Organic Amnesia - Memory, The Brain, and Amnesia Types of Amnesia
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Memory, The Brain, and
Amnesia
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Types of Amnesia
Organic Amnesia Inorganic Amnesia
Retrograde Amnesia Dissociative Fugue
Anterograde Amnesia Transient Global Amnesia
Psychogenic Amnesia
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Organic Amnesia
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Hippocampus
NEUROPSYCHIATRY CLASSICS
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Temporal Lobes and Amnesia
tional lobotomies have been performed, largely on se-
riously ill schizophrenic patients who had failed to re-
the uncus and underlying amygdaloid nucleus; all oth-
ers encroached also upon the anterior hippocampus, the
spond to other forms of treatment. The aim in these excisions being carried back 5 cm or more after bisecting
fractional procedures was to secure as far as possible the tips of the temporal lobes, with the temporal horn
any beneficial effects a complete frontal lobotomy might constituting the lateral edge of resection. In one case
In the late 1940s and early 1950s, surgeons
have, while at the same time avoiding its undesirable
tried to treat
only in this psychotic group all tissue mesial to the tem-
side effects. Andpsychological and psychiatric
it was in fact found diseasesporal
that undercutting with horns
surgery.
for a distance of at least 8 cm posterior to
limited to the orbital surfaces of both frontal lobes has the temporal tips was destroyed, a removal which pre-
an appreciable therapeutic effect in psychosis and yet sumably included the anterior two-thirds of the hippo-
By accident, these procedures often led
does not cause any new personality deficit to appear
to impaired
campal complex bilaterally.
cognitive
(Scoville, Wilk, and processing.
Pepe, 1951). In view of the known An equally radical bilateral medical temporal lobe re-
close relationship between the posterior orbital and me- section was carried out in one young man (H. M.) with
sial temporal cortices (MacLean, 1952; Pribram and Kru- a long history of major andBrenda
minor Milner
seizures uncontrol-
In 1953, patient H.M. underwent bilateral temporal lobe
ger, 1954), it was hoped that still greater psychiatric ben- lable by maximum medication of various forms, and
efit might be resection
obtained because his epileptic
by extending seizuresshowing
the orbital were not diffuse electroencephalographic abnormality.
undercutting soresponding
as to destroytoparts
medication.
of the mesial tem- This frankly experimental operation was considered jus-
poral cortex bilaterally. Accordingly, in 30 severely de- tifiable because the patient was totally incapacitated by
teriorated cases, such partial temporal lobe resections his seizures and these had proven refractory to a medi-
were carried out,The operation
either led to gross
with or without orbitalanterograde
under- calamnesia
approach.for
It was suggested because of the known
H.M.procedure has been described else-
cutting. The surgical epileptogenic qualities of the uncus and hippocampal
where (Scoville, Dunsmore, Liberson, Henry, and Pepe, complex and because of the relative absence of post-
1953) and is illustrated anatomically in Figure 1, Figure operative seizures in our temporal lobe resections as
William Scoville
2, Figure 3, and Figure 4. All the removals have been compared with fractional lobotomies in other areas. The
bilateral, extending for varying distances along the me- operation was carried out with the understanding and
sial surface of the temporal lobes. Five were limited to approval of the patient and his family, in the hope of
FIGURE 1. Area removed bilaterally from the medial temporal lobes demonstrating 5 cm as well as 8 cm removals through supra-orbital
trephines.
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104 J Neuropsychiatry Clin Neurosci 12:1, Winter 2000
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Organic Amnesia
Retrograde amnesia
Anterograde amnesia
Episodic memory is affected.
Potential causes for anterograde amnesia:
• Surgery
• Closed-head injury, strokes, tumors
• Korsakoff’s syndrome (chronic alcoholism)
• Alzheimer’s Disease
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Characteristics of Anterograde Amnesia
• Intact sensory functioning, intact language (not aphasia)
• Relatively normal I.Q. (memory is part of the test)
• Normal short-term / working memory
• Normal general knowledge (semantic memory)
• Normal memory for life events before brain injury?
• Extraordinarily rapid forgetting after a delay
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Patient K.C.
• Motorcycle accident at age 30
• Medial temporal lobe damage
• Normal intelligence (94 IQ)
• Normal STM
K.C.
• Intact semantic memory
• Complete anterograde and retrograde amnesia of episodic
memory
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No episodic memory - lost in time
Preserved semantic memory, including that of personal
information
No episodic memory of any specific events
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Preserved working memory
No episodic memory even after deep encoding and a
short retention interval!39
Unable to envision the future.
Episodic memory allows mental time travel - in both
the forward and backward directions!
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Can Amnesiacs Learn?
Claparede worked with an amnesic patient to whom
he introduced himself every day, but she had no
recollection of ever meeting Claparede.
One day, when introducing himself, he hid a pin in
his hand and pricked the patient with the pin when
they shook hands.
Thereafter, the patient refused to shake the doctor’s Edouard
hand -- though she could not say why she refused, Claparede
nor did she remember Claparede from their previous
encounters.
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Implicit Memory
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Implicit Memory
A new term that refers to an old idea: The notion
that people can demonstrate after-effects of an
experience in their behavior without being able to
consciously recollect the experience.
Ebbinghaus: Savings in Relearning (1885)
Interest in unconscious influences on behavior (Freud)45
Warrington & Weiskrantz (1970)
Tested 4 amnesics and 8 controls
Subjects studied a list of words and were then tested in
one of 4 ways:
Elizabeth
• Free recall Warrington
• Recognition
• Word-stem completion: cha__
• Word-fragment identification
Lawrence
Weiskrantz
Controls Amnesics
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0.8
0.6
Amnesiacs: deficits on recall
0.4
and recognition tests
0.2
0.0
Free Recall Recognition
0.8
However, amnesiacs were
identical to controls on the other 0.6
two tests (implicit tests).
0.4
!
Availability vs. Accessibility 0.2
0.0
Word Fragment Word Stem
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Implicit vs. Explicit Test
Explicit Test: Make direct reference back to a prior
episode and measure intentional retrieval.
Implicit Test: Do not make direct reference to the
past, measure the effects of past experience on
current behavior -- incidental retrieval.
Priming: Facilitation, relative to some baseline, on a
task that does not require conscious recollection of
prior experiences.
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Dissociating Explicit and Implicit Memory
If explicit and implicit memory are indeed different forms of
memory, then one should be able to dissociate them even
within health, non-amnesic, subjects.
Jacoby and Dallas (1981)
Subjects studied words under three levels of processing
conditions (structural, phonemic, semantic).
Two different memory tests:
• Standard yes/no recognition test
• Word naming (words flashed for 50ms) -- name the Larry Jacoby
briefly presented word.49
Recognition Memory Word Naming
1.0 1.0
0.9 0.9
Equivalent Priming
Probability Correct
0.8 0.8
0.7 0.7
0.6 0.6
0.5 0.5
0.4 0.4
Structural Semantic Structural Semantic
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Manipulations that have powerful
influence on explicit memory can have
no influence on implicit memory.
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Retrieval Mode
Memory is cue-dependent, a product of what is encoded and what is
in the retrieval cue. Appropriate cues are necessary for remembering.
But there is one more critical piece: According to Tulving (1983), you
must also be in retrieval mode.
A cognitive mode (or mental set) in which you are ready to
intentionally retrieve.
Example: Ocean
Potential retrieval cues are all around -- but you must be in retrieval
mode to use them.
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Amnesiacs are unable to retrieve information from
episodic memory because they cannot enter retrieval
mode.
But implicit memory does not require one to enter
retrieval mode.You can also read
