Topographic distribution of sleep spindles in young healthy subjects

Abstract

SUMMARYThe application of an automatic sleep spindle detection procedure allowed the documentation of the topographic distribution of spindle characteristics, such as number, amplitude, frequency and duration, as a function of sleep depth and of recording time. Multichannel all-night EEG recordings were performed in 10 normal healthy subjects aged 20-35 years. Although the interindividual variability in the number of sleep spindles was very high (2.7±2.1 spindles per minute stage 2 sleep), all but two subjects showed maximal spindle activity in centro-parietal midline leads. Moreover, this topography was seen in all sleep stages and changed only slightly -to a more central distribution -towards the end of the night. On the other hand, slow (11.5-14 Hz) and fast (14-16 Hz) spindles showed a completely different topography, with slow spindles distributed anteriorly and fast spindles centro-parietally. The number of sleep spindles per min was significant depending on sleep stages, with the expected highest occurrence in stage 2, and on recording time, with a decrease in spindle density from the beginning towards the end of the night. However, spindle amplitude, frequency and individual duration was not influenced by sleep depth or time of the night.

Cortical locations of maximal spindle activity: magnetoencephalography (MEG) study

“…The present study used wholehead MEG to examine the cortical regions involved in maxima of spindle amplitude activity in healthy, normal sleeping individual subjects during a morning nap. Despite the fact that in the present study spindles were obtained from stage 2 sleep during morning nap, our results show that sleep spindles have multiple cortical sources that are seen in frontal, temporal and parietal brain regions that correspond to the previous EEG and ⁄ or MEG findings (Anderer et al, 2001;Broughton and Hasan, 1995;Gibbs and Gibbs, 1950;Ishii et al, 2003;Lu et al, 1992;Manshanden et al, 2002;Shih et al, 2000;Urakami, 2008;Zeitlhofer et al, 1997;Zygierewicz et al, 1999). In addition, a new approach for spindle localization used in this study, such as averaging spindle amplitude and localizing the source of the maximal activity, showed specific locations for the maximal spindle activity centered at precentral and postcentral gyri.…”

“…Our findings also show that this maximal activity probably reflects a unifying network for both slow and fast spindles within these regions. The complex nature of the spindle activity, especially slowand fast-frequency spindle activity was revealed by topographic EEG studies (Anderer et al, 2001;Zeitlhofer et al, 1997;Zygierewicz et al, 1999;for a review, De Gennaro and Ferrara, 2003). The findings from these studies show that the neuronal network underlying these two types of spindles is topographically distinct.…”

“…Multiple widespread generators for sleep spindles were suggested by human studies using whole-head EEG (Anderer et al, 2001;Zeitlhofer et al, 1997;Zygierewicz et al, 1999) and magnetoencephalography (MEG) (Ishii et al, 2003;Lu et al, 1992;Manshanden et al, 2002;Shih et al, 2000;Urakami, 2008). In humans, attempts to localize spindle activation were performed and studies have found common brain regions that are active during the occurrence of sleep spindles (Brazier, 1968;Montplaisir et al, 1981) and that the amplitude of sleep spindles is the highest in the frontal-central regions (Caderas et al, 1982).…”

Impaired Off-Line Consolidation of Motor Memories After Combined Blockade of Cholinergic Receptors During REM Sleep-Rich Sleep

“…To calculate spindle density, mean spindle counts were divided by the number of analyzed 30-s epochs. The two separate spindle bands were chosen based on earlier studies which showed the presence of two kinds of spindles in humans possibly linked to different aspects of cognitive function, ie, slow spindles that prevail over the frontal cortex, and show greater topographical variability than the fast spindles that concentrate over the parietal cortex (Zeitlhofer et al, 1997;Schabus et al, 2007).…”

Sleep spindle detection through amplitude–frequency normal modelling

“…Therefore, the 'classical' 12-14 Hz spindle definition is believed to be too narrow (Jankel and Niedermeyer, 1985). The difficulty in finding the optimum frequency bounds has produced a large number of proposed values, among them: 11.5-15 Hz (Fish et al, 1988), 11.5-16 Hz (Zeitlhofer et al, 1997), 11-15 Hz (Ktonas et al, 2009), 11-16 Hz (Clemens et al, 2005, 10.5-16 Hz (Ventouras et al, 2005;Huupponen et al, 2007), and 10-16 Hz (Zygierewicz et al, 1999;Huupponen et al, 2000a;Estévez et al, 2002). Beside the often cited 12-14 Hz frequency range proposed by the National Institute of Neurological Diseases and Blindness of the U.S. Department of Health, Education, and Welfare (Rechtschaffen and Kales, 1968), various organizations have suggested other values to score spindles: 11-16 Hz by the American Academy of Sleep Medicine (Iber et al, 2007), 11-15 Hz by the International Federation of Clinical Neurophysiology (Noachtar et al, 1999), and 12-16 Hz by the Japanese Society of Sleep Research (Hori et al, 2001).…”