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Memory
Gateway to Learning
Introduction
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What is memory?
Positive and Negative Memory
What is learning?
Importance:Reward and punishment
– Role of hippocampus
– Survival
• Areas for storage:
– spinal cord reflexes
– Higher centers
• Neural basis of memory
– Strength of synapse
• Consolidation
• Condification
Stages of memory
• Encoding-information for each memory is
assembled from the different sensory
systems and translated into whatever form
necessary to be remembered. This is
presumably the domain of the association
cortices .
• Consolidation• Storage• Retrieval-
There is more than we can tell…
How many stripes did
you see on the cat?
Mechanism of presynaptic facilitation underlying
behavioral sensitization
1. Serotonin is released by modulatory interneuron
and binds to GPCR
Classification
• Short term (working memory)
• Intermediate term
• Long term
Mechanism of long-term synaptic
enhancement
Number of Neurons and Their
Connectivities
Often Change Significantly During
Learning
• Learning” is achieved in adult human
beings and animals by modification of
numbers of neurons in the memory circuits
• Use it or lose it!
Many Structures are Involved in Memory
Implicit memory
• Procedural memory
– skills and habits, which, once acquired, become
unconscious and automatic.
• Priming
– is facilitation of recognition of words or
objects by prior exposure to them. An example
is improved recall of a word when presented
with the first few letters of it.
Implicit memory
• In nonassociative learning,
– the organism learns about a single stimulus.
• In associative learning,
– the organism learns about the relation of one
stimulus to another.
Working Memory
Sensory
Input
Sensory
Memory
Attention
Working or
Short-term
Memory
Hippocampus
Maintenance Rehearsal
Sensory
Input
Sensory
Memory
Attention
Encoding
Working or
Long-term
Short-term
memory
Memory Retrieval
Implicit Memory
• Does not require conscious awareness
Amnesia - Loss of Memory
• Retrograde amnesia
– loss of memory for the time period before a trauma
– typically is gradational from essentially complete loss just
before trauma to less and less complete loss
earlier and earlier before trauma
• Anterograde amnesia
– inability to form new memories
Causes of Amnesia
• Causes
– concussion, chronic alcoholism, encephalitis, brain
tumor, stroke
• Transient amnesia
– Probably caused by interruptions in cerebral blood
flow
– Blows to head, physical stress, drugs
Bilateral removal of the
hippocampus
– Studied patients with surgical interventions
to treat epilepsy
– Bilateral removal of the hippocampus and
neighboring regions of the temporal lobe
• Most famous case was “H.M.”
The Diencephalon
• Three regions have been
implicated in memory
processing:
– Anterior nucleus of
thalamus
– Dorsomedial nucleus
of thalamus
– Mammillary bodies in
hypothalamus
• The thalamus &
mammillary bodies
receive nerve fibers from
the medial temporal lobe
Effects of lesion
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Lesion in dorsomedial thalamus:
– Cognitive ability normal but memory impaired
– Caused moderate retrograde amnesia and profound
anterograde amnesia
• Short term memory and preservation of old
memories was intact.
• Suggests that both the temporal lobe and parts of
the thalamus may be involved in the formation of
long-term declarative memories.
Neocortex and Working Memory
• Humans have much more prefrontal cortex
than any other animals
• Pathways:
– Medial temporal lobe >> hypothalamus >>
anterior nucleus of thalamus >> cingulate cortex
– Medial temporal lobe >> dorsomedial nucleus of
thalamus >> frontal cortex
• Experiments suggest that frontal cortex is
involved with working memory for problem
solving and planning of behavior