The Oscillatory Systems of the Brain and Individual Variability of the Defensive Cardiac Reflex in Humans

Abstract

The present study presents an analysis of the central mechanisms of the individual variation of cardiovascular stress reactivity in humans. The cardiovascular system is one of the leading effectors of motivated activity, and the nature of the obligatory "rearrangements" of hemodynamics to the chosen program of adaptive behavior is determined by the operation of psychosomatic integration mechanisms, the efficacy of which varies over a wide range in health and is impaired in arterial hypertension [4,35,36]. A new direction in studies of the question of cardiovascular reactivity is provided by analysis of the contribution of the activity of the two major motivational systems of the brain -the aversive/defensive system and the positive reinforcement system, initiating cascades of cognitive, emotional, visceral, and motor reactions -to the central mechanisms regulating cardiovascular stress reactivity [18].We report here our studies of the activity of the defensive motivational system, which, using immobilization or active defensive reactions, prepares the body to cope with threats [18]. Assessment of the reactivity of this system was based on a psychophysiological test in which presentation of a discrete stressor evokes a hemodynamic response altering the defensive cardiac reflex (DCR) [1,38]. The DCR profile includes short-and long-latency complexes of BP and HR reactivity [2]. Marked individual variability is the main distinguishing feature characteristic of the DCR and is reflected mainly in the presence or absence of a long-latency increase in BP [1,38]. The phenomenon of the long-latency increase in BP is of potential clinical interest, as it is an indicator of activation of the defense system, organizing resource mobilization and defensive coping reactions [1,2,38]. In turn, hyperactivity of the defense system can be regarded as a neuThe defensive cardiac reflex (DCR) is a reaction of the cardiovascular system with a specific profile of short-and long-latency reactivities (mainly of arterial blood pressure (BP) and heart rate (HR)). The DCR reflects activation of the defensive motivational system and defensive coping programs in humans. The aim of the present work was to evaluate the contribution of the brain oscillatory systems to the mechanisms of individual variability of the DCR. The oscillatory dynamics of multichannel (64-channel) electroencephalogram (EEG) were assessed using evoked synchronization/desynchronization in different frequency ranges and hemodynamics were assessed using simultaneously recorded beat-by-beat measures of cardiovascular reactivity (Finapres ® technology). This is the first report showing significant linkage between θ 2 (6-8 Hz) EEG activity with short-latency DCR reactivity and between α 2 (10-12 Hz) activity and long-latency reactivity. Hyperreactivity of the long-latency BP component was shown to be associated with the absence of a concomitant phase α 2 synchronization evoked. It is suggested that high-frequency θ EEG oscillations are involved in the central magnitude scaling m...

Linkage of Brain Oscillatory Systems with the Cognitive (experience and valence) and Physiological (cardiovascular reactivity) Components of the Emotions

“…The literature currently contains limited data on the connection between EEG oscillator activity and cardiovascular reactivity, especially BP reactivity [3][4][5]18]. This is largely due to the low availability of instruments for combined recording of the EEG and "beat-by-beat" measures of BP reactivity and other hemodynamic indicators (such as TPVR), which allow the dynamics of evoked changes to be combined correctly in the analysis.…”