An exploratory study of the effects of spatial working-memory load on prefrontal activation in low- and high-performing elderly.

Older adults show more bilateral prefrontal activation during cognitive performance than younger adults, who typically show unilateral activation. This over-recruitment has been interpreted as compensation for declining structure and function of the brain. Here we examined how the relationship between behavioral performance and prefrontal activation is modulated by different levels of working-memory load.

Transfer function analysis for the assessment of cerebral autoregulation using spontaneous oscillations in blood pressure and cerebral blood flow.

Cerebral autoregulation (CA) is a key mechanism to protect the brain against excessive fluctuations in blood pressure (BP) and maintain cerebral blood flow. Analyzing the relationship between spontaneous BP and cerebral blood flow velocity (CBFV) using transfer function analysis is a widely used technique to quantify CA in a non-invasive way. The objective of this review was to provide an overview of transfer function techniques used in the assessment of CA.

Assessment of dynamic cerebral autoregulation and cerebrovascular CO2 reactivity in ageing by measurements of cerebral blood flow and cortical oxygenation.

With ageing, cerebral blood flow velocity (CBFV) decreases; however, to what extent dynamic cerebral autoregulation and cerebrovascular CO2 reactivity are influenced by ageing is unknown. The aim was to examine the dynamic responses of CBFV and cortical oxygenation to changes in blood pressure (BP) and arterial CO2 across different ages. Fifty-eight participants in three age groups were included, as follows: young (n = 20, 24 ± 2 years old), elderly (n = 20, 66 ± 1 years old), and older elderly (n = 18, 78 ± 3 years old).

Impaired cerebral autoregulation and vasomotor reactivity in sporadic Alzheimer's disease.

Background: Understanding the relationship between vascular disease and Alzheimer's disease (AD) will enhance our insight into this disease and pave the way for novel therapeutic research. Cerebrovascular dysfunction, expressed as impaired cerebral autoregulation and cerebral vasomotor reactivity, has been observed in transgenic mouse models for AD. Translation to human AD is limited and conflicting however.

Very-low-frequency oscillations of cerebral hemodynamics and blood pressure are affected by aging and cognitive load.

Spontaneous slow oscillations occur in cerebral hemodynamics and blood pressure (BP), and may reflect neurogenic, metabolic or myogenic control of the cerebral vasculature. Aging is accompanied by a degeneration of the vascular system, which may have consequences for regional cerebral blood flow and cognitive performance. This degeneration may be reflected in a reduction of spontaneous slow oscillations of cerebral hemodynamics and BP.

Effects of aging on cerebral oxygenation during working-memory performance: a functional near-infrared spectroscopy study.

Working memory is sensitive to aging-related decline. Evidence exists that aging is accompanied by a reorganization of the working-memory circuitry, but the underlying neurocognitive mechanisms are unclear. In this study, we examined aging-related changes in prefrontal activation during working-memory performance using functional Near-Infrared Spectroscopy (fNIRS), a noninvasive neuroimaging technique.

Incorrect performance of the breath hold method in the old underestimates cerebrovascular reactivity and goes unnoticed without concomitant blood pressure and end-tidal CO(2) registration.

Background And Purpose: The breath hold maneuver is a convenient and frequently used method to assess cerebrovascular reactivity (CR). This study aimed to assess feasibility and reproducibility of this method in healthy older persons.

Methods: Twenty-five healthy volunteers, aged 75 (SD 4) years, performed 2 consecutive breath holds after careful instruction.

Oscillations in cerebral blood flow and cortical oxygenation in Alzheimer's disease.

In Alzheimer's disease (AD) cerebrovascular function is at risk. Transcranial Doppler, near-infrared spectroscopy, and photoplethysmography are noninvasive methods to continuously measure changes in cerebral blood flow velocity (CBFV), cerebral cortical oxygenated hemoglobin (O(2)Hb), and blood pressure (BP). In 21 patients with mild to moderate AD and 20 age-matched controls, we investigated how oscillations in cerebral blood flow velocity (CBFV) and O(2)Hb are associated with spontaneous and induced oscillations in blood pressure (BP) at the very low (VLF = 0.

Cortical oxygen supply during postural hypotension is further decreased in Alzheimer's disease, but unrelated to cholinesterase-inhibitor use.

Cerebrovascular function and structure of the cortical cerebral microvessels are profoundly altered in patients with Alzheimer's disease (AD). The functional hemodynamic consequences of such changes, however, remain essentially unknown. Cholinesterase inhibitors (ChEIs) potentially affect brain perfusion through either augmentation or inhibition of cerebral vasodilatation.

The cerebrovascular role of the cholinergic neural system in Alzheimer's disease.

The intrinsic cholinergic innervation of the cortical microvessels contains both subcortical pathways and local cortical interneurons mediated by muscarinic and nicotinic acetylcholine receptors. Stimulation of this system leads to vasodilatation. In the extrinsic innervation, choline acts as a selective agonist for the α7-nicoticinic acetylcholine receptor on the sympathetic nerves to cause vasodilatation, and through this mechanism, cholinergic modulation may affect this sympathetic vasodilatation.

Dynamic cerebral autoregulation in the old using a repeated sit-stand maneuver.

The aim of this study was to assess the feasibility and reproducibility of a simple and nonobtrusive repeated sit-stand maneuver to assess cerebral autoregulation (CA) in healthy old subjects >70 years. In 27 subjects aged 76 (SD 4) years, we continuously measured blood pressure using photoplethysmography and cerebral blood flow velocity in the middle cerebral artery (transcranial Doppler ultrasonography) during 5 min of sitting rest and again during repeated sit-stand maneuvers at 10 s (0.05 Hz) and 5 s (0.