3. Learning and memory Flashcards
Engrams?
The link between memory’s and remembering is presumed
biochemical in nature
memory and learning is performed using _____ processing systems and not serial processing systems
memory and learning is performed using PARALLEL processing systems and not serial processing systems
What is the synaptic premises of Hebbian learning?
As cells fire simultaneously they increase the synaptic associations. This results in networks of cells which are synaptically linked - associative learning
I.e. Hebbian Learning
What is habituation?
decrease in response (& NT release ) with repeated stimulus
e.g. Driving with constant background noise, repeating siphon stroke
What is sensitisation?
Increase in response with repeated stimulation – mediated by an interneuron
e.g. sitting in lecture with someone poking you ==> rage
How is the difference between stimulus to siphon at skin and at the tail?
Repeated Siphon stroke on SKIN causes habituation as the sensory neuron EPSP reduces
Concurrent TAIL stimulation causes Sensitisation. The tail shock causes release of 5HT onto the pre-synaptic membrane of the siphon skin sensory neurons from interneurons. This prolongs the NT release and causes sensitisation
What is the mechanism of long term potentiation (LTP)?
- Stimulate pathway 1 with a single spike
- Stimulate pathway 1 with a train of spikes
- re-stimulate with a single spike and measure EPSP
- Stimulate pathway B with a single spike and measure the EPSP
- Enhanced response in Path 1 is long-lived and specific to that pathway
Long term synaptic changes requires genetic involvement
So…
AFTER STIMULATION WITH TRAIN OF SPIKES, SECOND SINGLE STIMULUS LEADS TO UPREGULATED EPSP
To prevent ‘whole brain potentiation’ there is a reverse effect (recall habituation)….
Long term depression (LTD)
How is long term depression achieved?
LTD is initiated by a slower train of stimulatory impulses over a longer period
LTD can modulate LTP or even reverse it
How are memory’s classified?
By duration!
Memory duration is used to define memory types and processes:
Short term memory, Long term memory, & Working memory
A short term memory is?
1) a very brief memory (seconds) either from an external
stimulus or retrieval from a long term memory
**2) easily displaced by another stimulus **
3) Can be extended into working memory by:
a) repetition in a phonic loop (temporal extension) or
b) chunking which links familiar chunks together to extend the size of chunk
example of phonic loop?
“MUST REMEMBER MY KEYS” REPEATING OVER AND OVER
Common clinical test for short term memory?
Digit span.
Subject reads an increasing series of numbers which they immediately repeat
The number of digits that can be repeated back immediately is the digital span. - Usually around 6-7 digits is normal
Technique to improve short term memeory?
Chunking
Grouping list logically to lessen number of individual items to remember
What is working memory?
The maintenance and integration of information in an active state for a relatively
brief time in order to achieve a short term task or goal
Made up of: s comprised of a mixture of short and/or retrieved long term memory
How do short term memories become working memories?
What happens when task is over?
As Short term memory only lasts a few seconds it must be repeatedly re-activated, its reactivation and subsequent duration is working memory (this is known as an executive function).
When the task is over, the working memory either is encoded into long term memory or is left to lapse
Note that it is also possible for LTM to be formed directly from ______ input under control of executive functions (pre-frontal cortex)
Note that it is also possible for LTM to be formed directly from sensory input under control of executive functions (pre-frontal cortex)
Subdivisions of logn term memory?
Declarative memory (explicit) \+ Non-declarative memory (automatic)
Classification of declarative long term memory…
(Conscious memory)
- Semantics (language/facts)
- Epispodic (events and experiences)
- Familiarity
- Recollection
1+2 Form the autobiographical memory
IN THE MEDIAL TEMPORAL LOBE STRUCTURES AND ASSOCIATION AREAS
What is the classification of non-declarative long term memory?
(Does not require conscious effort to form or access) 1. Procedural (habits and skills) @ basal gangia and cerebellum 2. Priming -Habituation e.g. traffic noise -Sensitisation e.g. paper cut pain 3. Associative learning -Classical conditioning e.g. @ hypothalamus -Emotional responses e.g. @ amygdala
Despite all subdivisions of long term memory, what are the 4 stages in the process of learning?
- Encoding (memory creation)
- Storage (persistence of memory traces)
- Retrieval (memory recovery)
- Consolidation (strengthening of memory traces)
Describe the events and structures involved in memory formation?
A) A series of events are encoded by the hippocampus, and a reference is made to their memory location – hippocampal index (File Allocation Table)
B) If this information is recalled prior to consolidation, the hippocampus performs the retrieval from its index of the events
C) After consolidation of the memory retrieval can be initiated directly from the sensory cortices
How is Plasticity in LTM is used ?
Treating post traumatic stress disorder.
Patients are asked to re-live the events leading to PTSD then given an adrenergic beta receptor blocker (propranolol) which blocks re-consolidation of the memory
Where does consolidating declarative memory take place?
Medial temporal lobe
