NROC61 Chapter 24
Types of Memory and Amnesia
Learning is the acquisition of new information or knowledge. Memory is the retention of learned
Declarative and Nondeclarative Memory
Memory for facts and events is called declarative memory.
Non-declarative memories fall into several categories. The one that this course focuses on is
procedural memory memory for skills, habits and behaviours.
Declarative memory can be accessed for conscious recollection, and non-declarative memories
Non-declarative memory is also frequently called implicit memory because it results from direct
experience whereas declarative memory is often called explicit memory because it results from
more conscious effort.
Declarative memories are easy to form and are easily forgotten. On the other hand, non-
declarative memories tend to require repetition and practice over a longer period of time but
are less likely to be forgotten.
Long-Term, Short-Term, and Working Memory
Long-term memories are those that you can recall days, months or years after they were
Memories that are readily lost are called short-term memories and these last on the order of
seconds to hours and are vulnerable to disruption.
Memories are stored in short-term memory and are selectively converted into a permanent
form via a process called memory consolidation (See Fig. 24.2).
Working memory is a temporary form of information storage that is limited in capacity and
There are reports of humans with cortical lesions who have normal memory for information
coming from one sensory system (e.g. they can remember the same number of visually seen
numbers as other people) but a profound deficit when information comes from another system
(e.g. they cannot remember more than one number spoken to them).
Serious loss of memory and/or the ability to learn is called amnesia.
If amnesia is not accompanies by any other cognitive deficit, it is known as dissociated amnesia.
Following trauma to the brain, memory loss can manifest itself in two different ways: retrograde
amnesia and anterograde amnesia (Fig. 24.3).
o Retrograde amnesia is characterized by memory loss for events before the trauma (i.e.
you forget what you already knew). It follows a pattern in which events of the months
or years preceding the trauma are forgotten, but memory is increasingly strong for older
o Anterograde amnesia is an inability to form new memories. If anterograde amnesia is
severe, a person might be completely incapable of learning anything new. In milder
cases, learning may be slower and requires more repetition than normal.
A form of amnesia that involves a much shorter period of time is called transient global
amnesia. It lasts only for a period of minutes to days and is often accompanied by retrograde
amnesia for recent events preceding the attack.
o During the spell, the person may appear disoriented and ask the same questions