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Dr. Brenda Milner Patient H.M. Amnesia. Retrograde Amnesia impairment of memory for events before the injury. Anterograde Amnesia impairment of memory for events after injury; that is, an impairment in learning. Memory Systems in the Brain. Memory Systems in the Brain. Patient H.M. - PowerPoint PPT Presentation
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Dr. Brenda Milner
Patient H.M.
Amnesia
• Retrograde Amnesia impairment of memory for events before the injury
• Anterograde Amnesia impairment of memory for events after injury; that is, an impairment in learning
Memory Systems in the Brain
Memory Systems in the Brain
Patient H.M.“Right now I'm wondering, Have I done or said anything amiss? You see, at this moment everything looks unclear to me, but what happened just before? That's what worries me. It's like waking from a dream; I just don't remember.”
“Every day is alone in itself, whatever enjoyment I've had, and whatever sorrow I've had.”
-- H.M.
Memory Systems in the Brain
Medial temporal lobe amnesia• Inability to form new explicit memories
(anterograde amnesia)
• Good IQ, good implicit learning
• Loss of memories from before injury
(retrograde amnesia)
Medial temporal (contains hippocampus) lesions and DNMS performance (working memory)
Medial Temporal Lobe Memory System
Visual Cortex
VentralStream
InferotemporalCortex
Perirhinalcortex
Parahippocampalcortex
Entorhinalcortex
hippocampus
Memory
Teng & Squire, 1999
Memory
Teng & Squire, 1999
Memory
Teng & Squire, 1999
MemoryModal view (eg. Alvarez & Squire, 1994; Eichenbaum & Cohen, 2001; McClelland et al., 1995): A representation of an event is stored very quickly as a readily induced pattern of LTP in limited-capacity hippocampal circuitryA very long-lasting representation is built up in slowly changing, very high-capacity neocortical circuitry as result of a lengthy process of repetitive patterned output from hippocampus.Hippocampal mnemonic specificity identical in retrograde and anterograde directions
MemoryOther view:
� There is a period of decreasing fragility of representations, but the process occurs within each network (not between)� Temporal gradients in retrograde amnesia arise because of a probabilistic degradation in a partially damaged network� If the hippocampus is intact, it is used (i.e. retrograde will have less specificity than anterograde)
Memory
Teng & Squire, 1999
Memory
Teng & Squire, 1999
Memory
Teng & Squire, 1999
Memory
Fanselow et al
Memory
Fanselow et al
Memory
Fanselow et al
Memory
1 4 12 3610
20
30
40
50
60
70
80
Control
HPC
First postsurgical no-platform probe
Training-surgery interval (wk)
Swim in correct quadrant (%)
Memory
1 4 12 362030405060708090100
ControlHPC
Postsurgery first dayVisual discrimination
Training-surgical interval (wk)
Percent correct
Memory
1 4 120
10
20
30
40
Control
HPC
Postsurgery responding to context
Training-surgery interval (wk)
Number of observations of freezing
Memory
1 4 12010203040
ControlHPC
Postsurgery responding to auditory stimulus
Training-surgery interval (wk)
Number of observations of freezing
SRT Results
before a f te r
Shi e t a l, Sc ie nc e 2 84 : 1 81 1 (11 J un 19 99 )
HippocampalDysfunction or lesion
