Non-invasive detection of cortical population spikes: Functional discrimination of pre- vs. postsynaptic components in SEP at 1 kHz

Introduction: Ultrafast EEG signals, featuring frequencies above 500 Hz, can be observed in scalp somatosensory evoked potentials (SEP). Usually, these recordings have a low Signal-to-Noise Ratio (SNR) because weak signals are overlaid by intrinsic noise of much higher amplitude as generated by biological sources and the amplifier. Scalp recordings of SEP show bursts above 400 Hz with submicro-volt amplitudes, which could be extracted from noise up to now only by the use of massive averaging (n > 1000) and digital signal processing. Methods: Here, we investigate SEP up to 1 kHz elicited by median nerve stimulati…