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Neuroplastic processes related to the ability
of the brain to change its functioning in
response to experience
Learning
◦ How experience changes the brain
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Memory
◦ How the changes are stored & later activated
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A patient that had a bilateral medial temporal
lobectomy as a treatment for his epilepsy
◦ Removal of the medial portions of both temporal
lobes; including most of the hippocampus,
amygdala & nearby cortex
◦ Alleviated most of his seizures, but had a
significant impact on his memory
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Much of our understanding of memory comes
from study of this man & the changes to his
memory
No one since has had this procedure
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Any pathological loss of memory
Retrograde amnesia
◦ Inability to remember information from the past
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Anterograde amnesia
◦ Inability to remember new information; can’t form
new memories
◦ Short term memory (STM)
 Storage of new info for a brief time while a person
attends to it
◦ Long term memory (LTM)
 Storage of new info once the person stops attending to
it
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Most of his memory from before the surgery was
intact
◦ With the exception of the 2 years prior to the surgery
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His short term memory was normal
But it was virtually impossible for him to form
new long term memories
◦ As soon as he stopped focusing on new information, he
forgot it
◦ He was effectively frozen in time
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Global amnesia
◦ Amnesia for memory presented in all sensory modalities
7 tests of his long term memory
1. Digit Span + 1 Test
2. Block-Tapping Memory-Span Test
3. Mirror-Drawing Test
4. Rotary-Pursuit Test
5. Incomplete-Pictures Test
6. Pavlovian Conditioning
7. ???
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Digit Span + 1 Test
1.
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Asked to repeat 5 digits that were read to him,
then those 5 + a new digit, etc.
Normal: 15 digits; HM: failure by 8
Block-Tapping Memory-Span Test
2.
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Asked to tap a series of blocks on a table in the
same order the experimenter did
Correct at 5 blocks, incapable of 6
3.
Mirror-Drawing Test
◦ Trace a star shape while looking at your hand in a
mirror; errors measured
◦ Repeated many times over a few days
◦ His performance improved over time, even though
he had no memory of having done the task before
Rotary-Pursuit Test
4.
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5.
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6.
Maintain contact between a stylus and a target on a
rotating disc
Again, improvement without him remembering the task
Incomplete-Pictures Test
Patient must identify the object in a drawing, with it
drawn to different levels of completeness
Again, improvement without him
remembering the task
Pavlovian Conditioning
◦ Eye-blink task
 Tone plays before a puff of air in the eye; eventually the tone
alone causes a blink
 HM able to learn this, although it took longer than normal
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Mild retrograde amnesia
◦ Only 2 years before surgery
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Extreme anterograde amnesia
◦ Short term memory was fine
◦ But long term memory was severely impaired
 However, tests showed that while he could not
consciously remember having done these tasks before,
his improved performance on them indicates some
type of memory was being formed
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Memory functions seem to be highly
dependent on the structures of the medial
temporal lobe
His differential ability to remember things
showed that there were distinctly different
types of memory storage
◦ His specific problem seemed to be with memory
consolidation, the translation of STM to LTM
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Because his performance improved but he
couldn’t remember the task, it was
determined there are 2 categories of LTM
Explicit memories
1.
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Things you consciously remember
2 types
1. Semantic

Memories of general facts or information
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Memories of events in your life (aka autobiographical memories)
2. Episodic
Implicit memories
2.
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Memories that are formed without conscious awareness
of them
Indicated by increased performance over time in tasks
such as mirror drawing
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Korsakoff’s syndrome is a memory disorder
common in chronic alcoholics
Brain damage results from thiamine deficiency
Late stages involve sensory & motor problems,
extreme confusion, personality changes &
potential organ failure
Amnesia similar to that of medial temporal lobe
amnesia
◦ Early on, anterograde amnesia for explicit episodic
memories is most prominent symptom
◦ Later, severe retrograde amnesia sets in
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First symptom of Alzheimer’s is the
deterioration of memory
Major anterograde & retrograde deficits in
explicit memory
Often have deficits in STM & some types of
implicit memory (verbal & perceptual, not
sensorimotor)
Acetylcholine depletion may be the cause of
amnesia in Alzheimer’s