How can proactive interference be demonstrated in a delayed matching to sample experiment
Biological Basis of Behaviour- Week 3
Lecture 6.1 & 6.2
Introduction to memory
Questions for today:
- We’ve studied animal learning - how to get the information in if you like- but what about
how to access it again?
- We’ll look at a number of issues in animal memory in this presentation: Including their ability
to remember in the long term, the nature of forgetting (do they lose the information or is it
still there somewhere?), and examine the evidence for episodic memory in animals.
Memory Taxonomy (way of classifying memory)
- Working memory vs short term memory: long term retention versus short term storage
- Episodic vs Semantic/reference memory: Episodic e.g: My first day of uni (what? Where?
When?) vs Semantic memory: knowing that Rescorla-Wagner is a model of associative
learning (how the world words- a fact without context
Forgeting
The Nature of forgetting:
Target memories could be lost because of
– Proactive interference from information acquired PRIOR to target
– Retroactive interference from information acquired AFTER target
– Decay due to the passage of time.
We’ll consider evidence for each of these mechanisms for forgetting in the online lecture. Here we
are more concerned with whether the forgotten memory is actually erased or simply harder to
retrieve.
Long term memory
We will consider retention over intervals of hours and days (and longer) rather than minutes. The big
issues here are:
- what transformations in the memory trace take place between original encoding and final
storage
- whether memories that are forgotten are lost completely or merely become inaccessible.
o The last point refers to the idea that forgetting should be considered as a failure to
retrieve, the memory is still there, it’s just that the animal is unable to access it
under present conditions.
In some sense, it’s almost impossible to fully answer that last question. Even if you found no
evidence of the memory still being present in some form, you could argue that you just haven’t
looked hard enough, provided the right cues, etc.
But, as we shall see, what’s intriguing is the evidence that apparently forgotten memories can be
accessed if the right cues are given. This makes the “impaired retrieval” hypothesis for forgetting
plausible.
, Consolidation
Consolidation as part of a theory of memory is very popular at the moment. It does lend itself,
however, to the idea that forgotten memories are irretrievably lost which causes difficulites with the
opposing view that they are not destroyed but hard to retrieve.
The idea: here is that the initial memory trace is fragile and relatively short-term, and needs to be
transformed (consolidated) into a more durable trace for the long term.
• Many studies looking at this idea have used avoidance learning in the shuttle box. In this
paradigm the rat (typically) is trained to move from one side to the other to avoid shock.
Shuttle box
Here is a simple diagram representing a
shuttle box apparatus.
- The rat has to move from one
side to the other to avoid shock.
- If it stays on one side for too long
(typically 30 to 60 sec) it gets a
footshock.
- I’ve shown it moving from the
lighter to the darker side, and to
do so it has to jump a very low
“hurdle” in the middle.
- We start by training the animals to do this and they acquire this response readily and will
move from one side to the other to avoid the shocks
- We then give electroconvulsive shock (ECS) at various times after the training session: this is
basically looking at the physiological disruption of consolidation
Physiological disruption of consolidation
Several types of physiological trauma prevent learning if and only if they occur shortly after a
stimulus or reward
• Examples include ECS (electroconvulsive shock: Duncan 1949), sudden heating or cooling,
drugs, concussive impact (American Football).
• Thus, after learning a shuttle response to avoid shock, ECS given shortly after training will
disrupt performance after a delay, whereas ECS given after that delay and just before test
will not be as effective.
Duncan (1949) – results from studies looking at Physiological Disruption of consolidation using
shuttle box
When we put the animal back in the shuttle
box after it’s completely rested, we see
whether it shuttles as before. (The higher
the score on the graph the better it is doing
at moving to avoid the shock, so better
shuttling).
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