A comparison of two sleep spindle detection methods based on all night averages: individually adjusted vs. fixed frequencies.
Sleep spindles are frequently studied for their relationship with state and trait cognitive variables, and they are thought to play an important role in sleep-related memory consolidation. Due to their frequent occurrence in NREM sleep, the detection of sleep spindles is only feasible using automatic algorithms, of which a large number is available. We compared subject averages of the spindle parameters computed by a fixed frequency (FixF) (11-13 Hz for slow spindles, 13-15 Hz for fast spindles) automatic detection algorithm and the individual adjustment method (IAM), which uses individual frequency bands for sleep spindle detection. Fast spindle duration and amplitude are strongly correlated in the two algorithms, but there is little overlap in fast spindle density and slow spindle parameters in general. The agreement between fixed and manually determined sleep spindle frequencies is limited, especially in case of slow spindles. This is the most likely reason for the poor agreement between the two detection methods in case of slow spindle parameters. Our results suggest that while various algorithms may reliably detect fast spindles, a more sophisticated algorithm primed to individual spindle frequencies is necessary for the detection of slow spindles as well as individual variations in the number of spindles in general.
Institute of Behavioral Science, Semmelweis University Budapest, Hungary.
Péter Przemyslaw
PP
Ujma
Department of General Psychology, Pázmány Péter Catholic University Budapest, Hungary.
Ferenc
F
Gombos
Centre for Cognitive and Neural Systems, University of Edinburgh Edinburgh, UK.
Lisa
L
Genzel
Department of Clinical Research, Max Planck Institute of Psychiatry Munich, Germany.
Boris Nikolai
BN
Konrad
Department of Cognitive Sciences, Budapest University of Technology and Economics Budapest, Hungary ; Nyírõ Gyula Hospital, National Institute of Psychiatry and Addictions Budapest, Hungary.
Péter
P
Simor
Department of General Psychology, Pázmány Péter Catholic University Budapest, Hungary.
Axel
A
Steiger
Department of Clinical Research, Max Planck Institute of Psychiatry Munich, Germany ; Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Centre Nijmegen, Netherlands.
Martin
M
Dresler
Institute of Behavioral Science, Semmelweis University Budapest, Hungary ; Department of General Psychology, Pázmány Péter Catholic University Budapest, Hungary.
Róbert
R
Bódizs
EEG; IAM; automatic detections; comparison; fixed frequency method; sigma waves; sleep spindles