Stress assessment based on EEG univariate features and functional connectivity measures.

The biological response to stress originates in the brain but involves different biochemical and physiological effects. Many common clinical methods to assess stress are based on the presence of specific hormones and on features extracted from different signals, including electrocardiogram, blood pressure, skin temperature, or galvanic skin response. The aim of this paper was to assess stress using EEG-based variables obtained from univariate analysis and functional connectivity evaluation. Two different stressors, the Stroop test and sleep deprivation, were applied to 30 volunteers to find common EEG patterns related to stress effects. Results showed a decrease of the high alpha power (11 to 12 Hz), an increase in the high beta band (23 to 36 Hz, considered a busy brain indicator), and a decrease in the approximate entropy. Moreover, connectivity showed that the high beta coherence and the interhemispheric nonlinear couplings, measured by the cross mutual information function, increased significantly for both stressors, suggesting that useful stress indexes may be obtained from EEG-based features.

Different acute tolerance development to EEG, psychomotor performance and subjective assessment effects after two intermittent oral doses of alprazolam in healthy volunteers.

BACKGROUND/AIMS: Benzodiazepines (BZDs) are the most effective of the psychotropic drugs in the treatment of anxiety disorders. Tolerance has been reported for the majority of BZDs after chronic administration. However, little attention has been paid to the possibility that tolerance might be present after the intermittent oral administration of BZDs. The objectives of the present study were to assess tolerance development after the administration of two intermittent single oral doses of alprazolam given 15 days apart in healthy volunteers, and to compare the results obtained using measures from different domains: neurophysiological, psychomotor and subjective. METHODS: Twenty-four healthy volunteers received 2 mg of alprazolam orally on two experimental days, 15 days apart. Plasma concentrations and pharmacodynamics (PD) were assessed before drug intake and at different times in the following 24 h. PD was assessed through EEG (relative alpha and relative beta-1 activities), cancellation task (total and correct number of responses) and visual analogue scales (activity and drowsiness). RESULTS: No differences were observed in the PKs of alprazolam between occasions. A proteresis was present in both administrations for impairments of psychomotor performance and relative beta-1 activity, whereas it was present only after the second administration for subjective assessments and relative alpha activity. The proteresis on the second occasion was higher than on the first one. CONCLUSIONS: The administration of two single oral doses of alprazolam, 2 weeks apart in healthy volunteers, yielded the same PKs on both occasions, but significant changes were observed in the PD profile. Acute tolerance was observed after the second administration. Two patterns of acute tolerance development were obtained: (1) impairments of psychomotor performance and relative beta-1 activity, and (2) subjective assessments and relative alpha activity.