3. Limbic association area
PAPEZ Circuit
Anterior nucleus of ----> Cingulate gyrus
thalamus
Mammillary bodies of <---- Hippocampus
hypothalamus
4. Forms of synaptic plasticity
• Post tetanic potentiation (PTP)
• Habituation
• Sensitization
• Long term potentiation
• Long term depression
5. Post tetanic potentiation (PTP)
• After tetanizing stimuli
• Lasts upto 60 sec
• Due to – increased Ca2+ intracellularly
6. Habituation
• Benign stimulus applied repeatedly
• Reduction in synaptic strength
• Due to decrease in intracellular ca2+ in
presynaptically
• Mechanisms:–
– Inactivation of Ca2+ channels
– Reduction in active zones
• Significance:– basis for negative memory
• Best example for non associative learning
• Can be short term and long term
7. Sensitization
• After habituation paired with noxious stimulus –
increased synaptic response seen
• Due to pre synaptic facilitation
• Features
– May occur as transient process
– If reinforced can exhibit short term and long term
memory
– Sensitising stimulus can occur outside the sensory
realm of potentiated reflexes
8. Long term potentiation
• After rapidly repeated stimulation – rapid
development of persistent enhanced post
synaptic response
• Initiation of LTP – requires depolarization of post
synaptic neuron
• LTP involves presynaptic changes
postsynaptic changes
