6_Modulation - Memory Modulation Memory Modulation 1....

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Memory Modulation
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Memory Modulation 1. Context matters to speed of acquisition, length of retention 2. Relevance or importance matters 3. Emotional content matters 4. Fatigue matters 5. Effects of each can be raised or lowered exogenously: Caffeine, Nicotine, Amphetamine Alcohol, Morphine and other opiates 6. Substitution is possible
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What is the neural basis for these modulatory influences?
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What is the neural basis for these modulatory influences? Or can we find endogenous factors that act in the same way and that are affected by the agents mentioned above? Answer: Yes, they can be described as three classes (although many cross boundaries) Many endogenous and exogenous modulators have dose-response effects that resemble an inverted U- curve
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The possibility of modulation requires: existence of receptors in the brain a pathway that can influence brain function widely evidence that it is modulated naturally in memory formation Or, more commonly, that altering the level of the substance either systemically or specifically in this pathway, alters capacity for learning or retention
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ACh Exists as a neurotransmitter There is a pathway that uses ACh from a coherent nucleus [n. basalis] whose axons project widely throughout cortex and hippocampus These neurons tend to degenerate with aging and are severely affected in Alzheimer’s disease both of which are associated with memory problems
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ACh Modulatory Pathway
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ACh Paths -- In Humans Too
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How do we study an NT pathway? Lesions Chemical assays Give drugs that modify it If so, pay attention to the Blood-Brain Barrier Permeable to O2 Fat-soluble molecules Small Molecules Some molecules with special transport mans But not Others!
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Modifying A Transmitter = 1. Altering the transmitter, its synthesis or its metabolism 2. Altering interactions with its receptor -- can either stimulate (agonist) or block the receptor (antagonist) 3. Alter the cellular machinery that the receptor normally acts on
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Role for ACh in Memory Lesions of the ACh system impair many sorts of learning Physostigmine [anti-AChE drug] affects learning [low doses improve, high doses impair] Nicotine [stimulates one ACh receptor] – ditto; affects both appetitive and aversive tasks Scopolamine (Anti-AChR) impairs learning Increasing choline in diet sometimes gives
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This note was uploaded on 02/23/2008 for the course PSYCH 3320 taught by Professor Devoogd, t during the Spring '07 term at Cornell University (Engineering School).

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6_Modulation - Memory Modulation Memory Modulation 1....

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