PSYC 2410 Chapter Notes - Chapter 11: Temporal Lobe, Anterograde Amnesia, Coronary Artery Bypass Surgery

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19 Apr 2016
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Learning, Memory, and Amnesia — Ch 11
Biopsychology
11.1 Amnesic Effects of Bilateral Medial Temporal Lobectomy
-amnesia = any pathological loss of memory
-Case of H.M
at age 27 had the medial portions of his temporal lobes removed (bilateral
lobectomy) for the treatment of a severe case of epilepsy
his memory deficits were instrumental in the achievement of our current
understanding of the neural basis of memory
bilateral medial temporal lobectomy = the removal of the medial portions of BOTH
temporal lobes, including most of the hippocampus amygdala, and adjacent cortex
lobectomy = an operation in which a lobe, or a major part of one is removed from
the brain
lobotomy = an operation in which a lobe, or a major part of one is separated from
the rest of the brain by a large cut but is NOT removed
entered surgery a reasonably well-adjusted individual with normal perceptual and
motor abilities and superior intelligence, and he left in the same condition
H.M did not suffer a great deal from retrograde amnesia aside from those events
that occurred in the 2yrs before the surgery
H.Ms short-term anterograde memory remained normal (ex. his digit span was 6)
had almost a complete inability to form new long term memory
H.M regained his health but lost his future
unable to remember people, conversations, placement of
objects, etc
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Medial Temporal Lobectomy
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-retrograde amnesia = loss of memory for events or information learned before the
amnesia-inducing brain injury
-anterograde amnesia = loss of memory for events or information learned after the
amnesia-inducing brain injury
-short-term memory = storage of new information for brief periods of time while a
person attends to it
-long-term memory = storage of new information once a person stops attending to it
Formal Assessment of H.Ms Anterograde Amnesia: Discovery of Unconscious
Memories
-tests on H.Ms severe deficits in LT memory indicated that H.Ms brain is capable of
storing LT memories but that he had no conscious awareness of those memories
-Digit Span + 1 Test:
a test of verbal LT memory
a participant is asked to repeat a sequence of 5 digits that is read to them at 1-
second intervals
on the subsequent trial the same 5 digits are read + 1 new one added on the end
(this pattern follows as more trials are held)
most people can corrects repeat 15 digits after 25 trials of this test; H.M was unable
to successfully repeat 8 digits
-Block Tapping Memory-Span test
H.M had global amnesia (i.e., amnesia for information presented in all sensory
modalities)
Milner demonstrated that H.Ms amnesia was not restricted to verbal material by
assessing his performance on the +1 version of the block-tapping memory-span
test
9 blocks were spread out on a board infant of H.M and he was asked to watch as
someone touched a sequence of them and then to repeat the same sequence of
touches
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H.M had a block tapping span of 5, which is the average, but he was unable to
correctly touch a sequence of any number higher than that
-Mirror Drawing Test:
sensorimotor test of memory
H.M was asked to draw a line within the boundaries of a star-shaped target by
watching his hand in the mirror
was asked to tracer the star 10x on each of 3 consecutive days, and the number of
times he went outside the boundaries was recorded
H.Ms performance improved over the 3 days, which indicated retention of the last
— however he was unable to remember having previously done the task before
first indication that H.Ms anterograde amnesia did not involve all LT memories
-Incomplete Pictures Test
sensorimotor tasks were the one exception to his inability to form LT memories
H.M could also form new memories in this test
a non-sensorimotor test of memory that employs five sets of fragmented drawings
each set contains drawings of the same 20 objects, but the sets differ in their
degree of sketchiness
-set 1: contains the most fragmented drawings
-set 5: contains the complete drawings
the subject is asked to identify the 20 objects from the sketchiest set, then those
objects that go unrecognized are presented in their set 2 versions, and so on, until
all 20 items have been identified
H.M had improved performance on this task 1 hour later from the 1st trial, however,
he could not recall previously performing the task
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