Module 12.1: Learning, Memory, and Amnesia

1. Module 12.1:Learning, Memory, and Amnesia

2. Learning, Memory, and Amnesia • An early influential idea regarding localized representations of memory in the brain suggested physical changes occur when we learn something new. • One popular idea was that connections grow between areas of the brain.

3. Learning, Memory, and Amnesia • Ivan Pavlov researched classical conditioning in which pairing of two stimuli changes the response to one of them. • Presentation of a conditioned stimulus (CS) is paired with an unconditioned stimulus (UCS). • Automatically results in an unconditioned response (UCR). • After several pairings, response can be elicited by the CS without the UCS, which is known as a conditioned response (CR). Ivan Pavlov (1849-1936)

4. Learning, Memory, and Amnesia • In operant conditioning,responses are followed by reinforcement or punishment that either strengthen or weaken a behavior. • Reinforcers are events that increase the probability that the response will occur again. • Punishment are events that decrease the probability that the response will occur again.

5. Learning, Memory, and Amnesia • Pavlov believed that conditioning strengthened connections between the CS center and UCS center in the brain. • Karl Lashley set out to prove this by searching for such engrams, or physical representations of what had been learned. • Believed that a knife cut should abolish the newly learned response. Karl Lashley (1890-1958)

6. Learning, Memory, and Amnesia • Lashley’s studies attempted to see if disrupting certain connections between cortical brain areas would disrupt abilities to learn associations. • Found that learning and memory did not depend on connections across the cortex • Also found that learning did not depend on a single area of the cortex.

7. Learning, Memory, and Amnesia • Lashley proposed two key principles about the nervous system: • Equipotentiality – all parts of the cortex contribute equally to complex functioning behaviors (e.g. learning) • Mass action – the cortex works as a whole, not as solitary isolated units.

8. Learning, Memory, and Amnesia Richard F. Thompson (1930-2014) • Research by Richard F. Thompson and colleagues focused on the cerebellum’s role in classical conditioning. • During an eye-blink conditioning task in rabbits, changes were recorded in cells of the lateral interpositus nucleus (LIP).

9. Learning, Memory, and Amnesia • Suppression of activity (through application of drugs or cooling the LIP) led to a condition in which the subject displayed no previous learning. • As suppression wore off, the animal began to learn at the same speed as animals that had no previous training. • Red nucleus of the midbrain found to temporarily suppress a response, but not learning

10. Learning, Memory, and Amnesia • Short-term memory (STM)– memory of events that have just occurred • Limited capacity • Fades quickly • Not affected by cues • Long-term memory (LTM)– memory of events from previous times • Unlimited capacity • Memories persist over time • Can be stimulated with a cue Donald Hebb (1904-1985) differentiated between two types of memory(1949):

11. Learning, Memory, and Amnesia Alan Baddeley & Graham Hitch • Later research weakened the distinction between STM and LTM. • Some memories do not qualify as distinctly short-term or long-term. • Working Memory • Proposed by Baddeley & Hitch (1994) as an alternative to short-term memory • Emphasis on temporary storage of information to actively attend to it and work on it for a period of time

12. Learning, Memory, and Amnesia Three major components of working memory include: • Phonological loop – Stores auditory input • Visuospatial sketchpad – Stores visual input • Central Executive – Directs attention and determines which items to store

13. Learning, Memory, and Amnesia • The delayed response task is a test of working memory which requires responding to a stimulus that one heard or saw a short while earlier. • Increased activity in the prefrontal cortex during the delay indicates storing of the memory. • The stronger the activation, the better the performance.

14. Learning, Memory, and Amnesia • Older people often have impairments in working memory. • Changes in the prefrontal cortex assumed to be the cause. • Declining activity of the prefrontal cortex in the elderly is associated with decreasing memory. • Increased activity is indicative of compensation for other regions in the brain.

15. Learning, Memory, and Amnesia • Amnesia is the loss of memory. • Studies on amnesia help to clarify different kinds of memories and their mechanisms. • Different areas of the hippocampus are active during memory formation and retrieval. • Damage results in amnesia.

16. Learning, Memory, and Amnesia • Patient HM is a famous case study in psychology who had his hippocampus removed to prevent epileptic seizures. • Afterwards HM had great difficulty forming new long-term memories. • STM or working memory remained intact. • Suggested that the hippocampus is vital for the formation of new long-term memories.

17. Learning, Memory, and Amnesia • Patient HM showed massive anterograde amnesia after the surgery. • Two major types of amnesia include: • Anterograde amnesia – the loss of the ability to form new memory after the brain damage occurred. • Retrograde amnesia – the loss of memory events prior to the occurrence of the brain damage.

18. Learning, Memory, and Amnesia • Patient HM had difficulty with declarative and episodic memory. • Episodic memory: ability to recall single events • Declarative memory: ability to put a memory into words • HM’s procedural memory remained intact. • Procedural memory: ability to develop motor skills (remembering or learning how to do things)

19. Learning, Memory, and Amnesia • HM also displayed greater “implicit” than “explicit” memory. • Explicit memory – deliberate recall of information that one recognizes as a memory • Implicit memory – the influence of recent experience on behavior without realizing one is using memory

20. Learning, Memory, and Amnesia • Hippocampus activity is more associated with memory performance than is the size. • The hippocampus is: • critical for declarative (especially episodic) memory functioning • especially important for spatial memory • especially important for configural learning and binding.

21. Learning, Memory, and Amnesia • Research in the role of the hippocampus in episodic memory shows damage impairs abilities on two types of tasks: • Delayed matching-to-sample tasks –a subject sees an object and must later choose the object that matches. • Delayed non-matching-to-sample tasks– subject sees an object and must later choose the object that is different than the sample.

22. Learning, Memory, and Amnesia Damage to the hippocampus impairs abilities on spatial tasks such as: • Radial mazes – a subject must navigate a maze that has eight or more arms with a reinforcer at the end. • Morris search task – a rat must swim through murky water to find a rest platform just underneath the surface.

23. Learning, Memory, and Amnesia • Hippocampus damage impairs configural learning and binding: • Configural learning – learning in which the meaning of a stimulus depends on what other stimuli are paired with it. • Animals with damage can learn configural tasks but learning is slow. • Indicates hippocampus is not necessary for configural learning, but is involved.

24. Learning, Memory, and Amnesia • Evidence suggests that the hippocampus is important in the process of “consolidation”. • Consolidation is the process of strengthening short-term memories into long-term memories. • Damage to the hippocampus impairs recent learning more than older learning. • The more consolidated a memory becomes, the less it depends on the hippocampus.

25. Learning, Memory, and Amnesia • Consolidation is influenced by the passage of time and emotions. • Small to moderate amounts of cortisol activate the amygdala and hippocampus where they enhance storage and consolidation of recent experiences. • Prolonged stress impairs memory.

26. Learning, Memory, and Amnesia • Different kinds of brain damage result in different types of amnesia. • Two common types of brain damage include: • Korsakoff’s syndrome • Alzheimer’s disease

27. Learning, Memory, and Amnesia • Korsakoff’s syndrome – prolonged thiamine (vitamin B1) deficiency impedes the ability of the brain to metabolize glucose. • Leads to loss or shrinkage of neurons in the brain • Often due to chronic alcoholism • Symptoms include apathy, confusion, and forgetting and confabulation (taking guesses to fill in gaps in memory).

28. Learning, Memory, and Amnesia • Alzheimer’s disease is associated with agradually progressive loss of memory often occurring in old age. • Affects 50% of people over 85. • Early onset seems to be influenced by genes, but 99% of cases are late onset. • About half of all patients with late onset have no known relative with the disease.

29. Learning, Memory, and Amnesia • Amyloid beta protein 42 which produces widespread atrophy of the cerebral cortex, hippocampus and other areas. • An abnormal form of the tau protein, part of the intracellular support system of neurons. Alzheimer’s disease is associated with an accumulation and clumping of the following brain proteins:

30. Learning, Memory, and Amnesia • Accumulation of amyloid beta and tau proteins results in: • Plaques – structures formed from degenerating neurons • Tangles –structures formed from degenerating structures within a neuronal body

31. Learning, Memory, and Amnesia Donepezil (Aricept)—cholinesterase inhibitor • A major area of damage is the basal forebrain and treatment includes enhancing acetylcholine activity.

32. Learning, Memory, and Amnesia • Lessons from studying amnesiac patients include: • One can be deficient in several different aspects of memory. • There are independent kinds of memory. • Various kinds of memory depend on different brain areas. Head Shot: In this diffusion spectrum image, fiber bundles are color coded according to their directions of impulse transmission. The Human Connectome Project uses diffusion spectrum and other cutting-edge neuroimaging techniques to map fiber pathways in the normal human brain.