Understanding Learning and Memory: Processes and Types

1. Chapter 14 The Biology of Learning and Memory

2. Learning and Memory Definition • Learning • A long term change in behavior as a function of experiences. • Memory • The capacity to retain and retrieve past experiences.

3. Types of Learning • Habituation • A decrease in response following repeated exposure to a non-threatening stimulus. • Sensitization • An increase in reactivity to a stimulus following exposure to an intense event. • Classical (Pavlovian)Conditioning • Occurs through associations between an environmental stimulus and a naturally occurring stimulus. • Operant Conditioning • Learning that occurs through rewards and punishments for behavior.

4. Types of Learning:Pavlovian Conditioning • Learning in which a neutral stimulus is paired with a stimulus that elicits a reflex response until the neutral stimulus elicits the reflex response by itself. • Unconditioned stimulus (US) - A stimulus that involuntarily elicits a reflexive response. • Unconditioned response (UR) - A reflexive reaction to an unconditioned stimulus. • Conditioned stimulus (CS) - An initially neutral stimulus that eventually elicits a conditioned response after pairing with a US. • Conditioned response (CR) - A learned reaction to a CS.

5. Classical Conditioning

6. Types of Learning: Operant Conditioning • Learning how to behave to obtain reinforcement • Reinforcers - events or activities that increase the frequency of the behavior that precedes that event or activity. • Punishers - events or activities that decrease the frequency of the behavior that precedes them. • Contingency -The specified relationship between a behavior and its reinforcement or punishment.

7. Operant Conditioning

8. Models of Memory Storage and Retrieval: Atkinson-Shiffrin model • An experience is sequentially stored in the sensory register, and the short-term store, and the long-term store.

9. Models of Memory Storage and Retrieval: Baddeley’s Rehearsal Systems approach • An alternative to Atkinson-Shiffrinin which Baddeley argued that memories go directly from the sensory register to long-term storage.

10. Models of Memory Storage and Retrieval: Craik and Lockhart • Craik and Lockhart - have a theory that memories differ in the extent to which they have been processed.

11. Types of Memories

12. Types of Memories

13. Declarative Memory • Memory whose formation does depend on the hippocampal formation • Memory that can be verbally expressed • Episodic memory • Semantic memory • Spatial memory • Slow-wave sleep facilitates consolidation of declarative memories

14. Role of the Hippocampus • Input from motor and sensory association cortexes and from subcortical regions such as basal ganglia and amygdala • Through efferent connections with these regions modifies the memories being consolidated there, linking them together • A gradual process controlled by the hippocampus transforms memories into long term storage in the frontal cortex • Before process completes, hippocampus is necessary for retrieval

15. Procedural Memory • Memory whose formation does not depend on the hippocampal formation • Collective term for stimulus-response, perceptual, and motor memory • Non-declarative memories control behaviors • Learning to drive, type • REM sleep facilitates retention of non-declarative memories • Ian Waterman

16. Perceptual Learning • Learning to recognize stimuli occurs when synaptic changes take place in the appropriate regions of the sensory cortex that establish new neural circuits • Learning to recognize sensory stimuli • Primary visual cortex • Ventral stream – object recognition • Dorsal stream – object location • Other sensory information activate similar areas of the association cortices

17. Perceptual Short-term memory • Activates the circuits and continues after the stimuli disappears • Successfully remembering short-term is a two step process • Filter out irrelevant information • Maintain relevant information • Also in prefrontal cortex • Manipulate and organize • Strategies for retrieval • Delayed matching-to-sample task • Faces – fusiform face area – face blindness • Places – parahippocampal place area

18. The Anatomy of Learning and Memory: Procedural Memory • Procedural or nondeclarative memory involves the neocortex and neostriatum. • Basal ganglia structures needed for procedural learning • Classical conditioning of reflexes depends on the cerebellum.

19. (Budson & Price, 2009)

20. The Memory Consolidation Process:Hebb’s Cell Assemblies • Cell assembly - A circuit of neurons that become active at the same time; serves as the site of permanent memory. • Reverberatory activity - Continued reactivation of a neural circuit following an experience. • Reverberatory activity is followed by physiological changes that produce a relatively permanent record of the event. • Phase sequence - interconnected cell assemblies all activated at the same time in order to control complex processes.

21. Structural Changes and Storing Experiences • Experience enhances Ca2+ ion entry into the hippocampus (Lynch, 1986). • Exposing more glutamate receptors to stimulation from other neurons, making the postsynaptic neuron more sensitive. • This may eventually cause changes in the terminal button and Lynch believes this may be the biological basis of learning and memory.

22. Importance of the Hippocampus • Damage results in memory deficits • Case of R.B. • hippocampal damage produced profound anterograde amnesia • Case of H.M. • memories acquired before surgery were retained suggesting that the hippocampus is involved in the storage of declarative memory but is not the site of storage. • Some researchers have found episodic encoding in the left frontal areas and episodic retrieval in the right frontal regions. PBS Nova – Aug 2009 Clive Wearing

23. Long Term Potentiation • A long term increase in the excitability of a neuron to a particular stimulus due to the repeated high-frequency activity of that stimulus • A long-lasting strengthening of synapses between nerve cells. • Long-term memories are thought to be based on LTP • Without LTP, learning some skills might be difficult or impossible.

24. Characteristics of LTP • A brief, sensitizing stimulus is sufficient to produce LTP; demonstrates that hippocampal neurons can change synaptic responsivity following a single event. • LTP-changed synaptic responsivity is confined to a specific neural pathway. • LTP can be produced by either a single stimulus or by the convergence of stimuli that individually would not produce LTP. • LTP can last for days or weeks, which suggests that it is not just a temporary change in synaptic responsivity.

25. Long-Term Potentiation in the Hippocampus • Long-term potentiation is an increase in the amplitude and duration of EPSPs in response to the test stimulus. • Three pathways involved in LTP • Perforantfiber pathway • Mossy fiber pathway • Schaffer collateral fiber pathway

26. LTP and the NMDA Receptor • In the mossy fiber pathway, glutamate binds to both the NMDA and non-NMDA receptors. • LTP apparently depends not on Ca2+ influx into the postsynaptic receptor, but on Ca2+ influx into the presynaptic cell after the LTP-inducing stimulus. • Kandel refers to this as nonassociative - the organism learns about the properties of a single stimulus. • Habituation and sensitization are examples of this type of learning.

27. Neuroplasticity in the Hippocampus • Neurogenesis - helps the brain to be modified in adaptation to changing environmental conditions. • Learning that involves the hippocampus results in new cells surviving at a higher rate. • The cells become part of neural circuits established by a temporal-based learning experience. • Enriched environments have been shown to increase the size of an animal’s brain, their level of cortical ACh, and their learning ability. • Studies have shown enriched environments increase hippocampal neurogenesis, even in adult animals.

28. The Role of the Mediodorsal Thalamus • Mediodorsalthalamus - A brain structure associated with profound memory impairment. • People with Korsakoff’s syndrome often have atrophy of cells in the mediodorsal thalamus caused by a deficiency of Vitamin B1. • Loss of declarative rather than procedural memory. • Patients are unaware that they don’t remember; make up stories (confabulation) to fill in the gaps. • Emotion is generally intact with medial temporal lobe damage but patients with mediodorsal thalamic damage tend to be emotionally flat and apathetic

29. Caudate Nucleus-Putamen Memory System • Caudate nucleus and putamen control the ability to develop procedural memory.

30. The Amygdala and Memory • Stimulation of the amygdala results in enhancing the memory of a task • Inhibition of the amygdala results in decreasing the emotional arousal effects on memory.

31. Alzheimer’s Disease • A type of dementia characterized by progressive neurological degeneration and a profound deterioration of mental functioning. • Early onset - before age 65 • Risk factors include familial clustering of cases, increasing age, and Down syndrome.

32. Alzheimer’s Disease

33. The Cellular Basis of Alzheimer’s Disease • Cellular basis of AD • Neurofibrillary tangles • Senile plaques • Amyloid beta protein

34. Alzheimer’s Disease:Genetics • There is a link with chromosome 21 • Another gene identified is ApoE on chromosome 19 • Some people have one or two ApoE4 alleles and have a greater risk of having late-onset AD. • The product of ApoE4 is not an effective antioxidant for amyloid beta protein as are the products of other alleles. • This may indicate a need to develop more effective methods to increase antioxidants in the brains of AD patients.