Development of Binocular Vision Flashcards
the ability of the brain to change as a result of experience
Plasticity
examples of plasticity in negative consequences
phantom pain, addictions, trauma, poor binocular vision
Limited time during which the nervous system displays heightened sensitivity to environmental stimuli. If the organism doesn’t receive the appropriate stimulation during this time window, it may be difficult, if not impossible, to develop certain functions later in life.
Sensitive periods aka “Critical periods”
Examples of sensitive periods
Imprinting
Binocular vision
birdsong
language
Order of sensitive periods
Seeing and hearing/visual & auditory cortex (first)
Receptive language/ speech production / angular gyrus, broca area
Higher cognitive functions/prefrontal cortex (last)
Do functions dependent on retinal neuron development have earlier or later critical period?
Earlier critical period
What takes the longest time to develop in vision? What does this make them vulnerable to?
Spatial and binocular vision. Makes them most vulnerable to effects of abnormal inputs.
What are the two earliest critical periods for visual functions in humans?
Absolute light detection and temporal resolution
What area does the Sweep VECP evaluate? What does it test?
cortical area V1
tets monocular and binocular visual functions to see if brain received signal
What kind of technique is forced-choice preferential looking?
Behavioral technique
What kind of response has to do with a looming target?
Avoidance response
When does a baby have reasonably accurate accommodation?
3-5 months
What direction does early smooth pursuits and OKN develop?
temporal visual field to nasal visual field
Nasal retina to temporal retina
What matures faster? Accurate convergence or divergence?
convergence matures quicker
During a visual cliff test, when would the child avoid the “deep side” of the cliff?
6-8 weeks
What develops first? Fine stereoacuity or fine monocular spatial resolution?
Fine stereoacuity
When do fusion and binocular summation develop?
3-5 months after birth
When does the LGN segregate into its layers?
3-5 months gestation
What develops first? Contralateral or Ipsilateral layers?
Contralateral layers
In the V1, what happens within the first 10 months of postnatal?
Dramatic increase in cortical volume
Dramatic increase in synaptic density
In the V1, what happens from 10 months to approximately 8-10 years?
Gradual decrease in cortical volume
Gradual decrease in synaptic density
Increased specificity of remaining synapses.
What are the 2 phases of resolution visual acuity development?
Very rapidly within the first several postnatal months
Very gradually during the subsequent decade
What is Hebb’s rule?
Connections synchronously active = strengthened
Connections not synchronously active = weakened
Amblyopia criteria
Acuity must be less than 20/40 to be defined as amblyopia, AND
there must be at least 2 lines’ difference in the Snellen acuity between the two eyes.
5 types of amblyopia
Strabismic
Anisometropic
Refractive
Meridional - astigmatism
Stimulus deprivation
What is congenital amblyopia usually associated with?
Cataracts or other opacities
What happens in the LGN parvocellular layers during artificial-induced strabismus?
Slight shrinkage
If there is constant strabismus during artificial-induced strabismus, what is there an increase of?
Category 1 cells
If there is alternating strabismus, what is the relation of category 1 and 7 cells?
They are equal.
Normal spatial frequency
Premature or low birth-weight infants have ____ times greater risk of strabismic amblyopia.
4-6x
What would an early-onset strabismus cause?
-amblyopia more likely with CONSTANT deviation.Results in deep constant “suppression scotoma” of (at least) the central visual field of the deviated eye.
-Severe spatial distortions in the amblyopic eye.
-Greater than normal crowding effects for acuity AND hyperacuity
What is likely to be UNAFFECTED by strabismic amblyopia?
Color vision
luminosity functions
dark adaptation
glare recovery
flicker and motion perception
What chemicals are represented high in critical period?
N-methyl-D-aspartate (NMDA)
Nerve growth factor
Norepinephrine
What is the primary inhibitory neurotransmitter in the V1?
GABA
When should treatment be provided for best development?
during critical period except anisometropia because full refractive correction too early can disrupt normal emmetropization
