During deep sleep, millions of neurons fire electrical pulses in the cerebral cortex and subcortical brain structures leading to a phenomenon known as slow waves. These slow oscillations travel across the cortex once every one to four seconds. This is the subject of research conducted by SLOW DYN, an EU-funded project. The team, led by Spanish scientists, has published a paper in the journal ‘Frontiers in Aging Neuroscience’ explaining their interest in slow oscillations which provide information about the underlying healthy or pathological network. They write that slow oscillations provide a robust unifying paradigm for the study of cortical function.
A second paper published in the same journal explains that the project has discovered differences in the process between healthy mice and those with cognitive decline associated with premature ageing, similar to Alzheimer’s. They detected a decrease in the frequency of the oscillations, which were also more irregular and had a lower high-frequency content of 15 to 100 hertz.
This shift is reminiscent of one of the principal hallmarks of electroencephalography (EEG) abnormalities in patients with Alzheimer’s disease, and adds evidence in support of the suitability of senescence-accelerated mice as a model of this disease.
When there are pathologies that disturb cortical circuits, they are often reflected in the disruption of slow waves. Quoted in the online science news site Science Daily Mavi Sanchez-Vives, director of the Neuroscience Systems group at the August Pi i Sunyer Biomedical Research Institute (IDIBAPS, Barcelona), says, ‘We are studying what those changes tell us about the altered underlying mechanisms.’ The wave alterations may be associated with sleep disruption which, in itself, can impact on memory and attention, influencing the development of a disease.
SLOW DYN (Slow Wave Dynamics: from experiments, analysis and models to rhythm restoration) is part of the Human Brain Project, funded as part of the EU’s FET Flagship ERA-NET. Using EEGs and other tools, researchers are monitoring their subjects’ brain activity while sleeping to develop a data constrained, realistic model of the generation of slow oscillations.
The project aims to collect information about the composition of sleep, the synchronisation of brain activity and the anomalies that can occur as a result of aging or specific pathologies. Researchers hope that these records will also give them clues about the therapeutic potential of restoring slow waves when they are impaired. ‘We are trying to understand a phenomenon which, although seemingly very simple, has the power to disconnect consciousness,’ says Sanchez-Vives.