Neuron Competition

Question 0

Patterns of co-activity….

Answer 0

… often determine the outcome of competition.

Question 1

“Cells that fire together…

Answer 1

….wire together”

Question 2

when a spontaneous release of neurotransmitter by developing Pre-Synaptic Axon produces….

Answer 2

…. a Post-Synaptic response,

active Post-Synaptic cell will release Neurotrophins that promote Pre-Synaptic cell survival

Question 3

So, if researchers block spontaneous firing….

Answer 3

…. brain will develop MORE CELLS and MORE CONNECTIONS than normal

Question 4

Neurotrophin release…

Answer 4

…is only (most) effective on ACTIVE Pre-Synaptic cells,

so the more correlated the Pre&Post activity of a given pathway, the more likely it is to strengthen,

and other LESS CORRELATED CONNECTIONS DIE OFF

Question 5

when out-competed cells die…

Answer 5

…remaining active one will produce COLLATERAL SPROUTS that will take over synapses

Question 6

Adjacent Pre-Synaptic cells…

Answer 6

…tend to CORRELATE their bursts of activity, so tend to develop connection to ADJACENT TARGETS

• this often results in Topographic Map,
  &raquo_space; e.g. where spatial relationships along a receptor surface are preserved in the brain

Question 7

Post-natal experience continues…

kittehs?

Answer 7

…to shape Synaptogenesis, esp. in infancy but even into adulthood

• kittens exposed only to vertical lines&raquo_space; developed connections in visual cortex responsive to vertical stimuli, but could NOT, as cats, detect horizontal lines (cells normally responding to horizontals were out-competed)

Question 8

Dendrites and development

Answer 8

• receive input from other Neurons
• continue to develop with experience, increasing “receiving” surface area
• dendrite development usually begins after migration and axonal growth, Dendritic Branching continues with experience

   - e.g. Rats in enriched (vs. deprived) environment show significantly more Dendritic Spines 
   - e.g. Musicians that finger string instruments, trained from childhood, show expanded somatosensory map for fingers of LEFT HAND (probably from increasing dendritic branching)

Question 9

Glia Cells and development

Answer 9

they continue to develop and differentiate many different structures and functions

EX: Myelination begins in the Spinal Cord then in Hindbrain then Midbrain, then Forebrain, then PNS
- some myelination still forming at age 20; in a few brain areas continues into adult life

Question 10

brain growth in humans continues after birth…

Answer 10

…. especially during the first 4 years of life (plus later spurt during adolescence)

newborn brain weighs about 350 grams, by 1 year 800 - 1000 grams, adult 1200 - 1400 grams

Question 11

post-natal increase mainly due to

Answer 11

increase in size of existing cells and Axonal and Dendritic branching

Question 12

new neurons are…

Answer 12

RARE!

Question 13

Learning!

Answer 13

our highly plastic brains continue to develop new connections, although NOT new neurons