Effect of novel short‐arm human centrifugation‐induced gravitational gradients upon cardiovascular responses, cerebral perfusion and g‐tolerance

Episodic increases in cerebrovascular perfusion and shear stress may have beneficial impacts on endothelial function that improve brain health. We hypothesized that water immersion to the level of the right atrium in humans would increase cerebral perfusion. We continuously measured, in 9 young (means ± SD, 24.6 ± 2.0 yr) healthy men, systemic hemodynamic variables along with blood flows in the common carotid and middle and posterior cerebral arteries during controlled filling and emptying of a water tank to the level of the right atrium. Mean arterial pressure (80 ± 9 vs. 91 ± 12 mmHg, P < 0.05), cardiac output (4.8 ± 0.7 vs. 5.1 ± 0.6 l/min, P < 0.05) and end-tidal carbon dioxide (PetCO2, 39.5 ± 2.0 vs. 44.4 ± 3.5 mmHg, P < 0.05) increased with water immersion, along with middle (59 ± 6 vs. 64 ± 6 cm/s, P < 0.05) and posterior cerebral artery blood flow velocities (41 ± 9 vs. 44 ± 10 cm/s, P < 0.05). These changes were reversed when the tank was emptied. Water immersion is associated with hemodynamic and PetCO2 changes, which increase cerebral blood velocities in humans. This study provides an evidence base for future studies to examine the potential additive effect of exercise in water on improving cerebrovascular health.

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Independent and interactive effects of incremental heat strain, orthostatic stress, and mild hypohydration on cerebral perfusion

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00109.2017 ◽

2018 ◽

Vol 314 (3) ◽

pp. R415-R426 ◽

Cited By ~ 3

Author(s):

R. A. I. Lucas ◽

L. C. Wilson ◽

P. N. Ainslie ◽

J. L. Fan ◽

K. N. Thomas ◽

...

Keyword(s):

Body Mass ◽

Heat Tolerance ◽

Cerebral Perfusion ◽

Thermal State ◽

Lower Body Negative Pressure ◽

Cardiovascular Responses ◽

Heat Strain ◽

Interactive Effects ◽

Hydration Status ◽

Arterial Blood

The purpose of this study was to identify the dose-dependent effects of heat strain and orthostasis [via lower body negative pressure (LBNP)], with and without mild hypohydration, on systemic function and cerebral perfusion. Eleven men (means ± SD: 27 ± 7 y; body mass 77 ± 6 kg), resting supine in a water-perfused suit, underwent progressive passive heating [0.5°C increments in core temperature (Tc; esophageal to +2.0°C)] while euhydrated (EUH) or hypohydrated (HYPO; 1.5–2% body mass deficit). At each thermal state, mean cerebral artery blood velocity (MCAvmean; transcranial Doppler), partial pressure of end-tidal carbon dioxide ([Formula: see text]), heart rate (HR) and mean arterial blood pressure (MAP; photoplethysmography) were measured continuously during LBNP (0, −15, −30, and −45 mmHg). Four subjects became intolerant before +2.0°C Tc, unrelated to hydration status. Without LBNP, decreases in [Formula: see text] accounted fully for reductions in MCAvmeanacross all Tc. With LBNP at heat tolerance (+1.5 or +2.0°C), [Formula: see text] accounted for 69 ± 25% of the change in MCAvmean. The HYPO condition did not affect MCAvmeanor any cardiovascular variables during combined LBNP and passive heat stress (all P > 0.13). These findings indicate that hypocapnia accounted fully for the reduction in MCAvmeanwhen passively heat stressed in the absence of LBNP and for two- thirds of the reduction when at heat tolerance combined with LBNP. Furthermore, when elevations in Tcare matched, mild hypohydration does not influence cerebrovascular or cardiovascular responses to LBNP, even when stressed by a combination of hyperthermia and LBNP.

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John Ludbrook APPS Symposium Neural Mechanisms In The Cardiovascular Responses To Acute Central Hypovolaemia

Clinical and Experimental Pharmacology and Physiology ◽

10.1046/j.1440-1681.2001.3473.x ◽

2001 ◽

Vol 28 (5-6) ◽

pp. 479-487

Author(s):

Roger G Evans ◽

Sabatino Ventura ◽

Roger Al Dampney ◽

John Ludbrook

Keyword(s):

Cardiovascular Responses ◽

Neural Mechanisms ◽

Central Hypovolaemia

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In Search of Somatic Precursors of Spontaneous Insight

Journal of Psychophysiology ◽

10.1027/0269-8803/a000188 ◽

2018 ◽

Vol 32 (3) ◽

pp. 97-105 ◽

Cited By ~ 2

Author(s):

Wangbing Shen ◽

Yuan Yuan ◽

Chaoying Tang ◽

Chunhua Shi ◽

Chang Liu ◽

...

Keyword(s):

Problem Solving ◽

Direct Evidence ◽

Electrodermal Activity ◽

Cardiovascular Responses ◽

Solution Time ◽

Problem Solution ◽

Insight Problem ◽

Creative Insight ◽

Insight Problem Solving ◽

Analytic Problem

Abstract. A considerable number of behavioral and neuroscientific studies on insight problem solving have revealed behavioral and neural correlates of the dynamic insight process; however, somatic correlates, particularly somatic precursors of creative insight, remain undetermined. To characterize the somatic precursor of spontaneous insight, 22 healthy volunteers were recruited to solve the compound remote associate (CRA) task in which a problem can be solved by either an insight or an analytic strategy. The participants’ peripheral nervous activities, particularly electrodermal and cardiovascular responses, were continuously monitored and separately measured. The results revealed a greater skin conductance magnitude for insight trials than for non-insight trials in the 4-s time span prior to problem solutions and two marginally significant correlations between pre-solution heart rate variability (HRV) and the solution time of insight trials. Our findings provide the first direct evidence that spontaneous insight in problem solving is a somatically peculiar process that is distinct from the stepwise process of analytic problem solving and can be represented by a special somatic precursor, which is a stronger pre-solution electrodermal activity and a correlation between problem solution time and certain HRV indicators such as the root mean square successive difference (RMSSD).

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