Lecture 16. Hippocampus and Memory (1).pptx - Lecture 16...

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Lecture 16
Memory and Amnesia
Reading: Chapter 9 Memory and Learning in
textbook (pages 257-272, first half of chapter)

What is memory?
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What is memory for?
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Amnesia is characterized by the inability to
form most new long-term memories,
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H.M. is the most famous studied case of
amnesia
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He participated in hundreds of studies over
more than five decades
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His amnesia esulted from a surgical
resection – a “planned” lesion – to control
his epilepsy
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Surgeon knew specifically which structures
were to be removed
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After his surgery, H.M. was unable to form
new long-term memories
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For example, he could not learn the
definition of new words even after hundreds
of trials!
Hippocampal damage causes amnesia, a disorder of
long-term memory

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Amnesia results from extensive damage to
the regions of the medial temporal lobe,
including the
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hippocampus, so named because its shape
resembles a seahorse
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dentate gyrus,
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amygdala, and
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neighboring parahippocampal area
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the parahippocampal, entorhinal, and perirhinal
cortices.
Hippocampal damage causes amnesia, a
disorder of long-term memory
Resection in H.M.’s
brain (right)

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A 3-D rendering of two hippocampi, with the subfields color-coded.
Abbreviations: CA1, cornu ammonis subfield 1; CA3, cornu ammonis
subfield 3; DG, dentate gyrus; SUB, subiculum.

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The anatomy of the hippocampus is such that information
from many different brain regions converges on the
entorhinal cortex
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From there the information enters the hippocampus via the
perforant pathway
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It travels in a unidirectional manner through the different
subfields of the hippocampus before exiting
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Back to the entorhinal cortex
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To other brain regions via the fornix
Hippocampal damage causes amnesia, a
disorder of long-term memory

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Amnesia can also result from
damage to the closely related
midline diencephalic region ,
involving particularly the
dorsomedial nucleus of the
thalamus and the mammillary
bodies of the hypothalamus.
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Damage to these regions can
originate in a number of ways –
for example, as occurs in
Korsakoff’s disease, following
chronic alcohol abuse, or
sometimes through an accident.
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Hippocampal damage causes amnesia, a disorder
of long-term memory

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Amnesia is characterized by a loss of memory that is global.
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It occurs across modalities regardless of whether
information is presented in the visual, auditory,
somesthetic, and even olfactory modalities.