Hey there Brainiacs! Welcome back to Neuro Transmissions.
In today’s world, it’s not /that/ hard to take a peek at your brain.
Thanks to modern technology like fancy electron microscopes
and beautiful fluorescent staining techniques,
we can get up close and personal with the cells
that make up your body’s processing powerhouse.
But...this wasn’t always the case.
Just about a hundred years ago,
we didn’t really know what our neurons looked like.
That is, until two rival neuroscientists -
and a mysterious black stain -
gave us a clearer picture.
By the 1800s, human biology was being studied under a new,
exciting light.
Scientists had recently realized that the body
was made up entirely of microscopic cells,
and that these cells all played different roles in the body.
Skin cells, fat cells, blood cells, muscle cells.
There was so much to explore!
But the brain was a different animal.
Brain tissue is super densely packed together,
which made it pretty hard to figure out
what the different cells looked like—
or how they worked. It was too clumped up to see through.
A lot of early neuroscientists worked hard to figure it out, but struggled.
In the late 1800s, an up-and-coming researcher named Camillo Golgi
invented a new way to visualize brain cells, called the “black reaction”.
Sounds ominous . . .
The black reaction uses the incredibly toxic chemicals
potassium chromate and silver nitrate to harden the tissue
and stain some sections of it.
When the tissue is cut and placed on a slide,
some of the individual neurons are completely stained black,
showing their axons and dendrites in all their glory.
Somehow, this particular technique only stains /some/ brain cells,
but not all of them—
but it always stains those individual cells clearly.
This technique was a total game-changer by
giving biologists the opportunity to see entire neuronal cells clearly, in all of their glory
Side note: During his career,
Golgi did a lot of amazing things,
like helping to prove that malaria was caused by a parasite,
and discovering the Golgi apparatus,
a piece of cellular machinery that’s critical for packing up and shipping out proteins.
But he wasn’t right about everything.
While Golgi’s incredible staining technique made for
some of the clearest glimpses at the structures of neurons,
he was still really attached to reticular theory,
which posited that all neuronal tissue was connected
in one continuous network called the reticulum.
He believed the nervous system
was made up of one really long network of nerve fibers.
Through his own observations,
Golgi claimed to be able to tell that the intricately tangled
networks of axons in the grey matter of the brain were the
diffuse neural network that transmitted the brain’s electrical signals throughout the
body.
But not everyone believed in this theory and this led to Golgi’s greatest scientific
rival:
Santiago Ramón y Cajal.
Cajal seriously challenged Golgi’s ideas,
backed by evidence he gained using Golgi’s own staining technique
and his remarkable artistic skills.
Ramón y Cajal didn’t fit many of the stereotypes of a scientist when he was young:
He was a troublemaker, not a nerd,
and he wanted to be an artist, not a scientist.
But under his father’s coaxing, he ended up studying anatomy,
and eventually got interested in histology,
which is the study of the microscopic structures in tissue.
Cajal learned about Golgi’s method for staining brain tissue,
and applied it to his own research.
He ended up completely enamored with the delicate,
complicated world of neuronal cell bodies, axons,
and dendrites that he saw through his microscope,
and would spend hours sketching what he could see.
His careful observation and attention to detail helped him further some important ideas
about the brain, including our knowledge that the nervous system,
like the rest of the body, is made up of unique, separate cells.
Cajal was also the first person to identify the special structure of most neurons;
he saw that they usually had a cell body surrounded by lots of little projections,
called dendrites, and one long projection leading away from the cell body called the
axon.
Later, scientists would learn that the dendrites receive incoming information
while the axon relays those signals out to other cells.
Through his microscope, Cajal could tell that neurons had distinct endpoints
at the tips of their axons and dendrites.
But since Cajal couldn’t actually see the physical /connections/ between the cells,
the debate between Golgi and Cajal lasted for the rest of their lives.
It wasn’t until the 1950s, when the electron microscope was invented,
that scientists were finally able to get up close and personal with the neuronal synapse
and /prove/ that neurons were discrete cells.
Cajal is responsible for kicking off our current understanding of the Neuron Doctrine:
the reality that the nervous system is made up of discrete, individual cells called neurons,
and that these neurons are connected with one another to send information throughout the body.
But both of these men had made revolutionary discoveries that pushed science forward.
Because of their contributions to neuroanatomy,
Ramón y Cajal and Golgi were jointly awarded the Nobel Prize in Physiology or Medicine
in 1906.
Cajal continued to be a prolific scientist and artist,
publishing over a thousand of his drawings in a huge, two-volume book set.
His classic drawings of the nervous system are still referenced by scientists today,
and are not just accurate, they’re also beautiful.
As for Golgi, the wild thing is, his mysterious “black reaction” is...still pretty mysterious.
150 years later, we still have no idea why, exactly,
the process only targets some neurons and not all of them.
For whatever reason, this approach seems to only stain neurons.
And leaving the tissue in the solution for longer leads to more cells being stained—
but no one knows exactly why some cells get stained first while others don’t.
That doesn’t stop scientists from using it, though!
It’s especially handy for trying to examine the structure of individual neuronal cells,
which can be challenging with other kinds of staining techniques,
because it’s difficult to stain the whole cell without blowing out the cell body
or ending up with axons and dendrites that are too faint to see.
I was even using this technique near the end of my dissertation to look at neurons
in the developing brain, to see if there was a relationship between one of the proteins
I was studying and the structure of neurons in certain genetic developmental disorders.
I….didn’t find anything, but that was a research problem, not a Golgi staining problem.
I’m excited to get to share the story of Golgi and Cajal with you today,
because we’re also featuring them in our book!
We’ve had tons of fun nerding out about psychology and neuroscience so far
and we can’t wait to share other cool neuroscience history like this with you when it comes out!
Feel free to subscribe and follow us on social media to get all the updates on that.
Thanks for watching this episode of Neuro Transmissions!
Until our next transmission, I’m Alie Astrocyte. Over and out.