W10 - Neuroplasticity Flashcards
What is the importance of plasticity?
- (Santiago Ramon y Cajal, 1852-1934)
- thought that the adult brain and its nerve paths were fixed and not able to regenerate. Idea of once growth is complete all axons and dendrites lose their ability to regenerate.
- (Jerzy Konorski (1903-73)
- The ability of the nervous system to change and mould
What are the 3 levels of the nervous system where plasticity occurs?
- synaptic plasticity
- spinal cord plasticity
- cortical plasticity
Habituation results from presynaptic depression of synaptic transmission study on fish:
A. Experimental setup - Gill sensitisation, Doing a conditioning stimulus allows you to enhance the reaction
Sensitisation - touching someone and yelling at the at the same time when they do not expect it = retraction reflex
B. Gill-withdrawal reflex circuit
When the siphon is touched then the gills will retract = withdrawal reflex
C. Habituation - provide a stimulus and after time of repeated stimuli you do not get the same response = eventually you run out of neurotransmitter
Describe classical conditioning of synaptic transmission
A. Unpaired pathway, 1. unpaired stimulation, 2. cell responses
- Touch siphon and get the same response each time as not enough time between stimuli = habituation BUT no sensitisation
B. Paired pathway, 1. paired stimulation, 2. cell responses = sensitisation
- We can change the way the system responds
Describe the human hippocampus:
Hippocampus is strongly in control of memories
- Slotting things into various regions of where they should go
- Comprised of different neurons
- CA3 in line with the slice, many can be connected to the same CA1 neurone
- CA1 go all the way down the body of the hippocampus
Allows us to manipulate on collateral neurone and use the other as the control model
What are Schaffer collateral neurones?
and how do they cause the long-term potential of CA1-synapses?
- multiple CA3 pyramidal neurons going to a singular CA1 pyramidal neuron
- A subthreshold stimulus (pathway 2), and a 4x200Hz in 100ms high freq (pathway 1) sent to the CA1 neuron causing tetanus
- this can last up to a year
Define:
- Specificity
- Associativity
There has to be a pairing and a firing of the neurones
Pairing stimulation with a strong stimulus strengthens the synapse = associativity
Describe the study by (Merzenich et al., 1984)
- was a representation of digits in somatosensory cortex that can be remapped in adult monkeys
After sewing the 2 digits together
But separates them before the experiment
- The orange area(new mapping) = the brain responds with either digit
So the brain can change
What did Jenkins et al., 1990 find about remapping adult monkeys somatosensory cortex?
After doing this for weeks causes more sensation in the finger tips
- So can be trained
What were the findings of Nudo et al., 1997?
- the motor cortex can be mapped & monkeys were then trained to pick food out of the wells
- Then induced a lesion (black space) in the brain - with a laser inducing a stroke
- Without rehab fingers and hand are not responding - actions switched to the other arm (mirrored) = negative plasticity, and lesion area gets slightly bigger, as not used
- In intense rehab prevented using other hand = positive plasticity BUT lesion remained
- Penundrum = area around lesion where the neurones are alive but need to be trained
What part of the brain is important for speech production?
- a rostral division of the lateral premotor cortex in the human brain, especially in the left hemisphere, has evolved to play a special role in the production of speech sounds.
- Broca’s area (corresponds to Brodmann’s areas 44 and 45, but may be localized to adjacent area 6 in some individuals), is critical for the production of speech
How can this be done in humans?
- by using a navigated transcranial magnetic stimulation
- Improved patients finger movements by him playing the piano
- also increased the hand area in the brain
What are the first 5 principles of neuroplasticity (Kleim & Jones, 2008)?
- Use it or lose it - practicing skills maintain specific connections firing in the brain, fading over-time
- Use it & improve it - practicing a skill often strengthens neural connections
- Specificity - Therapy exercises need to target the brain area you want to improve (task-specific)
- Salience - meaningful exercises, motivating & inspiring you to facilitate neruoplasticity.
- Transference - a skill that can be transferred to a new situation
What are the final 5 principles of neuroplasticity (Kleim & Jones, 2008)?
- Interference - improving skills in one area may interfere with another area of skills
- Time - recovery rate of change is dependent on the individual and amount of practice time
- Age - brains are more plastic when younger, so skills can be picked up rapidly. Ageing still allows us to learn a skill, but it may take longer
- Repetition - practicing rehab therapy frequently and consistently is key to see the most improvement
- Intensity - this can be number of times repeated or duration or difficulty level. the higher the intensity the more improvements seen
How is somatosensory info distributed?
where are descending projections of the somatosensory system found?
- Somatosensory information is distributed from the primary somatosensory cortex to “higher-order” cortical fields
- These pathways originate in sensory cortical fields and run to the thalamus, brainstem, and spinal cord.
- But there are fewer descending projections from the
somatosensory cortex than ascending somatosensory pathways. - There role is to modulate the ascending flow of sensory information at the level of the thalamus and brainstem
