deck_15908443 Flashcards
How does plasticity work?
- Information takes a pathway to the brain, travelling from one neuron to the next via synapses,
- When we’re presented with new information, new neural pathways begin to form,
- Using a neural pathway strenghtens it; the more the pathway is used, the stronger the connections between the neurons become,
- if a neural pathway is not used it becomes weaker.
Elbert et al. (1995), method
- Nine musicians who played either the violin, cello, or the guitar were compared to six non-musicians,
- A technique called magnetic source imaging was used to measure the area of the somatosensory cortex representing the digits of the left hand of each participant.
Elbert et al. (1995), results
- Area of the somatosensory cortex representing digits of the left hand was larger in the stringed instrument players.
Elbert et al. (1995), conclusion
- Findings suggest that the increased amount of sensory processing required from the left hands of stringed instrument players results in structural changes in the brain, provides support for plasticity.
Elbert et al. (1995), evaluation
- Researchers argue that the increased representation of the left hand digits in the musicians may have been genetic rather than the result of playing an instrument,
- Study used a fairly small sample size; may not be representative.
Maguire et al. (2000) findings?
- Studied the brains of London taxi drivers,
- Found a larger grey matter volume in the mid-posterior hippocampi of their brains,
- Alongside a positive correlation between this size and the length of time that they had been cabbies.
Karni et al. (1995) findings
- used MRI to show that learning and practising a sequence of finger movements over a period of four weeks led to an activation of a larger area of the motor cortex when carrying out the sequence,
- Suggests that some reorganisation had occurred.
Nudo et al (1996), method and findings
- Mapped the motor cortex of adult monkeys before and after training in a task which required use of the digits,
- Found that the representation of the digits in the motor cortex increased,
- They then carried out training in a task that mainly used the forearm,
- Found that the forearm representation increased and the digit representation decreased,
- Suggests that plastic changes are continuous and reversible (at least in monkeys).
How does plasticity allow for functional recovery after brain damage?
Brain damage can result in loss of function, e.g. damage to the Broca’s area can cause loss of speech. The brain has the ability to recover some of its lost function. This is thought to be due to plasticity - the brain begins to rewire itself. There is evidence that healthy areas of the brain located near the damaged section begin to take over function of the damaged area.
What is constraint-induced-movement therapy (CIMT)?
After a stroke which has caused loss of function on one side of the body, some patients are prevented from using their non-affected side. This forces them to ‘re-learn’ how to use the affected part.
Strengths of CIMT?
- Numerous studies have shown that CIMT produces cortical reorganisation which results in regained or improved function,
- The principles of CIMT can also be applied to patients who suffer from aphasia as a result of stroke damage. Instead of communicating in other ways, e.g. sign language, they play a game which requires them to try and speak a word presented on a card. Studies have shown that this therapy caused dysfunctional areas near the damaged area to become functional again.
Weaknesses of CIMT?
- Can be very frustrating for the patient,
- CIMT needs to be very intensive to be effective. Patients are often required to train the affected limb for several hours a day, for consecutive weeks and have their unaffected limb restrained for 90% of the time that they are awake,
- It is most effective in treating patients who have suffered mild to moderate strokes. If there is no damage to the brain, it can be much harder to regain function.
What is synaptic pruning?
The process by which extra neurons and synaptic connections are eliminated in order to increase the efficiency of neuronal transmission.
What is functional recovery?
The ability of the brain to transfer the functions of areas damaged through trauma to other healthy parts of the brain, thus allowing for normal functioning to carry on.
How is functional recovery achieved?
- Through the law of equipotentiality (where secondary neural circuits surrounding the damaged area become activated),
- Axonal sprouting (formation of new synapses and strengthening of axonal connections between damaged and healthy areas),
- Reformation of blood vessels,
- And recruitment of homologous areas on the opposite side of the brain.
What did Ramachandran et al. demonstrate?
Demonstrated negative plasticity through providing an explanation for phatom limb syndrome in terms of cortical reorganisation in the cortex and thalamus.
Found that areas of the somatosensory cortex adjacent to the missing limb’s representation expanded into the deafferented region, leading to sensations of the phantom limb when touching the face.
What was demonstrated in the case study of Jodie Miller?
- Demonstrated positive plasticity,
- Shows the power of recruiting homologous areas on the opposite side of the brain, axonal sprouting, and the reformation of blood vessels,
- Despite losing half her brain, she was able to regain normal movement and function over time. This was possible because the remaining left hemisphere adapted and took over functions typically managed by the right hemisphere.
What did Hubel and Weisel (1970) find?
Sealed one eye shut in newborn kittens for 6 months, monitoring brain activity,
Findings:
- The open eye took over more brain connections, showing ocular dominance plasticity,
- Just 3–4 days of eye closure caused a loss of binocular vision,
- Unused brain areas can be taken over by more active ones,
Impact: Proved a critical period for vision development and brain plasticity
What did Schneider et al. (2014) find?
- That of 769 patients studied, 214 achieved disability free recovery after 1 year,
- Of those 50.7% had between 12 and 15 years of previous education and 25.2% had more thant 16 years,
- Suggests that individuals who have been in education for a longer period of time may have developed the ability to form neuronal connections at a high rate, and therefore experience high levels of functional recovery.
What limit is there to functional recovery?
- Although after trauma the brain activates secondary neural circuites which contribute towards reinstating normal function,
- The brain can only repair itself up to a specific point, after which motor therapy or electrical stimulation is needed to improve recovery rates.
What di Lieperta et al. (1998) find?
That afte CIMT, the motor performance of stroke patients improved significantly. Therefore, this suggests that functional recovery cannot be relied upon to reinstate normal function.
