Mind Matters - October 27, 2009

The Root of Thought: What Do Glial Cells Do?
Nearly 90 percent of the brain is composed of glial cells, not
neurons. Andrew
Koob argues that these overlooked cells just might be the source of
the
imagination
By Andrew Koob

Andrew Koob received his Ph.D. in neuroscience from Purdue University
in 2005,
and has held research positions at Dartmouth College, the University
of
California, San Diego, and the University of Munich, Germany. He's
also the
author of The Root of Thought, which explores the purpose and function
of glial
cells, the most abundant cell type in the brain. Mind Matters editor
Jonah
Lehrer chats with Koob about why glia have been overlooked for
centuries, and
how new experiments with glial cells shed light on some of the most
mysterious
aspects of the mind.




Glial Cells

LEHRER: Your new book, The Root of Thought, is all about the power of
glial
cells, which actually make up nearly 90 percent of cells in the brain.
What do
glial cells do? And why do we have so many inside our head?

KOOB: Originally, scientists didn't think they did anything. Until the
last 20
years, brain scientists believed neurons communicated to each other,
represented
our thoughts, and that glia were kind of like stucco and mortar
holding the
house together. They were considered simple insulators for neuron
communication. There are a few types of glial cells, but recently
scientists
have begun to focus on a particular type of glial cell called the
'astrocyte,'
as they are abundant in the cortex. Interestingly, as you go up the
evolutionary
ladder, astrocytes in the cortex increase in size and number, with
humans having
the most astrocytes and also the biggest. Scientists have also
discovered that
astrocytes communicate to themselves in the cortex and are also
capable of
sending information to neurons. Finally, astrocytes are also the adult
stem cell
in the brain and control blood flow to regions of brain activity.
Because of all
these important properties, and since the cortex is believed
responsible for
higher thought, scientists have started to realize that astrocytes
must
contribute to thought.

LEHRER: Why have glia been neglected for so long?

KOOB: To understand this, you have to take a tour of the history of
brain
science. Glia were mainly a sidebar for 200 years in the struggle over
the idea
of the neuron. A few highlights were: In the late 18th century,
scientists
discovered the electrical properties of the neuron in the spine of
frogs.
Neurons have long tethers that are easy to study called 'axons' that
extend from
the cell body from the brain into the spine and the spine out to the
limbs and
body. Similarly, neurons in the senses were linked to the neurons in
the brain.
This is where the notion of neurons as the base of our thoughts took
root. In
the mid-19th century, glia were just being discovered, and researchers
figured
the glial cells simply held the neurons together (glia is greek for
glue). What
I find sort of hilarious is that scientists stumbled upon a very
numerous cell
in the brain, an organ responsible for our thoughts and personality,
but they
were so focused on neurons that they concluded the new cell was
worthless. In
the late 19th century a staining method was developed to look at cells
more
effectively in the brain. A brilliant researcher from Spain, Santiago
Ramon y
Cajal, took it upon himself to study the brain from the perspective of
neurons.
He meticulously mapped out a scheme for how they process information
and are
connected, which led to "The Neuron Doctrine." ("The Neuron Doctrine"
is a
belief that neurons are responsible for our thoughts.) However, Cajal
seemed
inconvenienced by glial cells. They were very numerous and obviously
hanging out
all over the cortex. Meanwhile, his brother Pedro, who was also a
scientist,
developed the theory that glial cells were 'support cells' that
insulated neuron
electrical properties. Cajal decided to back his brother's theory. And
since
1906 when he won the nobel prize, this has been the dogma.

LEHRER: Could you describe some of the early experiments that first
led
scientists to reconsider the role of glial cells?

KOOB: Glial experiments didn't get going until the 1960s. All
scientists knew
about glia was that if you put neurons in petri dish, you had to have
glia, or
neurons would die. Then, Stephen W. Kuffler at Harvard, for reasons
unknown,
decided to test Pedro's accepted theory of insulation. This was around
same
time that cell counts in the brain revealed glial cells to be nearly
90% of the
brain (this is where the neuron based idea that we only use 10% of our
brain
comes from). Kuffler is notable because he ironically established the
Harvard
'neuro' biology department while he was performing these
groundbreaking glial
experiments. Anyway, Kuffler took astrocytes from the leech and mud
puppy and
added potassium, something that is known to flow out of neurons after
they are
stimulated. He thought this would confirm Pedro's theory that glial
cells were
insulators. What he found instead was that the electrical potential of
glial
cells responded to potassium. Kuffler and colleagues found that
astrocytes
exhibited an electrical potential, much like neurons. They also
discovered in
the frog and the leech that astrocytes were influenced by neuronal ion
exchange,
a process long held to be the chemical counterpart to thought. Since
then many
researchers have completed experiments on the communicatory ability of
glial
cells with neurons, including in the late 80s and early 90s when it
was
discovered glial cells respond to and release 'neuro' transmitters.

LEHRER: Why are calcium waves important?

KOOB: In short, calcium waves are how astrocytes communicate to
themselves.
Astrocytes have hundreds of 'endfeet' spreading out from their body.
They look
like mini octopi, and they link these endfeet with blood vessels,
other
astrocytes and neuronal synapses. Calcium is released from internal
stores in
astrocytes as they are stimulated, then calcium travels through their
endfeet to
other astrocytes. The term 'calcium waves' describes the calcium
release and
exchange between astrocytes and between astrocytes and neurons.
Scientists at
Yale, most notably Ann H. Cornell-Bell and Steven Finkbeiner, have
shown that
calcium waves can spread from the point of stimulation of one
astrocyte to all
other astrocytes in an area hundreds of times the size of the original
astrocyte. Furthermore, calcium waves can also cause neurons to fire.
And
calcium waves in the cortex are leading scientists to infer that this
style of
communication may be conducive to the processing of certain thoughts.
If that
isn't convincing, it was recently shown that a molecule that
stimulates the same
receptors as THC can ignite astrocyte calcium release.

LEHRER: You suggest that glia and their calcium waves might play a
role in
creativity. Could you explain?

KOOB: This idea stems from dreams, sensory deprivation and day
dreaming. Without
input from our senses through neurons, how is it that we have such
vivid
thoughts? How is it that when we are deep in thought we seemingly shut
off
everything in the environment around us? In this theory, neurons are
tied to
our muscular action and external senses. We know astrocytes monitor
neurons for
this information. Similarly, they can induce neurons to fire.
Therefore,
astrocytes modulate neuron behavior. This could mean that calcium
waves in
astrocytes are our thinking mind. Neuronal activity without astrocyte
processing
is a simple reflex; anything more complicated might require astrocyte
processing. The fact that humans have the most abundant and largest
astrocytes
of any animal and we are capable of creativity and imagination also
lends
credence to this speculation.

Calcium is also released randomly and without stimulation from
astrocytes'
internal stores in small bursts called 'puffs.' These random puffs can
lead to
waves. It is possible that the seemingly random thoughts during dreams
and
sensory deprivation experience could be calcium puffs becoming waves
in our
astrocytes. Basically, it is obvious that astrocytes are involved in
brain
processing in the cortex, but the main questions are, do our thoughts
and
imagination stem from astrocytes working together with neurons, or are
our
thoughts and imagination solely the domain of astrocytes? Maybe the
role of
neurons is to support astrocytes.

Source: Scientific American
http://www.scientificamerican.com/article.cfm?id=the-root-of-thought-what

On 29 Oct, 12:23, Lance  wrote:
> Mind Matters - October 27, 2009
>
> The Root of Thought: What Do Glial Cells Do?
> Nearly 90 percent of the brain is composed of glial cells, not
> neurons. Andrew
> Koob argues that these overlooked cells just might be the source of
> the
> imagination
> By Andrew Koob
>
> Andrew Koob received his Ph.D. in neuroscience from Purdue University
> in 2005,
> and has held research positions at Dartmouth College, the University
> of
> California, San Diego, and the University of Munich, Germany. He's
> also the
> author of The Root of Thought, which explores the purpose and function
> of glial
> cells, the most abundant cell type in the brain. Mind Matters editor
> Jonah
> Lehrer chats with Koob about why glia have been overlooked for
> centuries, and
> how new experiments with glial cells shed light on some of the most
> mysterious
> aspects of the mind.
>
> Glial Cells
>
> LEHRER: Your new book, The Root of Thought, is all about the power of
> glial
> cells, which actually make up nearly 90 percent of cells in the brain.
> What do
> glial cells do? And why do we have so many inside our head?
>
> KOOB: Originally, scientists didn't think they did anything. Until the
> last 20
> years, brain scientists believed neurons communicated to each other,
> represented
> our thoughts, and that glia were kind of like stucco and mortar
> holding the
> house together. They were considered simple insulators for neuron
> communication. There are a few types of glial cells, but recently
> scientists
> have begun to focus on a particular type of glial cell called the
> 'astrocyte,'
> as they are abundant in the cortex. Interestingly, as you go up the
> evolutionary
> ladder, astrocytes in the cortex increase in size and number, with
> humans having
> the most astrocytes and also the biggest. Scientists have also
> discovered that
> astrocytes communicate to themselves in the cortex and are also
> capable of
> sending information to neurons. Finally, astrocytes are also the adult
> stem cell
> in the brain and control blood flow to regions of brain activity.
> Because of all
> these important properties, and since the cortex is believed
> responsible for
> higher thought, scientists have started to realize that astrocytes
> must
> contribute to thought.
>
> LEHRER: Why have glia been neglected for so long?
>
> KOOB: To understand this, you have to take a tour of the history of
> brain
> science. Glia were mainly a sidebar for 200 years in the struggle over
> the idea
> of the neuron. A few highlights were: In the late 18th century,
> scientists
> discovered the electrical properties of the neuron in the spine of
> frogs.
> Neurons have long tethers that are easy to study called 'axons' that
> extend from
> the cell body from the brain into the spine and the spine out to the
> limbs and
> body. Similarly, neurons in the senses were linked to the neurons in
> the brain.
> This is where the notion of neurons as the base of our thoughts took
> root. In
> the mid-19th century, glia were just being discovered, and researchers
> figured
> the glial cells simply held the neurons together (glia is greek for
> glue). What
> I find sort of hilarious is that scientists stumbled upon a very
> numerous cell
> in the brain, an organ responsible for our thoughts and personality,
> but they
> were so focused on neurons that they concluded the new cell was
> worthless. In
> the late 19th century a staining method was developed to look at cells
> more
> effectively in the brain. A brilliant researcher from Spain, Santiago
> Ramon y
> Cajal, took it upon himself to study the brain from the perspective of
> neurons.
> He meticulously mapped out a scheme for how they process information
> and are
> connected, which led to "The Neuron Doctrine." ("The Neuron Doctrine"
> is a
> belief that neurons are responsible for our thoughts.) However, Cajal
> seemed
> inconvenienced by glial cells. They were very numerous and obviously
> hanging out
> all over the cortex. Meanwhile, his brother Pedro, who was also a
> scientist,
> developed the theory that glial cells were 'support cells' that
> insulated neuron
> electrical properties. Cajal decided to back his brother's theory. And
> since
> 1906 when he won the nobel prize, this has been the dogma.
>
> LEHRER: Could you describe some of the early experiments that first
> led
> scientists to reconsider the role of glial cells?
>
> KOOB: Glial experiments didn't get going until the 1960s. All
> scientists knew
> about glia was that if you put neurons in petri dish, you had to have
> glia, or
> neurons would die. Then, Stephen W. Kuffler at Harvard, for reasons
> unknown,
> decided to test Pedro's accepted theory of insulation. This was around
> same
> time that cell counts in the brain revealed glial cells to be nearly
> 90% of the
> brain (this is where the neuron based idea that we only use 10% of our
> brain
> comes from). Kuffler is notable because he ironically established the
> Harvard
> 'neuro' biology department while he was performing these
> groundbreaking glial
> experiments. Anyway, Kuffler took astrocytes from the leech and mud
> puppy and
> added potassium, something that is known to flow out of neurons after
> they are
> stimulated. He thought this would confirm Pedro's theory that glial
> cells were
> insulators. What he found instead was that the electrical potential of
> glial
> cells responded to potassium. Kuffler and colleagues found that
> astrocytes
> exhibited an electrical potential, much like neurons. They also
> discovered in
> the frog and the leech that astrocytes were influenced by neuronal ion
> exchange,
> a process long held to be the chemical counterpart to thought. Since
> then many
> researchers have completed experiments on the communicatory ability of
> glial
> cells with neurons, including in the late 80s and early 90s when it
> was
> discovered glial cells respond to and release 'neuro' transmitters.
>
> LEHRER: Why are calcium waves important?
>
> KOOB: In short, calcium waves are how astrocytes communicate to
> themselves.
> Astrocytes have hundreds of 'endfeet' spreading out from their body.
> They look
> like mini octopi, and they link these endfeet with blood vessels,
> other
> astrocytes and neuronal synapses. Calcium is released from internal
> stores in
> astrocytes as they are stimulated, then calcium travels through their
> endfeet to
> other astrocytes. The term 'calcium waves' describes the calcium
> release and
> exchange between astrocytes and between astrocytes and neurons.
> Scientists at
> Yale, most notably Ann H. Cornell-Bell and Steven Finkbeiner, have
> shown that
> calcium waves can spread from the point of stimulation of one
> astrocyte to all
> other astrocytes in an area hundreds of times the size of the original
> astrocyte. Furthermore, calcium waves can also cause neurons to fire.
> And
> calcium waves in the cortex are leading scientists to infer that this
> style of
> communication may be conducive to the processing of certain thoughts.
> If that
> isn't convincing, it was recently shown that a molecule that
> stimulates the same
> receptors as THC can ignite astrocyte calcium release.
>
> LEHRER: You suggest that glia and their calcium waves might play a
> role in
> creativity. Could you explain?
>
> KOOB: This idea stems from dreams, sensory deprivation and day
> dreaming. Without
> input from our senses through neurons, how is it that we have such
> vivid
> thoughts? How is it that when we are deep in thought we seemingly shut
> off
> everything in the environment around us? In this theory, neurons are
> tied to
> our muscular action and external senses. We know astrocytes monitor
> neurons for
> this information. Similarly, they can induce neurons to fire.
> Therefore,
> astrocytes modulate neuron behavior. This could mean that calcium
> waves in
> astrocytes are our thinking mind. Neuronal activity without astrocyte
> processing
> is a simple reflex; anything more complicated might require astrocyte
> processing. The fact that humans have the most abundant and largest
> astrocytes
> of any animal and we are capable of creativity and imagination also
> lends
> credence to this speculation.
>
> Calcium is also released randomly and without stimulation from
> astrocytes'
> internal stores in small bursts called 'puffs.' These random puffs can
> lead to
> waves. It is possible that the seemingly random thoughts during dreams
> and
> sensory deprivation experience could be calcium puffs becoming waves
> in our
> astrocytes. Basically, it is obvious that astrocytes are involved in
> brain
> processing in the cortex, but the main questions are, do our thoughts
> and
> imagination stem from astrocytes working together with neurons, or are
> our
> thoughts and imagination solely the domain of astrocytes? Maybe the
> role of
> neurons is to support astrocytes.
>
> Source: Scientific Americanhttp://www.scientificamerican.com/article.cfm?id=the-root-of-thought-...

Very interesting, thanks.  Speculative but promising?

Dave Smith