learning + memory Flashcards
retrograde vs anterograde amnesia
anterograde = unable to form new memories
retrograde = unable to recall past memories (memory loss)
role of hippocampus in learning/memory
- hippocampus is highly conserved neural structure across mammalian species.
- most investigated brain region for memory processes.
- important for declarative and spatial memory
- as in HM, patients with bilateral damage/lesion to hippocampus have profound anterograde amnesia
- in rodents, hippocampus important for spatial learning
role of the striatum in learning/memory
• cognitive functions such as
– motivation
– learning habits/addiction
- dysfunction of striatum underlies neurological (such as parkinson’s disease) and psychiatric conditions (such as obsessive compulsive disorder)
- unsure exactly how it functions
role of the amygdala in learning/memory
- key centre for associative learning and memory
- aberrant activity in the amygdala is thought to underpin anxiety and panic disorders
- in humans, bilateral damage or loss of amygdala profound loss recognising stressful/fearful facial expressions
role of the cerebral cortex in learning/memory
- likely to be location of long term memory (HM’s childhood memories were intact)
- also priming type of learning such as auditory and visual priming (HM performed well in priming experiments)
role of the cerebellum in learning/memory
- key role in non-declarative learning and memory (dancing, swimming, driving)
- probably plays a role in other types of memory as well.
describe the T-maze test
what is the affect of silencing the hippocampus / striatum during this test
rat placed in T-intersection with a reward on the right pathway
after 1 week training, rat turns to right on the test i.e. places cue
after 2 weeks, the maze is flipped 180º. rat turns to left on test i.e. habitual response
silencing the hippocampus impairs ‘place’ recognition but no effect on habit response
silencing striatum affects habit response but no effect on ’place’ recognition
how does LTP induce both biochemical and biophysical changes?
LTP = long term potenation
repeated firing of one neuron to another strengthens the connection and increases the efficiency of the firing
pre-synaptic neurons (especially excitatory) make synaptic contacts on the dendritic spines of post-synaptic neurons = BIOCHEMICAL
LTP leads to increased insertion of additional receptors in the dendritic spine of the post-synaptic neuron
LTP induces formation of of new dendritic spines = BIOPHYSICAL
associative property of LTP
LTP can be induced on a weak pathway by pairing with a strong pathway
associative property of LTP is considered as correlate for associative learning process
compare LTP and sensitisation
SENSITISATION:
• occurs in spinal cord in vertebrates + invertebrates
• sensitisation of one pathway enhances overall excitability to other stimuli
• example: pain pathways
LTP:
• occurs in brain of vertebrae
• pathway specific
• associative property: weak pathway can be potentiated when combined with strong pathway during potentiation
what determines LTP or LTD?
time of spike determines type of plasticity
LTP = presynaptic inputs before/synchronous with postsynaptic spikes (evoked by a second pathway or by current injection)
LTD = presynaptic input followed postsynaptic spikes
what are the short and long term effects of plasticity?
SHORT-TERM:
• ↑ in pre+post synaptic [Ca2+]
• ↑ post synaptic receptors
LONG-TERM:
• gene expression
• protein expression
• structural changes
how does epilepsy occur?
what is the kindling model of epilepsy?
what are the similarities between LTP and kindling?
long-term LTP induces epilepsy
• distorts conscious perception
• seizures
key feature is aberrant high freq. electrical activity in ECG
kindling model:
• a seizure may increase the likelihood that more seizures will occur
• repeated stimulation lowers the threshold for more seizures to occur
• key regions involved include the amygdala and the hippocampus
both kindling and LTP: • require high frequency stimulation • cause synaptic facilitation • require protein synthesis • cause structural synaptic changes it is thought that changes that occur during LTP during memory formation when goes unchecked may lead to aberrant excitability (as in kindling) and epileptogenesis
what is a cell assembly?
neurons are organised into networks with frequent connections
if one neuron is activated, activity spreads extremely rapidly throughout the networks
this network of circuits = CELL ASSEMBLY
how do oscillations in brain activity correlate to behaviour?
most frequent oscillations 1. alpha 2. beta 3. theta 4, gamma least frequent oscillations
different behaviours generate different types of oscillations
there are correlations between how networks are activated and the types of behaviour exhibited by an organism
