Exam 4: Learning and Memory Pt 2 - Plasticity

Question 1

how the brain learns and remembers

Answer 1

plasticity

Question 2

ability to change both synaptic connections and functional properties of neurons in response to stimuli and experience alters effects on what neurons?

Answer 2

postsynaptic

- changes likelihood of action potentials

Question 3

Hebb’s Rule

Answer 3

when 2 neurons are repeatedly activated together, their synaptic connection will become stronger
- neurons that fire together, wire together

Question 4

engrams

Answer 4

memory traces in the brain

Question 5

synapses that are enhanced by coincident activity between pre and postsynaptic neuron - could act together to store memory traces

Answer 5

hebbian synapses

Question 6

what are the synaptic changes that underlie simple forms of learning

Answer 6

long-term potentiation (LTP)

Question 7

what are the 2 types of glutamate receptors in LTP

Answer 7

NMDA and AMPA

Question 8

NMDA glutamate receptors

Answer 8

ionotropic
- Ca and Na ion channel - when glutamate binds it opens

Mg2+ ion blocks channel pore at rest

Question 9

AMPA glutamate receptor

Answer 9

ionotropic

- Na ion channel

Question 10

NMDA receptors - what ejects the Mg from the ion channel to allow glutamate to bind

Answer 10

when the cell becomes depolarized!

Question 11

Upon glutamate binding to NMDA receptors…

Answer 11

• glutamate stimulation of AMPA receptors depolarizes the membrane, releasing Mg from NMDA receptors
• channel opens and Ca enters

Question 12

calcium entering cell activates second messenger cascades responsible for…

Answer 12

LTP

Question 13

the influx in Ca activates intracellular enzymes that cause changes in postsynaptic AMPA receptors: (3)

Answer 13

• existing receptors move to the active synapse
• increased conductance of ions
• more receptors produced

Question 14

when a postsynaptic cell is strongly stimulated it releases ________ that travels back across the synapse to enter the ________

Answer 14

retrograde transmitter
presynaptic neuron
- if gas no transporter is needed

Question 15

what does the retrograde transmitter ensure?

Answer 15

more glutamate will be released from the presynaptic neuron and further strengthen the synapse

Question 16

LTP requires what 2 events

Answer 16

• activation of synapses

- depolarization of the postsynaptic membrane

Question 17

LTP induced structural changes

Answer 17

• change in size/shape of dendritic spines
  (thin to fat)
• new dendritic spines
  (old spines may form perforated spines or multiple spines)
  
  • 2 synapses produced as result

Question 18

what is LTP necessary for?

Answer 18

long term retention of information

Question 19

where does LTP occur?

Answer 19

hippocampal formation

- hippocampus, dentate gyrus, CA1-3, hippocampal gyrus (entorhinal cortex, subiculum, parahippocampal gyrus)

Question 20

during normal activity, glutamate released at synapses in CA1 activates only _____ receptors

Answer 20

AMPA

Question 21

changes in _____ are responsible for acquisition of a conditioned response also involve LTP

Answer 21

lateral amygdala

Question 22

AMPA receptors move into the postsynaptic density in response to the learned association between _____ and ______

Answer 22

a tone and footshock

Question 23

what are AMPA neurons increased between

Answer 23

lateral amygdala neurons and axons that provide auditory input

Question 24

what do you need to strengthen a response

Answer 24

coactivation of auditory and amygadala

Question 25

long term depression (LTD)

Answer 25

opposite of LTP

- weakening synapses (decreases efficacy of synapse)

Question 26

LTD leads to long term _____ in excitability of a neuron to a particular synaptic input

Answer 26

decreases

Question 27

LTD results from

Answer 27

low frequency stimulation while postsynaptic neuron is hyperpolarized or slightly depolarized
- dec glutamate, dec NMDA activation , dec strength

Question 28

characteristics of LTD (3)

Answer 28

• dec glutamate release from presynaptic neuron
• NMDA dependent, but diff type than LTP
• removal/dec in number of AMPA receptors on dendritic spines