Interactive Powerpoint_How to Master effective communication
Coursera neurobiology
1. Understanding the Brain: The
Neurobiology of Everyday Life
On chewing neural circuits or
the privilege of chewing without biting
your tongue at the same time!
(Most of the time).
By Miguel Camarena
2. A little bit about me
• I’m an electronics engineer working at a
semiconductor company with a passion for
neuroscience.
• I’m also interested in biology and I’m a
supporter and newbie collaborator to
Openworm.org, which is an open-source
scientific project whose goal is to simulate a
full biological model of the worm
Caenorhadbitis elegans.
3. Project Requirements
1. Identify the parts of the nervous system that are active in your
example: CPG, motor neuron (MN), synapse, genioglossus MN,
masseter muscle MN, styloglossum MN, jaw closing MN (JCMN),
digastric MN, protractor MN, premotor neurons pMN,
retrograde virus transport in neurons.
2. Describe the functions of the nervous system that are apparent
and/or impaired in your example: muscular junctions, feeding
behavior, jaw closing and opening behavior.
3. Explain in detail the ways in which this course has allowed you to
better analyze the events and phenomena around you.
Understanding of basic components of motion, understand
function of CPGs, understanding of MNs, retrograde virus
infection a la polio, motor hierarchy. In the slides’ notes more
details will be expounded.
4. Introduction
• We take so much for granted in our lives, specially the
most apparently simple motor actions.
• It is amazing how the brain has evolved to facilitate
actions that seems so useful in every day life.
• Chewing involves coordination of jaw and tongue
motion circuits, otherwise we would bite ourselves
during every meal.
• In these slides we will review a fascinating approach
that was invented to illuminate the architecture of…
chewing circuits!
5. Simultaneously performing
two motor tasks is hard!
• Tasks such as circularly rubbing your tummy
whilst tapping your head are hard without
practice. This is a classice example as seen in
previous classes. (P Masson., 2011).
• Other instances occur as we age. For example, it
appears that talking while walking becomes
increasingly difficult (Lundin-Olsson et al., 1997).
• It is even more difficult to simultaneously execute
two movements using the same group of
muscles, such as talking and chewing. With
noxious consequences… such as choking.
6. Muscles involved in chewing
that we need to keep a track of
• We can divide chewing into two phases. The jaw
opening phase (JO) and the jaw closing phase
(JC). We’ll see pictures of these muscles in the
next slide.
– During the JO phase, the digastric muscles (which
opens the jaw) and the genioglossus muscle (which
protracts the tongue) are active.
– Whereas in the JC phase, the masseter muscles
(which closes the jaw) and the styloglossus (retracts
the tongue) are both on the go during the jaw closing
(JC) phase.
7. A brief foray into human
oro-facial anatomy
Masseter
Digastric
Genioglossum
Styloglossum
Muscles
for JC phase
Muscles
for JO phase
8. Temporal sequence of the chewing
behavior
• What the spiking diagram below illustrates is
that MN chewing behavior occurs in
sequence: when the jaw is closed by the
masseter muscles, the tongue protractor
muscle is inhibited to avoid biting one’s
tongue.
9. How do we find the right circuits?
• To being understanding this behavior we need to
determine the architecture or connectivity of the
neurons and muscles involved.
• An fluorescence-based imaging technique will be
exposed that sheds light into the architecture of
the chewing behavior.
• This technique also allows to discard competing
hypothesis of circuit connections as we reveal the
actual components of the chewing circuits.
• This protocol was developed by Fang et al.
10. *Mapping of the oro-facial motor neuron circuits.
Morquette P , and Kolta A eLife Sciences 2014;3:e03235
*Firstly we need to
label the neurons
involved.
*Then we determine which circuit architecture is
reflected in reality. It could be either B or C (or none or
something else).
11. Fluorescent labelling of neurons
We use the virus with
fluorescent red and green
tags as a molecular tracer
to detect which neural
paths are involved in the
studied behaviors.
The mice’s neural tissue
were sliced thinly to allow
illumination of those
neurons towards which the
virus migrated.
12. Dedicated
circuits
hypothesis
One model proposes that
there are two dedicated
circuits for each process JC
and JO.
One circuits shunts the
other one in sequence. This
implies parallel sets of IMNs
and CPGs.
Extensive imaging discarded
this oro-facial circuit
hypothesis.
13. The authors propose to use a
single multipurpose circuit.
The complete dynamical
workings of the circuits
haven’t been established but,
hey, we need first to be sure
what are the parts involved.
Eventually this first part is
done. They have provided an
overview of the neural
architecture.
Multipurpose
circuits
hypothesis
14. Conclusions
• The course helped me understand the paper
and how the components used for the
experimental assay are logically used.
• It helped me understand the neuronal parts of
the chewing behavioral components involved
in the circuit.
• It was also lots of fun!
15. Thanks!
• Thanks for this great course Peggy!
• Thanks TAs and all the MOOC students who
made this a great MOOC.
16. Bibliography
• Eric Kandel et al, Principles of Neural Science, 2013,
McGraw-Hill.
• Dale Purves et al, Neuroscience, 2011, Sinauer.
• Peggy Mason, Medical Neurobiology, 2011, Oxford
University Press.
• Fan Wang, Monosynaptic premotor circuit tracing reveals
neural substrates for oro-motor coordinations, 2014, eLife.
• Philippe Morquette et al, Orofacial coordination: How do
we walk and chew gum at the same time?, 2014, eLife
– http://elifesciences.org/content/3/e03235
Editor's Notes
The course has helped me appreciate, filled with awe, that there’s a great intricacy of neuronal circuits and systems that allow us to perform our everyday lives seamlessly.
During the course we were exposed to the difficulty of attempting simultaneous motor action. Our brain is not designed to perform such functions voluntarily without significant practice. It is a relief that there are specialized circuits that can helo us deal with coordinated motor actions.
In the lectures about movement, we explored how muscles are attached to motorneurons and require intricate connections of other interneurons
in order to modulate movement. The course helped me understand the paper I’m referencing and learn to expect certain structures we studied (great
pedagogical application of visual attention circuits by the way!).
Temporal sequencing relates to the neural spiking patterns that we can register when a behavior is perfomed. During the lectures
We saw that stimulus intensity translates to spiking rates.
During the course and lab videos, we learned that it is really critical to understand and make sure we are visualizing the right structures
so that we can determine what are the correct functions of the circuits involved.
This is a slide from the authors’ paper. More reference information in the notes below. Text marked by * was written by me. Slide notes are from the authors.
Mapping the neural circuits responsible for orofacial coordination.(A) When viruses labelled with green and red fluorescent tags are injected into the left and right muscles that close the jaw, three different sets of premotor neurons can be seen when the fluorescence is imaged: those that project to the motoneurons that drive the muscle on the left (green); those that project to the motoneurons that drive the muscle on the right (red); and those that project to both sets of motoneurons in order to coordinate the movements of the two muscles (green and red). The virus can move across the synapse between the motoneurons and the premotor neurons when it is complemented by a glycoprotein (G) that is expressed in the motoneurons of the mice: this movement is indicated by the black arrows. (B and C) During chewing, the digastric muscles (which open the jaw) and the genioglossus muscle (which protracts the tongue) are active during the jaw opening (JO) phase, while the masseter muscles (which close the jaw) and the muscle that retracts the tongue (styloglossus) are both active during the jaw closing (JC) phase. The green and red traces show that the jaw closing motoneurons (JCMN) and the protractor motoneurons (protractor MN) are active at different times. The results of Stanek et al. suggest that orofacial coordination is performed by multifunctional circuits rather than dedicated circuits. In dedicated circuits (B), motoneurons do not share their premotor neurons, and those that are active at the same time receive inputs from their central pattern generator (CPG), which inhibits activity of other circuits. In multifunctional circuits (C), sets of motoneurons driving different muscles can share their premotor neurons. The same CPG activates premotor neurons that are shared by the motoneurons that are active at the same time, and this same CPG also inhibits (as indicated by the black neurons that end in a black circle) the premotor neurons that project to motoneurons that are active at other times.
The sections on the molecular biology of neurons allowed me to understand how virus can migrate retrogradely to infect neural circuits.
In this case this is a cool application that allows us to harvest the power of molecular biology for neuroscience imaging purposes. Here
The masseter muscles on each side of the mouse are injected to determine how MNs and IMNs are connected.
Throughout the course, we have learned that neural systems try to perform actions as economically as possible. This circuit reflects such
economy. CPG interconnection to other IMNs is still not determined.
