Transcript Amnesia Cartoon

Memory Has Temporal Stages: Short, Intermediate, and Long
• Iconic memories are the briefest memories and store sensory
impressions that only last a few seconds.
• Short-term memories (STMs) usually last only for up to 30
seconds or throughout rehearsal.
– Short-term memory is also known as working memory.
• An intermediate-term memory (ITM) outlasts a STM, but is
not permanent.
• Long-term memories (LTMs) last for days to years.
– Long-term memory has a large capacity.
– Information can also be forgotten or recalled inaccurately.
Stages of Memory Formation
Memory Has Temporal Stages: Short, Intermediate, and Long
Working memory can be subdivided into three components,
all supervised by an executive control module:
• Phonological loop—contains auditory information
• Visuospatial sketch pad—holds visual impressions
• Episodic buffer—contains more integrated, sensory
information
A functional memory system incorporates three aspects:
• Encoding—sensory information is passed into short-term
memory.
• Consolidation—short-term memory information is
transferred into long-term storage.
• Retrieval—stored information is used.
Hypothesized Memory Processes: Encoding, Consolidation, and Retrieval
Memory Has Temporal Stages: Short, Intermediate, and Long
Mechanisms differ for STM and LTM storage but are
similar across species.
• The primacy effect is the higher performance for
items at the beginning of a list (LTM).
• The recency effect shows better performance for the
items at the end of a list (STM).
Serial Position Curves from Immediate-Recall Experiments
Successive Processes Capture, Store, and Retrieve
Information in the Brain
• Multiple brain regions are involved in encoding, as shown by fMRI.
• For recalling pictures, the right prefrontal cortex and
parahippocampal cortex in both hemispheres are activated.
• For recalling words, the left prefrontal cortex and the left
parahippocampal cortex are activated.
• Thus, the prefrontal cortex and parahippocampal cortex are
important for consolidation.
• These mechanisms reflect hemispheric specializations
(left hemisphere for language and right hemisphere for spatial
ability).
Encoding, Consolidation, and Retrieval of Declarative Memories
Event-related fMRI studies of episodic encoding and retrieval
J. Spaniol et al. / Neuropsychologia 47 (2009) 1765–1779
Fig. 1. ALE maps thresholded at p < .05, corrected. Enc = encoding success; Ret =
retrieval success. For the Enc vs. Ret difference map, areas more active for
encoding than for retrieval are shown in green. Areas more active for retrieval than
for encoding are shown in blue.
Successive Processes Capture, Store, and Retrieve
Information in the Brain
• The process of retrieving information from LTM can cause
memories to become unstable and susceptible to disruption or
alteration.
• Reconsolidation is the return of a memory trace to stable longterm storage after it’s temporarily volatile during recall.
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Reconsolidation can distort memories.
Successive activations can deviate from original information.
New information during recall can also influence the memory trace.
Leading questions can lead to ‘remembering’ events that never happened.
‘Recovered memories’ and ‘guided imagery’ can have false information
implanted into the recollection.
Role of the Hippocampus in Reconsolidation
• Damage to the hippocampus
– can produce Anterograde amnesia
– as in the case of H.M.
– can not consolidate new information
• What role does the Hippocampus play in LTM?
– LTM is not stored in hippocampus
– Hippocampus may be needed for retrieval of “recent” LTM whereas
“older” LTM is only processed by cortex
– Reconsolidation concept implies that LTM is processed through
hippocampal circuits i.e. working memory
– Frequent? Or Regular? Retrieval produces LTM that is independent
of the hippocampus
• Neural mechanism for working memory and LTM would be
different
Amnesia
• Reterograde
– “Backward”
– Loss of info just prior to
trauma.
• Anterograde
– “Forward”
– Inability to add new
information to memory.
Neurological examination of Amnesia Patients
• Based on Scoville and Milner's amnesic patient Henry Molaison
(H.M.), it has been known that the medial temporal lobes play a
critical role in our ability to form new memories.
• Also demonstrated that not all forms of memory are equally
affected by damage to the medial temporal lobes.
– Declarative or explicit memory is disrupted.
– Nondeclarative or implicit memory is largely intact, allowing patients to
acquire perceptual and motor skills, conditioned responses, and to
demonstrate priming.
Brain Tissue Removed from Henry Molaison (Patient H.M.)
Henry’s Performance on a Mirror-Tracing Task
HM mirror-tracing
HM could show implicit learning
Two Main Kinds of Memory: Declarative and Nondeclarative
There Are Several Kinds of Memory and Learning
Damage to other areas can also cause memory loss.
Patient N.A. has amnesia due to accidental damage to the left dorsal
thalamus, bilateral damage to the mammillary bodies (limbic
structures in the hypothalamus), and probable damage to the
mammillothalamic tract.
Like Henry Molaison, he has short-term memory but cannot form
declarative long-term memories.
Patient K.C. cannot retrieve personal (episodic) memory due to
accidental damage to the cortex and severe shrinkage of the
hippocampus and parahippocampal cortex; his semantic memory is
good.
Two subtypes of declarative memory:
• Semantic memory—generalized memory
• Episodic memory—detailed autobiographical memory
The Brain Damage in Patient N.A.
Subtypes of Declarative and Nondeclarative Memory
Preservation of musical memory in an amnesic professional cellist
• Are there special neural circuits for musical memory?
• Patient PM with brain damage following encephalitis
• lesions of the right medial temporal lobe, large portions of the
left temporal lobe and parts of left frontal and insular cortex
• Severe amnesia
• persistent ante- and retrograde amnesia.
• Profound deficits in semantic and episodic memory.
• Lack of recall for biographical information from childhood
through adulthood including professional events
• unable to recall or recognize lyrics of well-known songs
• could not recall any famous cellist and remembered the name of
only one composer (Beethoven)
• Musical memory
• able to sight-read and to play the cello
• normal for all aspects music perception
Tests of Specific Attributes of Memory
Different Brain Regions Process Different Aspects of Memory
• Early research indicated that animals form a cognitive map—a
mental representation of spatial relationships.
• Latent learning is when acquisition has taken place but has not
been demonstrated in performance tasks.
• The hippocampus is also important in spatial learning.
• It contains place cells that become active when in, or moving toward, a
particular location.
• Place cells remap when a rodent is placed in a new environment.
• Grid cells and border cells are neurons that fire when animal is at an
intersection and at the perimeter of an abstract grid map, respectively.
Different Brain Regions Process Different Aspects of Memory
• Imaging studies help to understand learning and nondeclarative
memory for different skills:
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Sensorimotor skills, such as mirror-tracing.
Perceptual skills—learning to read mirror-reversed text.
Cognitive skills—planning and problem solving.
All three of these depend on functional basal ganglia; the motor cortex
and cerebellum are also important for some skills.
• Imaging studies of repetition priming show reduced bilateral
activity in the occipitotemporal cortex, related to perceptual
priming.
• Perceptual priming reflects prior processing of the form of the
stimulus.
• Conceptual priming (priming based on word meaning) is
associated with reduced activation of the left frontal cortex.
The Delayed Non-Matching-to-Sample Task
Memory Performance after Medial Temporal Lobe Lesions
Brain Regions Involved in Different Kinds of Learning and Memory