PSY290H5 Lecture Notes - Lecture 7: Prefrontal Cortex, Cell Adhesion Molecule, Synaptic Plasticity
PSY290
Lecture 7: Development of the Brain
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How our brain changes over our lifetime
Perspective of the changes early in life: neural development
Next class, explore how our brain changes with learning
oLinks associated with changes in connectivity over lifetime
Third lecture, relevance to where our learning takes place and where information is stored
The Development of the Brain
Critical periods of development
oLanguage : genie, the 13-year-old, who was emotionally and physically deprived of all human
contact for 13 years but she couldn’t fully develop language and physical movement as well.
oAt the age of 13, a lot of those experiences that were necessary are passed and we are no longer
to induce them
oBird song development: during a first day or two, birds have to hear their parent’s song or they
will never be able to reproduce that song later even if its present everyday
oPeriod of time where you have to be exposed to something to produce the phenotype pf that
behaviour
When do critical periods happen?
oIt’s easy to think that all this learning happens on very early in life
oHow learning happens during childhood is different than adulthood
oLearning is taking place in our brains all the time
oThere are experiences that can have profound impacts on how we behave
Events affect us differently
If a child is born with an infantile cataract (prevents light from entering eye), if it’s not dealt with during
the first 2 months, even if we restore the function, eye will never gain proper sight again.
If that same cataract happens to an adult person, as long as we correct it, they will gain normal sight
oThe timing of the event determines plasticity
Example: Margaret works at McMaster comes studies clinical psychology and she focuses on unique
and powerful life experience that she had during early 20s. she got married in 2001 and when they got
married, they decided to spend honeymoon in Portugal. Midway during the flight, the pilot was doing a
simple fuel check and decided that one fuel tank had more fuel than the other so they had to switch.
During the switching, they ejected the fuel outside to the Atlantic Ocean so they had to inform everyone
that they were out fuel. Azores islands. Their pilot spent pilot hours being a drug runner and spent 5
years in prison after being caught with drugs. He was used to fly in shady situations and he figured out
he can land on the Azores and every single person landed and survived. Half of those people suffered
from PTSD: development from random sensation of being overly scared, about obsessing about flight
events and recalling every single detail. Margaret has PTSD but her husband does not. What is the
difference between people who got PTSD and the ones that did NOT get it? what allows for the brain to
change like that?
Early in life: experiences need to be simpler and less powerful
Neural Development
When sperm meets egg: zygote forms
First couple of days, sperm and egg divide and become more than a single cell
oTiny cluster of grapes
o4 cells
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2 4 8 16
cell proliferation starts within the first week of development
this bundle is called a blastocyst: single layer ball of cells
there is a small little layer inside that called the inner cell mass: start to proliferate and start to become
all these amazingly different things
there is a coordination within this division cycle
80 billion neurons aligned in appropriate place: interconnected together
ostructural connections and functional connections
37 trillion cells
more than 200 types of cells
ophotoreceptors
oskin cells
oneurons
olung tissue
ored blood cells
otaste buds
omacrophages
In only 8 weeks: the basic foundation of the brain and body is present during the first 8 weeks of post-
fertilization embryo is about the size of my thumb
Our brains are in their last stages of development
In about 40 years old, Alzheimer’s can start if it is present to develop
Development of the Brain
Early division of the nervous system
The six stages of neural development
Blastocyst starts to take shape with an outer cell mass and an inner cell mass
Gastrulation: the emergence of two key elements
oDistinction of cell layers
oStretching out of ball of cells into an elongated tube
oConsists of 3 layers of cells
o2 to 2 and a half two weeks in, an elongated stripe emerges above the forming bundle of cells
obetween 10-18 days of age, there are distinctions in cell layers: germ layers
outer surface: ectoderm
develops into epidermis, hair, nails, epithelium... etc external structures
shaded in red: mesoderm
develops into muscle tissue, kidney tissue, and red blood cells
yellow cells: endoderm
develops into the stomach, the colon, liver, and urinary bladder
oall germ layers take on different roles in our bodies
ectoderm and the mesoderm play a role in the brain development
obrain development from the ectoderm
Day 18 (2 and a half weeks post-fertilization)
Elongation + germ layers
We also see the stripe that forms down the middle of this elongating tube
Where the brain is developing from
The neural plate
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Characterized by thin line running through it
This layer looks thicker than anything around it
The development of the neural plate is the first major stage of neural
development
What is driving this development is signals coming rom the mesoderm which
are called the organizers
oThey are being sent and received by the ectoderm that causes the
neural plate to get thicker
Day 20: the neural groove deepens and the crest begins to develop
the edges form ridges called crests
othis area takes on some functional properties
The ends darken to symbolize that this area becomes to take on different
functional property
Yellow: the central nervous system
Red (the neural crest) becomes the peripheral nervous system
Cells along this area are pluripotent --> can become a number of different
things within a subset of neurons
oTotipotent: capable of giving rise to any type of cell
oWhat is the difference between totipotent, pluripotent, and
multipotent?
Totipotent cells can form all the cell types in a body, plus the
extraembryonic, or placental, cells. Embryonic cells within the
first couple of cell divisions after fertilization are the only cells
that are totipotent. Pluripotent cells can give rise to all of the
cell types that make up the body; embryonic stem cells are
considered pluripotent. Multipotent cells can develop into more
than one cell type, but are more limited than pluripotent cells;
adult stem cells and cord blood stem cells are considered
multipotent.
Those cells close to the midline become cells of the sensory system
Cells closest to the neural crest become primary sensory neurons in the body
The most lateral row gives rise to sensory neurons
The middle row gives rise to interneurons
The medial row gives rise to primary motor neurons
Flattened neural groove is where the stem cells are
Those closest to the midline (groove) are going to become cells of the primary
motor system
This division is NOT random
Cells closest to the neural crest are going to become primary sensory neurons
Peripheral central system divided into central nervous system
Day 22: that neural groove is completely closed and the neural crest starts to form a
layer on top of what we call the neural tube
Going to become our cerebral ventricles
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
How our brain changes over our lifetime. Perspective of the changes early in life: neural development. Next class, explore how our brain changes with learning: links associated with changes in connectivity over lifetime. Third lecture, relevance to where our learning takes place and where information is stored. If a child is born with an infantile cataract (prevents light from entering eye), if it"s not dealt with during the first 2 months, even if we restore the function, eye will never gain proper sight again. If that same cataract happens to an adult person, as long as we correct it, they will gain normal sight: the timing of the event determines plasticity. Midway during the flight, the pilot was doing a simple fuel check and decided that one fuel tank had more fuel than the other so they had to switch.
