2. • Memory comprises; the ability to grasp and retain new information. It
requires processing, registration and recall. It is modality- specific and
related to auditory, visual, sensory or olfactory. It may be related to
abstract or internalized experience.
• In assessment of memory, there should be consideration of the patient’s
educational status, degree of enlightenmentand personal interest. Asking
an eighty year old uneducated woman the winner of 2011 cricket world
cup will be inappropriate if she has no interest in cricket. Personal issues
relating to her marriage, children and occupation will be more appropriate
because of her personal interest.
3. • Memory can be classified in many different ways. However, the commonly
used classifications are the following;
• a) Classification according to Content (Considered part of long term memory)
• b) Classification according to Duration.
• Classification according to the content has two classes
1. Declarative (Explicit)
2. Procedural (Implicit).
• Declarative memory is explicit and needs to be retrieved.
4. Declarative memory is further subdivided into two:
Episodic and Semantic.
Episodic memory is memory in time and space. Episodic memory answers all the questions
that start with; When? Who? Where? How? What? And Which? What is her name? Who is the
governor? How many students were in the class? Episodic memory fades after a while in all
normal persons. However, it can be reinforced by personal interest, novel, pleasant and
traumatic experiences. Hence somebody may easily remember the name of a stranger because
it is her brother’s name. Alzheimer’s disease causes early loss of the episodic memory.
The second type of declarative memory is semantic memory which comprises all unchanging
facts, principles, associations and laws. Unchanging facts like the days of the week, months of
the years, countries and their capitals constitute the semantic memory. Unchanging principles
like the physical attributes, colour of skin belong to a particular race also constitutes the
semantic memory. In some cases, the semantic memory may also be episodic e.g. Who was the
president of the country in the year 2012? It answers the question that starts with ‘Who?’
(Episodic) and it is also an unchanging fact (Semantic).
5. • Procedural or implicit memory comprises all acquired skills which have
become innate and do not need retrieval. All skills acquired (taking a bath,
dressing, driving, sewing, cooking, surgical skills) belong to the procedural
memory. They are performed with ease without conscious retrieval.
Alzheimer’s disease markedly affects the procedural memory such that the
individual is unable to carry out procedures he has done with ease for many
years. He may not remember the ingredients of an everyday dish. One of the
author’s patients was reported to have come out of the bathroom without
rinsing off the soap during a bath.
6. • Classification of memory according to Duration however is the commonest
classification. It is the one usually assessed in most neurology clinics.
• It comprises
1. sensory
2. short term
3. Recent
4. long term memory
7. • Long term Memory:
• Long term memory is tested by asking the patient to recall events occurring at
least five years earlier.
• This may include the names of past presidents of his country, major events in
the country, state or town like elections, tragedies sporting events etc. Asking
family accounts, personal issues and interests (marriages, births, deaths in the
family, patient’s education, and jobs businesses) usually give better results and
can be assessed while taking the history.
• The patient’s accurate account of the history especially past medical history
and coherence is a good assessment of his mental status. The long term
memory is relatively resistant to the effects of neurological and psychiatric
diseases hence patients with memory impairment may not remember very
recent events but recall events that took places decades earlier with
astounding clarity.
• The first name is everybody’s earliest memory and is never lost. All
neurological and psychiatric patients can speak still remember their first
names.
8. • Recent Memory/ Secondary memory In chronic organic brain disorders,
memory for recent events is diminished.
• The degree to which recent memory is lost is an index of the severity of
organic brain disorder. You can test the recent memory by asking about
recent television programmes, the last meal or details of recent major events
in the community, city or country .
• This could be politics, natural disasters or sports. A person’s accurate
description of his illness during history taking is also a good test for recent
memory.
9. • Short term /Immediate Memory
• Short term memory is the memory for events of few seconds or minutes past. It
has limited capacity of 7+/-2 numbers. To examine the short term memory, ask
the patient can to say a name and then address and repeat it 5 minutes later. You
can also ask the patient to repeat a sentence.
• Repeating a sequence of digits (Digit span) is another method. The numbers are
increased one at a time as the patient repeats e.g. say after me 342, he,replies
342 then 2157 and he replies 2157 then continually increase the digits, 43528,
8563247, 249803.
• Most people should be able to repeat seven digits forward and five digits
backwards. Note that chunking increases this limited capacity e.g. 0025-6742-
9812-0534.
• This number which has a total of 16 digits has been split into chunks of 4 and
memorized 4 at a time. In this manner, it is easy to commit 16 digits to memory.
• Short term memory is particularly impaired in WerKorsakoff’s syndrome and in
10. • Visual and auditory memory Visual and auditory memory is actually poorly
understood aspects of memory.
• The visual memory may be stronger than the auditory memory and vice
versa. The author has a great auditory memory but a very poor visual
memory. Visual memory can be tested by giving the patient a picture and
finding out how many objects he noticed in the picture. The person with a
poor visual memory will not see some of the objects. This test can also
indicate other lesions like hemineglect or Simultagnosia. Persons with
hemineglect will see only objects on one side while those with Simultagnosia
may see only the small objects and not see the larger ones or vice versa.
They are unable to see all the objects simultaneously.
• Auditory memory is tested by asking the patient to repeat a previously
spoken message. All the answers to the specific questions on memory should
be recorded verbatim.
11. • Hippocampus: where short-term memories are
converted to long-term memories
MEMORY-BASICS
Neurobiological systems regulating the
consolidation of memory
12. • Multiple brain regions are involved in encoding (as
shown by fMRI) -term memory.
13. • 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.
• Consolidation of memory involves the hippocampus but the hippocampal system does not
store long-term memory.
• LTM storage occurs in the cortex, near where the memory was first processed and held in
short-term memory.
• Hippocampus and nearby structures related to sin of transience
• Parts of the frontal lobe related to transience, but even more central to absent-mindedness
and misattribution (and maybe suggestibility)
• Area near front of temporal lobe related to blocking
• Amygdala closely related to persistence
14. • Hippocampus
• Important for formation of new episodic memories
• Important for encoding perceptual aspects of memories
• Novel events, places, and stimuli
• Important for declarative memory
• Especially as part of medial temporal lobe
• Recollection vs. Knowing (familiarity)
• Eldridge et al have shown the hippocampus is selectively
involved in R, not with K.
15. • Diencephalic amnesia - damage to
the medial thalamus and mammillary
nuclei
• Medial temporal lobe amnesia -
damage to the hippocampal
formation, uncus, amygdala, and
surrounding cortical areas
• Other implicated regions include
Anterior Lateral Temporal Lobe and
Frontal Lobes
