Summary: Researchers discovered age-related alterations in the coordination between neuronal activity and brain oxygenation.
By utilizing infrared light and electrical activity measurements, they studied the imperfect timings of bodily rhythms and their coordination. They found dramatic changes in the strength and coherence of these rhythms in older individuals.
These findings have significant implications for assessing treatments and monitoring neurodegenerative disorders like Alzheimer’s disease.
The study revealed changes in the coordination between brain oxygenation and neuronal activity as people age.
Novel non-invasive techniques were used to measure the function of neurovascular units in living humans for the first time.
These findings could enable non-invasive evaluations of neurovascular function decline in aging and neurodegenerative disorders.
Source: Lancaster University
Researchers investigating brain activity in older people say the coordination between neuronal activity and the brain’s oxygenation is altered.
The findings are published in Brain Research Bulletin by scientists from Lancaster University, UK and the University Medical Centre in Ljubljana, Slovenia.
The brain requires as much as 20% of the body’s energy consumption so the brain and the cardiovascular system have to work closely together to ensure sufficient energy supply to each part of the brain. This is done by many “neurovascular units” tasked with feeding the neurons.
Non-invasive recording of the function of these neurovascular units in living humans has never been done before, but has now been achieved by using several measurement techniques coupled with novel analysis methods developed at Lancaster University.
The living brain’s blood oxygenation was measured using infrared light, which easily penetrates the skull. The neuronal activity in the brain is associated with electrical activity, which was simultaneously measured on the surface of the scalp.
The body is humming with rhythms, with the best-known rhythm being the heartbeat. Other rhythms include respiration, brain waves, and processes controlling blood pressure and blood flow by changing the diameter of blood vessels.
Simultaneously measuring oxygenation, brain electrical activity, respiration and electric activity of the heart let the researchers capture these rhythms and their imperfect timings. They then studied the strength of these rhythms and their coordination, by computing their “phase coherence”.
The results illustrate that the magnitudes of the oscillations in brain vasculature and the brain waves are altered in the older group. But more dramatic are changes in the coherence between them, indicating that the coordination between the energy supply and demand in the brain is adversely affected by age.
The world population is ageing and the incidence of dementia is increasing. Hence, the ability to follow up treatment and monitor disease progression will grow more and more important in the years to come, especially in the possibility of assessing new drugs for Alzheimer’s disease.
Professor Aneta Stefanovska from Lancaster University said: “The approach could thus be used for non-invasive evaluation of the decline of neurovascular function in normal ageing, as well as for monitoring the efficacy of treatment or lifestyle changes in a wide range of neurodegenerative disorders.
“The results promise a relatively simple and non-invasive method for assessing the state of the brain in healthy aging, and in neurodegenerative disorders such as Alzheimer’s disease.”
The researchers included Juliane Bjerkan, Gemma Lancaster, Trevor Crawford, Peter McClintock and Aneta Stefanovska from Lancaster University and Bernard Meglič and Jan Kobal from the University Medical Centre in Ljubljana, Slovenia.
About this brain aging and neuroscience research news
Aging affects the phase coherence between spontaneous oscillations in brain oxygenation and neural activity
The risk of neurodegenerative disorders increases with age, due to reduced vascular nutrition and impaired neural function. However, the interactions between cardiovascular dynamics and neural activity, and how these interactions evolve in healthy aging, are not well understood.
Here, the interactions are studied by assessment of the phase coherence between spontaneous oscillations in cerebral oxygenation measured by fNIRS, the electrical activity of the brain measured by EEG, and cardiovascular functions extracted from ECG and respiration effort, all simultaneously recorded.
Signals measured at rest in 21 younger participants (31.1 ± 6.9 years) and 24 older participants (64.9 ± 6.9 years) were analysed by wavelet transform, wavelet phase coherence and ridge extraction for frequencies between 0.007 and 4 Hz.
Coherence between the neural and oxygenation oscillations at ∼ 0.1 Hz is significantly reduced in the older adults in 46/176 fNIRS-EEG probe combinations. This reduction in coherence cannot be accounted for in terms of reduced power, thus indicating that neurovascular interactions change with age.
The approach presented promises a noninvasive means of evaluating the efficiency of the neurovascular unit in aging and disease.