The detectability of neuronal fast (1 ms) action potentials ('spikes') defines a striking contrast between invasive (microscopic) and noninvasive (macroscopic) EEG: While noninvasive records reflect summed postsynaptic potentials (representing neuronal input), invasive microelectrodes reveal also the very output of neural computation – spikes. This micro/macro gap has been narrowed recently based on high-frequency EEG/MEG: This lecture will (i) address the basic neurophysics distinguishing slow from fast neuronal activities, (ii) elaborate on high-frequency (hf > 600 Hz) somatosensory responses as a key paradigm for noninvasive spike-related recordings, and (iii) report on novel neurotechnology enabling high-resolution scalp mappings of EEG/MEG activities even above 1 kHz which reflect noninvasive correlates of human neocortical population spikes. Critically, when recording conditions provide optimal SNR, event detection of single-trial (unaveraged) hf-bursts becomes feasible, offering a unique perspective to monitor human neocortical population spikes noninvasively.

Affiliation: Charité Universitätsmedizin Berlin