79 - Memory and Learning Flashcards
Learning
Learning
– A process by which new information is acquired by the nervous system (brain) and adaptive changes in behavior are produced.
Memory
Memory
– Encoding, storage, and retrieval of learned information
– Record stored as the interpreted experience
– Ability to forget information that is only temporarily useful
– Involves a wide array of neuronal circuits and a process for activation (recall)
– Stored in some context (codification)
– Cross-referencing – various ‘entry points’, contexts
– Memory trace (engram) - pattern of activity unique to the record (memory)
Types of learning
- Associative
- Non-associative (simple)
- Non-associative (complex)
What is associative learning?
Learning regarding the relationship between two or more stimuli
Two types of associative learning
- Passive
- Operant
Passive associative learning
Passive
1) Simple conditioning
2) Temporal relation between stimuli
Operant associative learning ***
Operant
1) Primary stimulus is associated with a different reinforcement
stimulus
2) Reinforcement stimulus may be positive or negative (aversive)
What is the role of reinforcement in associative learning?
- Generally, time sensitive; will vary with the reinforcing stimuli
- Positive reinforcement will enhance the occurrence of the response
• e.g. sex, money, cocaine and other abused drugs (positive
reinforcers, activate the endogenous reward pathways) - Negative reinforcement; will reduce the occurrence of a particular behavior to avoid an undesirable condition
• Aversive learning will reduce the occurrence of the response. e.g. disciplining a child
Two types of non-associative (simple) learning
- Habituation (tolerance)
- Sensitization
Habituation (tolerance)
Diminished response following a repeated stimuli, e.g. lecture
Sensitization
Enhancement of a response by the addition of a second strong or noxious stimulus, e.g. loud noise or other noxious stimuli
Two types of non-associative (complex) learning
- Imprinting
- Vicarious or latent
Imprinting
1) Bonding or behavioral attraction of a young animal to a parent
2) A developmental process that must occur during a ‘critical period’
Vicarious or latent
1) Simple experience of familiarity
2) No motivation or reinforcement (reward) necessary
3) Imitation or observation
Now onto memory…
Need to memorize categories
What are the two qualitative categories of human memory?
- Declarative (explicit)
- Non-declarative (implicit, procedural, motor)
Declarative (explicit)
a. Types of information
1) Semantic (facts)
2) Episodic (events)
b. Brain area involved
1) Medial temporal lobe (hippocampus and surrounding structures)
2) Diencephalon (basal forebrain, thalamus)
c. Can be brought to a conscious level and described or examined
Non-declarative (implicit, procedural, motor)
a. Skilled movements and habits (motor behavior)
• Striatum, motor cortex, cerebellum, spinal reflex circuits
b. Priming (process of completing a word/picture, i.e. ‘activating’ a memory). when only presented with a portion of the information; based
upon prior experience
• Neocortex
c. Basic associative learning
1) Emotional responses
• Amygdala and limbic circuits
2) Skeletal musculature
• Cerebellum; spinal reflex circuits
d. Non-associative learning
• Complex reflexive pathways
Three temporal (time) categories of memory
- Short term
- Working
- Long term
Short term memory
seconds – minutes – hours
Working memory
− Has short-term nature, but is very different from other forms of shot term memory.
− Process for ‘holding’ information in a useable form for basic cognitive activities
− The contents of WM can be recalled from long-term storage or can represent a recent even that is temporarily held in mind
− To guide behavior and inhibit inappropriate actions
− Limited capacity; easy to distract
− Involved brain regions mature late in developmental stages
− Fragile process: targeted by aging, stress, etc
Long term memory
days to years
Three domains of memory
- Cognitive
- Psychomotor
- Affective
Domains are NOT mutually exclusive
Cognitive domain
To recall, calculate, discuss, analyze, problem solve, etc.
Psychomotor domain
To dance, swim, ski, dive, drive a car, ride a bike, etc.
Affective domain
To like something or someone, love, appreciate, fear, hate,
worship, etc.
Memory processing - three steps
1 - Sensory input
2 - Memory storage
3 - Memory extinction
Another name for sensory input
Acquuisition
Describe the steps of memory storage and location
a. Consolidation (hippocampus)
- while an active process, consolidation seems to require sleep
b. Rehearsal and recall
c. codification, the context or category in which memory is stored
What is memory extinction?
Forgetting
Fear memory extinction
AKA repression
- Fear memory extinction relies on a network of three structures.
- The amygdala stores both conditioning and extinction memories.
- CS information enters the amygdala, hippocampus, and prefrontal cortex(PFC).
- The PFC integrates CS information with contextual
information from the hippocampus in order to determine extinction retrieval. - In the extinction context, the PFC inhibits amygdala output, to reduce fear.
- Outside the extinction context, amygdala output is
uninhibited.
There are five memory systems
1 - Episodic 2 - Semantic 3 - Perceptual representation 4 - Procedural 5 - Working
Episodic memory system
a. Recollection of events in the context of a particular time and place relative to a person’s past experiences
b. Medial temporal lobes, especially the hippocampus are critical for acquisition and consolidation of this memory system. The prefrontal cortex/frontal lobes are also involved.
What clinical condition is associated with the episodic memory system?
‘Source amnesia’ - a condition in which the patient retains the ability to learn new facts but cannot recall when or where they were learned
• Observed in the elderly, especially in association with frontal
lobe dysfunction/pathology
• Observed in young children with immature frontal lobes
• Associated with ‘false memories’ in frontal lobe damage
Semantic memory system
a. General knowledge of facts and concepts without reference to time and place as to when they were ‘learned’
b. Medial temporal lobes vital for acquisition and consolidation; integrity of anterior and lateral aspects of the temporal lobe, especially in the left hemisphere
What clinical condition is associated with the semantic memory system?
Semantic dementia’ – seen in elderly patients with a lack of knowledge for the properties of a specific object yet intact episodic memory
• Though both episodic and semantic memory are considered ‘declarative/explicit’ they can be dissociated as evidenced by pathology
Perceptual representation memory system
Identification of words and objects based upon their form and structure
Perceptual representation contributes to four skills
- Visual work recognition
- Auditory recognition
- Structural description
- Facial recognition
Visual work recognition
- Extrastriate visual cortex (form)
* Temporal and frontal cortex (meaning)
Auditory recognition
Auditory association cortices, temporal lobe
Structural description
- Relation of parts of an object to the entire structure
* Occipitotemporal junction
Facial recognition
• Areas of the ventral occipitotemporal cortex are rich in
‘face cells’
• Though bilateral, the right hemisphere predominately
processes the ‘face’ as a whole while the left hemisphere
tends to break it into components
• Frontal cortex interprets facial ‘emotions’ particularly
through activity in the amygdala
Procedural memory system
a. Skills and behavioral habits, including rules for classification, organizing sequences and grammatical rules
b. Corticostriatal projections, basal ganglia, motor cortex and cerebellum, probably spinal cord as well, for some simple reflexive behaviors)
Working memory system
Process for ‘holding’ information in a readily useable fashion for basic cognitive activities such as reasoning, problem-solving, comprehension and evaluation
Working memory system consists of three interrelated components
i. Executive component - to coordinate information
ii. Phonological loop - involves left temporal and frontal
language areas for verbal-type information
iii. Visuospatial component - visual association cortex, inferior parietal and inferior prefrontal cortex, particularly of the right hemisphere for visual and spatial information
There are three plausible mechanisms of memory formation
- Recurrent circuit
- Synaptic plasticity
- Synaptogenesis
Recurrent circuit
a. Positive feedback system
b. Capable of producing persistent neural activity, but for a short term period
c. Rapid extinction
d. Proposed neural correlate of working memory
Synaptic plasticity
Plastic changes that either strengthen or weaken synaptic
transmission
Short term plasticity
Short-term plasticity: lasting for a few minutes or less
- Synaptic efficacy
− habituation
− sensitization
Long-term plasticity
Long-term plasticity: lasting for hours or more
- Long-term potentiation (LTP)
- A given stimulus to the afferent pathways of hippocampus, for example, produces a characteristic and reproducible response. Following a strong,
sustained stimulus or high frequency stimulus, the response to the previously defined stimulus is greatly enhanced. This enhanced response (potentiation) lasts for a very long period (minutes→ hours inn vitro, and
hours –> days in vivo)
- Induction mechanisms of some types of LTP are dependent on NMDA receptors
- The expression mechanisms of LTP involve both presynaptic and postsynaptic.
- As a process for encoding memories, synaptic responses can be suppressed (long-term depression, LTD) or scaled back after LTP.
Synaptogenesis
Synaptogenesis - changes in the number of active synapses
- Morphological neuronal plasticity
- Requires protein synthesis
- Synaptogenesis plays a role during development as well as throughout life
Modulation of memory systems
There are both intrinsic factors and external impacts on memory processing
Intrinsic factors
Intrinsic factors
- Developmental stages
- Aging
- Hormones
External impacts (many)
External impacts (many)
- Stress
- Concussion
Amnesia
The inability to recall or form memories
Anterograde amnesia
- Inability to form NEW memories
- Primarily a defect in consolidation though it could involve acquisition
- Hippocampal damage (consolidation of declarative memory)
- left hippocampus - verbal information (words, writing)
[broad generality] - right hippocampus - nonverbal information (complex visual and auditory patterns) [broad generality]
- left hippocampus - verbal information (words, writing)
- Affects declarative and not procedural memory
- Anesthetic and sedative hypnotics (CNS depressants) may
induce an anterograde amnesia (e.g., as in surgery) by an
impairment of acquisition and consolidation
Retrograde amnesia
Retrograde
- Inability to recall previously stored memories
- Temporal quality; older memories are more resistant to ‘loss’ while new more recent memories are more vulnerable
- Defect in recall; rarely is the memory trace itself lost
Alzheimer’s disease
Most common form of cortical dementia in humans
Symptoms of Alzheimer’s
Symptoms include: – aphasia (inability to speak) – apraxia (disordered motor planning) – agnosia (inability to process sensory information like recognize people) – amnesia
Pathology of Alzheimer’s
• Neurofibrillary tangles (tau) & senile plaques (β-amyloid)
• Risk factors: age, family history, risk genes (ApoE, APP PS1,2)
• Etiology not well understood
• Memory impairment associated with neuronal loss in the hippocampus, cortex & basal forebrain (cholinergic)
− anterograde amnesia (hippocampal damage)
− disease progression → retrograde amnesia (cortex and
forebrain)
