Download 3FA3M1-P

Differential Effects of Early
Hippocampal Pathology on Episodic
and Semantic Memory
Vargha-Khadem et al. 1997
Group B1!! Is…
Mohamed Sharif, Brandon Thomas
And Presenting Tonight: Meesha Sidhu and Marc Del Zotto
Meesha Sidhu
Some Background
• Declarative Memory
– Episodic: Memory for events, placed specifically in
time. Context-Rich variety.
– Semantic: General world knowledge, facts, and, of
course, meanings of words.
Meesha Sidhu
What had been shown:
• Dissociation between Episodic/Semantic
memories:
– Previous patients lost Episodic but not Semantic
Meesha Sidhu
But Question:
• Is semantic memory preserved because the
existing base of knowledge helps by providing
links for new information?
OR…
• Do Semantic and Episodic memory systems
operate effectively independently; do they use
different neural machinery?
Meesha Sidhu
How can we test this?
Meesha Sidhu
Meet:
• Beth – Now 14
– Likely hypoxic brain injury, followed by seizures
after birth.
• Jon – Now 19
– Born at 26 weeks gestation (14 weeks premature).
Convulsions at age 4.
• Kate – Now 22
– Toxic dose of asthma medication at age 9,
followed by seizures and respiratory arrest.
Meesha Sidhu
Shared Symptoms
• Major memory deficits
– Spatial
– Temporal
– Episodic
Meesha Sidhu
Results of neuropsychological tests
-1
-16
-20
+7.1
Marc Del Zotto
Recall Tests
A – Story recall
Immediate and 90 min delay
B – Reproduction of Geometric Design
Immediate and 40 min delay
C – Word recall
Immediate and 20 min delay
Marc Del Zotto
Rey-Osterreith Complex Figure
• 3-5 min copying period
• 40 min delayed recall
Marc Del Zotto
3D imaging Slices
A – Normal individual
image
B – Amnesic patient image
(Beth)
Diffuse hippocampal
atrophy
Slice used for
1H MRS analysis
Marc Del Zotto
Hippocampal cross-sectional area
Marc Del Zotto
Magnetic resonance data
A – Hippocampal volumes
Left and right hippocampi
B – Hippocampal T2 values
Left and right hippocampi
C – MRS signal intensity ratios
Left and right temporal
lobes
Marc Del Zotto
What does this mean?
Two Possibilities:
• Episodic and Semantic
memories were really
spared to the same degree
OR
• Context-Rich and ContextFree memory systems
depend differentially on
the Hippocampus and
surrounding Cortical areas
Marc Del Zotto
SO, how can we tell the
difference?
Look at Human and Non-Human
Primate test results, and compare:
• These three patients tested
and compared to controls
• Only sig. differences shown
were object-place and
voice-face recognition
• Results similar to those
obtained in non-human
primates with hippocampal
lesions and subjacent
cortices left intact
Marc Del Zotto
This suggests:
• More specific rather than diffuse functionality
of hippocampus and surrounding cortical
areas.
– Episodic (Context Rich; requires hippocampal
processing)
– Semantic (Context-Free; surrounding cortical
areas are sufficient)
Thanks for listening!