knowledge such as the date one was born, one’s nation-
ality, the names of close relatives. Semantic memories
are often acquired implicitly, but they can be retrieved
explicitly while episodic memories are acquired and re-
trieved explicitly.
p0025 Finally, procedural long-term memory is a relatively
heterogeneous concept broadly regrouping complex
sensorimotor knowledge and skills that are acquired
implicitly or explicitly and, once fully automatized, are
difficult to verbalize (e.g., skilled reading, speaking,
writing, advanced music playing, running a cycle, skilled
typing on a computer keyboard).
s0010 SHORT-TERM MEMORY DISORDERS
p0030 Impaired short-term memory is reflected by a reduced
ability to temporarily store and reproduce verbal and/or
visuospatial information that has just been presented.
Children with impaired verbal short-term memory will
thus show poor ability in the immediate reproduction of
verbal sequences (e.g., lists of digits, words or unfamil-
iar words) and/or visuospatial patterns (e.g., object
copying, spatial sequence reproduction). Given the im-
portance of short-term memory as a first step toward
long-term learning of new information, these children
will typically also have difficulties in learning new
verbal inform ation such as a new vocabulary, new
definitions, and in learning associations between
abstract concepts as for example needed in chemistry
(Baddeley et al., 1998). Furthermore given the implica-
tion of short-term memory during mental calculation
and reasoning, difficulties will also be observed in ar-
ithmetic and sentence comprehension. The d eficit can
be selective for verbal or visual information, or involve
both modalities. Although short-term memory deficits
do not prevent successful comple tion of primary and
secondary school education, they will nevertheless
cause a significant handicap by slowing the affected
child’s learning rate and his/her comprehension o f
the explanations a nd task assignments provided by
the teaching staff.
p0035 The observation of a selective short-term memory im-
pairment, in the absence of any other cognitive deficit, is
extremely rare. This is partly due to the fact that short-
term memory deficits are the consequence of lesions in
the inferior parietal lobule and/or the inferior frontal gy-
rus, most often as a result of a cerebrovascular accident
in the territory of the left middle cerebral artery. This
kind of accident is rare in children. Furthermore, trau-
matic brain injury, more common in populations of chil-
dren, rarely leads to focal and selective lesions in these
areas, although short-term memory disorders are a fre-
quent consequence of traumatic brain injury in associa-
tion with other memory impairments (episodic memory).
Three cases have been described presenting a selective
verbal short-term memory disorder in the absence of
any documented brain insult, but with the predicted ac-
companying difficulties in learning new verbal informa-
tion (Baddeley, 1993; Baddeley and Wilson, 1993; Hanten
and Martin, 2001). However, at least for two of these
cases, more general language impairment could not be
completely excluded.
p0040At the same time, short-term memory disorders are
most often observed in association with broader cogni-
tive impairment. Children with specific language im-
pairment and children with dyslexia typically show
poor verbal short-term memory and working memory
spans; the reduction in verbal short-term memory in
these populations cannot be fully explained by their
poor langu ag e abi lit ie s, an d henc e it is like ly that
the short-term memory deficits f urther contribute to
the already protracted language development in these
children. More generally, verbal short-term memory
deficits are a residual deficit in many populations which
initially presented more global language impairment
patients who presented specific language impairment,
childhood aphasia, or epileptic childhood aphasia
(Landau-Kleffner syndrome) during childhood can
show relatively good language r ecovery at adulthood
but verbal short-term memory impairment will still be
present(Majerusetal.,2004).
p0045A number of genetic syndromes are also character-
ized by poor short-term memory spans, either for verbal
short-term memory, such as in Down syndrome (trisomy
21) or for visual short-term memory, such as in
Williams syndrome (7q11.23) and X-related syndromes
(Fragile X, Turner syndrome, Klinefelter syndrome,
and Rett syndrome). Velo-cardio-facial syndrome
(microdeletion 22q11.21) is particularly interesting here
since a specific deficit for the retention of order
information has been observed: affected child ren can ac-
curately maintain and reproduce the items (e.g.,
words, digits) that have been presented to them but they
will have more important difficulties in maintaining
and reproducing the order in which the items have been
presented (Majerus et al., 2007). Recent studies
suggest indeed that one of the major functions of
short-term memory is to maintain the order of events
that just occurred, the events themselves being directly
coded via temporary activation of the respective long-
term knowledge bases (i.e., the language system for ver-
bal information) (Majerus, 2009). Finally, we should
note that in Fragile X syndrome, the short-term memory
impairment is typically more general, including poor
retention for verbal, visual, and order information,
most likely related to more fundamental attentional dif-
ficulties during encoding of information in short-term
memory.
Comp. by: pdjeapradaban Stage: Revises1 Chapter No.: 27 Title Name: HCN
Date:7/2/13 Time:11:31:03 Page Number: 2
2 S. MAJERUS AND M. VAN DER LINDEN
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