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Chapter 5

chapter 5


Department
Psychology
Course Code
PSYB57H3
Professor
George Cree
Chapter
5

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Chapter 5 Encoding and Retrieval from Long-Term Memory
1.The Nature of Long-Term Memory
The ability to remember the people, places, and things encountered in the
course of daily life is a fundamental form of cognition that guides behaviour
Memory the internal repository of stored information
oRelies on a set of processes by which information is encoded,
consolidated, and retrieved
oMemory is essential to the functioning and even the survival of human
and other animals
oWithout memory, we could never learn from our experience and would
operate aimlessly, without plans or goals
oMoto skills and language ability would be lost
oEven the sense of personal identity we all possess would be gone
Long-term memory information that is acquired in the course of an
experience and that persists so that it can be retrieved long after the
experience is past
oSome forms of long-term memory can be consciously retrieved, so that
we can use our remembrance of things past to guide present thought
and action
William James (1890) described this kind of memory as the
knowledge of a former state of mind after it has once dropped from
consciousness
By contrast, other forms of long-term memory influence our present thinking
and behaviours while operating outside awareness
In such instances, past experience unconsciously affects the present.
1.1: The Forms of Long Term Memory
Theorists believe that there are multiple forms of long-term memory that differ in
their basic information processing properties and in the brain structures that
support them
These various forms of memory are thought to fall into 2 general classes
Declarative memory (explicit memory) refers to forms of long-term
memory that can ordinarily be consciously recollected and declared to
other people, such as memory, for facts. Ideas, and events
oEncompasses episodic memory, the memory of events in our own personal
past, and semantic memory, our general knowledge about things in the
world and their meaning , a distinction proposed by Endel Tulving in 1972
oEpisodic memory the conscious knowledge of temporally dated, spatially
located, and personally experienced events or episodes.
Supports memory for individual life, has a context
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Ex. When collecting details about one of the people you met in
the hall- her political view, her food taste you engage in a
kind of mental time travel to your earlier meeting, and you
were aware that the information you possessed about her was
bound to that particular autobiographical experience
oSemantic memory knowledge about words and concepts, their properties,
and interrelations
When you retrieve your semantic memory of, say, the main
ingredients of Italian cuisine, that memory is not bound to the specific
context in which you acquired that knowledge because you likely
accumulated the knowledge across multiple experiences in a variety of
contexts
Declarative memory tests that assess declarative memory are termed explicit
memory tests because they require the retrieval of an explicit description or report
of knowledge from memory
oIs highly flexible, involving the association of multiple pieces of information
into a unified memory representation thus, we may have different routes to
retrieval of a given memory
Both forms of declarative memory, episodic and semantic, depend on the operation of
the medial temporal lobes.
Nondeclarative memory (implicit memory) refers to non-conscious forms
of long-term memory that are expressed as a change in behaviour without
any conscious recollection
oTests of non declarative memory are called implicit memory tests
they do not require description of the contents of memory, but rather
reveal memory implicitly through observed changes in performance, such
as the gradual acquisition of a motor skill
oNondeclarative memory in comparison to declarative memory tends to
be more restricted in ways that this knowledge can be retrieved
oThe various forms of nondeclarative memory do not depend on the
medial temporal lobe structures that are important for declarative
memory. Rather, various forms of nondeclarative memory are
implemented in different brain regions
1.2: The Power of Memory: The Story of H.M.
Much of the research describing and classifying types of long term memory has a
very human foundation in the experience of a patient known as H.M.
oThe pattern of catastrophic memory deficits observed in this man initiated a
revolution in our understanding of memory, revealing that our ability to
encode and retrieve new episodic and semantic memories depends on a
particular set of brain structures in the medial and temporal lobesthe
hippocampus and surrounding entorhinal, perirhinal, and parahippocampal
cortices ^
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oThe story of H.M. highlights the centrality of memory to our lives, and shines
a spotlight on the powerful role the medial temporal lobes play in
documenting our experiences
oTests of H.M.`s cognitive abilities reveal that his deficit was highly specific,
as his intelligence and some memory functions are relatively preserved
Ex. When presented with a short list of numbers and asked to
remember them for 30 seconds, H.M. performs as well as those with
intact medial temporal lobes
This observation indicates that working memory , information that
is maintained over a period of seconds or minutes, does not depend on
medial temporal lobe structures
oEven though some memory functions are preserved, to this day H.M. suffers
from a severe anterograde amnesia - the inability consciously to
remember information encountered after brain damage
Applies to both episodic and semantic knowledge
Thus, although H.M. can briefly retain a short list of numbers
( because his working memory is intact), he will immediately and
completely forget them as soon as the information is lost from working
memory
This catastrophic forgetting reveals an inability to form, retain, and
retrieve new episodic memories
H.M.`s anterograde amnesia is global; that is, he cannot consciously
remember new events irrespective of their content or modality
He cannot remember the people, places, and objects he sees even after
repeated encounters.
It is clear that his amnesia does not reflect a perceptual deficit or a
generalized impairment in intelligence; rather, H.M. suffers from a
domain-general memory deficit
H.M. was unable to form new semantic memories following his
surgery
Thus, when his semantic memory was tested for phrases such as
flower child that had entered the language after his surgery but to
which he had been repeatedly exposed to, H.M. did not know the
meanings
oH.M. also demonstrates retrograde amnesia the forgetting of events
that occurred before the damage to the brain
An important aspect of H.M.s retrograde amnesia is that it is
temporally graded : the closer an event had occurred to his
surgery, the more likely it is to have been forgotten
In particular he has greater difficulty remembering
experiences that had occurred during the 11 years immediately
preceding his surgery than in recalling more remote
experiences from his childhood
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