Learning and memory Flashcards
What is learning?
The process of acquiring information
What is memory?
Stored, retrievable information
Not a copy but interpretation of the environment often subjective, emotionally loaded representation
What are the memory processes?
Encoding
Storage
Retrieval
Reconsolidation/ Updating/Forgetting
What is encoding?
Converting information into useable, “processable” and “storable” form
What is storage?
Holding information (later use)
What is retrieval?
Recall of stored information
What is reconsolidation?
Memory traces become labile when recalled. Review/ repetition reconsolidates the trace
What is updating?
New experience modifies earlier memory traces. Similar situations can result in recall but then consolidation of an altered memory trace
What is forgetting?
“fading” and removal of stored information. Lack of reconsolidation?
What is Semantic memory?
Facts- words and their meanings, people, faces, objects, concepts- all filled into discrete categories. Conscious
What is Episodic memory?
“Snapshots” of life events. Conscious
What is declarative memory?
“Knowing that”
Memory of facts and events, and refers to those memories that can be consciously recalled
What is procedural memory?
“Knowing how”
Information acquired and retrieved unconsciously,including motor and cognitive skills and classical conditioning
Where in the brain is semantic and declarative memory occur?
Neocortex
Where in the brain does episodic memory occur?
Hippocampus
Where is the brain does procedural memory occur?
Basal ganglia, cerebellum
What is priming?
A earlier stimulus facilitates the recognition/identification of a second related stimulus
What is non-associative learning paradigms?
Learning about a single stimulus
Habituation (decreasing response to the stimulus)
Sensitisation (increasing response to the stimulus)
What is associative learning paradigms?
Classical conditioning- learning a relationship between two stimuli (cerebellum)
Fear conditioning- instantaneous association between a neutral and a fearful stimulus (depends on the amygdala)
Operant conditioning- learning a relationship between the organism’s behaviour (e.g. movement/act) and the consequences of that behaviour
What did Pavlov do?
Pavolv’s dog
Conditioned dog to associated bell sound with getting food
What is operant conditioning?
Skinner’s operant conditioning chamber (1930/31)
Animal’s action (e.g. pressing a lever) and consequence of that action for the animal
What is reinforcement?
e.g. food reward→ action repeated with increasing probability/frequency
What is punishment?
e.g. food shock→ action will be avoided
What is self stimulation?
Stimulating electrode or drug application canule in the brain- model of addictive behaviour (Olds and Milner, 1954)
What are other forms of learning?
Imprinting
What is imprinting
Instantaneous non-conditional form of learning: e.g. “filial imprinting” in which a young animal (hatching birds) learns the characteristics of its parents
Examples of imprinting
Konrad Lorenz (1903- 1989) Studied instinctive behaviour and imprinting in birds Angelo d’Arrigo (2006). Bird chicks hatch under the wing of his glider, and imprinted on him. Subsequenty, he taught the fledglings to fly, hunt and to migrate
What is the most common model which explains the formation of long-term (declarative) memories?
The multi-stage model
What is the multi-stage memory model?
Information is presumed to be stored for increasing length of time at a series of “stages” in the brain:
Sensory memory
Short-term (working) memory
Long-term memory
Depending on condition, information can be “transmitted” from one stage to the next and stored for a longer period OR erased/ forgotten
What is sensory memory?
Initial short-term storage of sensory information in its “elementary” form
Decays rapidly if not attended
What is iconic memory?
Visual sensory memory system. Capacity/level of detail high. Duration- approximately ½ second
What is echoic memory?
Auditory sensory memory system. Duration- typically 2-3s; but could last up to 10 seconds
What is short term (working) memory?
A low capacity system in which information is consciously held for a short period (e.g. remember a telephone number until dialing). Requires active maintenance (e.g. rehearsal of the verbal information or refreshing visual information)
What is the capacity of STM?
Approx. 7 plus or minus 2 units (Miller, 1956)
What is the capacity of STM enhanced by?
“chunking” (optimal: 3-element chunks)
What is the duration of STM?
approx. 20-30 seconds
How can information be transferred to long-term memory?
Extensive rehearsal (e.g. linking new information with existing knowledge in long-term memory)
What are disorders of memory?
Retrograde amnesia
Anterograde amnesia
Dementia
What is retrograde amnesia?
Loss of memories (But ability to learn is preserved)
What are mild forms of retrograde amnesia?
Typical, ‘mild’ form- post-traumatic amnesia due to head injury (concussion) no memories of the events preceding/leading to the accident
What are the severe forms of retrograde amnesia?
Infections (e.g. encephalitis), sever head injury all past/personal memories erased
What is anterograde amnesia?
Loss of the ability to form new memories, to learn (BUT past memories are preserved
What was the case of HM?
Had drug-resistant temporal lobe epilepsy
At the age of 27, H.M. underwent brain surgery middle part of his temporal lobe including the hippocampus was removed
H.M. was “cured”: he had no epileptic seizures BUT he developed a severe anterograde amnesia
Over the years he developed a very good working memory (enhanced time span by rehearsal)
Could also learn new skills/motor tasks
What is our ability to form new memories dependent on?
Hippocampus
What are the affects of dementia?
Affects memory (amnesia): Progressive loss of memory Progressive loss of the ability to learn But there is also: Deterioration in language, thinking and other cognitive functions
What are the forms of dementia?
Alzheimer’s (50%)
Vascular (20%)
Lewy body (20%)
Other (10%)
What are the brain symptoms in early AD?
Symptoms include progressive memory loss, decline of abstract thinking, poor judgment, confusion, mood changes, depression and/or anxiety
What happens in the brain in early AD?
Signs of AD are first noticed in the entorhinal cortex and the hippocampus. Neurones in these regions degenerate and die
Cholinergic neurons of the basal forebrain also start to degenerate early in the disease
What happens in the brain in severe AD?
In severe AD, extreme shrinkage occurs in the brain affecting the entire cortex
At this stage, patients are completely dependent on others for care
What is the hippocampus?
Phylogenetically old, simple cortex in the temporal lobes
Part of the so called limbic system
Where are the inputs and outputs of the hippocampus?
Neurocortex via the entorhinal cortex
What does the hippocampus play a role in?
Essential role in learning memory
What does the hippocampus interact with to form memories?
Neocortex
What was Ramon y Cajal (1897)?
Neurons are structural and functional units of the brain Neurons communicate via synapses Neurons are “polarised” • Dendrites- input • Axon- output
What is the information flow in networks?
The strength of synapses defines how information flows from one level to the next → Change in strength of synapses (synaptic plasticity) can serve learning
What is the concept of Hebb’s learning rule (1949)?
Synaptic strength is not constant and not randomly “assigned” but synapses become stronger between neurons if the two cells are simultaneously active
What is the experimental evidence of Hebb’s learning rule?
Long-term potentiation (LTP) (Bliss and Lomo, 1973)
What are synapses in memory?
Synapses can “remember” if they receive high-frequency strong leading to activation of the postsynaptic neurons. A long-term increase in the synaptic responses (long term potentiation, LTP) develops and serves as a “memory”
What are the properties of LTP?
Co-operativity
Associativity
What do co-operativity and associativity depend on?
Simultaneous activation of two inputs
What is cooperation?
Two weak inputs can produce LTP if activated together
What is association?
A weak input can produce LTP if paired with a strong one
What are AMPA receptors?
Fast, reliable transmission
Permeable for Na+
What are NDMA receptors?
Transmission depends on voltage
Blocked by Mg2+ at rest
Depolarisation relieves blockade
High Ca2+ permeability (Ca2+ acts as second messenger)
NDMA receptor behaves in a “Hebbian-manner”, as it detects simultaneous presynaptic (transmitter release) and postsynaptic activity (depolarisation)
