to experimental manipulations.
Signal characteristics:
- Frequency range: 300 Hz - 6 kHz (though full spikes extend higher)
- Amplitude: 50-500 µV (depends on distance from neuron)
- Duration: ~1 ms
- Waveform: Triphasic or biphasic, neuron-specific shape
Isolation quality: "Single-unit" means spikes are well-isolated from other neurons and noise. Quality metrics: spike amplitude > 3× noise, <1% refractory period violations, stable waveform shape.
Comparison with MUA: Multi-unit activity (MUA) includes spikes from several neurons that cannot be distinguished. SUA requires careful spike sorting to separate individual neurons' contributions.