1. The Biology of Learning and Memory
Chapter 14
The Biology of Learning and Memory

2. Learning and Memory Definition
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 Sensitization
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-Shiffrin in 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

14. 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

15. The Anatomy of Learning and Memory: Declarative Memory
Squire and others have identified areas of the brain involved in declarative memory.
Medial temporal lobe - Hippocampus and surrounding cortical areas relay information to diencephalic areas where it is processed and relayed to the frontal lobe.
Frontal lobe - Medial temporal lobe structures and the medial thalamus jointly may be essential for the formation of long-term memory
connections between these structures and the frontal lobe may provide a route by which memories can influence behavior.

16. 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

17. 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

18. 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

19. 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

20. The Anatomy of Learning and Memory: Procedural Memory
Procedural or nondeclarative memory involves the neocortex and neostriatum.
Basal ganglia structures (caudate nucleus and putamen) needed for
procedural learning
Classical conditioning
of reflexes depends
on the cerebellum.

21. (Budson & Price, 2009)

22. 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 - The 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.

23. Is Reverberatory Activity Essential for Memory Storage?
Studies have used electroconvulsive shock to break up the consolidation of memory.
ECS tends to produce retrograde amnesia supporting the idea that reverberatory activity is necessary for memory consolidation.
CS reminders have brought back memories apparently lost after ECS
Therefore, forms of brain intervention affect memory retrieval rather than consolidation.

24. The Cellular Basis of Learning and Memory
Cellular Modification Theory – the view that learning permanently enhances the functioning of existing neural circuits or establishes new neural connections.
Kandel’s studies of learning in Aplysia californica indicated both habituation and sensitization exist in this animal.
Normal classical conditioning occurs in Alypsia with a CS of a light touch to the mantle or siphon paired with an electric shock to the tail.

25. 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.

26. The Medial Temporal Lobe
H.M. had his medial temporal lobes, including the hippocampus, amygdala, and surrounding cortical tissue, removed as a treatment for epilepsy.
Resulted in severe anterograde amnesia
His procedural memory is intact.
PBS Nova – Aug 2009
Clive Wearing

27. The Importance of the Hippocampus
Damage to the hippocampus 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.

28. 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.

29. 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.

30. 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
Perforant fiber pathway
Mossy fiber pathway
Schaffer collateral fiber pathway

31. Characteristics of LTP
LTP seems to occur through modification of the NMDA receptor in the Perforant and Schaffer collateral pathways.
This may be a basis for operant and classical conditioning.

32. 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.

33. 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.

34. The Role of the Mediodorsal Thalamus
Mediodorsal thalamus - 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

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

36. 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.

37. 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.

38. Alzheimer’s Disease

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

40. 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.