Rapid recovery (20 ms) of human 600 Hz electroencephalographic wavelets after double stimulation of sensory nerves.
Non-invasive scalp-recordings of human somatosensory evoked potentials (SEP) contain high-frequency (600 Hz) wavelet bursts, presumably generated by synchronized thalamocortical and/or intracortical population spikes. Here, double pulse stimulation (interval 20 ms) in 12 healthy subjects revealed significantly different burst recovery for mixed vs. sensory-only nerves. For median nerves the second burst response was decreased (11/11 subjects), possibly due to interfering reafferent (e.g. muscle spindle) input. In contrast, for sensory-only superficial radial nerves (containing less fibers than median nerves), weak bursts were detected in 6/11 subjects and were found fully recovered in 4/6 subjects. This potential for rapid burst recovery at 20 ms intervals renders contributions from neurons emitting bursts based on slowly recovering low-threshold calcium spikes unlikely and favors the generation of macroscopic SEP bursts by specialized cell populations, e.g. inhibitory interneurons and/or chattering cells the latter of which are capable to discharge rapidly repeating (50 Hz) high-frequency (600 Hz) bursts of fast sodium spikes.
Mackert
B M
BM
Neurophysics Group, Department of Neurology, Klinikum Benjamin Franklin, Freie Universität, 12203 Berlin, Germany. macbm@zedat.fu-berlin.de
Weisenbach
S
S
Nolte
G
G
Curio
G
G
D000200:Action Potentials / Q000502:physiology; D004558:Electric Stimulation; D004569:Electroencephalography; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D006801:Humans; D008475:Median Nerve / Q000502:physiology; D009431:Neural Conduction / Q000502:physiology*; D009434:Neural Pathways / Q000166:cytology / Q000502:physiology; D009475:Neurons, Afferent / Q000166:cytology / Q000502:physiology*; D010525:Peripheral Nerves / Q000166:cytology / Q000502:physiology*; D011826:Radial Nerve / Q000502:physiology; D013003:Somatosensory Cortex / Q000166:cytology / Q000502:physiology*; D013997:Time Factors