History of Imaging and Technology in Neuroscience
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(Part 1)
Neuroscience has come a long way since early “doctors” attempted to treat things like migraines by drilling holes in skulls of their live colleagues. Here we overview some significant advances in the history of imaging and technology. Many of these inventions inspired EyeWire badge accomplishments — you’ll have to play to find out which ones!
10,000 B.C.: Neolithic Trepanning
Migraines. Seizures. Mental disorders. What were our new stone age ancestors to do in their quest to treat such tragic ailments? They’d drill or scrape a hole in a person’s skull. Ow. Considering that humans were just inventing farming and domesticating animals, the fact that there was any attempt at medical treatment seems notably less barbaric than how we tend to see trepanning in today’s context. Trepanning continued through the Renaissance.
600 B.C.: Greek Ostagra
Life was hard back in the day. Say a laborer was building something like the colosseum and a rock fell and smashed in his skull. A physician would likely use an ostagra, aka bone forceps. According to Greek physician Soranus of Ephesus “fractured bone is to be removed in fragments, with the fingers if possible, if not, with a bone forceps.” Yikes.
1500s: Microscopes
No one knows exactly who invented the first simple optical microscope; however, Wikipedia has a nifty list of significant events in the history of microscopy.
Zacharias Janssen is credited with the creation of the first compound microscope in 1590. A compound microscope is similar to a simple microscope except it has two converging lens systems: the objective and the eyepiece. The objective lenses offer different magnification levels (in modern microscopes, typically 4x, 10x, 40x and 100x). The eyepiece adds another magnitude of magnification (today typically 10x), resulting in 40x, 100x, 400x and 1,000x total zoom. Compound microscopes usually also have a condenser lens that focuses light on the object. This is most useful at higher zoom.
1895: x-ray
Wilhelm Conrad Rontgen invented the x-ray. He went on to receive the 1901 Nobel Prize in Physics for this breakthrough innovation. UNC describes the cool story of Rontgen’s invention:
He discovered x-rays at the University of Wurzburg while experimenting with electron beams in a gas discharge tube. He noticed that a fluorescent screen in his laboratory began to glow when the tube was turned on. This surprised him because he thought that the heavy cardboard surrounding the tube would catch most of the radiation. This also shows that x-rays penetrate most materials. Rontgen began to place different things between the tube and the screen, but none of them stopped the screen from glowing. Finally, he placed his hand in between the tube and the screen and the silhouette of his bones was shown on the screen.
The x-ray was a remarkable discovery. For the first time, doctors were able to look through tissue and see things like broken bones.
1927: Cerebral Angiography
First, what’s angiography? The word comes from Greek angeion, “vessel”, and graphein, “to write” or “record.” This imaging technique used to see the inside of cavities in the body, such as blood vessels, organs or the heart. During angiographic imaging, a doctor injects iodine-containing dye into the blood. When viewed through x-ray (ionizing radiation), the dye fluoresces and generates an image or angiogram of where the blood flows. Without Rontgen’s discovery of the x-ray, angiography wouldn’t be possible.
Egas Moniz was the first person to apply this technique to the brain, inventing cerebral angiography. His innovation won him the 1949 Nobel Prize in Physiology and Medicine. During cerebral angiography, a catheter is inserted through a major artery in the leg or arm and moved to a localized area. Here, dye is injected and the vasculature can be imaged. In the brain, angiography can be used to detect aneurysms and treat strokes at source.
1932: Electron Microscope
To understand the significance of the electron microscope, it is useful to consider the fundamental idea of how optical (light) microscopes work. In a nutshell, light reflects off an object and is focused through lenses into the eye of a person looking through the eyepiece. This allows magnification up to about 1,000x or roughly 1 micron (see Scale of the Universe).
But what if you need to see in higher resolution or look at something smaller, say at the nanoscale, such as DNA? Scientists began to realize that they could use something with a smaller wavelength than light to generate ultra high resolution images – namely, electrons. Modern electron microscopes can image up to around .05 nm, coming in at about 4,000x better than the best optical microscope. This resolution is roughly 4 million times better than the naked eye.
The electron microscope uses electrostatic and electromagnetic lenses to control the electron beam and focus it to form an image. These electron optical lenses are analogous to the glass lenses of a light optical microscope. Wikipedia
Nobel Prize winning Physicist Ernst Ruska and electrical engineer Max Knoll co-invented the electron microscope in 1932. FEI has created a thorough description of microscopy which you can check out here.
1971: MRI
Like most of modern neuroscience’s imaging modalities, MRIs are hard to wrap your mind around. The NIH has one of the web’s best descriptions:
Magnetic resonance imaging (MRI) uses the body’s natural magnetic properties to produce detailed images from any part of the body. For imaging purposes the hydrogen nucleus (a single proton) is used because of its abundance in water and fat.
The hydrogen proton can be likened to the planet earth, spinning on its axis, with a north-south pole. In this respect it behaves like a small bar magnet. Under normal circumstances, these hydrogen proton “bar magnets” spin in the body with their axes randomly aligned.
When the body is placed in a strong magnetic field, such as an MRI scanner, the protons’ axes all line up. This uniform alignment creates a magnetic vector oriented along the axis of the MRI scanner. MRI scanners come in different field strengths, usually between 0.5 and 1.5 tesla.
When additional energy (in the form of a radio wave) is added to the magnetic field, the magnetic vector is deflected. The radio wave frequency (RF) that causes the hydrogen nuclei to resonate is dependent on the element sought (hydrogen in this case) and the strength of the magnetic field.
The strength of the magnetic field can be altered electronically from head to toe using a series of gradient electric coils, and, by altering the local magnetic field by these small increments, different slices of the body will resonate as different frequencies are applied.
When the radiofrequency source is switched off the magnetic vector returns to its resting state, and this causes a signal (also a radio wave) to be emitted. It is this signal which is used to create the MR images. Receiver coils are used around the body part in question to act as aerials to improve the detection of the emitted signal. The intensity of the received signal is then plotted on a grey scale and cross sectional images are built up.
We’re going to stop there for now. In the future we’ll get to more rad tech such as voltage clamps, stains like those of Golgi plus imaging innovations ranging from fMRIs and CAT to NMR and PET…and we haven’t even gotten to genetically engineering neurons to generate action potentials if you shine light on them. Give yourself an REM cycle to let this sink in. More neurotech will roll out on the blog soon.
Until then, join 100,000 people who are making neuroscience discoveries today on eyewire.org.