9. Plasticity & Learning Flashcards
For the sensory system to deveop fully, normal ... is necessary. This is most pertinent during the ...., which is when the developing visual system is .... Changes specific to critical period involve ... and ..., ...-dependent competition, pruning of ..., neuromodulators etc. After the critical period, it is ....
For the sensory system to deveop fully, normal visual experience is necessary. This is most pertinent during the critical period, which is when the developing visual system is most susceptible to environmental influences. Changes specific to critical period involve axonal and dendritic sprouting, experience-dependent competition, pruning of axons, neuromodulators etc. After the critical period, it is impossible to induce changes in early sensory areas.
What are the 3 theories about termination of the Critical Period?
Critical period terminates when…
* Axonal growth stops and when axons lose the ability to change terminal length due to changes in ECM or due to myelination by glia
* Synaptic tranmission has fully matured due to changes in the post-synaptic receptors (glutamate, NMDA, GABAergic inhibition etc.)
* Activtiy of neuromodulators (norepinephine, acetylcholine etc) in certain cortical areas decline.
Experience-dependent plasticity is enabled by ... such as ... and long term depression. Donald Hebb theorised that when an axon of cell A excites cell B and repeatedly or persistently takes part in firing it, ..., so that A’s effcieincy as one of the cells firing B is ....
Experience-dependent plasticity is enabled by Hebbian synaptic mechanisms such as long term potentiation and long term depression. Donald Hebb theorised that when an axon of cell A excites cell B and repeatedly or persistently takes part in firing it, some growth process or metabolic changes takes place in one or both cells, so that A’s effcieincy as one of the cells firing B is increased.
Can plasticity be restored beyond the critical period?
Yes, sometimes. Neural stem cells have been shown to divide, differentiate and even find the right targets and behave within normal physioloigcal ranges. Axons and dendrites can be stimulted to sprout beyond the critical period.
Magnetoencephalography (MEG) images reveals the human brain’s special ... during ‘reading’. The activation initiates at the ... at the back on ... by 170msec, which then extends to the ..., also known as the brain’s .... This is thought to be where ... area extracted from the visual scene. The same areas were activated when imaging blind individuals who were reading via ....
Magnetoencephalography (MEG) images reveals the human brain’s special Visual Word Form Area (VWFA) during ‘reading’. The activation initiates at the occipital pole at the back on both sides by 170msec, which then extends to the left occipito-temporal region, also known as the brain’s letterbox. This is thought to be where word forms area extracted from the visual scene. The same areas were activated when imaging blind individuals who were reading via Braille.
A small number of both early- or late-blind people can teach themselves ... using the ... of sound they produce. This is simliar to what ... do. In both, activation can be shown to occur in the ` …. In both, activation was also seen in the … and nearby cortical regions when they … reflected from …`.
A small number of both early- or late-blind people can teach themselves echolocate using the reflections of sound they produce. This is simliar to what bats do. In both, activation can be shown to occur in the calcarine (visual) cortex. In both, activation was also seen in the middle temporal and nearby cortical regions when they listened to echoes reflected from moving targets.
What was done to restore plasticitiy beyond the critical period in amblyopic rats?
Amblyopic rats who received chronic treatment with fluoxetine showed recoery in both visual acuity and in C/I VEP ratio in the deprived eye. Control rats had lower VA in amblyopic eye and overall less C/I VEP than fluoxetine rat.
The sensory homunculus is a map along the ... of where each part of the body is processed. The thumb sensory area is close to the face. If the hand is amputated, stimulation of the face .... This is speculated to be due to ..., where the thumb cortex area lost its ... and now receive input from ... sensory areas.
The sensory homunculus is a map along the cerebral cortex of where each part of the body is processed. The thumb sensory area is close to the face. If the hand is amputated, stimulation of the face may still trigger phantom sense of the thumb. This is speculated to be due to cortical reorganisation, where the thumb cortex area lost its afferent input and now receive input from adjacent sensory areas.
How can phantom limb symptom be cured with mirrors? What does this indicate?
This indicates that there are visual inputs to the somatosensory system. Px is asked to look at the mirror reflection of their non-amputated arm and watch it get stimulated. Some px may feel pain due to thinking their amputated side having a very tight fist. Make px watch themselve open up their fist through mirror reflection can help ease the pain. Visual mirror therapy is proven to be effective in studies on post-stroke hemiparesis.
In an experiment that look at receptive fields after deliberate laser lesions on the retina found that around ...% of single neurones in the ... had ectopic visual discharge fields displaced to .... The sizes of the ectopic discharge fields were ... from the sizes of normal discharge fields. These ectopic fields demonstrated ... and preferred ... which were indistinguishable from those found when the cells were stimulated via the normal eye. However the responses to stimuli presented via ectopic discharge fields were ... than those to presentation via normal discharge fields, and were characterised by a ....
In an experiment that look at receptive fields after deliberate laser lesions on the retina found that around 75% of single neurones in the Lesion Projection Zone (LPZ) had ectopic visual discharge fields displaced to normal retina. The sizes of the ectopic discharge fields were not significantly different from the sizes of normal discharge fields. These ectopic fields demonstrated orientation tuning and preferred stimulus velocities which were indistinguishable from those found when the cells were stimulated via the normal eye. However the responses to stimuli presented via ectopic discharge fields were generally weaker (lower peak discharge rates) than those to presentation via normal discharge fields, and were characterised by a lower than normal upper velocity limit.
Stages of response to a partial loss of input to the topographically-arranged representations in sensory cortex:
1. Immediate to hours = ...
2. Hours to days = ..., ...
3. Weeks to months = ...
Stages of response to a partial loss of input to the topographically-arranged representations in sensory cortex:
1. Immediate to hours = unmasking of new responsiveness
2. Hours to days = new filtering of the unmasked responsiveness, synaptic plasticity
3. Weeks to months = Structural changes - local axonal sprouting & dendritic remodelling
What is the reason why we assume things are continuous in our visual world even though we don’t see them as continuous?
Orientation columns help reconstruct the world.
What are the 4 pereptual learning where repetition of the tak will lead to improved performance?
- Discrimination of two very similar direction of motion
- Discrimination of gratings
- Texture discrimination
- Stereoacuity with some random dot kinematograms
Perceptual learning is in most cases specific to the ..., thus leading to the idea that it occurs ..., probably in .... However, perceptrual learning is also influenced by ... such as ... and ... across different coordinate frames.
Perceptual learning is in most cases specific to the retinal location of the stimulus, thus leading to the idea that it occurs early along the visual pathway, probably in area V1. However, perceptrual learning is also influenced by top-down processes such as attention and sptial integration across different coordinate frames.
