Brain Plasticity Flashcards
What is synaptic pruning?
Each neutron can receive a finite number of synapses.
Capacity 1.5x larger for immature vs adult neutrons.
Neurons which do not make efficient contact with other neurons die.
Synaptic density peaks short after birth.
What is thicker in blind people?
Their visual cortex as there is a lack of visual stimuli.
What is Hebbian modification?
Neurons which fire together…
Donald Hebb.
When does synaptic rearrangement occur?
Consequence of neural activity + synaptic transmission.
What has hemispherectomy shown us?
Plasticity in childhood - little deficit of function.
Brain very malleable.
What is the sensitive period?
Brain development period - experiences have a large impact. Inputs needed for brain to form correct structure + connectivity.
Some mechanisms sustained into adulthood.
What are the two types of plasticity?
Use-dependent + injury-induced.
What has the homunculus shown us?
Same blueprint but individual differences in organisation of somatosensory + motor systems.
Explain cortical representation of fingers in LH string players.
Increased representation.
Location of brain activity shifted + response strength was greater.
Correlation between time playing + magnitude of change.
RH stimulation showed no change.
Reverse causality issue - could have been born with the tools to play an instrument?
Explain finger representation in congenital syndactyly.
Sensory areas reorganise if input is changed.
Explain finger representation in Braille readers.
Representation of fingers overlapped in somatosensory cortex.
Fuses input over different fingers = info can be processed as a whole.
How is the auditory cortex different in the blind?
Larger.
Expansion due to reliance on sounds.
Function consequences? Compensation?
Blind individuals have better detection performance (peripheral). Centre was same for all subjects.
Explain how the blind have contributed to our understanding of brain plasticity.
Greater reliance on other senses = cortical reorganisation + better performance in those modalities (functional consequences).
But what about the visual cortex? Visual cortex activated during Braille reading. Cross-modal plasticity.
Cohen - TMS to disrupt visual cortex function = Braille-reading errors + distorted tactile perceptions. No effects in controls.
Cross-modal plasticity supports superior tactile perceptual abilities in blind.
Name three ways in which brain plasticity depend on the nature of stimulation.
Increase stimulation = expansion of representation - musicians.
Simultaneity/dissociation of stimulation = fusion/separation of body part representation - congenital syndactyly.
Loss of stimulation = changes in modality-specific processing - blind.
All these have functional consequences.
What mechanisms are behind plasticity?
Motor learning associated with reorganisation of motor cortex.
Can occur rapidly, through practicing a movement.
TMS has mapped motor cortex as it causes movements by changing position of coil.
