Chapter 12: Learning and Memory

Learning

Adaptive behavior change that results from experience.

Associative Learning

The process by which an association between two stimuli is established

Nonassociative Learning

Change in the strength of response to a stimulus after repeated exposures

Associative Learning (Conditioning) Includes

classical conditioning, operant conditioning, appetitive conditioning, avoidance/aversive conditioning (active/passive avoidance)

Nonassociative Learning Includes

Sensitization and Habituation

Appetitive Conditioning

Reinforcement of a behavior by a positive outcome.

Avoidance Learning

A change in behavior to avoid some noxious outcome (or to end a negative stimulus/reinforcer)

Active Avoidance

a type of learning in which an individual must perform an action to avoid a noxious situation

Passive Avoidance

a type of learning in which an individual must suppress some behavior that would otherwise be exhibited

Sensitization

Progressive amplification of a response after repeated administrations of a stimulus

Habituation

Decrease in response to a stimulus after repeated exposures.

Memory

The encoding, storage, and retrieval of information about past experience.

Memory Includes

Sensory Memory, Short-term Memory (spatial and nonspatial), Working Memory. and Long-term Memory (spatial and nonspatial)

Long-term Memory

can be divided into declarative and procedural memory

Working Memory

the part of short term memory involved with immediate conscious perceptual and linguistic processing

Declarative Memory

Memory for facts and events.

Procedural Memory

Memory that stores long-term information about how to perform procedures, such as walking, swimming, riding a bike

Arousal and Learning

If arousal is too low or too high, learning is affected negatively

Measuring spatial memory in rodents with 2 Methods:

Morris Water Maze and Radial Arm Maze

Morris Water Maze

Rats must swim to find a submerged platform using only extra-maze clues around the tank. If normal, rats will learn to navigate to the platform from any position. Each day rats swim more directly. If neocortex lesioned, rats swim aimlessly until they discover submerged platform.

Radial Arm Maze

Maze open at the top and has many arms (more arms = more difficult). during training, rat learns that some arms are baited with food reward. To be successful, rat must make one trip down each baited arm and avoid unbaited arms. Navigation via extra maze clues. Task uses short term (working) memory and long term memory.

Epinephrine and Memory

E enhances memory, but it is dose- and time-dependent (otherwise too high/low blood levels of E impair memory)

E increases blood glucose, which facilitates the movement of glucose into neurons, which stimulates the release of more Ach into synapses

Time-dependent E injections

Most effective when given 1 minute after training. After 1 hour, ineffective.

Optimal E dose in rats

0.1 mg/kg which yield 1500 pg/mL blood concentration of E. (middle of inverted U curve)

Glucocorticoids and Memory

Acutely high levels of glucocorticoids (stress) enhance memory, but chronically high or levels too low impair

Effect of Glucocorticoids

They influence the structure/function in the hippocampus and amygdala

Food-caching Mountain chickadees

Corticosterone increased when receiving limited and unpredictable food vs ad libitum food

fewer sites inspected = better memory performance when receiving unpredictable food

Sex Differences in Radial Arm Mazes

Male rats and mice outperform Females

Males make more correct choices and fewer errors than Females

Sex Differences in Learning

Male rodents often outperform females in spatial tasks.

Estradiol and Memory

Estradiol enhances memory, especially spatial memory in human and non-human animals

Estrogens support memory but depends on:

which cognitive processes being studied

timing of hormone administration

gonadal state of individual

Androgens and Learning/Memory

Don't have major effects on learning/memory in rats (castrated and in-tact males learned the maze equally well)

However, learning/memory effects reported during breeding season in some species, when androgens are higher

Peptides that enhance memory

ACTH, Vasopressin (dose- and time-dependent), Cholecystokinin (CKK)

Peptides that impair memory or have inconsistent findings

Oxytocin (inconsistent/contradictory), Endogenous opioids

Cholecystokinin (CCK) and Learning/Memory

CKK enhances memory in mice

• Mice from 2 food-restricted groups, and 1 group that was fed freely

• Mice learned to avoid electric shock from one arm of T-maze

• 1 food-restricted group and 1 group that was fed freely received food immediately after training, whereas the other food-restricted group received food 3 hrs after training

CKK and Memory in Mice (Results)

The food-restricted mice that were fed immediately had the best retention when tested after 1 wk

Food caused hungry mice to secrete CKK shortly after training.

Peptides and E in the CNS

They act centrally in the CNS affecting memory

They act as NT rather than Hormones