Wk11 Neuroplasticity & Brain Damage Flashcards
what are two windows ‘periods’ which show time dependence? What do they mean?
Critical period - asbolutely essential the experience occurs Sensive period - experience in this can still have an influence outside interval
What can experience/use of neural circuits achieve? 4
Maintenance Neurogenesis Synapse formation Myellination
What does “use it or lose it” imply about nature vs nurture?
Nurture is a key part of how things are established and maintained, both are important.
what are the effects of environmentally deprived mice? 2 (neuronal + behavioural)
Fewer synapses and dendritic spines Poor depth and pattern perception
what illustrates the effect of critical periods in deprived/open eye mice?
long term deprivation is not drastically worse than short term. One week alone causes a lot of damage, little more is acquired after that
When adult rats are exposed to enriched environments where was neurogenesis found? 2
Dentate gyrus of HC + olfactory bulbs
What is associated with adult rat neurogenesis in enriched environments? 2
Exercise and interaction with environment — not enough to just sit around in the new environment
What evidence shows that exercise is superior to learning alone, for neurogenesis? When do these benefits emerge?
Van Praag et al 2000: rats in Runner and Enriched conditions had new cell survival than Learning alone. After one day learning shows new cells, but these only sustain in exercise conditions.
What did voss et al 2013 show about adult neurogenesis in enriched, running, run+enriched?
Running was a key to increasing dentate gyrus new cells
how does the object sniffing test for rats work? What does it tell us?
Rats are measured on how long they sniff three objects. 24 hrs later a new object is introduced and the sniffing time for this is assessed relative to old objects. This measures rats preferentially exploring novel objects.
What do object sniffing tests show about adult neurogenesis in rats?
Rats sniff novel objects more when exercise or enrichment are provided, but the more noticeably when Ex and En are provided together.
What was a problem with early experiments on rat adult neurogenesis? How is this controlled these days?
Exercise and enrichment were confounded. Housing is used to separate the two influences.
Does exercise induced adult neurogenesis happen in humans and where? What tasks are involved in testing this?
Yes, shown in dentate gyrus. Auditory list learning.
What happens to kittens with a shut eye from birth to 2.5mo? What does this illustrate?
no contralateral activation of ocular dominance columns. Critical period for the development of these cells.
What happens to kittens with an eye shut from 12 mo to 38 mo? What does this show?
Overall V1 cortical activity diminished but no change in ocular dominance. Sensitive period where deprivation can still have negative effects.
What are the phases of activity-dependent myelination?
- ATP is released and taken by OPC to form oligodendrocytes 2. Action potentials signal astrocytes to myelinate 3. Neuronal firing modulates adhesion molecules
Does social isolation cause reduced myelination? What the implications?
Yes. But in rats. this may be a potential mechanism for a range of psychosocial mental problems, but its a large leap to apply this to humans.
What demonstrates neuroplasticity of sensory cortex maps?
When vision is displaced through prism lenses, auditory maps compensate and shift. Within a couple of days.
Can cortical digit representation increase in adults? How long does this effect last?
Yes, increased for trained movements, but specific to that movement. Lasted up to 8 weeks without training.
What is anterograde degeneration?
From the point of damage, further connections die
What is retrograde degeneration?
Backwards from the point of damage, the cell dies
What is trans neural degeneration?
Damage affects a whole network of neurones, damage spreads.
What are the cumulative effects of concussions? 2
Internal bleeds linear and rotational forces lead to cell death (microtubules)
What type of damage do we see and not see in concussions?
Not structural neuronal damage, but cell death due to microtubules damage.
What do P300 EEG responses show about footballers and concussions?
People with concussions show less responsivity to unattended stimulus
Is a blow to the head necessary for a dead injury?
No, even pressure waves from a nearby explosion can increase intracranial pressure and brain motion.
What are two types of closed hear injruies?
Contusions (bruise from brain slamming skull) Haematomas (bleeds, sheared blood vessels)
What is Oedema?
brain swelling due to fluid
What are two ways closed head injuries can cause loss of consciousness?
Downward pressure on brainstem Brain moving forward twists inside skull, disrupting brain stem functions
How do brain injuries cause epilepsy??
Disrupted tissue starts to impair neural activity
What are things that can happen in a penetrating head injury? 5
Closed HI: - oedema - loss of consciousness - epilepsy - infections - scarring (epilepsy)
How does TBI cause behavioural disturbances?
Neurones that resprout atonal projections form unwanted connections.
How much oxygen does the brain take up?
20% of O2 consumption
What is a haemorrhage?
Bleed into the brain
What is ischaemia? What are 3 types?
Disruption in blood supply; thrombus, embolus, arteriosclerosis
How long before ischaemia develops consequences?
Typically a few days to see consequences
What is an infarct?
Area of dead tissue caused by stroke
What is a penumbra?
Area surrounding dead tissue (infarct) which is alive but dysfunctional
Can penumbras be recovered? How?
Yes there is a potential for recovery. They can be supplied blood from other vessels and function rehabilitated.
Why do doctors not usually right away how bad stroke damage will be?
The penumbra has not yet died, its functions may be retained.
What is secondary energy failure in stroke? How is it caused?
Cerebral hypoxia leads to mitochondrial failure. Even when blood supply restored after stroke, neurones can still die.
What is peculiar about the inflammatory effect of microglia? And what could this mean?
Microglia can act from a distance and so interfere with other areas of the brain which were not damaged. (People present as having TBI consistent and inconsistent symptoms. This is why)
What are key variables influencing neural regeneration in adults? 2
- Capacity is high in early development and drops with maturity 2. PNS and CNS work differently (PNS better due to Schwann cells)
How does neural regeneration work in the PNS if Schwann cells not damaged?
Axons can re-grow through myellin sheaths.
What happens in the PNS if there is complete but small separation of axons and myellin?
Axons may regrow but into the wrong sheaths, signals get mixed.
In the PNS, what happens if there is large separations of nerves due to damage?
Axons may regrow into a tangle with no destination, antero- and retro-grade degeneration.
What happens in the PNS when an axon degenerates?
Collateral sprouting. Neighbouring neurons can begin to synapse on the target/vacated sites.
What is a new line of therapy for PNS axon all regeneration?
Growth hormone.
Why doesn’t collateral sprouting happen in undamaged areas?
Active neuronal connections inhibit each other and create boundaries.
What are 2 mechanisms of CNS reorganisation?
- New connections via collateral sprouting 2. Strengthen existing connections (due to less neighbouring inhibition)
When can age be good and bad for recovery of function? And why? 2
During neurogeneis = good - brain just makes more neurons During neural migration = bad - neurones are still connecting to endpoints
Can damage after neural migration phases be recovered from?
Yes, after migration there is a period of synaptogenesis which can allow compensatory synaptogenesis.
How can rehabilitative training post stroke be improved?
Restraining competing limbs. because neural systems are competing, more energy can be given to affected areas.
