063 064 Learning and Memory

Question 1

What did the kluver and bucy experiment show?

Answer 1

Shows that removal of the medial temporal lobe will cause loss of visual recognition.

Question 2

What memory does the perirhinal cortex produce?

Answer 2

Declarative memory

Question 3

Which part of the brain is responsible for spatial related memory?

Answer 3

Hippocampus

Question 4

What is the pathway for declarative working memory?

Answer 4

temporal lobe cortex, amygdala –> dorsal medial nucleus of thalamus –> prefrontal cortex

Question 5

Which part of the cerebellum is damaged in korsakoff’s syndrome?

Answer 5

Purkinje fibres in the vermis

Question 6

Describe the circuit of papez

Answer 6

Hipppocampus –> fornix –> mamillary body –> mamillothalamic fibres –> anterior nucleus of the thalamus –> cingulate cortex –> entorhinal cortex –> hippocampus

Question 7

What cerebellar effects are affected in korsakoff’s syndrome?

Answer 7

Gait is affected but distal control of limbs is not.

Question 8

Describe long term potentiation?

Answer 8

1. NMDA receptors activated during depolarisation to remove Mg2+ ion block.
2. Ca2+ is allowed into NMDA receptor.
3. Ca2+ activates protein kinases, which phosphorylates existing AMPA receptors.
4. Long term structural changes e.g. insertion of AMPA receptors and growth of new synapse.

Question 9

Describe cerebellar long term depression?

Answer 9

1. Activation of parallel fibre activates metabotropic glutamate receptor and activates AMPA receptor.
2. Metabotropic glutamate receptor stimulate DAG to activate PKC (Ca2+ dependant).
3. In purkinje cells (no NMDA receptors), climbing fibre depolarises and cause influx of Ca2+ through voltage gated channels.
4. Ca2+ acts with PKC to phorphorylate AMPA in parellel fibre.
5. This phosphorylation inhibits transmission of AMPA receptors in parallel fibres.

Hence, conjunctive activation of climbing fibre inputs and parallel fibre inputs leads to long term depression of paralell fibre synapses upon purkinje cells.

Question 10

Describe the nictitating membrane response.

Answer 10

Unconditional stimulus –> corneal air puff
Conditional stimulus

1. Unconditional stimulus carried by climbing fibres
2. Conditional stimulus carried by mossy fibres
3. Unconditional stimulus causes long term depression of parallel fibres, and purkinje cells.
4. Purkinje inhibitory outputs are reduced
5. Movements of the eyelid occur in cerebellar nuclei and motor neurons.