Transcript 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!