Long-Term Memory: Ch. 9 & Lab 6

• Long-term memory is the main focus, with assigned reading from Ch. 9 and Lab 6 due March 21, instructed by Dr. Mugon at the University of Victoria, Spring 2025.

The Definition of Memory

• Memory encompasses processes, types, systems, and tasks, studied through methods like lesions and double dissociation.
• Short-term and long-term memory are distinct categories.
• Memory can be implicit or explicit.

Implicit Long-Term Memory

• This includes non-associative learning, conditioning, skill learning, and priming.

Explicit Long-Term Memory

• Semantic and Episodic memory fall under this category along with consolidation and reconsolidation.
• Learning is closely related to memory.
• Memory employs encoding, storage, retrieval, and potentially reconsolidation to maintain information.
• Memory involves multiple processes, including encoding, storage, and retrieval.
• Memory also contains semantic, episodic, and procedural types.
• Systems include the hippocampus, cortex, and amygdala.
• Tasks involve free recall, stem completion, and motor sequence learning.
• Memory requires physical changes in the nervous system and is pervasive within it.

Memory and Time

• Encoding is the initial step where incoming information creates memory traces in the brain.
• Consolidation involves the continued organization and stabilization of these memory traces over time.
• Storage is the retention of memory traces over time.
• Retrieval is the process of accessing or using stored information from memory traces.
• Reconsolidation may involve the reorganization and restabilization of memory traces after retrieval.

LTM Types & Systems

• Long-term memory splits into Declarative memory (explicit) and Nondeclarative memory (implicit).
• Declarative memory encompasses event or episodic memory and facts or semantic memory.
• Nondeclarative memory has procedural memory, perceptual representation, classical conditioning and nonassociative learning

Dissociating Short-Term & Long-Term Memory

• The question posed is whether STM and LTM are separate systems.
• Dissociation logic suggests separate systems if performance differs across tasks.
• Single dissociation occurs if one function is impaired while the other is spared, however this does not necessarily mean they are separate systems.
• Double dissociation, where two patterns are flipped, indicates stronger evidence for separate systems relying on different brain mechanisms.

Memory Task Examples

• Standard Short-term memory task involves hearing and immediately recalling a sequence of three words.
• A Standard Long-term memory task involves hearing a list of ten words and immediately recalling them in any order, repeating until all are recalled.

Patient Studies

• Patient K.F. with damage to the left temporoparietal cortex, exhibits single dissociation.
• Short-term memory tasks rely on the temporoparietal junction, which long-term memory tasks do not.
• Alternative explanations include the possibility of a single system damaged to varying degrees or compensation in one task due to damage.
• Patient H.M., with damage to bilateral medial temporal lobes, shows different dissociation patterns compared to K.F.
• Double dissociation, consisting of two areas of damage and two opposing single dissociations, is strong evidence that short-term and long-term memory are separable systems

Short-term vs. Long-term memory

• Short-term memory has timescales of seconds, limited capacity, and depends on sustained neuron activation.
• Long-term memory operates on timescales from minutes to years, possesses massive capacity, and relies on the number and strength of synapses.
• Explicit memory involves conscious recall, while implicit memory does not.

Dissociating Implicit & Explicit LTM

• An implicit memory task involves perceptual identification, where subjects are briefly shown words after a prior study phase.
• An explicit memory task involves word recognition, where subjects respond "yes" or "no" to indicate if words were from a prior study phase.

Patients with Impaired Memory

• Patient M.S., with damage to the right occipital lobe, shows impaired implicit memory (priming) but intact explicit memory (word recognition).
• Amnesia patients, such as those with Korsakoff’s syndrome or epilepsy, show impaired explicit memory (word recognition) but larger than normal priming effects in implicit memory.
• Double dissociation between cognitive and brain systems involved in perceptual identification and word recognition are evidence that systems are distinct.

Types of Long-Term Memory

• Implicit long-term memory is non-declarative, independent of conscious awareness and can include procedural memory, conditioning, non-associative learning, or priming.
• Explicit long-term memory is declarative, available to conscious awareness, and can be semantic or episodic.
• Implicit memory has a timescale of minutes, hours, days, years and capacity for thousands of motor skill sequences
• Explicit memory has a timescale of minutes, hours, days, years and capacity potentially 20,000 word families Both rely on the number and strength of synapses for neural basis.

Implicit Memory: Non-Associative Learning

• Non-associative memory results from a change in response to a single stimulus after repeated exposure.
• Habituation is a reduced response to a repeated stimulus, such as no longer noticing a clock's ticking.
• Sensitization is an increased response to a repeated stimulus.
• Non-associative learning involves sensory-motor reflex pathways.

Neural Basis of Non-Associative Memory

• First evidence was done by Eric Kandel by studying sea slug Aplysia.
• Habituation process where presynaptic depression occurs, the action potential remains the same but neurotransmitter release is reduced, causing a smaller EPSP.
• Sensitization process involves presynaptic facilitation, where the action potential remains same but increased neurotransmitter release and larger EPSP.
• "Short-term" changes in habituation/sensitization last minutes and is due to changes in neurotransmitter release
• "Long-term" changes in habituation/sensitization last hours, days, or weeks and is due to changes in synapse numbers

Classical Conditioning

• Pavlov noticed that a dog learned to salivate in response to a bell that predicted food.
• Unconditioned stimulus (US) is food.
• Unconditional response (UR) is salivation.
• Neutral stimulus (NS) is a bell before pairing.
• Conditioned stimulus (CS) is the bell after pairing.
• Conditioned response (CR) is salivation after pairing.
• US causes UR and paired CS causes CR
• Fear conditioning causes freezing

Fear Conditioning

• US is shock in fear conditioning
• UR, CS and CR is all freezing
• CS and US converge in lateral nucleus of amygdala

Motor skill learning

• Motor skill learning is motor system dependent.
• Motor adaptation relies on cerebellar loops.
• Motor sequence learning involves cortico-basal ganglia-thalamocortical loops.
• Cerebellum uses a forward model to predict the results of motor commands.
• Uses differences between actual results and what you predicted for: online error correction, motor learning and feedback.

Skill Learning: Motor Sequence Learning

• Serial reaction time (SRT) task involves responding to a sequence of lights, with repetition leading to faster response times without conscious awareness.
• Serial reaction time (SRT) depends on basal ganglia thalamo cortical loops
• Depends on basal ganglia and reinforcement learning for action performance, comparing predicted and actual rewards to update expectations.
• Dopamine signals prediction error, with larger responses for better outcomes and smaller for worse.
• Reinforcement learning is where unexpected rewards generate dopamine signals from the substantia nigra, exciting the direct pathway. Dopamine allows modification of behavior based on reward.