Learning & Memory

Made by @agreyr

Learning

The process of aquiring information

Memory

The ability to store and retrieve the information learned

Patient H.M. (Henry Gustav Molaison)

Bicycle accident when young led to the development of severe epilepsy

At 27, surgeon performed bilateral medial temporal lobectomy in an attempt to stop his seizures

Bilateral medial temporal lobectomy

Removal of the medial portions of both temporal lobe, including most of the hippocampus, amygdala, and adjacent cortex

Amnesia

Severe impairment of memory

Retrograde amnesia

Loss of memories formed before a brain injury

Anterograde

Loss of memory for things occurring after a brain injury; inability to make new memories

Declarative memory

Explicit; things you know and can tell others; facts and information; semantic vs episodic memory

Semantic vs episodic memory

Semantic memory revolves around facts; episodic memory revolves around events

Non-declarative memory

Implicit; procedural memory; demonstrated by improved performance without conscious recall or recognition

Skill learning (sensorimotor), priming (words or pictures), and associative learning

Digit-span task

A test used to measure short-term memory where patients are asked to recall an increasingly longer series of numbers

Continued memory tests

Mirror drawing task, incomplete pictures task

Skill learning (sensorimotor)

Process of learning how to perform a challenging task by simply doing it over and over again; does not require the medial temporal lobe, but requires basal ganglia, cerebellum, and motor cortex

Priming (words or pictures)

A change in the way you perceive a stimulus, especially because you’ve seen it or something similar before; associated with reduced activation in the occipitotemporal cortex (word form) or left frontal cortex (word meaning)

Associative learning

Learning relationships between events (classical and instrumental conditioning)

Classical conditioning

In its simplest form, it requires cerebellum, not hippocampus

Instrumental conditioning

Learn that a certain action yields a certain consequence; no consistent brain region identified

Press the lever, food pellet; poke the nose hole, get foot shock

Global amnesia

Amnesia for information in all sensory modalities

Scientific contributions from H.M. and others

Memory functions are NOT diffusely and equivalently distributed throughout the brain

There are different modes of storage for short-term and long-term memories; demonstrated a role for medial temporal lobe in memory consolidation

Different mechanisms exist for procedural and non-procedural recall

Animal models of memory

Hippocampus, amygdala, and rhinal cortex are all damaged by bilateral medial temporal lobectomy; necessitated the creation of animal models to study brain-damage-induced amnesia

Object recognition memory tests/studies

Delayed nonmatching-to-sample test, Mumby box

Delayed nonmatching-to-sample test (monkeys)

Loss of the hippocampus, amygdala, and associated cortex in monkeys leads to impairments in object recognition

Mumby box (rats)

Only loss of the rhinal cortex in rats showed deficits in object recognition

Spatial recognition memory

Bilateral lesions of the hippocampus disrupt performance in spacial recognition tasks; many hippocampal neurons are place cells

Birds that store food have large hippocampi!

Spatial recognition tasks

Radial arm maze, use of cognitive maps

Place cells

Neurons that respond when a subject is in a specific location in the test environment

Memory systems summary

Short-term memory (working memory) —> prefrontal cortex, different regions for different attributes

Long-term memory —> declarative (explicit) vs nondeclarative (implicit)

Components of memory

Sensory buffers/input: fleeting memories/glimpses of a scene that vanish quickly

Short-term memory: short period of time during which you are actively attending to the information; waking memory refers to the ability to actively manipulate information while in STM

Long-term memory: Long lasting memories that persist even when you no longer attend to the information

Memory processes

Encoding, consolidation, retrieval, reconsolidation

Encoding

Getting raw sensory information into STM

Consolidation

Moving info from volatile STM to more durable LTM

Retrieval

Calling stored information back into working memory (STM) for use

H.M. showed that the medial temporal lobe…

…is NOT required to encode sensory info or retrieve the info from STM

… is CRUCIAL for consolidating declarative information from STM to LTM