Learning and Memory Flashcards
BRAIN CHANGES
- some brain changes (BD/brain stimulation) can effect human beh/perception/cog/emotions/memory
- other changes occur in brain/NS during prenatal development in early life
- changes continue in later life w/ongoing experience/when aging/in dif contexts/environments as during early years
EXPERIENCE-DEPENDENT PLASTICITY
- changes caused by previous experience can be observed at level of:
BEHAVIOUR - actions/emotions/knowledge
NEURONS - neural network activity
SYNAPSES - interactions between individual neurons
HM
- BD often causes memory loss for earlier events (retrograde amnesia) within limited time period of hours/days/years
HM (1926-2008) - severe epilepsy; underwent bilateral medial temporal lobotomy; anterograde amnesia (LTM loss for new events/newly learned info) after surgery
- most of HM’s hippocampus/amygdala/subcortical regions/entorhinal cortex = damaged; some probs spared
- parahippocampal cortex fully removed
DIF BRAIN AREAS INVOLVED IN MEMORY FORMATION
- HM’s cog abilities/STM/episodic memories/info learned pre-operation = largely preserved
- could acquire new motoric skills (ie. tracing shape in mirror) BUT couldn’t recall performing same task before
SCOVILLE & MILNER (1957) - provided first evidence for involvement of hippocampus in memory formation (confirming Bekhterev’s observations)
THE MEMORY ENGRAM
LASHLEY (1929/1950)
- maze-learning exps w/rats w/parts of cerebral cortex surgically removed
- unsuccessful in attempts to find memory engram (localised memory trace in cortex)
- concluded that learning & memory not located in single area of rat cortex BUT distributed widely across brain
NEUROPSYCHOLOGY/PSYCHIATRY RESEARCH LIMITS
- major limits for investigating causal relations between neural substrates/beh/psych processes in humans
- ethical consideration of brain manipulations/measurements
- number of patients w/lesions = small
- cases don’t generalise
- coarse damage across functional units
- possible compensatory processes (beh change/functional reorganisation of brain circuits)
NEUROPSYCHOLOGY/PSYCHIATRY RESEARCH POSITIVES
- (specifically animal models)
- overcome some ethical limits
- replication/precision of lesions
- availability/sample sizes (2-3 pps in primates; more in rodents/non-mammalian models (ie. sea hare Aplysia/Drosophila flies/zebrafish larvae)
- systematic study of wider method/beh/psych processes range providing circuit/synaptic level insights
SURGICAL LESIONS VARY IN PRECISION
- rhinal cortex includes entorhinal/perirhinal cortex in medial temporal lobe
- traditional method in experimental neuroscience to causally infer bran area function
- neurons ablated applying physical (ie. suction)/pharmacological (ie. neurotoxin injections/pathologically high neurotransmitter concentrations) methods
- neuron loss = permanent/significant damage of non-target tissues in surrounding areas
OPTOGENETICS: PRECISE TEMPORARY INACTIVATION OF NEURONS
- ChR2 = channel-rhodopsin
- NpHR = halo-rhodopsin
- functional control of targeted cell types using light of specific wavelength
- micro-stimulations during beh tests w/high spatial/temporal precision
- reversible/temporary manipulations allowing in-pp comparisons
- light-sensitive molecules inserted in membrane via genetic tools; animals selectively bred to generate transgenic lines to investigate specific brain circuits
- genetically tractable models (ie. mice/Drosophila flies/zebrafish larvae)
EPISODIC-LIKE MEMORIES IN NON-HUMAN ANIMALS
- episodic memory = recall of unique experiences explicitly located in past (“mental time travel”) as conscious experience; language based reports
- delayed non-matching to sample task (DNMST)
- test requirements = specific events/objects; familiarity/novelty; context/environment; time
- ability to form/recall memories for personally experienced past events tied to specific context
- novelty/familiarity judgements (delayed non-matching to sample)
CLAYTON & DICKINSON (1998) - retrieval of when/where/what memories
- learning of context-dependent tasks in scrub jays
TARGETED LESIONS IN MEDIAL TEMPORAL LOBE
SQUIRE & ZOLA-MORGAN (1991)
- hippocampus involved in encoding specific items in context during LTM formation
- perirhinal cortex important for familiarity sense
- parahippocampus encodes context representations
DECLARATIVE LTM MEMORY
CLARK (2019)
FAMILIARITY/KNOWING WHAT
- declarative (episodic (events)/semantic (facts)) -> medial temporal lobe
- hippocampus (HM)
- mamillary bodies (NA/Korsakoff syndrome)
- neocortex (KC)
NON-DECLARATIVE LTM MEMORY
CLARK (2019) KNOWING HOW 1. PRIMING - neocortex - exposure to stimulus improves responses to same/similar stimulus 2. NON-ASSOCIATIVE - reflex pathways - brainstem; medial cerebellum parts - startle response 3. PROCEDURAL - striatum - basal ganglia - acquisition of motor skills/habits 4. CLASSICAL CONDITIONING (EMOTIONAL/SOMATIC) - E = amygdala (fear conditioning) - S = cerebellum (eye-blink conditioning/sensorimotor tasks)
NON-ASSOCIATIVE LEARNING: HABITUATION
- response weakens w/repeated stimulus presentation due to repetition BUT not due to senses/fatigue adaptation
- NOT extinction of associations acquired via learning
NON-ASSOCIATIVE LEARNING: DISHABITUATION
- repeated tactile stimulation of siphon leads to reduced gill withdrawal response
- response reinstated after stimulation via dis stimulus
LTM X NON-ASSOCIATIVE LEARNING
CAREW (2000)
- training sessions over 4 days (T1-T4)
- memory recall test on next day (R1)
- test week later (R2)
- memory retained for 3 weeks (R3)
PAVLOV’S DOG
PAVLOV (1849-1936)
- when dog receives food, it salivates (UR (unconditioned response)); dogs already salivating before given food
PD: CS-US CONTINGENCY
- if sound (CS) always shortly precedes food (US) then dog will learn that sound predicts food SO starts to salivate (CR) on hearing sound
- contingency = CS predicts occurrence of US meaning; its contingent on prior occurrence of CS
PD: APPETITIVE ASSOCIATION
- degree of CS/US coincidence determines learning outcome
- temporal contiguity = reinforcement most effective if reward coincides/follows CS shortly after (forward CS/US pairing)
- US should be unexpected/surprising prior to conditioning; animal needs to attend CS
EYE-BLINK CONDITIONING
- prior to training:
- US = air puff; UR = eye blink
- CS = tone; CR = tone alone elicits eye blink
- neuronal circuit involves cranial nerves/nuclei connecting interneurons/cerebellum
- sensory input US: trigeminal nerve (cranial nerve V)
- CS input = auditory nuclei
- motor output = cranial nerves VI/VII (fascial/eye muscles)
CONTEXTUAL/CUED FEAR CONDITIONING
- mild foot shock elicits freezing/increased blood pressure/heart beat
- cued conditioning (tone predicts punishment)
- contextual conditioning (box alone predicts punishment)
STIMULUS-RESPONSE LEARNING
THORNDIKE (1898)
- proposed animals learn based on outcomes of actions (Law of Effect)
- when response followed by reinforcer, stimulus-response (S-R) connection strengthened
OPERANT CONDITIONING
WATSON/SKINNER
- strongly influence ideas -> 1920s behaviourism emergence as research field dedicated to operant conditioning study
- reinforcement learning = if beh reinforced, it’ll be repeated/extinguished
- animals mainly tested in boxes (Skinner’s box)
TEMPORAL MEMORY FORMATION STAGES
- shortest memories in sensory buffers (iconic memories) ie. during reading when eye makes saccade
- STM/WM = few seconds to maximally few min long
- intermediate memory = longer but not like LTM
ENCODING/RETRIEVAL/CONSOLIDATION
- brain activation patterns differ when info encoded/acquired and later recalled (ie. recognition of visual stimulus)