Von Bartheld: Plasticity Flashcards
Muscle fibers initially receive innervation from (blank) neurons, but following a period of elimination of synapses, each mature muscle fiber receives innervation from only (blank) neuron
several; one
*Similar elimination of polyneural innervation occurs in ganglia and among climbing fibers that innervate Purkinje cells in the cerebellum
(blank) require a certain minimal level of trophic support to persist.
synapses
Relevant factors are secreted in limited amounts by the (blank) cells in response to synaptic activation.
target cells *postsynaptic
Synapses can utilize trophic support only if their activity and that of the (blank) coincide.
target cell
Depriving an animal of normal visual experience during a restricted period of early postnatal life irreversibly alters (blank) in the visual cortex
neuronal connections
The brain translates the effects of early experience (neural activity) into (blank).
permanently altered wiring
Information from the two eyes is first integrated in the (blank) where afferent fibers from the lateral geniculate nucleus terminate. The afferent terminals form an alternating series of eye-specific domains in cortical layer IV, called (blank).
primary visual cortex; ocular dominance columns
While the input from LGN to layer IV is still segregated (eye- specific), cells at the border of layer IV and in layers above and below layer IV integrate inputs from (blank), responding to binocular visual stimuli
both eyes
Anatomical studies have shown that monocular deprivation changes the ocular dominance columns such that the columns of the deprived eye (blank), and the ones related to the open eye (blank).
shrink; expand
When individual geniculocortical terminals are examined, the ones from the deprived eye have reduced arborizations in layer IV, while the ones from the open eye are normal or hypertrophic. Thus, input from the (blank) eye takes over some of the territory from the (blank) eye
active; deprived
*this can be interpreted as a competition between the inputs from the two eyes, and the ones from the active eye have a competitive advantage over the ones from the deprived eye.
Roughly equal numbers of cells in the visual cortex respond to the right or the left eye. This normal distribution is altered by closure of one eye (monocular deprivation) during a (blank) period
critical postnatal
If you deprive an eye of vision during the postnatal critical period, very few cells can be driven from the deprived eye. The peripheral visual pathways (retina and lateral geniculate nucleus) remain normal. Thus, the deprived eye becomes functionally disconnected from the (blank), and can cause functional blindness in the deprived eye. This cortical blindness is permanent. The same manipulation, monocular deprivation, in the adult has no effect on the response of neurons in (blank). The cortical neurons are susceptible to monocular deprivation only during a certain (blank) of development.
visual cortex; visual cortex; critical period
What’s this?
“Coordinated activity of a presynaptic terminal and a postsynaptic neuron will strengthen the synaptic connection between them.” Or: synaptic terminals strengthened by correlated activity will be retained or sprout new branches, while those that are weakened by uncorrelated activity are eliminated.
Hebbs’ postulate
Accordingly, ocular dominance columns are generated by cooperation between inputs carrying (blank), and by competition between inputs carrying (blank)
similar patterns of activity; dissimilar patterns
Strabismus is a condition in which one eye muscle is dysfunctional so that the two eyes are not aligned. While the amount of activity in the two eyes stays the same, the (blank) of activity is different. This leads to a (blank) of the ocular dominance columns, and to a (blank) of the binocular neurons in the cortex
pattern; sharpening; loss
Discuss the eye experiment which provided direct evidence for the notion that the PATTERNS of activity are crucial for the formation of connections in cortex
When normal activity in the retina is prevented by intraocular injections of tetrodotoxin, the optic nerves can still be electrically stimulated. When the right and left optic nerves are stimulated in a correlated, synchronous fashion, almost all neurons remain binocular. When the optic nerves are asynchronously activated, the ocular dominance profile resembles that of strabismic animals (loss of binocular neurons).
Observations on experimental animals have important implications for children with strabismus. How so?
If children with ocular deviations do not have them corrected within the critical period, they will have poor binocular vision and diminished depth perception
Studies on the development of ocular dominance columns have shown the importance of (blank). (blank) are thought to be a common phenomenon in the development of the brain and behavior. Other examples are (blank) which occurs in newly hatched birds.
critical periods; critical periods; imprinting
Another example of the clinical importance of critical periods in the eye is the (blank).
congenital cataract
*A cataract is an opacity of the lens that prevents normal vision. Infants with an untreated cataract never regain normal vision in that eye even after cataract extraction in later life. In contrast, when cataracts develop in adults and are removed years later, the patient usually recovers normal vision.
While changes in wiring are more prominent in development, changes at the level of synapses continue throughout life. What is this referred to as?
plasticity
What is this an example of?
Many action potentials in rapid succession can deplete the neurotransmitter if the mechanisms for reuptake of vesicles is overwhelmed. The intense activity can lead to an increase in calcium in the nerve terminal, and this can lead to an increase in the number of synaptic vesicles available for transmitter release. After an initial period of depression, the next action potential can lead to enhanced transmitter release. These changes in synaptic strength are brief, in the range of millisecond to minutes.
Short-term synaptic plasticity
What are two ways to establish long-term potentiation? Think about learning…
- repetitive activation
2. pairing of stimuli *one strong, one weak
(blank) is induced specifically in those synapses which are activated together, but not in other, inactive inputs which contact the same neuron.
long-term potentiation
The induction of LTP can be explained by the biophysical properties of the NMDA and the non-NMDA channels. During low-frequency stimulation, glutamate binds to both NMDA and non-NMDA receptors, but NMDA receptors are blocked by (blank), and current flows only through the non-NMDA receptors. During high-frequency stimulation, or when the postsynaptic site is directly depolarized, the (blank) block is removed from the NMDA receptors, and current flows through both the NMDA and non-NMDA receptors
magnesium; magnesium
(blank) also plays an important role in the induction of LTP. The pore of the NDMA receptor is more permeable to calcium, an important second messenger. Calcium- dependent protein kinases are essential for LTP, and removal of intracellular calcium prevents LTP. Insertion of additional (blank) receptors is another important mechanism to strengthen synapses.
Calcium; AMPA
If LTP was the only mechanism to alter the strength of synpases, soon all synapses would operate with maximal efficacy. To make LTP a useful mechanism, other sets of synapses must be (blank). What is an example of this?
weakened; long term depression
A brain disorder characterized by periodic seizures which are caused by the synchronous firing of large groups of neurons; may be caused by mechanisms that contribute to LTP
epilepsy
For a long time, the wiring of the adult cortex was thought to be stable (hard-wired). More recent experiments have shown that, to some extent, a reorganization of cortical circuits remains possible. Give an example of one such experiment.
When a finger is amputated, and the cortical map is re-examined several months later, the cortical neurons which formerly responded to the amputated finger now respond to stimulation of the adjacent, intact digits.
*Also, performing tasks such as playing the piano can expand areas of cortex devoted to performing that task
