Somatosensory evoked potentials and magnetic fields elicited by tactile stimulation of the hand during active and quiet sleep in newborns.
OBJECTIVE
Our objective was to characterize the effects of sleep stages on tactile somatosensory evoked responses in full-term newborns.


METHODS
Somatosensory evoked potentials (SEPs) and magnetic fields (SEFs) to tactile stimulation of the tip of the index finger and/or thenar eminence were measured from 14 healthy newborns. The stimulus was a gentle tap produced by a moving membrane driven by an air-pressure pulse.


RESULTS
SEPs and SEFs to tactile stimulation of the skin were similar in waveform and latency to SEPs known to be produced by electrical stimulation of the fingertip of neonates. The two most distinguishable positive deflections of SEPs, P1 and P2, within 300 ms of the stimulation, and their magnetic counterparts were clearly smaller in active compared to quiet sleep.


CONCLUSIONS
Our study demonstrates for the first time that it is possible to record SEFs in neonates, and that clear late cortical somatosensory responses are produced by tactile stimulation. In addition, the effect of sleep stage on these responses indicates differences in the processing of the incoming information, at least in the somatosensory modality, in active and quiet sleep.


CONCLUSIONS
Tactile stimulation may be useful as a completely non-invasive technique for studying the physiology of the somatosensory system in neonates. Methodologically, since the effect of sleep stage is profound, one must carefully monitor the sleep stages in studies of event-related responses in newborns, or else this effect may confound the phenomena being studied.
Pihko
Elina
E
BioMag Laboratory, Helsinki University Central Hospital, P.O. Box 340, FIN-00029 HUS, Finland. pihko@biomag.hus.fi
Lauronen
Leena
L
Wikström
Heidi
H
Taulu
Samu
S
Nurminen
Jussi
J
Kivitie-Kallio
Satu
S
Okada
Yoshio
Y
D004569:Electroencephalography; D004574:Electromagnetic Fields; D004576:Electromyography; D004585:Electrooculography; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D005260:Female; D005385:Fingers / Q000294:innervation / Q000502:physiology; D006225:Hand / Q000294:innervation / Q000502:physiology*; D006801:Humans; D007231:Infant, Newborn; D015225:Magnetoencephalography; D008297:Male; D010812:Physical Stimulation / Q000379:methods; D012894:Sleep Stages / Q000502:physiology*; D013003:Somatosensory Cortex / Q000502:physiology*