Cognitive Neuroscience (2) – Textbook
Chapter 8: Memory: Varieties and Mechanisms
Memory allows us to learn from the past, understand the present, and plan for the future.
All cognitive abilities depend on memory to one degree or another.
Memory Phases, Processes, Systems, and Tasks
Memory is the series of processes whereby the nervous system acquires information from new
experiences, retains this information over time, and eventually uses it to guide behavior and plan
future actions.
Three basic memory phases:
1. Encoding: the processes whereby experiences can alter the nervous system (memory traces).
2. Storage: retention of memory traces over time.
3. Retrieval: accessing of stored memory traces, which may lead to a change in behavior and
sometimes is associated with the conscious experience of remembering.
Learning (synonym of encoding) can also describe gradual changes in behavior as a function of
training.
Researchers distinguish among different memory systems.
Memory systems
= groups of memory processes and associated brain regions that tend to interact to mediate
performance over a class of similar memory tasks.
Some tasks depend primarily on one memory system, most tasks are sensitive to the contributions of
more than one memory system.
During the 1970s psychologists found evidence that retaining information across delays of seconds or
minutes (short-term memory) involves mechanisms that are different from those used for retaining
information across delays of hours, days, or weeks (long-term memory).
Memory systems:
Working memory: mediates the maintenance and manipulation of information online for a
few seconds or minutes.
Long-term memory systems: mediate the retention of information for longer periods.
o Declarative memory: conscious memory for events (episodic memory) and facts
(semantic memory).
o Nondeclarative memory: memories that are expressed through performance
independently of consciousness (implicit memory).
1
,Dissociating Memory Systems
Working memory versus declarative memory
The most telling evidence supporting the distinction between working memory and declarative
memory has been provided by cases of amnesia.
Childhood amnesia: normal lack of memory for events that took place during the first few
years of life.
Psychogenic amnesia: memory loss due to psychological trauma.
Anterograde amnesia: memory loss affect information acquired after the damage.
Retrograde amnesia: memory loss affect information acquired before the damage.
Amnesia due to brain lesions most often arises from bilateral damage to the medial temporal lobe.
Patients may display severe anterograde amnesia with some degree of retrograde amnesia.
o Patients cannot form new memories for events.
Patients with amnesia can maintain a normal conversation.
This implies that working memory is spared, since conversing requires remembering what
was said during the last few seconds or minutes.
Being impaired in declarative memory but not in working memory represents a single dissociation. To
make the argument stronger, a double dissociation is needed.
A double dissociation occurs when there are patients who are impaired in working memory
but not in declarative memory.
Such patients have been identified, and their brain lesions are typically located in the left
temporoparietal cortex.
Declarative versus nondeclarative memory
Patient H.M.
Bilateral damage to medial temporal lobes.
Impaired declarative memory.
Normal nondeclarative memory (skill learning and priming).
Patient M.S.
Damage to right occipital regions (primary and secondary visual cortex).
Impaired nondeclarative memory.
Normal declarative memory.
Researchers compared patient M.S. to healthy controls and amnesic patients on two types of
memory tasks.
2
, Implicit (nondeclarative) memory/priming
o M.S. showed no priming effect, likely due to his visual impairment, whereas healthy
participants and amnesic patients did show normal priming.
o A word is flashed briefly on a screen; if someone has seen a word before, they
typically identify it more quickly (priming).
Explicit (declarative) memory/recognition
o M.S. performed normally on declarative memory tasks, while amnesic patients
showed impairments.
Nondeclarative Memory
All forms of nondeclarative memory have in common the facts that they are expressed through
performance and are independent of conscious awareness.
Forms of nondeclarative memory:
Priming: change in the processing of a stimulus due to a previous encounter with the same or
a related stimulus (completing a word fragment with a previously read word).
Skill learning: gradual improvement in performance due to repeated practise.
Conditioning: simple responses to associations between stimuli.
Priming can occur from a single encounter with a stimulus, while skill learning and conditioning
involve multiple learning trials.
Conditioning typically simpler responses and associations than skill learning.
Priming
3
, = a change in the efficacy of stimulus processing arising from a previous encounter with the same or a
related stimulus, in the absence of conscious awareness about the first encounter.
The requirement that participants be unaware that they are using information from the first session is
crucial.
Depending on the relationship between the stimulus that generates the priming effect (the prime)
and the stimulus eliciting that effect (the target), priming can be classified as direct or indirect.
Direct priming (repetition priming): prime and target stimuli are the same.
o Perceptual priming: the test cue and the target are perceptually related.
o Conceptual priming: the test cue and the target are semantically or associatively
related.
Indirect priming: prime and target are different.
o Semantic priming: the prime and the target are semantically related (e.g., envelope
and letter).
Perceptual priming
Perceptual priming depends on brain systems different from those underlying declarative memory.
Patients with medial temporal lobe amnesia were impaired in episodic memory but not in
perceptual priming.
Patient M.S. with occipital lobe damage was impaired in perceptual priming but not in
episodic memory.
Perceptual priming depends on sensory regions of the cortex (e.g., visual regions of the occipital
lobe).
Perceptual priming decreases when the format of information changes between study and test
phases (study-test format shifts), such as:
Switching from pictures to words,
Switching modalities (e.g., auditory visual).
Single-cell recording studies in monkeys have shown that neurons in visual processing regions show a
decreased level of firing when a new visual stimulus is repeated.
= repetition suppression: previously encountered stimuli result in weaker responses.
Objects repeated in the identical format elicited reduced activity in bilateral fusiform regions.
o Reduced activity in the left fusiform gyrus, but not in the
right fusiform gyrus (more activity).
o Left fusiform gyrus for priming.
Theories of repetition suppression:
4
Chapter 8: Memory: Varieties and Mechanisms
Memory allows us to learn from the past, understand the present, and plan for the future.
All cognitive abilities depend on memory to one degree or another.
Memory Phases, Processes, Systems, and Tasks
Memory is the series of processes whereby the nervous system acquires information from new
experiences, retains this information over time, and eventually uses it to guide behavior and plan
future actions.
Three basic memory phases:
1. Encoding: the processes whereby experiences can alter the nervous system (memory traces).
2. Storage: retention of memory traces over time.
3. Retrieval: accessing of stored memory traces, which may lead to a change in behavior and
sometimes is associated with the conscious experience of remembering.
Learning (synonym of encoding) can also describe gradual changes in behavior as a function of
training.
Researchers distinguish among different memory systems.
Memory systems
= groups of memory processes and associated brain regions that tend to interact to mediate
performance over a class of similar memory tasks.
Some tasks depend primarily on one memory system, most tasks are sensitive to the contributions of
more than one memory system.
During the 1970s psychologists found evidence that retaining information across delays of seconds or
minutes (short-term memory) involves mechanisms that are different from those used for retaining
information across delays of hours, days, or weeks (long-term memory).
Memory systems:
Working memory: mediates the maintenance and manipulation of information online for a
few seconds or minutes.
Long-term memory systems: mediate the retention of information for longer periods.
o Declarative memory: conscious memory for events (episodic memory) and facts
(semantic memory).
o Nondeclarative memory: memories that are expressed through performance
independently of consciousness (implicit memory).
1
,Dissociating Memory Systems
Working memory versus declarative memory
The most telling evidence supporting the distinction between working memory and declarative
memory has been provided by cases of amnesia.
Childhood amnesia: normal lack of memory for events that took place during the first few
years of life.
Psychogenic amnesia: memory loss due to psychological trauma.
Anterograde amnesia: memory loss affect information acquired after the damage.
Retrograde amnesia: memory loss affect information acquired before the damage.
Amnesia due to brain lesions most often arises from bilateral damage to the medial temporal lobe.
Patients may display severe anterograde amnesia with some degree of retrograde amnesia.
o Patients cannot form new memories for events.
Patients with amnesia can maintain a normal conversation.
This implies that working memory is spared, since conversing requires remembering what
was said during the last few seconds or minutes.
Being impaired in declarative memory but not in working memory represents a single dissociation. To
make the argument stronger, a double dissociation is needed.
A double dissociation occurs when there are patients who are impaired in working memory
but not in declarative memory.
Such patients have been identified, and their brain lesions are typically located in the left
temporoparietal cortex.
Declarative versus nondeclarative memory
Patient H.M.
Bilateral damage to medial temporal lobes.
Impaired declarative memory.
Normal nondeclarative memory (skill learning and priming).
Patient M.S.
Damage to right occipital regions (primary and secondary visual cortex).
Impaired nondeclarative memory.
Normal declarative memory.
Researchers compared patient M.S. to healthy controls and amnesic patients on two types of
memory tasks.
2
, Implicit (nondeclarative) memory/priming
o M.S. showed no priming effect, likely due to his visual impairment, whereas healthy
participants and amnesic patients did show normal priming.
o A word is flashed briefly on a screen; if someone has seen a word before, they
typically identify it more quickly (priming).
Explicit (declarative) memory/recognition
o M.S. performed normally on declarative memory tasks, while amnesic patients
showed impairments.
Nondeclarative Memory
All forms of nondeclarative memory have in common the facts that they are expressed through
performance and are independent of conscious awareness.
Forms of nondeclarative memory:
Priming: change in the processing of a stimulus due to a previous encounter with the same or
a related stimulus (completing a word fragment with a previously read word).
Skill learning: gradual improvement in performance due to repeated practise.
Conditioning: simple responses to associations between stimuli.
Priming can occur from a single encounter with a stimulus, while skill learning and conditioning
involve multiple learning trials.
Conditioning typically simpler responses and associations than skill learning.
Priming
3
, = a change in the efficacy of stimulus processing arising from a previous encounter with the same or a
related stimulus, in the absence of conscious awareness about the first encounter.
The requirement that participants be unaware that they are using information from the first session is
crucial.
Depending on the relationship between the stimulus that generates the priming effect (the prime)
and the stimulus eliciting that effect (the target), priming can be classified as direct or indirect.
Direct priming (repetition priming): prime and target stimuli are the same.
o Perceptual priming: the test cue and the target are perceptually related.
o Conceptual priming: the test cue and the target are semantically or associatively
related.
Indirect priming: prime and target are different.
o Semantic priming: the prime and the target are semantically related (e.g., envelope
and letter).
Perceptual priming
Perceptual priming depends on brain systems different from those underlying declarative memory.
Patients with medial temporal lobe amnesia were impaired in episodic memory but not in
perceptual priming.
Patient M.S. with occipital lobe damage was impaired in perceptual priming but not in
episodic memory.
Perceptual priming depends on sensory regions of the cortex (e.g., visual regions of the occipital
lobe).
Perceptual priming decreases when the format of information changes between study and test
phases (study-test format shifts), such as:
Switching from pictures to words,
Switching modalities (e.g., auditory visual).
Single-cell recording studies in monkeys have shown that neurons in visual processing regions show a
decreased level of firing when a new visual stimulus is repeated.
= repetition suppression: previously encountered stimuli result in weaker responses.
Objects repeated in the identical format elicited reduced activity in bilateral fusiform regions.
o Reduced activity in the left fusiform gyrus, but not in the
right fusiform gyrus (more activity).
o Left fusiform gyrus for priming.
Theories of repetition suppression:
4
