Learning and memory

what is significant about the HM study in memory research

he had anterograde amnesia, which is the inability to form new memories

What brain structures were removed in HM's surgery?

Amygdala, hippocampus, and part of the frontal cortex.

what are some tests of memory

recognition and recall

paired association task

digit span + 1 task

priming tasks

What types of memory tasks did HM perform poorly on?

Recall, paired association, and digit span tasks.

what are recognition and recall tests

given lists of words or images to study, and asked to recall the list

what is paired association task

given pairs of unrelated words to remember

what is digit span +1 task

asked to repeat back numbers, adding a number each time to the sequence after successful recall

what are priming tasks

word stem compeltion

perceptual identification task

what is word stem completion

list of words given to study; the stem of the words are given (app_)

what is perceptual identification task

list of images given to study, an image is flashed quickly and asked to identify image

what are some tests of learning

mirror tracing task

reading mirror-reversed text

familiarity

what is mirror tracing task

trace various shapes using visual guidance via mirror

track errors per trial and track performance over multiple days

what is a typical progression of mirror tracing task

day 1 is improvement across trials

day 2 is baseline improvement

day 3 is mastery of task

what is reading mirror-reversed text

a perceptual task

what is familiarity test

shown images seen before and ask to guess whether the image was seen before

what is a test of association

classical conditioning paradigms

what is classical conditioning

netural stimuli, paired with an unconditioned stimulus that elicits a natural response

what is significant about patient KC

had retrograde amnesia and anterograde amnesia due to damage in frontal cortex and shrinkage of hippocampus from motorcycle accident

what is important about memory

memory is complex

memory is not in one spot (hippocampus)

not all memory is consious

what are the 2 types of long-term memory

declarative

nondeclarative

what is declarative long-term memory

things you know that you can tell others

what is nondeclarative long-term memory

things you know that you can show by doing

describe the proposed flow of information through the brain

sensory processing in cortex → parahippocampal, entorhinal, perirhinal cortex → hippocampus → medial diencephalon including mammillary bodies → declarative memory storage in cortex

describe the long-term memory tree

describe the convergence hierarchy into the hippocampus

What are the receptive field properties of lateral entorhinal cortex (LEC) neurons?

LEC neurons respond to non-spatial features such as object identity, odor, or contextual cues—they encode information about what is present.

What are the receptive field properties of medial entorhinal cortex (MEC) neurons?

MEC neurons, including grid cells, encode spatial information—specifically, location, head direction, and movement speed.

What are place cells, and where are they found?

Place cells are neurons in the hippocampus that activate in specific spatial locations, forming a spatial map.

What are grid cells and where are they located?

Grid cells in the medial entorhinal cortex fire in a hexagonal spatial pattern and provide a spatial coordinate system.

What experimental setups are used to infer receptive fields of LEC neurons?

Tasks involving object recognition, novelty detection, or object-in-place associations in arenas with discrete items.

What experimental setups are used to infer receptive fields of MEC neurons?

Open-field exploration tasks with no objects, often testing for grid-like firing patterns during movement through space.

what are border cells

a type of neuron found in the medial entorhinal cortex (MEC) that fire specifically when an animal is near the edge or boundary of its environment

what are head direction cells

cells whose firing pattern depends on head direction

What is a place field in the hippocampus?

It’s the specific location in an environment where a place cell fires most strongly, forming a neural map of space.

What does the Lateral Entorhinal Cortex (LEC) code for?

LEC encodes object-related information, including object identity and position.

what are object cells and where are they found

cells that respond to objects placed within an envrionment that is located in the LEC

what are trace cells and where are they found

encode where an object was and fire when object is removed, located in the LEC

How can animal models of spatial navigation relate to other cognitive functions?

Tasks like maze navigation and context discrimination also model episodic memory, context-dependent learning, and cognitive flexibility relevant to human cognition.

What types of evidence test whether the hippocampus is necessary for memory?

Lesion studies, temporary inactivation, and optogenetics show that disrupting the hippocampus impairs tasks like spatial learning, contextual fear, and episodic memory.

what are the conclusions for lesion studies of LEC and MEC

LEC lesion impairs object memory

MEC lesion impairs contextual memory

what is global remapping

when one spatial map is replaced by another when an entity goes into 2 different environments

what is rate remapping

occurs when nonspatial/less spatial stimuli (local cues, objects, testing chamber) change but main environment remains the same

How is episodic memory formed in the brain?

Through convergence of spatial (MEC) and object (LEC) inputs in the hippocampus, forming rich contextual representations.

What type of memory is the hippocampus most critical for?

Declarative (explicit) memory, especially episodic memory—memory for events tied to specific times and places.

What are three alternate memory systems to the hippocampus and their brain regions?

• Striatum: Procedural memory (habits, skills)

• Amygdala: Emotional memory (fear conditioning)

• Cerebellum: Motor learning (e.g., eyeblink conditioning)

what is the key characteristics of early sensory processing

firing rate increases directly with stimulus intensity

what are the key characteristics of higher-level memory processing

complex, distributed patterns encode specific experiences

What is the function of the dorsal striatum in memory?

It supports habit learning and stimulus-response associations.

How does the amygdala influence memory?

It enhances memory consolidation via emotional arousal and mediates both fear and reward-based conditioning.

What was shown in hippocampal lesion studies using water mazes?

Hippocampal lesions impair flexible spatial navigation but not simple place learning.

what are the subtypes of nondeclarative long-term memory

skill learning

priming

associative learning

what is priming

exposure to a stimulus faciliatates subsequent responses to the same or similar stimulus

what is skill learning

learning to perform a task requiring motor coordination

what is associative learning

the association of two stimuli or of a stimulus and a reponse

what are the different types of skills

sensorimotor skills (mirror drawing task)

perceptual skills (mirror reading task)

cognitive skills (puzzles involving planning and problem solving)

what are the brain areas involved with skill learning

basal ganglia

motor cortex

cerebellum

what are the differences between hippocampal and dorsal striatum memory systems

hippocampal

• cognitive/place/detailed/rational memory

dorsal striatum

• habit, stimulus-response

what are the advantages of cognitive vs. habit memory

hippocampal memory — flexible

striatum/habit: fast, automated, unconscious

support each other, lead to the same goal/behaviour

what are the tradeoffs of cognitive vs. habit memory

habits can lead to mistakes when a response is applied in the wrong situation

impaired hippocampal function/overactive striatum may contribute to exaggerated habit-like behaviour in addiction, anxiety, autism, tourette’s syndrome

what are the types of associative learning

reflexive conditioning

appetitive/aversive conditioning

what is reflexive conditioning

conditioned automatic reflexive behaviour — cerebellum

what is appetitive/aversive conditioning

an organism learns to associate a neutral stimulus with an emotionally significant outcome — either positive (rewarding) or negative (punishing).

What is the role of the amygdala in fear conditioning?

It forms associations between neutral stimuli and aversive outcomes, producing conditioned fear responses.

What is a 'cell assembly' in Hebbian theory?

A network of neurons with strengthened connections due to repeated simultaneous activation, allowing pattern completion and associative memory.

What is the principle behind Hebbian plasticity?

cells that fire together, wire together. simultaneous activation strengthens synaptic connections

What is long-term potentiation (LTP)?

A long-lasting increase in synaptic strength following high-frequency stimulation of a synapse, often considered a cellular basis for learning and memory.

What is late LTP (L-LTP)?

A longer-lasting form of LTP (hours to days or more), requiring gene expression, protein synthesis, and structural changes at synapses.

What is early LTP (E-LTP)?

A short-lasting form of LTP that lasts minutes to hours and involves post-synaptic modifications without requiring new protein synthesis.

What are three fundamental properties of LTP?

• Input specificity – Only the active synapse is strengthened

• Cooperativity – Multiple weak inputs can trigger LTP if they co-activate

• Associativity – Pairing a weak input with a strong one can strengthen both

What initiates NMDA receptor activity during LTP?

Glutamate binding + postsynaptic depolarization (removes Mg²⁺ block).

What changes occur at the synapse after LTP?

Increased AMPA receptor function and number, and enhanced neurotransmitter release.

What is synaptic tagging and capture?

a mechanism where a weakly stimulated synapse can capture memory proteins made during a nearby strong stimulus, enabling long-term memory formation

what is flashbulb memory

a type of vivid, detailed, and long-lasting memory for the context in which a person first learned about a surprising, emotionally significant, or shocking event.

How have scientists artificially activated specific memories?

Using optogenetics, researchers can label neurons active during learning and later reactivate them with light to trigger recall or behavioral responses.

What is an example of artificial memory activation in rodents?

In one study, rodents formed a memory in context A, but when neurons from A were reactivated in context B using light, the rodents froze—indicating recall of the fear memory.

What are 'engram cells'?

Neurons that store specific memories. Artificial reactivation (e.g., via optogenetics) can induce recall of the encoded memory.

How can false memories be created using optogenetics?

By activating engram cells during an unrelated aversive experience, causing mice to associate fear with a previously safe context.

describe negative to positive memory conversion

session 1: negative memory engram cells labelled with ChR2

session 2: activating those negative engram cells when mice enter a certain place causes mice to avoid that place

session 3: negative engram cells are activated while mice undergo a positive experience

session 4: subsequent activation of those engram cells, when mice visit a certain place, causes mice to prefer that place