5 to 3 s, while the K-complex is a phasic EEG waveform of approximately 0.5 s, characterized by a well-delineated negative component followed by a positive deflection. K-complexes may be spontaneous or elicited by stimulation. While sleep spindles are often viewed as playing a sleepprotective role and contributing to sleep maintenance, the functional significance of K-complexes remains a matter of debate. In fact, K-complexes are considered to be elementary forms

of arousal during slow-wave sleep (SWS). They carry characteristics of evoked potentials, which provide subattentive information processing. There has been Inhibitors,research,lifescience,medical a debate as to whether the appearance of a Kcomplex in response to a stimulus is indicative of a partial arousal process that leaves the central nervous system more likely to arouse if further stimulation occurs,12,49 or whether it reflects a sleep maintenance process involving a response to stimulation that would inhibit arousal and prevent the fragmentation of sleep.50,51 The interrelationship between Inhibitors,research,lifescience,medical sleep spindles and K-complexes is not entirely clear, although they are often associated.52 There are reports of spindles and Inhibitors,research,lifescience,medical K-complexes varying together, for example, in the case of dementia where both spindles and K-complexes are reduced.53 Spindle density has been reported to be drastically

decreased in Alzheimer’s disease.54 Dysthymic patients have fewer Kcomplexes and arousals than controls, though

they do exhibit a higher rate of nocturnal awakenings.55 Rapid eye movements REMs are controlled by a cholinergic-aminergic Inhibitors,research,lifescience,medical balance.56 They constitute a major event in the scoring of REM sleep, but their frequency or density can also be used to quantify the intensity of REM sleep process. According to Kupfer and Reynolds,57 EEG sleep changes in depression include much more than shortened sleep latency. The frequency of REM, or REM density, is dependent on the subject’s Inhibitors,research,lifescience,medical mood, and is higher in patients suffering from depression.58,59 REM density is also higher in dreams with strong emotional content60 and after stressful situations.61 However, due to its very large variability, it is questionable whether overall REM density can be considered as a biological marker for affective illness.62 REM density has been found to be increased in schizophrenia,63,64 Montelukast Sodium but, in contrast, in other reports, previously treated and drug-naive patients with schizophrenia were reported to show normal REM density.62,65-67 In a recent study,68 borderline personality disorder patients were compared with patients with major depression and matched healthy control subjects. All patients fulfilled the LY335979 chemical structure International Classification of Diseases, 10th revision (ICD10) criteria.69 In both patient groups, REM density for the whole night, as well as rem density for the first REM period, was significantly increased compared with the control group.