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Effect of heart rate on regulative features of the cortical activity-flow coupling
B Rosengarten1, C Budden, S Osthaus
1Department of Neurology, Faculty of Medicine, Justus Liebig University of Giessen, Germany.
Insights
Heart rate does not significantly influence cerebral blood flow regulation during neural activity. Study findings suggest an integrative principle in flow regulation, supporting simpler models of blood flow adaptation.
Area of Science:
- Neuroscience
- Physiology
- Cerebrovascular Regulation
Background:
- Heart rate is crucial for arterial pressure regulation but its role in dynamic organ perfusion adjustment is less understood.
- Activity-flow coupling mechanisms adapt local cerebral blood flow to cortical activity.
- Heart rate variability is often observed in experimental conditions.
Purpose of the Study:
- To investigate the influence of heart rate on the activity-flow coupling mechanism in cerebral blood flow.
- To compare cerebral blood flow responses across different heart rate groups using observed heart rate variability.
- To evaluate flow responses under stable heart rate conditions.
Main Methods:
- 168 healthy young volunteers were grouped by heart rate (60-100 beats/min).
- Transcranial Doppler technique assessed visually evoked flow velocity responses in the posterior cerebral artery.
- Control system analysis evaluated peak systolic and end diastolic data.
Main Results:
- No significant correlation was found between heart rate and baseline flow velocity or control system parameters (gain, attenuation, rate time, natural frequency).
- Analysis of variance (ANOVA) showed no significant differences in flow responses among heart rate groups.
- Flow velocity responses exhibited similar time courses across groups with up to 50% heart rate variation.
Conclusions:
- Increased heart rate and associated stress factors do not appear to impact the regulatory features of activity-flow coupling.
- Consistent flow velocity responses across varying heart rates suggest an integrative principle in cerebral blood flow regulation.
- Findings support simplified models of cerebral blood flow adaptation.
Objective:
Heart rate plays an important role in compensatory conditions of arterial pressure changes. Very little information, however, exists on its role in the dynamic adjustment of stimulated organ perfusion. We studied the influence of heart rate on the activity-flow coupling mechanism which adapts local cerebral blood flow in accordance with cortical activity. Since it does not affect heart rate or arterial blood pressure by itself, the commonly observed heart rate variability in test conditions was used to compare the flow response between different heart rate groups. For evaluation under stable heart rate conditions we performed a short test paradigm with a transcranial Doppler technique with the necessary high time resolution.
Methods:
168 healthy young volunteers (24 +/- 3 years of age) were grouped according to their heart rate in decade steps from 60 to 100 beats/min (mean: 82 +/- 9 beats/min). The visually evoked flow velocity responses in the posterior cerebral artery were evaluated according to a control system approach. Peak systolic and end diastolic data were evaluated separately.
Results:
A correlation analysis between heart rate and baseline flow velocity as well as each of the control system parameters, i.e. gain, attenuation, rate time and natural frequency, revealed no significance. The flow responses did not differ among the heart rate groups as concluded from an ANOVA test.
Discussion:
The increase in heart rate and the possible stress factors responsible for this seem to be of no relevance in regulative features of the activity-flow coupling. The almost identical time course of flow velocity responses among the groups showing a heart rate difference of up to 50% indicates an integrative principle in flow regulation supporting simplified concepts of flow adaptation.