Neuroplasticity

Question 1

what is the hebbian plasticity theory

Answer 1

neurons that fire together, wire together

• # more connections and APs that are sent = stronger connection
• less firing = weaker connection

Question 2

what does plasticity signify

Answer 2

learning is taking place

Question 3

what is unimodal plasticity

Answer 3

synaptic plasticity through experience (ex: learning braille) can lead to growth of specific portions of the body map in S1

Question 4

what is cross modal plasticity

Answer 4

strengthening of somatosensory and auditory cortex input through LTP due to blindness or other loss of sense

ex: through congential blindness - cross modal more prevalent in people who were blind early in life

Question 5

what causes LTD

Answer 5

low frequency stimulation (< 1Hz) applied to schaffer collaterals

small, slow rises in post synaptic calcium leads to LTD

Question 6

what happens during LTD

Answer 6

opposite of LTP - removal of AMPA receptors and shrinking / eventual removal of the synapse / dendrite

Question 7

why is LTD necessary

Answer 7

needed to prune out neurons not following Hebb’s law
(not being used / stimulated so connection weakens)

Question 8

what are place cells

Answer 8

fire APs when they are in a particular location within their environment

(used to recognise places)

Question 9

where are place cells found

Answer 9

posterior hippocampus

(can experience anatomical changes (growth) as people learn more places)

Question 10

what is the dentate gyrus

Answer 10

one of the only locations in the brain where the birth of new neurons occurs (neurogenesis)

Question 11

why does neurogenesis occur in the dentate gyrus

Answer 11

constantly experiencing new places so new place cells are needed

Question 12

what is the difference between specificity and associativity

Answer 12

specificity = LTP is specific to one synapse when the other is inactive

associativity = strong stimulation can cause growth (LTP) at a pathway with weak stimulation

Question 13

how does a bicep curl represent associativity

Answer 13

both biceps and triceps fire - even though triceps have a weak stimulation there would be no movement without them

Question 14

during LTP, why do EPSPs increase and then decrease back to baseline

Answer 14

LTP causes dendritic spines to grow

• growth = more ions flowing in but increased SA means its more leaky
• leakiness causes EPSPs to return to baseline

Question 15

what does the morphology of dendritic spines determine

Answer 15

their electrical properties which can have direct effects on EPSP/IPSP amplitudes

Question 16

what does repeated activation of post synaptic neuron cause

Answer 16

additional AMPA (glutamate) receptors are inserted into the post synaptic membrane

Question 17

which receptor(s) does glutamate bind to

Answer 17

both AMPA and NDMA receptors

Question 18

which receptor does glutamate activate and which ion is allowed to flow

Answer 18

activates AMPA
sodium flows (only ion flow at the beginning of EPSP)

Question 19

what does sodium flow through AMPA lead to

Answer 19

makes post synaptic potential more positive leading to an EPSP

Question 20

what is the effect of an EPSP on NDMA

Answer 20

magnesium blocker on NDMA is repelled by EPSP and both sodium and calcium and flow through

Question 21

what are CaMKII and PKC

Answer 21

calcium activated protein kinases (enzymes)

calcium binds to these enzymes to initiate the process of LTP (more AMPA receptors added to post synaptic neuron)
- blocking these enzymes stops LTP

Question 22

what are the two phases of LTP

Answer 22

1. AMPA receptors inserted into post synaptic membrane
2. growth of dendritic spines is stimulated

Question 23

what are the pros and cons of dendritic spines

Answer 23

pro = reduces axoplasmic resistance in the dendrite (easier for ions to flow from the head to the dendrite)
con = increases SA (more room for ions to leak out)

Question 24

what are the basic steps that lead to LTP (6)

Answer 24

1. glutamate binds to AMPA
2. sodium only flows through (makes more positive)
3. EPSP caused
4. NDMA magnesium blocker repelled by EPSP
5. sodium and calcium flow occurs
6. more AMPA receptors added as communication continues

Question 25

what is the initial benefit of more AMPA receptors during LTP

Answer 25

leads to larger EPSPs (easier to achieve / more sensitive)
more channels to let sodium in