382: Stress, Memory, and Imagination

1. Learning
1. process by which experiences change our nervous system and hence our behavior
2. Memory
1. the ability to store and retrieve information
3. Associative Learning
1. understanding relationship between events
4. Classical Conditioning (Pavlovian conditioning)
1. dogs salivate when they hear the bell after being conditioned by a meal
5. Instrumental Conditioning (Operant Conditioning)
1. Behavior 
2. The consequences of behavior
6. Nonassociative Learning
1. Involves a single stimulus presented once or repeated
2. Three types
1. Habituation
1. a decreased response to repeated presentations of a stimulus
2. Dishabituation
1. restoration of response amplitude after havituation
3. Sensitization
1. prior stong stimulation increases response to most stimuli
2. something had a strong effect so next time you'll have an even stronger response
7. Types of Memory
1. Declarative (explicit)
1. deals with the "what"
2. facts and information
3. Two types
1. S
2. Nondeclarative (implicit)
1. deals with the "how"
2. performance rather than information
8. Temporal Stages of Memory
1. Iconic
1. the briefest and store sensory impressions
2. Short-term memories (STMs)
1. Usualy last only for seconds, or throughout rehearsal
2. aka working memory
1. working memory is a bottleneck
1. There is a ton of sensory information but you can only store about 7 chunks of it in your working memory.  Then the memory stream it broadens again once it becomes long term memory.  Long term memory can store a "ton" of information.
3. Intermediate-term Memory (ITM)
1. Outlasts a STM, but is not permanent
2. For example, you remember where you parked your car after you come out of a movie
4. Long-term Memories (LTMs) 
1. last for days to years
5. Primacy and Recency Effects
1. Recency effects work better
6. Functional Memory incorporates 3 aspects
1. Encoding
1. sensory info is encoded into short-term memory
2. Consolidation
1. Info may be consolidated into long-term storage
3. Retrieval
1. Stored info is retrieved
2. Anxiety is the big memory killer
9. Memory Is Not Perfect Or Complete
1. Only details relevant to the individual (you) are remembered
2. The function of memory is to help us survive
1. so we focus on the helpful and avoid the threatening
3. Shereshevskii
1. photographic memory but had problems writing
1. He had such a large amount of information that other tasks started to be disrupted
10. Biology of the Temporal Stages
1. Consolidation
1. Involves the hippocampus but the hyppocampal system does not store long term memories
2. LTM
1. Occurs in the cortex where the memory was first processed and held in short-term memory
11. Photographic Memory
12. Memory is Neuronal Remodeling
1. We don't have a fixed amount of brain cells.  There are neurons dying and more being born.
2. Neuroplasticity
1. the ability of neurons and neural circuits to be remodeled by experience or environment.  Memory is, in a way, synonymous with neuroplasticity.  That is to say, you cannot not add a new memory or experience without the neural circuits in your brain being altered in some way.
3. Long-term Potentiation
1. a stable and enduring increase in the effectiveness of synapses
4. Tetanus
1. A brief increase of electrical stimulation that triggers thousands of axon potentials
2. "Neurons that fire together wire together"
13. Synaptic Change
1. Process
1. Hippocampal circuits have both NMDA and AMPA receptors
2. Glutamate activates AMPA receptors
3. NMDA receptors do not respond until enough AMPA receptors are stimulated and the neuron is partially depolarized
4. NMDA receptors at rest have a magnesium ion (Mg 2+) block on their calcium (Ca 2+) channels
5. After partial depolarization, the block is removed and the NMDA receptor allows CA 2+ to enter in response to glutamate
6. Strong stimulation of a post synaptic cell release a retrograde messenger that travels across the synapse and alters functions in the presynaptic neuron
7. More glutamate is released and the synapse is strengthened
8. The large Ca 2+ influx...
1. causes more AMPA receptors to be produced
2. Causes more AMPA receptors to be inserted in the postsynaptic membrane
2. Example Experiment
1. Put rats in an impoverished condition, a normal condition, and an enriched condition
1. Enriched Condition
1. heavier thicker cortex
2. altered gene expression
3. enhanced recovery from brain damage
4. etc.
14. Remembering and Imagining
1. Memory Trace
1. record of learning experience, can be affected by other events before or after original event
2. We only remember pieces of the original event that were relevant to us.  However, depending on our current state, our brain will fill in the missing pieces to build the whole picture.  A whole picture that turns out to be very subjective.
3. "A memory recalled is a memory modified"
1. Every time you remember a memory that memory is changed.  
2. Because your state is different for each recollection it will slightly alter the memory
15. The Prospective Brain
1. "...imagining the future depends on much of the same neural machinery that is needed for remembering the past"
2. "crucial function of the brain is to use stored information to imagine, simulate and predict possible future events"
3. So does this mean that if we have had a traumatic past, we are destined to always imagine and predict a traumatic future?
16. APS is better than APA