PSY 201 Lecture Notes - Lecture 7: Neuromodulation, Eyewitness Testimony, Lesion
1 Jun 2018
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Chapter 7
Memory
• Memory: the acquisition, storage, and retention of skills and knowledge
• Encoding: information is acquired and processed into neural code
• Storage: information is stored in the brain
• Retrieval: information is retrieved when it is needed
• Karl Lashley: figuring out where in the brain memories are stored
o Engram: refers to the physical site of memory storage
o Trained rats to run a make the removed different areas of their cortices
• Size of removed area important factor in predicting retention
Brain Regions associated with memory
• Prefrontal cortex: working memory
• Temporal lobe: declarative memory
• Amygdala: fear learning
• Cerebellum: motor action learning and memory
• Hippocampus: spatial memory
Types of Learning
• Sensory Memory: a trace of the sensory input is retained for a brief period
o High capacity and very short duration (up to a few seconds)
o Easily accessible but vulnerable
• Working memory (short-term Memory): attentive/conscious processing occurs here.
Information can enter from both sensory memory and LTM
o Small capacity and short duration (seconds or minutes with active rehearsal)
o Easily accessible but vulnerable
• Long term memory: the stored representation of knowledge gained from previous
experience
o Large capacity and indefinite duration (up to decades/lifetime)
o Difficult to access but durable
• Explicit (declarative) learning: learning facts and information of which we can be aware
o Episodic: autobiographical memories
o Semantic memory: generalized memory of facts
• Implicit (nondeclarative) learning: memory about perceptual and motor procedure of
which we are unaware
o Priming: exposure to one stimulus alters response to another
o Motor (skill) learning: learning how to control the body in order to respond
appropriately
o Conditioning: learning the relationship between stimuli (classical conditioning) or
between behaviors and outcomes (operant learning)
Cellular Mechanisms of Learning
• Donald Hebb: proposed that memory results from alterations in synaptic connections
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o Memories are stored in multiple regions of the brain that are linked through memory
circuits
o Hebbian Rule: a synapse is strengthened if it is repeatedly active when the
postsynaptic neuron fires
• "neurons that fire together wire together"
• Synaptic plasticity: the basis of learning involving a change in a synaptic structure or
biochemistry that alters the efficiency of the synapse in a positive or negative way
o Plasticity= the capacity for being molded or altered
• Long -Term Potentiation (LTP): a mechanism by which synaptic connections are
strengthened, allowing for a larger excitatory post synaptic potential (EPSP) in the
postsynaptic neuron (postsynaptic neurons are more easily activated)
o Potentiation: to strengthen or make more potent
o Effects of LTP:
• Causes insertion of additional glutamate receptors into postsynaptic membrane
• Causes structural changes of the synapse that lead to the creation of new
synapse
• Causes creation of the neuromodulator Nitric Oxide, which diffuses to
presynaptic neuron and enhances glutamate release
• NMDA receptors: are receptors for the neurotransmitter glutamate that
o open only if a nearby neuron fires at the same time
o The firing neuron releases glutamate into the synapse and this neurotransmitter binde
with the NMDA recptors on the postsynaptic neuron
o Before priming:
• If a molecule of glutamate binds with NMDA receptor, calcium channel cannot
open because Magnesium ion is blocking the channel
o Priming:
• an EPSP arrives from nearby synapses; depolarization evicts the magnesium
ion
o Activation:
• A molecule of glutamate binds with NMDA receptor and opens the calcium
channel
▪ Because membrane is still depolarized, magnesium ion is still gone;
calcium ion enters cell and initiates changes responsible for long-term
potentiation (LTP)
Evidence for role of LTP in learning
• LTP prominent in brain areas involved in learning
• Drugs that block LTP also impair learning abilities
• Drugs that facilitate LTP also enhance learning abilities
• Mice genetically-enhanced to have more NMDA receptors and have better learning
abilities
• Doogie mice: smarter but more susceptible to chronic pain
Brain structures involved in memory
• Prefrontal Cortex (working memory)
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find more resources at oneclass.com
