Characteristics of Oscillatory Brain Systems and the Cardiac Defensive Reflex in Patients with Newly Diagnosed Arterial Hypertension

Abstract

The stress reactivity of the defensive motivation system can be evaluated using the cardiac defensive reflex (CDR) – the reaction of the cardiovascular system to an unexpected unconditioned aversive stimulus. The aim of the study was to assess the possible contribution of brain oscillatory systems to the central pathogenetic mechanisms of impairments to increased arterial blood pressure (BP) stress reactivity in a clinical model of its altered regulation in patients with newly diagnosed untreated primary grade 1–2 arterial hypertension (aHT) (“naive hypertensives”). Healthy subjects (n = 19) and patients with aHT (n = 17) were studied. Dynamic beat-by-beat recordings were made of arterial hypertension and oscillatory EEG activity (64 channels) was evaluated using evoked synchronization/desynchronization (ES/ED). Along with anomalous increases in BP in baseline conditions, patients with aHT were found to have significantly reduced circulating platelet serotonin concentrations and increased tonic activation of the left hemisphere, reflected as an asymmetrical decrease in delta (2–4 Hz) and theta-1 (4–6 Hz) power in the central and parietal cortex of this hemisphere. CDR in patients was characterized by hyperreactivity of the short- and long-latency components of BP. Dynamic analysis showed that EEG long-latency component hyperreactivity could be due, among other mechanisms, to weakening of top-down inhibitory control, this mechanism including high-frequency EEG alpha oscillators (10–12 Hz) in the medial components of the central-parietal cortex of both hemispheres of the brain.