PSYA02H3 Lecture Notes - Genetic Programming, Cognitive Development, Jargon
Psychology- Chapter 12 Lecture notes
Brain Wiring and Plasticity
Life begins with conception, when a single cell, made from sperm and egg forms a zygote. This
divides multiple times and everything that follows came from that single cell.
From this point a neural tube forms, the bottom which become the spinal cord and top the
brain. The brain is not wired at conception and connections between nerve cells are made in the
So many highly complicated connections but the question becomes how?
The video shows the incredible fest of development. How is it that each neuron knows where to
go and how to behave?
There are trillions of these interconnections are they all equally important?
There are 10000 nerve cells in one piece of brain the size of a grain of rice. Even a baby’s brain is
extremely complex. There are trillions of connections and nerve cells. But how does the brain
know how to connect itself and behave the way it does.
500000 neurons are formed every minute
Most of the cells in the body die and are replaced, i.e. skin cells ( 90pound of skin lost in a life
time) but not neural cells. The ones you are born with, you will also die with
Brain wires itself by following a highly specified genetic blueprint, connections follow specific
Brain wiring is all specified genetically, like wired telephones between Boston and New York
If connections are being used they are strengthened and if not they are weakened. “Use it or
lose it mentality”
In a premature birth- the process of brain wiring is only partly over, a huge amount of wiring
needs to be done in the nursery
Can nature trump nurture?
Experiment with the ferret: the brain of a ferret was restructured, visual input to eye wired to
hearing (auditory cortex)
The question they wanted to answer was: could hearing come to have the same circuits or
connections as vision
If NO- then nature is important, If YES- then nurture is important
Regular ferret, pinwheel colour scheme observed
Experiment ferret, pinwheel colour scheme also observed but not organized
Conclusions: Yes, it is true that the environment shapes the brain, but it cannot completely
change genetic destiny. The experiment with ferrets tells us that the brain has a remarkable
amount of plasticity
Remark: Gabrielle Gibbons: able to stand but not able to talk. Women are more bilateral it
terms of the language as we saw in the language section so maybe she will be able to gain that
Neural plasticity will be very important in determining how she progresses.
Plasticity in terms of the brain is basically the fact that through tapping in we can rely of
different pathways in the brain in order to do things, if one other way is obstructed or
something. But again it is not a simple matter
Birth is an extremely delicate process
Scale used by health care professionals to quickly assess newborns overall health condition
APGAR stands for: activity (muscle tone), pulse, grimace (reflex, irritability), appearance (skin
colour) and respiration
Babies are tested 1 minute and 5 minutes after birth
Each category on the scale can receive a maximum of 2 points, for a grand total of 10 points
Most infants score between 7-10 on the APGAR which is good. Score or 4-6 is considered fair
condition and 0-3 is considered non responsive and the baby needs immediate life saving care.
Reflexes are inborn automatic responses, natures toolkit to help an infant adapt
Some of them include breathing, swallowing, and sucking; these all have survival value
Others like Moro, grasping and stepping are considered leftover from evolutionary heritage
Survival reflexes become voluntary but the primitive reflexes disappear after the first year
Some reflexes are predominantly related to nourishment of the infant i.e. child starts sucking on
doctor’s finger, or just about anything that comes near its mouth
Stroke the corner of baby’s mouth and you can see the rotating reflex; child turns head in
direction of stroke, for finding food
Moro or startle(spreading of arms when let go) reflex disappears at about 5 months of age, if
Moro is not there at birth or reappears after the 5 month period, then there may be damage to
central nervous system
Swimming reflex occurs when you place a baby over water while still holding them; they start to
paddle like they’re swimming
Reflexes are used to determine normal brain activity.
The absence or persistence beyond normal times and the reappearance later in life is a hint at
significant neurological problems
Bubinski reflex: bottom of foot is stroked, big toe flexes forward toward top of foot and other
toes fan out
Normal in children under 2 years of age, after that time if it is still there it indicates damage to
the nerve paths connecting the spinal cord and the brain
Imitation, Habituation, Early Perception
Newborns are able to imitate a number of adult facial gestures. Aiden only a week old can stick
his tongue out and imitate the looks his mother gives him
Older infants reproduce behaviours on cue
Habituation to a repeated stimulus also provides evidence for early learning. Habituation is
getting bored with something and then paying attention to a new or novel stimulus
A toy initially interests the child but it is shown repeatedly until she habituates or becomes
disinterested and stops responding. When a new or novel toy is presented the child responds or
dishabituates and she notices something else.
Infants are well equipped to face the world, they are actually well developed before birth, and
they turn their heads in the direction of sounds. Babies are very responsive to familiar voices like
mom and dad.
Newborns are especially sensitive to high pitched tones
Vision is the least developed of the senses, babies are very near sighted, which is well suited for
looking into the eyes of the caregiver holding or feeding them
Newborns have clear visual preferences, they will gaze longer at bold patterns with strong
contrast, it is also more interesting for them to look at human faces
Smell: Baby’s sense of smell is very discriminating; they like and don’t like the odours of certain
things. They like fruity smells and hate the smell of vinegar
Taste: infants sense of taste is also well developed, vinegar also taste gross as opposed to
something sugary sweet and fun to eat
Vision: matures rapidly: infants begin to coordinate visual and motor activity
They progress from just scanning the visual scene to grabbing for them as the pass by.
Eleanor Gibson: psychologist who developed the cliff test for babies to see if they can perceive
It involves a table with Plexiglas attached to it. The child is placed on one end and is coaxed into
coming across, but even with the encouragement of parents they will not come over. As much
as they want to they see this simulated cliff and that is a threat because they may fall. This tells
us that YES babies do have depth perception.
We know that children do not mature in a vacuum. There are certain critical periods where
a child must have certain experiences that help them develop normally.
For example to perceive depth, a child’s eyes must receive sensory input between 1-3 years
of age. Between 1-3 is a critical period, try stimulation at for and its lost.
When a child has a weak eye, doctors put a patch on the good eye so they will be forced to
use the weak eye and this must be done urgently, or if it passes this critical period, eyesight
in weak eye may never be stabilized