Lecture 3 Flashcards
Declarative vs procedural memory
Forms of memory loss (X2)
Declarative = facts/events
Procedural = learning a skill
Anterograde memory loss: inability to form new memories
Retrograde memory loss: inability to RECALL old memories.
Hippocampus involvement in memory formation
Involved in spatial memory.
May also be involved in non-spatial memory (stored for a short time in hippocampus then LTM stored elsewhere).
Case of H.M.
Which tissues were removed?
Tests used?
Medial Temporal Lobe damage (includes hippocampus).
Knocked down by bike when 6 y/o, started having minor epileptic fits 3 years later then began having major fits.
Received bilateral medial temporal lobe resection. Difficult surgery because area is so central. Suction used to remove brain tissue.
Removed tissue included amygdala, anterior two thirds of hippocampus and surrounding cortical tissue. Seizures became controllable by anticonvulsants.
Selective loss of DECLARATIVE memory (non-declarative was fine, he could learn new motor skills but couldn’t remember learning them or training items. E.g. mirror drawing (stars) = improved performance but no memory of training - episodic amnesia). Also had spatial memory deficit.
MTL specialized for declarative memory. Other brain regions mediate learning of skills (procedural memory)
Complete anterograde amnesia (couldn’t learn new declarative things) and partial retrograde amnesia for DECLARATIVE memory.
Types of memory (all types)
Divided into DECLARATIVE (“tell”) and NON-DECLARATIVE/PROCEDURAL (“show”)
Former divided into EPISODIC (remembering first day of school) and SEMANTIC (knowing the capital of France). Both stored in neocortex.
Latter divided into SKILL LEARNING, PRIMING (being more likely to use a word you heard recently) and CONDITIONING
(see chart)
Perceptual Memory
Gollins partial picture task
Learning ABOUT things (e.g. what/where) rather than what to do with them. Dependent upon sensory association cortex and NOT MTL.
Intact in H.M.
e.g. Gollins partial picture task: fragmented line drawings of familiar objects presented, starting with most fragmented in first trial and ending with complete picture in last trial. Repeat an hour later - normally can determine what images are in earlier trial.
H.M. performed this almost normally.
Patient R.B.
Heart attack –> temporary cessation of blood circulation –> brain damage (more selective region than H.M)
Primary symptom: anterograde amnesia (no retrograde).
Field CA1 destroyed.
Clear evidence for hippocampal involvement in anterograde amnesia.
DNMTS
MTL lesions in macaque:
Given delayed non-match to sample (DNMTS) training. First presented with an object. Displacement –> finds food underneath. After a delay (seconds to minutes) they are presented with the object again, plus a new object. Over series of trials with new items, they learn that food is always present under the new object.
Amnesia increases with hippocampal lesion (H) and even more so when included adjacent entorhinal cortex & parahippocampal cortices (H+). Even more so with anterior entorhinal and peripheral cortices (H++). H++ lesion given to macaques and then retrained using new objects.
8 minute delay - no difference in number of times correct. Longer delay - large impairment in lesioned animals. Preserved STM and imparied LTM.
Due to ability to retain information outside MTL for short periods. MTL NOT REQUIRED FOR STM.
Human data similar results.
MTL also not required for procedural learning.
Object discrimination task (macaques)
Pairs of objects with choice of one object reinforced. Acquired memory for 100 pairings over 4 months. Hippocampus + associated cortex lesioned in half.
Pairs that were learned 4 months before surgery were remembered just as well in both groups. Pairs that were learned 2 weeks before surgery were much worse in lesioned group. (More recent memories worse in lesioned)
Extent of hippocampal loss correlates with extent of retrograde amnesia.
MTL not required for LTM.
MTL overview
NOT required for STM or LTM (or procedural memory)
IS required for conversion of STM –> LTM (especially hippocampus)
