Different origins of low- and high-frequency components (600 Hz) of human somatosensory evoked potentials.

Full Abstract

OBJECTIVE: Human median nerve somatosensory evoked potentials (SEPs) contain a low-amplitude (<500 nV) high-frequency (approximately 600 Hz) burst of repetitive wavelets (HFOs) which are superimposed onto the primary cortical response 'N20.' This study aimed to further clarify the cortical and subcortical structures involved in the generation of the HFOs. METHODS: 128-Channel recordings were obtained to right median nerve stimulation of 10 right-handed healthy human subjects and in 7 of them additional to right ulnar nerve. Data were evaluated by applying principal component analysis and dipole source analysis. RESULTS: Different source evaluation strategies provided converging evidence for a cortical HFO origin, with two different almost orthogonally oriented generators being active in parallel, but with a phase shift of a quarter of their oscillatory period, while the low-frequency 'N20' is adequately modeled by one tangential dipole source. Median and ulnar derived low-frequency and HFO cortical sources show a somatotopic order. Additionally, generation of the HFOs was localized in subcortical, near-thalamic and subthalamic source sites. The near-thalamic dipole was located at significantly different sites in HFO and low-frequency data. CONCLUSIONS: The cortical HFO source constellation points to a 'precortical' source in terminals of thalamocortical fibers and a second intracortical HFO origin. Furthermore, HFOs are also generated at subcortical and even subthalamic sites. Near-thalamic, the HFO and low-frequency signals are generated or modulated by different neuron populations involved in the thalamocortical outflow.

Author information

Author/s: Gobbelé, R (R); Waberski, T D (TD); Simon, H (H); Peters, E (E); Klostermann, F (F); Curio, G (G); Buchner, H (H);

Affiliation: Department of Neurology, RWTH Aachen, Pauwelsstrasse 30, 52057 Aachen, Germany. rgobbele(-atsign-)ukaachen.de

Journal and publication information

Publication Type: Journal Article; Research Support, Non-U.S. Gov't

Journal: Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology (Clin Neurophysiol), published in Netherlands. (Language: eng)

Reference: 2004-Apr; vol 115 (issue 4) : pp 927-37

Dates: Created 2004/03/08; Completed 2004/04/15; Revised 2008/09/10;

PMID: 15003775, status: MEDLINE (last retrieved date: 2/18/2009)

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