Origin of P16 median nerve SEP component identified by dipole source analysis--subthalamic or within the thalamo-cortical radiation?
Following median nerve stimulation, several monophasic peaks were recorded at the scalp in the 15-18 ms time range. Source analysis, using three different methods, modelled a source near the centre of the head with an orientation towards the activated hemisphere and a peak activity at 16 ms post stimulus. Magnetic recordings detected no signal in this time range, which confirmed a subcortical location of the source. From dipole localization it was not possible to assign the exact origin of the P16 source to either the subthalamic level or the thalamo-cortical radiation, because of the limited spatial resolution at the centre of the spherical head model. An estimate of the conduction velocity of the medial lemniscus pointed towards a subthalamic origin. The P16 source was preserved in two patients with a lesion of the thalamo-cortical radiation and the ventral thalamus. Further evidence for a subthalamic location of P16 was derived from the physical mechanisms generating far-field potentials.
Buchner
H
H
Philips Research Laboratories, Hamburg, Germany.
Waberski
T D
TD
Fuchs
M
M
Wischmann
H A
HA
Beckmann
R
R
Rienäcker
A
A
D000328:Adult; D002540:Cerebral Cortex / Q000000981:diagnostic imaging / Q000502:physiology* / Q000503:physiopathology; D002561:Cerebrovascular Disorders / Q000000981:diagnostic imaging / Q000503:physiopathology; D004558:Electric Stimulation; D004569:Electroencephalography; D004574:Electromagnetic Fields; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D005260:Female; D006257:Head / Q000502:physiology; D006801:Humans; D008297:Male; D008475:Median Nerve / Q000502:physiology*; D008875:Middle Aged; D008959:Models, Neurological; D009949:Orientation / Q000502:physiology; D013028:Space Perception / Q000502:physiology; D013787:Thalamic Nuclei / Q000000981:diagnostic imaging / Q000502:physiology* / Q000503:physiopathology; D014057:Tomography, X-Ray Computed