Neurophysiology 2 Flashcards
What describes the contrast
sensitivity function in strabismic amblyopes?
Localized deficit at the location of their suppression scotoma
What describes the CSF in anisometropic amblyopes?
Overall optical defocus
This is the ability to detect positional inaccuracies and
spatial localization
Hyperacuity
Name 1 thing that is not a monocular sensory deficit in amblyopic eye.
Stereopsis
T/F: The visual system remains more plastic for longer periods of time at higher levels of procesing.
True
What’s the most plastic: retina, LGN or Visual cortex?
Visual cortex
This is the initial formation of neuronal circuits that is not dependent on visual experience.
Pre-critical period
This is a distinct onset of robust plasticity in response to visual experience when the initially formed circuit can be modified by experience.
Critical period
This is after the end of the critical period, the same visual experience no longer elicits the same degree of plasticity.
Closure of critical period
When does a humans CP start, heighten and plateau?
Start: at birth
Heightens: 1-3 yo
Plateau: 7yo
What is the result from brief monocular deprivation of cats?
- only took 8 days
- ocular dominance columns were driven by non-deprived eye
How do we determine/measure the critical period in humans?
Inter Ocular Transfer test
The IOT test found that the CP for binocularity initiates between __ and __ of age.
6 mo and 1 year of age
Astigmatism and anisometropia leads to amblyopia if they persist for how long?
2 years
Cataracts and stimulus deprivation have a much more ____ effect than aniso.
severe
This is the development of the synaptic connections between the neurons and the retention of these connections.
Binocular competition
- inputs from both eyes will compete for synapses onto the cortial binocular cell
How do we strengthen the synaptic connection from the blured eye in order to balance the competition?
Occlusion therapy! (patch!)
What is the main concern of full-time reverse occlusion?
May cause Bilateral amblyopia
What amount of hours is needed for part-time reverse occlusion to be useful (in kittens)?
5 hours
- more equalization vs. 3.5 hrs
Full time reverse occlusion in monocular deprived cats led to what finding?
Occlusion amblyopia, reduced acuity in the previously open eye
What was the conclusion from the study of dark rearing cats?
- The critical period is delayed
- CP only begins when the animals are first exposed to light (need visual experience)
Why was there a visual change in the dark-reared adult rat showing that monocular deprivation was effective?
- adult dark-reared rats have decreased levels of GABA receptors (increased plasticity of cortex)
What is the important receptor when we’re talking about ocular dominance?
NMDA receptor
What was the conclusion of PEDIG ATS 2A?
For moderate amblyopes (better than 20/80), 2 hours of patching with 1 hour of near work produces an improvement in VA similar to 6 hrs of patching.
What was the conclusion of PEDIG ATS 2B?
For severe amblyopes (20/100-20/400), 6 hours of patching and 1 hour of near work was comparable to full-time patching
What is the MOA of pharmaceutical agens acting to tx amblyopia?
Reduces gabanergic inhibition to restore plasticity in the visual system
The drug, Levodopa/Carbidopa, showed what 3 results when studied in patients with amblyopia?
- 2 lines improvement in VA
- greater improvement in patients younger than 8 yo
- No reversal of improved VA at 6 mo followup
The critical period in animal models can be _____ depending on visual experience.
delayed
The hebbian model suggests that the _____ is the neuronal location where plasticity changes occur
synapse
The NMDA receptor is made up of 2 subunits, the NR2b, which is more common at ______; and the NR2a which binds during_____.
Nr2B = birth Nr2A = during adulthood
Dark rearing has shown ______ the onset of critical period in adult rats and cats, proving that _____ is necessary to trigger the events of ocular dominance.
delay, visual experience
PEDIG now recommends _____ with 1 hour near work for moderate amblyopes and ______ w/ 1 hr near work for severe amblyopes.
2 hrs, 6 hrs
Adult plasticity studies showed that the critical period is never fully _____.
closed
Levodopa/Carbidopa increase ____ levels in the CNS.
dopamine
Reduced GABAergic ___ facilitates synaptic plasticity.
inhibition
_____ enhances histone acerylation levels, which promotes plasticity in adult rat’s visual cortex
Valproic Acid
Fluoxetine infusion studies have shown a novel ______ creation in V1 of adult amblyopic rats, with a corresponding rescue of the previously MD eye.
synapse
Drugs that ___ inhibition should promote plasticity, and this has led to pharmacological intervention as a potential avenue for amblyopia tx.
reduce gabanergic inhibition
