Estimation of the time course of slow-wave sleep over the night in depressed patients: effects of clomipramine and clinical response.

The distribution of slow-wave activity during sleep has been analyzed using a method related to the two-process model of sleep regulation. This method is applied to the analyses of data collected from 21 inpatients with unipolar depression who received the antidepressant clomipramine (CMI) in a pulse-loading protocol. CMI infusion was found to redistribute slow-wave activity, producing more concentration in the early part of the night, and also significantly reduced the fluctuation in slow-wave power as a function of time. These measures also distinguished clinical responders from the nonresponders. Drug responders had a significant redistribution of slow-wave activity to the earlier part of the night as compared to nonresponders. This suggests that measures of the distribution of slow-wave activity over the night may represent a good measure of clinical response to antidepressant therapy and have implications for the interpretation of the two-process model and sleep in depression.

Nonlinear analysis of EEG sleep states.

Recent advances in the field of nonlinear dynamics have provided new conceptual models as well as novel analytical techniques applicable to neuropsychopharmacologic studies. One measurement technique that has been recently developed in an attempt to characterize nonlinear systems in physics and biology is the estimation of dimension. Dimension may be seen as a measure of the information required to describe the current behavior of a system. We have applied these techniques to the analysis of the sleep EEG, and have found that the dimension of rapid eye movement (REM) sleep is significantly higher than non-rapid-eye-movement (NREM) sleep. These data support a preliminary hypothesis that EEG dimension may represent the number of nonlinear modes activated in the brain. Thus, sleep states of low arousal or low input would be envisioned as having low dimension (e.g., slow-wave sleep) whereas increased arousal (REM) would activate more nonlinear modes. Although more investigations will be needed to explore this hypothesis, these studies suggest that further development of nonlinear approaches to the analysis of brain systems are likely to generate new clinical measures as well as new ways of viewing brain electrical function.

EEG dimension in sons of alcoholics.

Recent advances in the field of nonlinear dynamics have provided new conceptual models, as well as novel analytical techniques applicable to studies in alcohol research. One measurement technique, which has been developed in an attempt to characterize nonlinear systems in physics and biology, is the estimation of attractor dimension. This dimension may be seen as a measure of the information required to describe the current behavior of a system. We have applied these techniques to the analysis of EEG collected from 17 men with alcoholic fathers and 19 men with no alcoholic relatives. The men with alcoholic fathers were found to have a lower EEG attractor dimension than their matched controls. This suggests that the EEG of young men with alcoholic fathers may be "more organized" or "less complex" than men with no alcoholic relatives. Although more studies will be needed to explore this hypothesis, these studies suggest that further development of nonlinear approaches to the analysis of brain systems are likely to generate new clinical measures, as well as new ways of viewing brain electrical function and alcoholism.