Quiz #2 Flashcards
What processes occur during experimental phase of neural development?
- experience changes synapses from the time of birth throughout and individuals life
- wiring by firing = Hebb’s rule
What processes occur during the developmental phase of neural darwinism?
- genetics present before birth of child
- neural darwinism and apoptosis
What is Neural Darwinism?
- theory of neuronal group selection
What is Developmental Selection?
- genes generate a hugee population of neural and glial cells to select for network building (making network larger through life and death of neural and glial cells)
What is Experiential Selection?
- experience leads to changes in connection strength of synapses, which favour some pathways and weaken others
What are the 2 forms of Neural Darwinism?
- Developmental
- Experiential
What is the organization of the ocular dominance column?
the columns are found in layer 4 of the striate cortex (of the monkeys)
In ocular dominance column, what is the distribution of LGN and where do the zones appear?
- LGN serves one eeye
- zones appear in patches within layer 4 (zebra stripes if superficial 1-3 layers peeled away)
What do dark bands get information from? light bands?
dark bands - get information from one eye
light bands - get information from the other eye
* alternating stripes - ZEBRA LOOK
Input from the LGN serving the 2 eyes are intermingled in where? over time?
- layer 4
- over time - ocular dominance columns in layer 4
The zebra stripes begin to form due to what?
competition dominance
What is the critical period?
- if eye covered at birth then lose segregation and sending of information from that eye => lack of dominance and see black shapes (due to lack of information from the monocular eye development)
What does monocular input beginning at birth lead to?
complete eye dominance
When is the process of ocular dominance column formation?
complete by 6 week
What is monocular deprivation in the early stages post birth?
lose eye information and less striping in layer 4 of the cortex
What does deprivation at 2,3,6 weeks have on monocular deprivation?
weaker effect on the ocular dominance columns since they become more segregated with time
What is the Hebbs synaptic learning/plasticity rule for LTP and LTD?
when an axon of cell A is near enough to excite a cell B and repeatedly or persistently takes part in firing it, some growth process or metabolic change takes place in one or both cells such that A’s efficiency, as one of the cells firing B, is increased
What is a Hebbs synapse?
- pre and post synaptic simultaneous/ concurrent activity
- produces increased synaptic transmission efficiency/strength
- initially signal is only strong enough so that A fires
What is an Anti-hebbian synaptic process?
- an unused connection decays
- triggered by non-concident pre and post synaptic activity
- produces a weakening r decrease in synaptic strength and efficiency, if depression is persistent (LTD)
- initially cell A or B doesnt fire (silent) => synapse A-B weakened
What does LTD stand for?
Long Term Depression
What does an inactivation of cell B do to an active cell A?
depression
What does an active cell B do to an active cell A?
potentiation
What does and inactive cell B do to an inactive cell A?
no change
What is Hebbs view?
chief mechanisms of learning and memory is simply the strengthening of synaptic connections between brain cells of an assembly