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Chapter 5

PSY342H1 Chapter Notes - Chapter 5: Temporal Lobe, Henry Molaison, Long-Term Memory


Department
Psychology
Course Code
PSY342H1
Professor
Ari Silburt
Chapter
5

Page:
of 12
Chapter 5 Encoding and Retrieval from Long-term Memory
The Nature of Long-Term Memory
Memory is the internal repository of stored information and guides our behaviour
Memory relies on a set of processes by which information in encoded, consolidated
and retrieved
Long-term memory comprises of information that is acquired in the course of an
experience and that persists so that it can be retrieved long after that experience is past
Long-term memory can be consciously retrieved so and we can direct our behaviour
using our previous experiences
Long term memory can also influence our present thinking and behaviour while
operating outside awareness – past experience can unconsciously affect the present
The Forms of Long-Term Memory
There are multiple forms of long term memory that differ in their basic information
processing properties and in the brain structures supporting them.
Declarative memory (explicit memory) refers to a form of long-term memory that
can be consciously recollected and ‘declared’ or described to other people such as
memories of facts, ideas and events. Declarative memory includes two types of
memories:
i. Episodic memory; the memory of events in our own personal past. It is the
conscious knowledge that is temporally dated and spatially located. Such type
of memory has a context e.g. meeting a friend in a room
ii. Semantic memory; our general knowledge about things in the world and their
meaning. It is the knowledge of words and concepts, their properties and their
interrelations. This type of memory is not context bond because we acquire the
knowledge across multiple experiences in a variety of contexts.
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.
Declarative memory is highly flexible and involves the association of multiple pieces
of information and integrates them together to form a unified representation
Declarative memory depends on the operation of medial temporal lobes
Non-declarative memory (implicit memory) refers to non-conscious forms of long-
term memory that are expressed as a change in behaviour without any conscious
recollection.
Tests of non-declarative memory – called implicit memory tests – do not require the
description of the contents of memory but rather reveals the memory implicitly by
changes in performance.
Non-declarative memory is more restricted in the ways that it can be retrieved
The different forms of implicit memories e.g. habituation/conditioning/learning of
skills operates on different regions of brain
The Power of Memory: The Story of HM
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Information about memory comes to a large extent from a patient HM who underwent
bilateral removal of medial temporal lobes (included hippocampus, amygdala) and
suffered from a memory loss, but his working memory was intact
Working memory is composed of information that in maintained over a period of
seconds or minutes and it does not depend on medial temporal lobe structures
HM also has preserved episodic and semantic memory of information acquired before
his operation
HM suffered from severe anterograde amnesia; the inability to consciously remember
information encountered after brain damage. As soon as the information acquired
disappeared from his working memory, he almost completely forgot it. This forgetting
reveals an inability to form, retain or retrieve new episodic memories. HM was frozen
in time i.e. he was unable to update his personal life narrative because of the inability to
remember daily experiences. This amnesia is the failure to remember new events
regardless of the content or modality i.e. failure to form episodic and semantic memory
HM also demonstrated some retrograde amnesia; the forgetting of events that
occurred before brain damage. This amnesia was temporally graded; the closer an
event occurred to the surgery, the more likely it was forgotten.
This pattern of forgetting suggests that memories do not permanently depend on the
medial temporal lobes, otherwise HM would have forgotten early memories too. It
indicates that over time, memories become strong even after damage to medial
temporal lobes
Multiple Memory Systems for Long-Term Learning and Remembering
Medial temporal lobes are not necessary for all types of long-term memory because
HM was able to acquire new motor skills at a normal rate e.g. HM was able to remap
the visual perception onto motor actions
Non-declarative memories (implicit memories) that operate outside our awareness
are preserved despite damage of medial temporal lobe
Amnesic patients demonstrate normal priming effects when they are asked to complete
a word by using the first word that comes to their mind but if asked to complete a word
by recalling the word they previously heard, they encounter more difficulty
Amnesic patients are also able to improve their performance on perceptual and
conceptual tasks but they lack the episodic memory of it
Encoding: How Episodic Memories are Formed?
Encoding is the term used for various processes by which information is transformed
into a memory representation. These processes are set in motion at the time of the
experience and form a mental representation by recording some aspects
We can uncover the properties of encoding by determining the factors that strengthen
encoding of information
Encoding is influenced by degree to which we attend to the information and the extent
to which we ‘elaborate’ on its meaning
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Elaboration involves interpreting information, connecting it with other information
and reflecting on it.
Other influences that strengthen encoding are conscious retrieval of information and
practicing the information by spacing it out in time.
Medial temporal lobes play a critical role in episodic encoding
The Importance of Attention
Forgetting is a neural consequence of ineffective coding of an experience into episodic
memory
Poor encoding often occurs when we fail to attend to an event; attention may be divided
Frontal lobes support the ability to attend during learning and affect episodic encoding
Levels of Processing and Elaborative Encoding
Intent is required for effective memory formation but its only important because the
intent to encode can motivate attention
Encoding is an automatic by-product of attending to and processing a stimulus, the
critical point if how we process the stimuli and not why we do it
Levels of Processing Theory: Arguments and Limitations
Levels of processing theory draws on the fact that there are various aspects of any
given stimulus that can be attended and processed. In this view, encoding is a by-
product of stimulus processing; when we process a stimuli it leaves a residue in the
system that can guide later remembering of information.
Different aspects of stimulus processing correspond to different levels of analysis:
i. Structural: is the shallow/superficial level of perceptual analysis
ii. Phonological: is the intermediate analysis e.g. rhyming
iii. Semantic: is the deep analysis that actively relates the incoming information to
knowledge already present in the memory
According to the levels of processing theory, encoding relies on the level of processing
performed on a stimulus; the deeper the processing is, the more durable is the
representation
Episodic memory benefits from deep or elaborative processing
Incidental learning is the learning that occurs not as the result of a purposeful attempt
but as a by-product of performing a task. There is no intention of learning but yet we
learn, type of learning that takes place in the everyday life
A limitation involved is that we have no way of measuring/quantifying the level of
processing required by a particular encoding task
Another is the question of interpretation, does levels of processing differ in their
strength and durability of encoding or do they differ in terms of the stimuli that they
select for encoding and retrieving?. Most researchers argue that the type of encoding
used depends on the demands of retrieval. E.g. if retrieval demands perceptual details
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