Kolb Chapter: 4
Title: Brain Development and Recovery
Student name: Andra Caulder
Key Points:
1. Stages in developmental growth dictate the extent recovery after brain injury
and deficits may arise or disappear later in life.
2. Recovery varies with the type of behavioural deficit; cognition may be easier to
recover then innate behaviours.
3. The hemisphere’s condition contralateral to the site brain damage influences
the ability to recover.
Student name: Megan Cook
1. Although the order of events in neocortical development is similar across
mammalian species, there is variability between species in the timing of
these events relative to birth.
2. Similar brain damage at different ages leads to varying consequences.
3. Extent of recovery following brain injury depends on the behaviour being
studied and the age of assessment.
Student name: Tyler Bugden
1. First, deficits resulting from a brain injury many not be immediate, but
instead shows itself as one ages and develops.
2. Brain injuries can have different consequences depending on the
developmental brain stage in which the injury occurs.
3. Brain damage very early in life (prenatally to days after birth) may be worse
than brain injury later because the “foundation” for which brain growth
depends on can be damaged.
Student name: Stephanie Brown
1. While animal models are very useful for early brain injury, it is difficult to
determine the same developmental stages across species.
2. The greatest chance of recovery from brain injury happens during the height
of dendritic differentiation and synaptic formation (~2 years of age)
3. Lesions that include or remove an entire area are much harder to recover
from than partial lesions.
Jestine Naus
1. It is very difficult to determine the equivalent developmental stages
in different species.
2. The development of the brain includes several stages: cell
proliferation, cell differentiation, dendritic and axonal growth,
synaptogenesis, cell and synaptic death, and gliogenesis.
3. Cerebral injury during the time of cell migration is particularly
damaging, whereas injury later, during the time of dendritic growth,
allows better recovery.
Student name: Jill Harris
1.
If neurons can differentiate in adulthood, then it is possible the mammalian
brain has the ability to regrow neurons lost to injury.
2. Cognitive tasks may show better recovery than inflexible, innate
behaviours because there may be only one way for the cortex to control
innate behaviours.
3. Behavioural outcome varies directly with the developmental stage of the
cortex at the time of injury.
Student name: Thomas Ferguson
1. Recovery is incredibly variable, depends on the location and size of the
lesion, and the time of development when the lesion occurred is incredibly
important as well, with early damage to the brain sometimes being better,
sometimes worse than later damage to the brain.
2. A bit counterintuitive, but damage early in life can be at times worse than
damage later in life, due to lack of critical building blocks. Another critical
time is during neuronal migration.
3. Kolb mentions how not all plasticity is beneficial, example seen in SS who
had frontal deficits despite a right parietal injury
Student name: Olivia Wale
1. Neurons can differentiate in adulthood, meaning that mammals are able to
regrow neurons lost to injury1`
2. The brain has different developmental stages (eg. Axon and dendrite
development, synaptic development), therefore plasticity and recovery are
dependent on the different stages of brain development. The recovery
process may occur largely during the period of synaptic pruning rather than
synaptic growth.
3. Recovery of function may result in future deficits in brain areas not directly
affected by the trauma.
Student name: Thomas van Heyningen
1. There is variability in recovery and plasticity of the developing brain
depending on which stage the injury occurs in.
2. Not all plasticity is good plasticity, loss of function can occur due to invasion
of a lost function to a different area of the brain.
3. Kennard Principle not necessarily the central dogma regarding recovery of
function. Damage to the frame work may not allow for development of other
important functions later in development.
Study Questions:
1. Q: What fundamental problems does Kolb scrutinize about in Kennard
principle?
A: Not all developing brains are the same, thus important to know what
developmental stage you are testing and how you are testing the subject.
- Damage to a structure early in life may alter the development of other
areas further along the developmental path
2. List 3 factors that affects behavioural outcome after injury
a. The developmental stage of the cortex at the time of injury
b.
3.
The size of the lesion (an entire functional area or just part of a
functional area)
c. The laterality of the lesion
A group of researchers were testing the effects of prefrontal lesions on rats
early in development, and found that the lesion group performance was
equal to controls a few months after the surgery had occurred. The
researchers concluded that their lesions had no effects on the behaviour of
the rats. Why is this conclusion possible incorrect according to Kolb?
A- Because although behaviour may appear to be normal early, the animals
may “grow into their deficits”. If the researchers tested the animals later in
development they may have found that performance of the lesion group
would have decreased to significantly lower than controls, because as the
pre-frontal cortex gets more important, it’s deficits become more
pronounced.
4.
What time will result in the best outcome for an animal to have brain
damage?
5.
The best outcome occurs when neurons are developing dendrites and
synapses.
What are the two fundamental principles with the Kennard Principle:
Answer: First it assumes that all developing brains are the same; incorrect in
that the brain goes through several stages of development and is a different
brain from one stage to another.
Second, it ignores the fact that development of the brain is much like
building a house; there is an important and necessary sequence in both
brain and cognitive development.
What does Kolb mean when he says children might pay a price for their
recovery?
A: children with left hemisphere damage in speech areas showed deficits in the
right hemisphere as well as IQ. Injury before the age of 1 showed a more
significant drop in IQ than after 1 year of age.
9. What is the Kennard Principle and what are two arguments against it?
The Kennard Principle is idea that brain damage is easier to recover from if it is
acquired early in life. Two main flaws in this Principle is that it doesn’t
acknowledge the brain develops in different stages that are incommensurable,
and early development provides a scaffold for later development. If there is
damage to the scaffold, the brain can not structure itself.
Discussion Question:
1. Do you think society is stuck in the paradigm of the Kennard Principle or
Hebb’s principle?
2. In what situations can synaptic plasticity be a “bad” thing?
3.
Kolb states that S.S had a right posterior injury at birth but had symptoms
common to frontal lobe injury. Do you believe her experiences as a child
could have caused the difference in symptoms?
4.
Why would brain injury prior to 2 years of age produce more impairment
later on in life compared to injury acquired after age 5?
5.
There may be a general principle in plasticity that there is an overgrowth
and subsequent pruning of synapses. Would a brain that was injured before
the synaptic pruning phase be more likely to recover than a brain that was
injured after the synaptic pruning stage was complete? Before synaptic
pruning it would seem likely that there are more synapses that could take
over any function that was “lost” due to brain injury. Or is there something
wrong with the synapses that are “pruned”, other than they are not getting
used enough.
In that species-typical behaviours in rats show less recovery than cognitive
tasks, as there is likelyonly one way for the cortex to control these
behaviours, what type of behaviours may be affected in humans?
6.
6.
7.
What is one thing to consider when using an animal model to study early
brain injury in humans? ANSWER. The developmental stage of the brain in
the animal must be taken into consideration to determine the equivalent
stage in humans.
8. According to Kolb, what is the “Hebb Principle”?
The “Hebb Principle” is the idea that there is a vital sequence of events in brain
and cognitive development. In other words, certain facets of cognitive
development require the proper functioning of particular brain structures during
a specific time in development, or normal cognitive development will not
occur.
7.
The book mentions a variety of complications in studying the brain of
epileptic patients, including that lab animals do not suffer seizures after
surgery. Have you encounter any research that explains this fact, or what do
you believe the possible reason behind this is?
8.
If plastic processes can result in future deficits in the uninjured brain tissue
because these areas were involved in the plastic process, is there treatment
that can stimulate these connections and prevent such deficits from
occurring?
Kolb suggests that the recovery process appears to occur mostly during
synaptic pruning rather than synaptic growth (due to stubborn genetic
program) why might this be?
9.