Does cerebrovascular disease affect the coupling between neuronal activity and local haemodynamics?

Area of Science:

• Neuroscience
• Medical Imaging
• Cerebrovascular Medicine

Background:

• Severe cerebrovascular deficits can disrupt normal brain function.
• Assessing neurophysiological and cerebrovascular-metabolic coupling is crucial for understanding these deficits.
• Magnetoencephalography (MEG) and blood oxygen level-dependent functional MRI (BOLD fMRI) are advanced neuroimaging techniques.

Purpose of the Study:

• To investigate the relationship between neurophysiological (MEG) and cerebrovascular-metabolic (BOLD fMRI) findings in patients with severe cerebrovascular deficits.
• To compare MEG-evoked fields and BOLD fMRI responses using identical stimuli.
• To identify factors contributing to discrepancies between MEG and BOLD fMRI in this patient group.

Main Methods:

• Comparison of magnetoencephalographic (MEG) evoked fields and BOLD fMRI responses to median nerve stimulation.
• Inclusion of a control group (10 subjects) and a patient sample (10 subjects) with severe cerebrovascular deficits.
• Assessment of potential influencing factors: lesion site, white matter hyperintensities, medication, risk factors, neck vessel anatomy, and cerebral vasomotor reactivity (VMR) via transcranial Doppler (TCD).

Main Results:

• MEG and BOLD fMRI responses were uncorrelated in patients, unlike in controls.
• Patients exhibited clear MEG signals but inconsistent or absent BOLD fMRI activation.
• Altered cerebral vasomotor reactivity (VMR) was strongly related to the lack of fMRI activation, particularly in a patient with microangiopathy.

Conclusions:

• There is a significant uncoupling between neurophysiological and cerebrovascular-metabolic measures in severe cerebrovascular deficits.
• Cerebral vasomotor reactivity is a key factor influencing BOLD fMRI signal in these patients.
• BOLD fMRI may be more sensitive than TCD for detecting chronic microvascular impairments.