L21 - Neural Plasticity Flashcards
What is a neural network?
Networks of neurons that are formed through synaptic pruning as we age.
What is the process called that allows for neural networks to be created?
Neural plasticity
What determines the state of a neuron?
The balance between inhibitory and excitatory signals.
What is neural plasticity?
The brain’s ability to reorganize itself by forming new neural connections.
When do we have the most neural plasticity?
When we are born and it slowly decays as we age.
What benefits does neural plasticity have for us?
It allows us to compensate for injury
It allows us to gain more proficient pathways as we gain our level of expertise.
We can adjust to new activities and new environments
What is synaptic pruning?
The process by which extra neurons and synaptic connections are eliminated in order to increase the efficiency of neuronal transmissions.
What are the three profiles of plasticity?
- Constrained (not highly modifiable)
- Highly modifiable dependent on experience (but only during critical/sensitive periods)
- Highly modifiable throughout life
What is meant by critical periods in neural development?
Learning or plasticity is confined to a short and sharply defined period
This learning is subsequently irreversible in the face of later experience.
What do these 3 graphs represent?
A and B represent critical periods of plasticity
C represents plasticity in adulthood (to a lesser extent over time)
What is meant by a sensitive period in neural development?
The effects of experience on the brain are unusually strong during a limited period in development.
What happens to the brain if you reduce input to that region of the cortex?
- Its size is shrunk and the surrounding regions of the cortex are increased
When happens when cortex is transplanted?
- It develops characteristics of its new location rather than its origin
- Inputs can be ‘rewired’ to a different region of the brain, the new recipient develops properties of the normal target tissue.
How did Hubel & Wiesel show the sensitive period in cats for vision?
Closed one or both of their eyes for the first three months of life. Those with closed eyes never were able to gain the neurons required to see out of them.
When is the sensitive period for language development in infant humans?
Exposure to language in the first year of life is predictive of language and reading skill
Critical periods for certain elements of language development in deaf children ends at around 7 years (also much harder to learn a second language)
How does the brain compensate with activation after a stroke?
It will shift it’s activation to other parts of the brain before normal function is restored.
- When does loss of brain weight accelerate in humans?
- Where are the neurons primarily lost?
- How does the brain cope with this?
- When people hit sixty
- Prefrontal cortex (executive function)
Corpus callosum
Cerebellum (balance)
Glial cells
- With alternate pathways and broader activation
What does EEG stand for?
Electroencephalography
What type of resolution is EEG good at?
Temporal resolution
(Time: Good at looking at things with millisecond accuracy)
What does EEG measure?
Measures the activity of large numbers (populations) of neurons
How does EEG measure?
Measures voltage-differences at the scalp (where a cap is placed) in the microvolt range
It is done over numerous tests (min 20-30) where the average wave pattern is averaged out to get rid of interfering signals.
What is an event-related potential? (ERPs)
Small changes in the spontaneous electrical activity of the brain that are time-locked to certain sensory or cognitive events.
(This wavelength is an ERP in response to a stimulus)
In ERP what does ‘amplitude’ refer to?
How high the peak is in the waveform.
(peak at N400)
What did the Lutz et al (2004) EEG results show regarding buddhist monks and meditation?
That Buddhist monks have a much higher rate of gamma waves in a neutral state and could increase them in a meditative state when compared to normal participants who could not increase gamma with meditation.
High correlation between hours of time of meditation experience and gamma wavelengths
This spectral analysis was trying to determine when the best frequency for memory recall was and at what time did they have to be experiencing those wavelengths.
What do these results show?
That the best wavelength to have was ‘theta’ waves (4-7 Hz) about 150ms just prior to the stimulus in order to remember something.
What is the output of an fMRI
A brain with coloured activation
How does magnetic resonance work in an fMRI?
The MRI scanner applies a magnetic field that causes the protons in hydrogen (H) to align.
These give off energy as they return to the orientation of the magnetic field (MR signal).
What are voxels in fMRI imaging?
Voxels are a cube of space in the brain (a slice and then put a matrix over each slice) to create a 3d space.
This allows us to measure the level of oxygenated blood in the area
