Pattern Recognition by Matched Filtering: An Analysis of Sleep Spindle and K-Complex Density under the Influence of Lormetazepam and Zopiclone

Abstract

The evaluation of sleep EEG patterns is mostly accomplished by visual analysis. With modern personal computers however, it is possible to perform signal detection within a reasonable length of time automatically. This paper presents a method for signal processing based on matched filtering. This allows the detection of sleep spindles and K-complexes in a sleep EEG recording with a high degree of accuracy. First the technique is described, and the results of a validation study based on the comparison of visual evaluations and computer analysis are presented. Thereafter, results of an application study are presented. Sleep spindle and K-complex density under the influence of lormetazepam and zopiclone were examined. Under both medications sleep spindle density increased while K-complex density decreased. Computation of Pearson’s correlation coefficients demonstrated that the interindividual sleep spindle and K-complex variations under both treatments are highly correlated. The data suggest that lormetazepam and zopiclone, although chemically different, have a similar mode of action and display comparable effects on the sleep EEG.

An E-Health Solution for Automatic Sleep Classification according to Rechtschaffen and Kales: Validation Study of the Somnolyzer 24 × 7 Utilizing the Siesta Database

“…Finally, for the chin EMG, trimmed means of squared amplitudes (omitting all values above the 80% percentile) were computed for 1-second epochs. For each 30-second epoch minimum, maximum and mean of these 1-second values were de- [17], adaptive noise cancellers with varying weights [18], independent component analysis [19] Artifacts Identifi cation: voltage threshold (overfl ow check) [12], discriminant analysis [20], adaptive thresholds (moving median) [21], unsupervised network (NeoART) [22,23], distance rejection [22,23], uncertainty rejection [22,23], automatic relevance determination [24], probabilistic graphical methods [25], model-based rejection [27] Delta waves Period-amplitude analysis [26], spectral analysis, digital band-pass fi lter, model-based detector [27] Sleep spindles Digital fi lters [28], neural networks [29], matched fi ltering [30], wavelets [31] K-complexes Neural networks [32], matched fi ltering [30], wavelets [31], model-based detector [33] Vertex sharp waves…”

ECG Activity in the Sleep of Insomniac Patients under the Influence of Lormetazepam and Zopiclone

“…Since the design of the pharmacologi cal trial has been described in detail elsewhere [18,19], only a brief outline is given here: 16 elderly subjects (12 females and 4 males; mean age ± SD:66.7 ± 5.8 years) with a chronic or subchronic form of psychophysiological insomnia were included in the trial [20], Sub jects with indications of a history of sleep apnoea syndrome or peri odic movements during sleep were excluded during the screening procedure. After an adaptation night, subjects were treated at weekly intervals in blocks of 3 consecutive nights with either lormetazepam (1 mg), zopiclone (7.5 mg) or placebo in randomised order.…”

Guidelines for the Recording and Evaluation of Pharmaco-Sleep Studies in Man: The International Pharmaco-EEG Society (IPEG)

“…Sleep spindles are rhythmic, sinusoidal waves characterised by progressively increasing, then gradually decreasing (‘waxing and waning') amplitudes. Sleep spindle properties (density, amplitude and frequency) are affected by age [96,97] or by sleep deprivation [98], and their frequency might be influenced by sleep disorders, neurological disorders, and hypnotic drugs [99,100]. Sleep spindles seem to play a major role in memory consolidation [101] and might be used as a biomarker for general cognitive and learning abilities [102].…”

“…K complexes represent a synchronised pattern consisting of alternating bursts of firing and silence within extended cortical networks during sleep, which trigger and synchronise other sleep activities in the thalamus [108] and are thought to relate to a sleep-protecting mechanism responsible for maintaining sleep [109]. Amplitude and frequency of occurrence of K complexes decrease with age [110] and under the influence of hypnotic drugs [99,100]. Both evoked and spontaneous K complexes show a frontal maximum [104,111,112] and are usually bilaterally symmetrical [113].…”

“…Different techniques have been applied to detect various patterns, such as sleep spindles [197,198,199], alpha waves [200], K complexes [100,201,202], arousals [203,204], CAPs [205], transient EEG events [206], or eye movements [207,208,209]. Time-frequency signal parameterisation methods, such as wavelets and matching pursuit, provide an elegant way to assess EEG recordings and to localise sleep patterns (e.g.…”