Memory 257to Learning Objective 2.12. This is one of the areas of the brain that shows damage
in people with Alzheimer’s disease. It is involved in consolidation, as researchers have found
evidence that the posterior cingulate is not only activated when engaging in active rehearsal
to first remember specific information, but it is also active when retrieving that memory
(Bird et al., 2015). Furthermore, improved memory appears to be related to how similar
brain activity during retrieval is to the activity in this same area during active rehearsal. It
is possible that active rehearsal and activity in the posterior cingulate strengthens memory
by helping link both episodic and semantic information (Binder et al., 2009; Bird et al., 2015).
When Memory Fails: Organic Amnesia
- 13 Identify the biological causes of amnesia.
From movies and TV, many people are familiar with the concept of repression, a type of
psychologically motivated forgetting in which a person supposedly cannot remember
a traumatic event. to Learning Objective 14.7. But what about an inability to
remember brought about by some physical cause? There are two forms of severe loss
of memory disorders caused by problems in the functioning of the memory areas of
the brain. These problems can result from concussions, brain injuries brought about by
trauma, alcoholism (Korsakoff’s syndrome), or disorders of the aging brain.
RETROGRADE AMNESIA If the hippocampus is that important to the formation of
declarative memories, what would happen if it got temporarily “disconnected”?
People who are in accidents in which they received a head injury often are unable to
recall the accident itself. Sometimes they cannot remember the last several hours or
even days before the accident. This type of amnesia (literally, “without memory”) is
called retrograde amnesia, which is loss of memory from the point of injury backward
(Hodges, 1994). What apparently happens in this kind of memory loss is that the consol-
idation process, which was busy making the physical changes to allow new memories
to be stored, gets disrupted and loses everything that was not already nearly “finished.”
Think about this: You are working on your computer, trying to finish a history paper
that is due tomorrow. Your computer saves the document every 10 minutes, but you are
working so furiously that you’ve written a lot in the last 10 minutes. Then the power goes
out—horrors! When the power comes back on, you find that while all the files you had
already saved are still intact, your history paper is missing that last 10 minutes’ worth of
work. This is similar to what happens when someone’s consolidation process is disrupted.
All memories that were in the process of being stored—but are not yet permanent—are lost.
One of the therapies for severe depression is ECT, or electroconvulsive therapy, in
use for this purpose for many decades. to Learning Objective 15.11. One of the
common side effects of this therapy is the loss of memory, specifically retrograde amnesia
(Meeter et al., 2011; Sackeim et al., 2007; Squire & Alvarez, 1995; Squire et al., 1975). While
the effects of the induced seizure seem to significantly ease the depression, the shock also
seems to disrupt the memory consolidation process for memories formed prior to the
treatment. While some researchers in the past found that the memory loss can go back as
far as three years for certain kinds of information (Squire et al., 1975), later research sug-
gests that the loss may not be a permanent one (Meeter et al., 2011).
ANTEROGRADE AMNESIA Concussions can also cause a more temporary version of the
kind of amnesia experienced by H.M. This kind of amnesia is called anterograde amnesia, or
the loss of memories from the point of injury or illness forward (Squire & Slater, 1978). Peo-
ple with this kind of amnesia, like H.M., have difficulty remembering anything new. This is
also the kind of amnesia most often seen in people with senile dementia, a mental disorder
in which severe forgetfulness, mental confusion, and mood swings are the primary symp-
toms. (Dementia patients also may suffer from retrograde amnesia in addition to antero-
grade amnesia.) If retrograde amnesia is like losing a document in the computer because
of a power loss, anterograde amnesia is like discovering that your hard drive has become
retrograde amnesia
loss of memory from the point of some
injury or trauma backwards, or loss of
memory for the past.