PSYC 132: Chapter 12

Learning and Memory

Learning

An adaptive change in behavior that results from experience

Associative learning (AKA conditioning)

Association between two stimuli is established

• Affected by hormones

Nonassociative learning

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

• Affected by hormones

Associative Learning: Types

• Classical

  • e.g. Pavlov’s dog

  • More reflexive behavior

• Operant

  • Punishment/reward

• Appetitive

  • Reinforcement via a positive outcome

• Avoidance/aversive

  • Change in behavior to avoid a noxious outcome

    • Active avoidance

      • Individual must perform an action to avoid noxious situation

      • * Negative reinforcement: Taking an Advil to get rid of an advil

    • Passive avoidance

      • Individual must suppress some behavior that would otherwise be exhibited

Nonassociative Learning: Types

• Sensitization

  • Progressive amplification of a response after repeated administrations of a stimulus

  • Increase of NT release

• Habituation

  • Decrease in response after repeated exposures

  • Decrease in NT release

Memory

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

• Sensory memory

  • Immediate (e.g. echoic memory)

• Short-term memory (spatial and nonspatial)

• Long-term memory (spatial and nonspatial)

Working memory

Part of short-term memory involved with immediate conscious perceptual and linguistic processing

Long-Term Memory

Can be divided

• Declarative (AKA Explicit)

  • Memory for facts or events

• Procedural (AKA Implicit)

  • Memory that stores long-term information about how to perform procedures

    • e.g. walking, swimming, how to ride a bike

Fig. 12. 2 Arousal and learning

Optimal performance on learning occurs at moderate levels of arousal

• Also influenced by hormones

Fig. 12.16: Morris water maze

A) Rats must swim to find a submerged platform hidden below the surface of milky water

• Requires relational learning (use cues around the tank)

• * More explicit learning

B) Healthy rats will learn to navigate directly to the platform

• If the hippocampus is lesioned, rats swim aimlessly until it finds the platform

Fig. 12.20 Radial arm maze

• Popularized by David Olton

• Open-top maze with 8, 12, 36, etc. arms depending on difficulty

• During training

  • Subject learns that only some arms are rewarded

  • Must learn to get reward on the first try

    • Requires LTM (reference) and STM (working; remembering which they went down already)

Memory: Epinephrine

(In general) Enhances memory but it’s dose- and time-dependent

• High and low blood levels of E impair memory

• Theory:

  • E increases blood glucose → movement of glucose into neurons → release of more ACh into synapses

Dose effect: Fig. 12.8 Effects of epinephrine on performance

Optimal dose in rats is about 0.1 mg/kg (1500 pg/ml)

Fig. 12.9 Effects of epinephrine on memory are time-dependent

Injections (1 mg/kg) are most effective in enhancing memory if given 1 minute after training.

• Effects diminish 60 mins after training

Glucocorticoids

Acutely high levels of corticoids (acute stress) enhance memory, chronically high (or low) levels impair

• Glucocorticoids seem to have effects by influencing the structure or function in the hippocampus and amygdala

Fig. 12.23: Food-changing mountain chickadees

• Corticosterone (stress) is elevated in birds receiving limited and unpredictable food as compared to birds receiving ad libitum food

  • Birds with unpredictable food visited fewer sites (indicating better memory performance)

Sex Differences in learning and memory

Male rodents perform better at spatial learning tasks than female rodents

• likely mediated by hormones

Estrogens

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

• Depends on:

  • Which cognitive processes are being studied

  • The timing of hormone administration

  • Gonadal state of individual

Fig. 12.26 Male rats and mice perform better on radial arm mazes than females

A) Male rats make more correct choices and make mistakes later in their tests

B) Males make fewer errors

Androgens

Do not have major effects on learning and memory in rats

• e.g. Castrated and intact male rats learned mazes equally well

  • Organizational effect

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

  • Activational effect

Peptides (5)

Adrenocorticotropic Hormone (ACTH)

• Enhances memory

Oxytocin

• Inconsistent results

Vasopressin

• Enhances memory but dose and time dependent

Endogenous opioids

• Usually have amnestic (decreased memory) properties

Cholecystokinin (CCK)

• Enhances learning and memory

• * These 5 peptides (+ E) have been noted to acted centrally (i.e. in the CNS) in affecting memory

  • Acting as NT rather than hormones

Fig. 12.36: CCK enhances memory in mice

• Mice learn to avoid an electric shock in one arm of a T-maze

• 3 groups:

  • 1) Food restricted mice fed immediately after training

  • 2) Food restricted mice fed 3 hours after training

  • 3) Freely fed mice fed immediately after training

• Food restricted that were fed immediately (1) performed the best

  • The food likely caused the hungry mice to secrete cholecystokinin (CCK) shortly after training