lecture 6 Flashcards
brain development - location specificity
what a neutron does depends on its input and therefore it depends on the place/location in the network
to produce neurons a
precursor structure must be in place - intermediate cell before they become differentiated
neurons and glia cells develop from
neural stem cells at the ventricular inner surface and travel to their eventual destination
steps of Brain development
1- cell proliferation
2-cell migration
3-connecting cells
cell proliferation
undifferentiated stem cells grows an extension to the surface
cell nucleus moves UP and duplicates its DNA
nucleus moves back DOWN
cell retracts extension and divides into two
cells behave differently depending on
whether the stem cell has divided vertically or horizontally
vertical split
both daughter cells repeat the process
horizontal split
one daughter cell repeats the process other moves away and not divide again
cell migration
different cell types gave different places of origin
pyramidal neurons and astrocytes originate
from dorsal areas and migrate vertically
inhibitory interneurons and oligodendroglia originate
from more ventral areas and migrate laterally
cortex is not
a single homogenous sheet
organised in a structured way
radial glia cells
in the ventricular zone they extend thin processes towards the surface in an ordered pattern
ventricular zone is a
photomap if the cortex
connecting cells what 3 problems must be solved
find the right direction
find the right target structure
find the right target cells inside target structure
find the right direction
right hand sensed and controlled by left hemisphere
right half of the visual field represented in left hemisphere
growing axons are guided by
chemical signals in the environment
depending on a neurons location it has
different chemical affinities - different likes and dislikes
find the right target structure
chemo affinity hypothesis - axons from a specific source structure are only attracted to chemicals from a specific target structure
find the right target cell
maps are important for action control
general strategy
use it or lose it
initially , axons synapse with cells in their target structure
pruning
useful synapse are maintained
useless ones disappear
what is a useful synapse
links two neurons that most of the time are either both active or both silent
correlated activity
useless
links two neurons that are rarely both active and silent
uncorrelated neural activity
hebbian modification
if activity of pre and post synaptic cell is highly correlated synapses strengthen
