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NEUROHUMORAL CONTROL OF CARDIOVASCULAR FUNCTION

Cerebral and systemic hemodynamic changes during cognitive and motor activation paradigms

¹Department of Medical Physics, University Hospitals of Leicester NHS Trust, and ²Department of Cardiovascular Sciences, Faculty of Medicine, University of Leicester, Leicester, United Kingdom

Submitted 14 December 2004 ; accepted in final form 26 January 2005

Cognitive and/or sensorimotor stimulations of the brain induce increases in cerebral blood flow that are usually associated with increased metabolic demand. We tested the hypothesis that changes in arterial blood pressure (ABP) and arterial PCO₂ also take place during brain activation protocols designed to induce hemispheric lateralization, leading to a pressure-autoregulatory response in addition to the metabolic-driven changes usually assumed by brain stimulation paradigms. Continuous recordings of cerebral blood flow velocity [CBFV; bilateral, middle cerebral artery (MCA)], ABP, ECG, and end-tidal PCO₂ (PET_CO2) were performed in 15 right-handed healthy subjects (aged 21–43 yr), in the seated position, at rest and during 10 repeated presentations of a word generation and a constructional puzzle paradigm that are known to induce differential cortical activation. Derived variables included heart rate, cerebrovascular resistance, critical closing pressure, resistance area product, and the difference between the right and left MCA recordings (CBFV_R-L). No adaptation of the CBFV_R-L difference was detected for the repeated presentation of 10 activation tasks, for either paradigm. During activation with the word generation tasks, CBFV changed by (mean ± SD) 9.0 ± 3.7% (right MCA, P = 0.0007) and by 12.3 ± 7.6% (left MCA, P = 0.0007), ABP by 7.7 ± 6.0 mmHg (P = 0.0007), heart rate by 7.1 ± 5.3 beats/min (P = 0.0008), and PET_CO2 by –2.32 ± 2.23 Torr (P = 0.002). For the puzzle paradigm, CBFV changed by 13.9 ± 6.6% (right MCA, P = 0.0007) and by 11.5 ± 6.2% (left MCA, P = 0.0007), ABP by 7.1 ± 8.4 mmHg (P = 0.0054), heart rate by 7.9 ± 4.6 beats/min (P = 0.0008), and PET_CO2 by –2.42 ± 2.59 Torr (P = 0.001). The word paradigm led to greater left hemispheric dominance than the right hemispheric dominance observed with the puzzle paradigm (P = 0.004). We concluded that significant changes in ABP and PET_CO2 levels occur during brain activation protocols, and these contribute to the evoked change in CBFV. A pressure-autoregulatory response can be observed in addition to the hemodynamic changes induced by increases in metabolic demand. Simultaneous changes in PCO₂ and heart rate add to the complexity of the response, indicating the need for more detailed modeling and better understanding of brain activation paradigms.

neurovascular coupling; brain stimulation; lateralization; cerebral autoregulation; CO₂ reactivity

This article has been cited by other articles:

				R. B. Panerai, M. Moody, P. J. Eames, and J. F. Potter Cerebral blood flow velocity during mental activation: interpretation with different models of the passive pressure-velocity relationship J Appl Physiol, December 1, 2005; 99(6): 2352 - 2362. [Abstract] [Full Text] [PDF]

				R. B. Panerai, M. Moody, P. J. Eames, and J. F. Potter Dynamic cerebral autoregulation during brain activation paradigms Am J Physiol Heart Circ Physiol, September 1, 2005; 289(3): H1202 - H1208. [Abstract] [Full Text] [PDF]