plasticity and learning Flashcards
(22 cards)
how does capacity for learning change over time?
- capacity does not stop with maturity
what is the difference between learning and memory?
- learning is acquiring new knowledge
- memory is the process by which that knowledge is encoded, stored and later retrieved
Wilder Penfield
- neurosurgeon mapping motor, sensory, and language functions of the cerebral cortex
- surgery was only cure for epilepsy in the 1950s
- on rare occasions, he found that electrical stimulation of ‘temporal lobes’ produced and ‘experiential response’
- coherent recollection of an earlier experience
- kept patients awake during surgery to know what parts of the brain to avoid
describe the case of HM
- suffered from untreatable seizures
- medial temporal lobes were removed bilaterally
- after surgery, seizures reduced but also major deficits to memory systems
- could learn skills but didn’t remember learning them previously
- lost declarative memory
what are the two classes of memory
Non-declarative (implicit)
- skills
- memory that is recalled unconsciously
- training of reflexive, motor, or perceptual skills
- can’t really describe implicit memory
- neocortex, striatum, amygdala, cerebellum, reflex pathways
declarative (explicit)
- memory about objects, people, events, etc.
- highly flexible
- bringing together associations between multiple elements
- medial temporal lobe
what changes occur when you learn something?
- something in your brain changes so that when the same sensory stimulus applies, something different happens
what is neural plasticity
- the capacity to change neuronal connections in an experience dependent manner
what is habituation
- the simples form of implicit learning
- animal learns that the properties of a novel stimulus are harmless
- reduces sensitivity for that stimulus
describe habituation in aplysia
- gill withdraws in response to tactile stimulus to the siphon
- after multiple rounds of squirting water with no damage, the gill retracts less
cellular basis for short vs. long term habituation
short
- number of synaptic vesicles released
- change the activity of the neuron
long
- structural change - fewer synapses
sensitization in aplysia
- Giving the Aplysia an electric shock sensitizes it and they are more aware of the water on their gill
- If you were chillin and someone tapped you, you wouldn’t mind but if you were watching something scary on tv and someone did that, you would be scared
what is the function of the hippocampus
- memory center of the brain
- bright red is hippocampus
- input comes through the entorhinal cortex
describe long term potentiation in the hippocampus
- CA1 is the post-synaptic neuron
- CA1 is stimulated by CA3
- Tetanus is high stimulation of muscles (here, it’s a high, almost unnatural frequency stimulus)
- The stimulus is potentiated after synapse was changed
what does the tetanus do?
- tetanus is a strong stimulus (coincident) - stimulates the whole neuron
- activates presynaptic and postsynaptic neuron
- LTP occurs from coincident activation of the CA3
- basis of associative nature of long-term potentiation
what happens during synaptic transmission at the molecular level
- Glu binds, which opens the Na and K channel
- NMDA receptors also respond to Glu, but they require the Mg to leave because it blocks the channel while its there
- both glutamate-dependent and voltage dependent
Calcium in postsynaptic neuron
two conditions for Calcium to enter:
1. the presynaptic neuron must be active and release glutamate
2. the postsynaptic neuron must be depolarized to remove Mg2+ from the NMDA pore
- more effective release of Glu from presynaptic neuron
LTP overview
how is associative LTP useful for encoding memory?
- if you have on strong stimulus, it can do something to the weak inputs that are going on at the same time
- Strengthens synapse
- Form arbitrary relations between inputs
- Specificity is important because only synapses that are active get strengthened
- Stimuli that occur that the same time can be associated together
specificity
- potentiation is specific to active synapses
associativity
- weak stimuli can be potentiated by coincident strong stimuli
how does LTP link to behavior
Morris water maze
- Morris designed a test maze for rats to test their spatial memory
- pool with murky water - rats can’t see the platform
- other features in the room helped the rat learn the location of the platform
- when NMDA receptors (necessary for LTP) are blocked, rats exhibit no evidence of spatial learning
- rats couldn’t learn without LTP
