Chapter 14Chapter 14The Biology of Learning and Memory

Learning and Memory Learning and Memory DefinitionDefinition

Learning• A long term change in behavior as a

function of experiences.

Memory•The capacity to retain and retrieve past experiences.

Types of LearningTypes of LearningHabituation

• 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.

Types of Learning:Types of Learning:Pavlovian ConditioningLearning 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.

Classical ConditioningClassical Conditioning

Types of Learning: Types of Learning: Operant Conditioning

Learning how to behave to obtain reinforcementReinforcers - 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.

Operant ConditioningOperant Conditioning

Models of Memory Storage Models of Memory Storage and Retrieval: and Retrieval: Atkinson-Shiffrin model An experience is sequentially stored in

the sensory register, and the short-term store, and the long-term store.

Models of Memory Storage and Models of Memory Storage and RetrievalRetrieval: : Baddeley’s Rehearsal Systems approachAn alternative to Atkinson-Shiffrin in

which Baddeley argued that memories go directly from the sensory register to long-term storage.

Models of Memory Storage and Models of Memory Storage and RetrievalRetrieval: : Craik and Lockhart

Craik and Lockhart - have a theory that memories differ in the extent to which they have been processed.

Types of MemoriesTypes of Memories

Types of MemoriesTypes of Memories

Declarative MemoryDeclarative MemoryMemory whose formation does depend

on the hippocampal formationMemory that can be verbally expressed

• Episodic memory• Semantic memory• Spatial memory

Slow-wave sleep facilitates consolidation of declarative memories

Role of the HippocampusRole of the HippocampusInput 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

Procedural MemoryProcedural MemoryMemory whose formation does not

depend on the hippocampal formationCollective term for stimulus-response,

perceptual, and motor memoryNon-declarative memories control

behaviorsLearning to drive, typeREM sleep facilitates retention of non-declarative memories Ian Waterman

Perceptual LearningPerceptual LearningLearning 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

Perceptual Short-term Perceptual Short-term memorymemoryActivates the circuits and continues

after the stimuli disappearsSuccessfully remembering short-term

is a two step process• Filter out irrelevant information• Maintain relevant informationAlso in prefrontal cortex• Manipulate and organize• Strategies for retrievalDelayed matching-to-sample task• Faces – fusiform face area – face blindness• Places – parahippocampal place area

The Anatomy of Learning The Anatomy of Learning and Memory: and Memory: Procedural MemoryProcedural or nondeclarative memory

involves the neocortex and neostriatum.Basal ganglia structures (caudate

nucleus and putamen) needed for procedural learningClassical conditioning of reflexes depends on the cerebellum.

(Budson & Price, 2009)

The Memory Consolidation The Memory Consolidation Process:Process:Hebb’s Cell AssembliesCell 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.

Structural Changes and Structural Changes and Storing ExperiencesStoring 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.

The Importance of the The Importance of the HippocampusHippocampusDamage 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.

Long Term PotentiationLong 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.

Characteristics of LTPCharacteristics of LTPA 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.

Long-Term Potentiation in Long-Term Potentiation in the Hippocampusthe 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

Neuroplasticity in the Neuroplasticity in the HippocampusHippocampus

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.

The Role of the Mediodorsal The Role of the Mediodorsal ThalamusThalamus

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

Caudate Nucleus-Caudate Nucleus-Putamen Memory SystemPutamen Memory System

Caudate nucleus and putamen control the ability to develop procedural memory.

The Amygdala and The Amygdala and MemoryMemoryStimulation of the amygdala results in

enhancing the memory of a taskInhibition of the amygdala results in

decreasing the emotional arousal effects on memory.

Alzheimer’s DiseaseAlzheimer’s DiseaseA 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.

Alzheimer’s DiseaseAlzheimer’s Disease

The Cellular Basis of The Cellular Basis of Alzheimer’s DiseaseAlzheimer’s DiseaseCellular basis of AD

• Neurofibrillary tangles• Senile plaques• Amyloid beta protein

Alzheimer’s Disease:Alzheimer’s Disease:GeneticsGenetics

There is a link with chromosome 21Another gene identified is ApoE on chromosome

19Some 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.