A study published in the journal Nature Communications describes a new microscope, capable of looking deep into the brain in a safe manner. Researchers have created the first-ever high-definition images of living mouse neural networks! Achieving this level of precision on brain tissue in vivo, without damaging it, is a first. For brain imaging, there is three-photon excited microscopy that transforms scattered photons into an image. When light – a laser – passes through an object, some photons pass directly through it, while others are deflected and scattered. Bones, especially the very thick ones in the skull, scatter the light in an unpredictable way, which makes it difficult to observe the brain, especially when you want to do it in depth.
These researchers therefore invented a new imaging technology: laser reflection array microscopy. They improved on excited three-photon microscopy by combining it with techniques related to… astronomy. They combined it with the power of adaptive optics, used in ground-based astronomy to correct optical distortions. It is after an image processing by correction algorithm that they obtained this level of definition. According to the authors, this method will be a valuable tool for neuroscience research.
Brain imaging: unlocking the mysteries of the brain
Brain imaging faces many challenges: visualizing the different brain structures, observing their functioning and their interactions. Today, the idea is to develop increasingly advanced technologies to gain resolution and analyze complex mechanisms. These advances will allow us to improve the diagnosis of certain pathologies and to better understand their impact on the brain.
The different neuroimaging techniques
Over the last 40 years, different imaging techniques have been developed to observe the human body. Some of them allow to precisely observe the brain, and this in a non-invasive way, i.e. without opening the skull. These imaging techniques use either radiation (emission of X-rays, detection of injected radioactive products), or the measurement of electrical activity or, more recently, magnetic fields. Recent advances in computer science have allowed a real leap forward in data and image analysis.
Structural imaging allows us to study the anatomy of the brain and anything that may disturb it (tumor, hemorrhage, pathological deformation, etc.). It is very useful for medical diagnosis.
The CT scan (tomography, CT-scan) is based on the use of X-rays to produce a series of X-rays taken in section and then associated by computer. Contrast agents such as iodine can be injected intravenously into the patient to improve the rendering of images (of tumors, for example). MRI (Magnetic Resonance Imaging) uses magnetic fields and the properties of water molecules in the brain. This examination takes longer but is more precise than a CT scan. Here too, a contrast agent can be used. It is useful in case of stroke, cancer, or degenerative diseases of the brain...
Functional imaging shows the activity of brain areas during certain tasks (speech, movement, etc.). It is used in fundamental research as well as in clinical practice, to identify epileptic foci (networks of neurons at the origin of epileptic seizures) or to identify areas of the brain that should be spared during surgery.
EEG (Electroencephalogram) is a non-invasive method. It measures the electrical waves that reflect the activity of the brain. Several electrodes are placed on the scalp. The result is not an image, but activity traces for each electrode, i.e. for each area of the brain studied. PET (Positron Emission Tomography, scintigraphy, PETscan) is a technique based on the use of a radioactive molecule injected intravenously. External sensors then measure the different amounts of radiation emitted in the area where it is located. Depending on the radioactively labeled molecule, this method can reveal different parameters: energy consumption (glucose), blood flow, hormone synthesis (e.g. dopamine), etc., which reflect brain activity.