Transcript Localisation of Memory

Localisation of Memory
Chapter 28
Memory
My Dog Boo- Purchased Saturday
26th February 1984
I was nine years old. I can remember the
address of the breeder and how much
we paid for her and also how she burnt
her nose on the radiator as soon as she
came home!! I can remember all sorts of
other details like what the breeder
looked like.
Different Types of Memory
These are associated with
different parts of the brain.
There is some overlap.
Declarative Memories (facts
and episodes) are needed
and drawn upon when
performing mental recall
operations such as identifying
a familiar object or recalling
past experience.
Procedural Memories (skills
and habits) are needed and
drawn upon in order to
perform mental skills such as
remembering how to read and
motor skills such as swimming
and cycling
Declarative Memories
(‘remembering that…’)
• Successful declarative memories are associated with
areas of the temporal lobes at the sides of the cerebrum
The limbic system surrounds
and parts of the limbic system
the hypothalamus. It possesses
a structure called the
hippocampus which projects
into the temporal lobe
Procedural Memories (‘remembering
how to….’)
• Procedural memories (skills and habits) are
needed and drawn upon in order to perform
mental skills such as remembering how to read,
how to play chess etc., and motor skills such as
swimming, cycling and knitting. The cerebellum
is involved these types of memories where
muscular co-ordination is involved.
Amnesia
• Amnesia is the partial or complete loss of
memory. It takes several forms and can result
from an injury, disease or stroke which affects
the brain; or from surgery or electric shocks
applied to the brain. Symptoms of amnesia
include being unable to remember childhood
events, problems recalling names, faces and
words and having difficulty remembering day-to
day events
Evidence for Localisation of
Memory- A Case History
The limbic system was removed from the brain of
a patient to relieve life-threatening epilepsy. This
patient was unable to recall new factual
information for any longer than a few minutes.
He could still recall old declarative memories
stored before the operation. He could also
retained procedural skills such as tying his laces
and reading a book although he was happy to
read the same book everyday because he failed
to retain any of the information that he had read..
He was able to retain procedural memories like
how to play a new sport.
Conclusions for Localisation of
Memory
• This case study shows that the limbic system is needed
for the formation and transfer of new declarative
memories but are not the storage sites.
• The declarative memories are stored in the temporal
lobes. This patient still had his temporal lobes so was
able to recall old declarative memories but not deposit
any new ones there hence he couldn’t store any of the
facts he was reading from the book.
• Procedural memories involve the cerebellum and so as
this part of the brain was not affected, the patient was
able to form and store new procedural memories like
learning to play a new sport after the operation and
retrieve old procedural memories like tying laces
Personal Versus General Memories
Some people suffering amnesia
forget the details of their
personal history but remember
general facts such as the
meaning of the words of the
language they speak. This is
because the personal and
general declarative memories
occupy different areas of the
brain. It is thought that personal
D.M are stored in the right
temporal lobe and General D.M
are stored in the left temporal
lobe.
Memory Circuits
• It is thought that each memory is held by a group of neurones and is
arranged in a particular way to form a memory circuit. In order to
retrieve the memory, a nerve impulse is passed through the memory
circuit reactivating it. This can be likened to operating an electrical
appliance by passing electricity through its circuit. It is thought that
neurotransmitters are needed to allow flow of impulses through
the memory circuits and the more often an impulse passes
through a circuit, the more likely it is that the memory will
become long lasting
Alzheimer’s Disease
• This condition is characterised by the presence
of numerous abnormal tangles of brain
neurones, the death of many brain cells and the
irreversible loss of parts of the memory. Loss of
acetylcholine- producing cells in the limbic
system is thought to be a factor in this condition.
Experiments on monkeys have shown that when
drugs are given to block acetylcholine, memory
is impaired. If drugs are given to enhance
acetylcholine production then memory is good.
Alzheimer’s and NMDA Receptors
• There is evidence to link Alzheimer’s with a breakdown
in NMDA receptors. The flow chart shows nerve
transmission in the hippocampus region of the brain’s
limbic system( the region needed for developing a new
memory)
The
neurones in
the limbic
system of a
normal
healthy
human are
found to be
rich in NMDA
receptors