K-complex studies in healthy humans: A neuromagnetic approach.

During Sleep EEG recordings (Slow Wave S!eep and stage 2). a sharp and large complex occurs. This activity, known as IK-complex, was first described in the ’30s (Loomis et al. 1935) but to our knowledge very few systematic studies have been performed. Neuromagnetic studies on general sleep patterns have been carried out recently(Ueno and lramina 1990; Lu et al. 1992). We present here preliminary results of a neuromagnetic study aimed to a classification of the different components of the K-complex and to a possible detection of the responsible sources. In fact, the K-complex is known to have at least three distinct components: N350, N550, P900, where the latency indication refers to the so-called evoked K-complex, which has the same morphology as the spontaneous one. The neuromagnetic acquisition is performed with a 28channel system covering an area of about 180 cm2, allowing to study, in several instances, the topography of the events and to retrieve information ahout source location, without repositioning the sensor. First results are suggestive of a different topography (and consequently a different structure and/or location of the sources) for the identified components of ?he complex. This investigation might bring very useful information about the possible correlation between the components of the K-complex and the different sensory modalities.