GGZ2025 Neuropsychological Disorders vvanbeek
TASK 5, PART 1 – MEMORY
MEMORY AND AMNESIA
Source: Kolb & Whishaw (2015)
The multiple memory systems classification
distinguishes transient short-term memory for
recent sensory, motor or cognitive information
from relatively permanent long-term memory.
Conscious, long-term memory may be explicit
(events and facts that you can spontaneously
recall) and either episodic (for personal
experiences) or semantic (for facts).
Implicit, nonconscious memory (like riding a bike) consist of learning skills, conditioned
responses, and events recalled on prompting. Emotional memory is vivid and has
characteristics of implicit and explicit memory.
CHILDHOOD AMNESIA
Everybody experiences amnesia to some extent. Childhood (infantile) amnesia in an
inability to remember events from infancy and early childhood. One reason for this failure is
that memory systems mature at different rates. Personal memories of early years may be lost
because the episodic memory system is not mature yet.
Another reason may be that the brain plays an active role in deleting memories, perhaps to
make room for new memories. Studies on mice suggest that as new hippocampal neurons
form new connections, they participate in forming new memories, but in doing so they disrupt
neural circuits that support memories already acquired. More-permanent memories are stored
when acquisition of new neurons by the hippocampus slows.
AMNESIAS RARE AND COMMON
Adults also forget. Referred to as fugue state, memory loss of personal history is sudden and
usually transient (NL; tijdelijk). Perhaps, the basis of the fugue state is the temporary
suppression of medial-temporal-lobe memory systems. Damage to restricted brain areas can
cause amnesia that takes very curious forms (for example, patients can be amnesic for fruits
and vegetables, but less for animals and birds.
Everybody experiences little everyday amnesias; forgetting people’s names or where we put
our keys. This kind of forgetting can increase with advancing age, in so-called senior
moments.
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, GGZ2025 Neuropsychological Disorders vvanbeek
ANTEROGRADE AND RETROGRADE AMNESIA
Memory of amnesic patients consists of two parts. When patients are
not able to acquire new memories, we call this anterograde amnesia.
When patients lose memories that have been accessible to them
before, this is called retrograde amnesia. The term anterograde
refers to the future with respect to the time at which a person incurred
damage to his brain. When many aspects of the ability to learn and
remember are affected, severe anterograde amnesia is referred to as
global anterograde amnesia.
Retrograde signifies that memory loss extends back in time relative to
the time of brain injury. Typically, memory is much better for events
that took place earlier in life than for more-recent events.
Traumatic brain injury (TBI) commonly produces time-dependent
retrograde amnesia, with the injury’s severity determining how far
back in time the amnesia extends. The retrograde extent of amnesia
(period of personal history is covers) generally shrinks with passage
of time.
SYSTEM CONSOLIDATION THEORY
The system consolidation theory states that the hippocampus consolidates new memories, a
process that makes them permanent. When consolidation is complete, the memories are stored
elsewhere in the brain. That is, memories are held in the hippocampus for a time, and they
consolidate somewhere in the neocortex.
The theory explains why older memories tend to survive hippocampal damage; they have
been transferred elsewhere for storage, whereas more-recent memories are likely to be lost
because they still reside in the hippocampus. If damage is limited to the hippocampus,
retrograde amnesia may extend back for only a few years. As more of the temporal lobe is
affected, retrograde amnesia can extend a lot further.
MULTIPLE-TRACE THEORY
Nadel & Moscovitch (1997) propose that multiple-trace theory accounts for individual
differences in amnesias;
❖ In any learning event memories of many types are encoded in parallel in different
brain locations. For example, autobiographical memory depends on the hippocampus
and frontal lobes, whereas factual semantic memory depends on temporal-lobe
structures.
❖ Memories change throughout a person’s life as they are recalled, re-evaluated
and restored. Autobiographical events, for example, through being recalled and
discussed, can also be stored as factual memory and perhaps even as general memory.
❖ Different kinds of memory being stored in different locations, are differentially
susceptible to brain injury. Because of this memory organization, after brain injury
usually only some aspects of memory will be affected, and older memories will be
more resistant to disruptions that newer memories.
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RECONSOLIDATION THEORY
The reconsolidation theory proposes that memories will rarely consist of a single trace or
neural substrate. We frequently recall memories. Each time a memory is used, it is
reconsolidated; the memory re-enters a labile phase and is then restored as a new memory.
Each use of memory is associated with a new phase of storage, resulting in many different
traces for the same event. Reconsolidation complicates the study of amnesia, because
spontaneous recall will change the memory that is the object fort investigation.
These three theories suggest that memory storage, memory type or frequency of use
contributes to the extent of amnesia. We can expect wide differences in the degree to which
people display anterograde and retrograde amnesia.
LONG-TERM EXPLICIT MEMORY
Explicit memory for events and facts is conscious and intentional, and consists of episodic
memories (personal experiences, what you did last night), and fact-based semantic
memories (2 x 2 = 4). Both types depend on conceptually driven top-down processing, in
which a person reorganizes data to store it. Later recall is thus greatly influenced by the way
the information was originally processed.
EPISODIC AND SEMANTIC MEMORY
Episodic (autobiographic) memory, a person’s recall of singular events, is uniquely
different from other memory systems in that it is memory of life experiences centered on the
person himself.
One function of autobiographical memory is providing us with a sense of continuity.
Autonoetic awareness, or self-knowledge, allows us to bind together the awareness of our
self as a continuous entity through time. Autonoetic awareness further allows us to travel in
subjective time, either into the past or the future.
Patients with hippocampal and frontal cortical injury often lose self-knowledge and have real
difficulty in daily living. Tulving (2002) proposes that ‘time-travel’ is a memory ability that
characterizes humans but not nonhuman animals, and depends on maturation and so will not
be found in babies and young children.
Figure: brain regions of episodic memory. The uncinate fasciculus is a fiber pathway that
connects the temporal lobe and ventral prefrontal cortex. Autobiographical memory depends
on the medial temporal lobe and the ventral prefrontal cortex and the connections between
them (the uncinate fasciculus).
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