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1. MENTAL RETARDATION AND DEVELOPMENTAL DISABILITIES
RESEARCH REVIEWSzyxwvutsrq
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NEUROPSYCHOLOGICAL PROFILE OF
DOWN SYNDROME:COGNITIVE SKILLS
AND BRAIN MORPHOLOGY
Paul P. Wang
Department of Pediatrics, University of Pennsylvania School of Medicine and Children’s Seashore House,
Philadelphia, Pennsylvania zyxwv
In children and young adults with Down syndrome, there
exists a profile of neuropsychological strengths and weaknesses.
Verbal short-term memory skills are diminished relative to subjects
with mental retardation resulting from other etiologies. On the
other hand, visual-motor skillsare comparatively well preserved.This
profile distinguishes the population having Down syndrome from
other impaired populations, although it may be confounded by
dementia in later adult years.
Down syndrome also results in a characteristicprofile of brain
morphology. In vivo magnetic resonance imaging studies have
shown that the frontal and temporal regions of the brain are
proportionally diminished in Downsyndrome, but that the volumes
of the subcortical nuclei are similar to those in control subjects.This
profile of brain morphology appears to correspond to both the
neuropathologic data on Down syndrome and to the profile of
cognitive skillsin individuals who havethis syndrome.
Impairment of fundamental cognitive processes such as
phonologic short-term memory is likely t o have implications
with regard to higher-order psychologicaland academic processes.
Effective educational intervention must take such impairments
into account during the development of individualized educational
plans. Q 1996 Wiley-Liss, Inc.
MRDD Research Reviews2: 102-108
~ ~~~~ ~~~~
Key Words: Down syndrome, neuropsychology, memory, visual-
motor skills, brain morphology
he bio-psychological study of Down syndrome can be
said to date from the time of its namesake description.
TDown’s report (1866) “Observation on an ethnic
classification of idiots,” was an earnest, though grossly wrong
and racist attempt to relate biology to cognition. Fortunately,
Down syndrome has become the subject of recent psychological
research that is theoretically and methodologically much more
sophisticated than Down’s musings.
Contemporary research on Down syndrome is motivated
by multiple factors, including the educational care of people who
have the disorder, exploration of the neurologic bases of
cognition, and various theoretical considerations from develop-
mental psychology. Mervis and her colleagues (Mervis, 1990),
for instance, have provided some of the most elegant explications
of language development in Down syndrome, demonstrating
universal principles of language acquisition that also apply to the
typically developing population. (Language development in
Down syndrome is reviewed more generally in this issue by zyxwvu
o1996 Wiley-Liss, Inc.
Kumin.) The recent compilations by Nadel (1988) and by
Cicchetti and Beeghly (1990) illustrate some of the other
productive avenues of investigation that Down syndrome has
provided to developmental psychology.
In contrast to these developmental psychological investiga-
tions of Down syndrome, which focus closely on single aspects
of cognition such as vocabulary acquisition or learning to count,
there also has been a long line of neuropsychological studies of
this syndrome. These studies have examined a broad array of
cognitive skills, each of which is hypothesized to have a distinct
brain basis. I will review these studies and the companion
investigations of in vivo brain morphology in Down syndrome.
AGE EFFECTS O N COGNITION
The earliest neuropsychological studies of Down syn-
drome were concerned with the effects of age on general
intellectual ability (reviewed by Hartley, 1986).A large number
of these studies found age-related decreases in the I Q of subjects
with this disorder. However, the ability to generalize these
results to current times is greatly limited by the fact that children
with Down syndrome now are much more likely to be raised in
stimulating home environments and to have challenging
educational opportunities. Even the early research found that
these variables are important predictors of cognitive ability in
these children. Furthermore, it is clear that regardless of the
course of their I Q scores, people with Down syndrome continue
to advance in mental age and to acquire new cognitive skills,
even through the third and fourth decades of their lives (Berry et
al., 1984).
A plethora of studies have been undertaken to investigate
the effects of advanced age on cognitive ability in Down
syndrome. As Wisniewslu reviews in greater detail in this issue,
adults with Down syndrome all begin to show the neuropatho-
logic hallmarks of Alzheimer’s disease after the age of 40 years,
with many showing such stigmata by the age 35 years. Many of
these older adults also develop clinical symptoms of dementia.
Careful neuropsychological scrutiny suggests that even those
without clinically diagnosed dementia may have mild impair-
ments of long-term memory, which often is the only sign of
Address corrcspondence to Dr Paul P. Wang, Children’s Seashore House, 3405 Civic
Center Boulevard, Philadelphia, PA 19104-4388.

2. early Alzheimer’s dementia (Brugge et
al., 1994).The cognitive abilities of adults
with Down syndrome who are over the
age of 35 years may thus result from the
interaction of two factors: a dementing
process and a pre-existing state of impair-
ment. The dissociability of these two
factors is supported by the case of a
45-year-old woman with Down syn-
drome resulting from mosaic chromo-
somal translocation. She was not clini-
cally retarded as a child and young adult,
but later developed a mild dementia
(Schapiro et al., 1992).Thus, in individu-
als with Down syndrome who are older
than 35 to 40 years, studies of cognition
are likely to be confounded by a superim-
posed dementing process. zyxwvutsrq
PROFILE OF COGNITIVE
SKILLS IN DOWN SYNDROME
Regardless of the effects of age, any
attempt to summarize the cognitive
abilities of people with Down syndrome
by means of a single measure such as I Q is
insufficient for either educational or
investigative purposes. Detailed study of
subjects with Down syndrome has shown
a profile of relative strengths and weak-
nesses from one cognitive skill to another.
This fact was first suggested by I Q studies,
such as that of Silverstein et al. (1982).
These authors analyzed Stanford-Binet
I Q results (Terman and Merrill, 1973)
from 377 institutionalized subjects with
Down syndrome (4 to 56 years old) and
age- and IQ-matched subjects with
mentai retardation having other etiolo-
gies. They found that the subjects with
Down syndrome performed better on
four items requiring visual-motor skills
and worse on five test items requiring
verbal responses, including a digit-span
item. Thase et al. (1984) found similar
results in a study of 165 subjects with
Down syndrome who ranged in age from
young adulthood to more than 50 years.
These subjects were matched for age and
IQ against 163 other subjects. O n a brief
neuropsycholog~cal
battery, these investi-
gators also found that the group with
Down syndrome scored significantly
worse on digit span than did the control
subjects. These results are reminiscent of
an earlier report by Rohr and Burr
(1978),who found lower verbal-auditory
skills than visual-motor skills in a group of
37 children with Down syndrome.
Although other early investigators
also explored the profile of neuropsycho-
logical skills in Down syndrome, the
studies by Silverstein et al. and Thase et
al. are notable for their large study
populations. Unfortunately, both of these zyxwvutsr
Fig. zyxwvuts
1. Corsi Blocks Task. The Corsi block-tapping task uses a wooden board to which
nine identical blocks are fixed. The examiner taps a sequence of two or more blocks and
asksthe subject to tap the same sequence.
surveys, as well as other older studies,
were limited by the large age range of
their subjects (some of whom were likely
to have had a dementing process), as well
as reliance on historical diagnoses, failure
to control for educational background,
and other design and statistical factors.
The de-institutionalization of people
with Down syndrome and advances in
the etiologic diagnosis of mental retarda-
tion are two of the major reasons that
these initial studies require more carefully
controlled replication. Other medical
issues that must be considered include the
presence of untreated hypothyroidism,
otologic complications, and a history of
congenital cardiac malformations, espe-
cially cyanotic lesions.
In 1989, Haxby took a similarly
broad neuropsychological approach, but
controlled for etiologic heterogeneity
and potentially confounding medical fac-
tors. He studied 19young adults between
19 and 35 years of age, all with trisoniy
21, who were not institutionalized, and
were documented as having no active
cardiac, thyroid, or other potentially
confounding disease. He administered a
broad battery of tasks, including the
Stanford-Binet I Q Scale, the Illinois Test
of Psycholinguistic Ability (ITPA) (Kirk
et al., 1968),the Peabody Picture Vocabu-
lary Test, and other measures of language,
memory, and visual-spatial abilities. Two
major findings stand out in his results.
First, these young adults performed much
better on a visual-spatial short-term
memory (STM) task than they did on a
verbal STM task. The verbal task was a
digit span test; the visual-spatial test was
adapted from Corsi’s block tapping test
(Fig. 1). Nonsyndromic adults almost
always show the opposite result: longer
verbal than visual-spatial spans. Second,
Haxby found that the young adults with
Down syndrome performed better on the
Manual Expression subtest of the ITPA
than on the Grammatical Closure subtest.
The Manual Expression test requires
subjects to imitate a sequence of hand
movements. The Grammatical Closure
subtest presents pictures and acconipany-
ing sentences to be completed, such as
“When he was playing in the field, David
saw a little mouse. But his friend Jenny
saw three zyxw
(mice).” Haxby suggests that
adults with Down syndrome “have selec-
tively weaker linguistic expressive abili-
ties relative to non-linguistic expression.”
Although this brief review may not
fully demonstrate it, two clear themes
emerge from a long, broad line of
neuropsychological studies on this disor-
der. First, in analogy to Haxby’s results,
children and young adults with Down
syndrome show relative strength in visual-
motor skills such as drawing and other
manual expression. Second, they show
relative weakness in auditory STM. This
profile holds true both in comparison to
other skills that have been tested and in
comparison to the skills of other popula-
tions with cognitive impairnients. (A
third theme found in studies of 1)own
syndrome is the relative impairment of
grammar. Language skills are discussed
further by Kumin in this issue.)
Sequential Versus Simultaneous
Processing Skills
The wide scope of the studies I
have reviewed so far is indispensable for
the thorough description of cognitive
skills in Down syndrome. Unfortunately,
that same breadth of scope can lead to
spurious results if the statisticalmethodol-
ogy is not sufficiently rigorous, and to a
surfeit of findings that are difficult to
interpret cohesively. Theoretically driven
investigations are better able to circuni-
vent the problem of type I statistical error
and the difficulty posed by confusing,
uncohesive results.
According to one model of cogni-
tion (Das et al., 1975), new information
may be processed in one of two ways:
sequentially, with an emphasis on the
temporal order and serial nature of the
stimuli; or simultaneously, which re-
quires a holistic, gestalt-like interpreta-
tion of the whole stimulus set. Both of
these processes fall under the rubric of
“fluid” intelligence in the Cattell-Horn
MRDD RESEARCH
REVIEWS NEUROPSYCHOLOCICAL
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OF DOWNSYNDROME WANC 103

3. Williams syndrome
Span
spin Blocks
Fig. zyxwvutsrqpon
2. Double dissociationon Corsi and digit-spantasks.Adolescent subjects with Down
syndrome and others with Williams syndrome showed opposite profiles on tests of
visual-spatialversus auditoryshort-term memory. zyxwvutsrq
theory of crystallized and fluid abilities
(Horn and Hofer, 1991). The Kaufman
Assessment Battery for Children (K-
ABC) (Kaufman and Kaufman, 1983)
was constructed specifically along the
theoretical lines of simultaneous and
sequential processing. It makes a further
distinction between visual and auditory
stimulus presentation. Two studies of
Down syndrome have used the K-ABC
as an experimental probe of cognitive
processing in grade-school children with
Down syndrome.
Pueschel et al. (1987) studied 20
children with Down syndrome and 20
nonretarded children matched for perfor-
mance on the Peabody Picture Vocab-
ulary Test (Dunn and Dunn, 1981).
Neither group showed a significant dis-
crepancy between sequential and siniulta-
neous processing scores. Hodapp et al.
(1992) found similar results in their
assessment of 10 boys with Down syn-
drome, despite the fact that their control
group of nonspecifically retarded chil-
dren and a group of children with fragile
X syndrome both showed better simulta-
neous than sequential abilities. However,
a closer analysis of subtest results from
both studies showed a distinctive pattern
of strengths and weaknesses in the groups
with Down syndrome. Both of these
groups performed much better on the
Hand Movements subtest (requiring the
mimicry of a sequence of hand move-
ments) than on Number Recall (verbally
repeating a sequence of numbers) or
Word Order (pointing to pictures in the
sequence verbally stated by the exam-
iner). All three subtests demand sequen-
tial processing, but they obviously differ
in the input stimulus modality. The same
pattern found by earlier studies was thus
demonstrated again: stronger visual-
motor skills, weaker auditory skills. zyxwvutsr
Visual-Spatial Versus Auditory
Short-Term Memory
In a smaller, more tightly focused
study, Wang and Bellup (1994) specifi-
cally tested short-term memory for verbal
and spatial stimuli in adolescents with
Down syndrome. The age range of our
subjectsavoided the potentially confound-
ing variable of dementia which occurs at
older ages, but also allowed examination
of a more mature population than those
in the K-ABC studies. Nine subjects with
Down syndrome were compared to ten
matched subjects with Williams syn-
drome, a genetic syndrome of nialforma-
tion that results from a microscopic
deletion on chromosome 7. The tasks
employed were digit span, reverse digit
span, and the Corsi block-tapping test
(Fig. 1). It was found that the adolescents
with Down syndrome performed signifi-
cantly worse on the digit span task, but
significantly better on the Corsi task. These
contrasts also held true when responseswere
scored without regard for order (i.e., as long
as the correct numbers or blocks were
indicated in any order). This “double
dissociation” (Fig. 2) of verbal and visual-
spatial STM performance provides strong
evidence that the two processes have
distinct neurobiological and genetic bases.
The results also stand in full agreement
with the previous results on children and
adults with Down syndrome,
Hulme and Mackenzie (1992) have
further elaborated these findings, illuini-
nating the developmental coui-seof STM
in children with and without Down
syndrome. Their results show that these
children have a shorter auditory sequen-
tial memory than do mental age-matched
nonsyndromic children and that their
auditory STM fails to develop at the same
rate that it does in controls. Fortunately,
the investigators’ preliminary results sug-
gest that this short-term memory deficit
may be at least partially remediable by
intensive practice.
It is possible that a deficit in
auditory STM has a profound impact on
other cognitive and academic skills.
STM, or working memory, appears to be
a basic resource that supports many other
cognitive processes. Numerous research-
ers are studying the role of phonologcal
STM in vocabulary acquisition, reading
development, language processing, and
other skills (Gathercole and Baddeley,
1993; Hulme and Roodenrys, 1995). A
better understanding of the relevance of
STM to these processes may advance our
understanding of other cognitive deficits
in Down syndrome and point the way to
appropriate methods of remediation.
Visual-Spatial Perception Versus
Visual-Motor Skills
The distinction between visual-
perceptual (input) skills and visual-motor
(output) skills is a salient one in Down
syndrome. Thus, although the studies I
have discussed repeatedly demonstrated
good visual-motor skills (drawing, block
building, imitating hand gestures) in
Down syndrome, they do not provide
any evidence of a particular strength in
visual-perceptive skills. In fact, Wang et
al. (1995) found no difference between
their Down syndrome and Williams
syndrome groups on the Motor-Free
Visual Perceptive Test. This battery of six
subtests taps figure-ground discrimina-
tion, visual closure, memory for visual
forms (as opposed to memory for loca-
tion, as in the Corsi task), and other
perceptual skills. The groups also failed to
differ on three other tests of perceptual
skills. Compared to published norms,
both groups performed within the range
of their general mental age.
By contrast, the group with Down
syndrome performed significantly better
on the Developmental Test of Visual-
Motor Integration (Beery, 1982), which
requires subjects to copy geometric fig-
ures. This correlates with the finding
discussed earlier (Silverstein et al., 1982)
that children with Down syndrome
perforni better on drawing tasks than do
matched children with idiopathic mental
retardation. Haxby’s data from the Manual
Expressions subtest of the ITPA (Haxby,
1989) and the results of Hodapp et al.
(1992) from the Hand Movements sub-
test of the K-ABC further document the
relative strength of visual-motor skills in
Down syndrome.
Wang, Heindel, and Bellugi (1994)
perfomied a further test of visual-motor
104 MRDD RESEARCH
REVIEWS NEUROPSYCHOLOGICAL PROFILE OF DOWN
SYNDROME W A N G

4. Fig. zyxwvutsrqpo
3. Typical brain morphology in Down syndromeand Williams syndrome. Midcallosalaxial slicesare shown for Down syndrome (left),
control (center), and Williams syndrome (right) subjects.The decreased frontal volume and normal thalamic volume in Down syndrome is
apparent. (With permission. FromJernigan et al., 1993. Copyright 1993, American Medical Association.) zyxw
skill in this disorder, using a “rotor
pursuit” task. This task requires subjects
to hold an electronic stylus on a small
metal disk as the disk revolves on a
turntable. An electronic timer keeps track
of how long subjects are able to maintain
contact between disk and stylus. Here,
adolescentswith Down syndrome reached
a higher level of mastery than did a
matched group of adolescents with Wil-
liams syndrome. Subjects with Down
syndrome thus demonstrate relatively
strong visual-niotor skills on a variety of
measures.
Long-temi visual-spatial memory,
visual imagery, and cognitive operations
that presumably are perfomied on mental
images (e.g., mental rotation) are among
the other visual-spatial functions that
have been studied in Down syndrome.
Uecker et al. (1993) have summarized a
number of these investigations, including
one by Mangan and Nadel (1990), who
demonstrated that children with Down
syndrome are less skilled than nonsyn-
dromic children at a place-learning task.
The task they employed requires subjects
to construct a mental map of a play area so
they can find a desired toy. Unfortu-
nately, many such studies have yet to
compare children with Down syndrome
to matched children with mental retarda-
tion of other etiologies. As a result, it is
not known whether their findings are
specific to Down syndrome or are more
generally applicable to populations men-
tal retardation. zyxwvutsrqp
MAGNETIC RESONANCE
IMAGING OF BRAIN
MORPHOLOGY
A great deal of research effort has
been expended on neuropathologic study
of the relationship between Down syn-
drome and Alzheimer’s disease. Corre-
spondingly, a large body of knowledge
has accumulated on the neuropathology
of the aging brain in Down syndrome.
(Zigman et al. reviews much of this
research in this issue.) Far less is known
about the younger brain in Down
syndrome. Although some early postmor-
tem descriptions of Down syndrome
neuroanatomy exist (Benda, 1971), a
large part of our knowledge of regional
brain morphology in the disorder is the
result of recent in vivo studies that have
used magnetic resonance imaging (MRI)
techniques.
Jernigan et al. (1993) performed
MRI scans on six adolescents with Down
syndrome,nine with Williams syndrome,
and 21 age-matched normal controls.
Computer-assisted techniques were used
to define stereotactic brain regions and to
classifj each image pixel as representing
white matter, grey matter, or cerebrospi-
nal fluid. The investigators found that
total cerebral volume was comparably
reduced in the Down syndrome and
Williams syndrome groups. However,
the two groups showed distinct patterns
of regonal brain morphology. In the
Down syndrome group, the proportional
size of the anterior cortex was dimin-
ished, as was the proportional size of the
temporal limbic cortex. The proportional
size ofthe posterior cortex, the diencepha-
lon, and the lenticular nuclei (putamen
and globus pallidus) were enlarged in this
group. These findings apparently do not
generalize to all etiologies of mental
retardation, as the Williams syndrome
group showed a different pattern of brain
morphology (Fig. zyxwvuts
3).
In a related study with inany of the
same subjects, Wang et al. (1992) scruti-
nized the corpus callosum in Down
syndrome and Williams syndrome. We
found that the width of the most rostra1
fifth of the callosum was decreased in
Down syndrome. This portion of the
callosum carries projections from the
prefrontal areas of the cortex. Therefore,
this observation concurs with the initial
findings of relative frontal hypoplasia in
this syndrome. It also is in accord with the
neuropsychological finding that subjects
with Down syndrome perform poorly on
certain tasks of verbal fluency (e.g.,
“Name all the animals you can think of in
60 seconds”) (Bellugi et al., 1994). Such
semantic fluency is believed to depend on
the coordinated function of right and left
frontal brain regons.
The interpretation of other MRI
studies of the brain in Down syndrome is
limited by those studies’ inclusion of
older subjects, in whom a confounding
pathologic process like that of Alzhei-
mer’s disease may have been present.
Nonetheless, it is notable that both Raz et
al. (1995) and Weis et al. (1991), in
remarkable parallel to the findings of
Jernigan et al. (1993), found significant
reductions in overall cerebral volunie but
preservation of basal ganglia volume. Kaz
et al. also reported a reduction in the
volume of the hippocanipal formation in
Down syndrome.
Concordance With
Neuropathological Studies
Without attempting to review the
body of neuropathologic studies on
Down syndrome, it is encouraging to
note that the in vivo MRI studies of gross
brain morphology correspond well with
the results of postmortem neuropatho-
logic investigations. In addition to the
overall reduction of brain volunie, post-
mortem studies have emphasized the
MRDD zyxwvutsr
RESEARCHREVIEWS NEUROPSYCHOLOCICAL
PROFILE OF DOWNSYNDROME WANG 10s

5. underdevelopment of the frontal lobes, as
well as hypoplasia in temporal lobe
regons. Evidence suggests that the latter
abnormalities stem from disorganization
and delays in the laminar development of
the cortex, starting at an early point in
fetal development (Golden and Hyman,
1994). zyxwvutsrqpo
Concordance With
Neuropsychological Studies
How are these neuroanatoinic find-
ings related to the neuropsychological
profile of Down syndrome? The forego-
ing discussion already has suggested that
the frontal hypoplasia and corresponding
rostra1 callosal diminution may be related
to certain language impairments. zyxwvuts
M-
though the dependence of semantic
fluency on right hemispheric integrity is
only one example of neuropsychological-
neuroanatomic association, it has been
suggested that the MRI and neuropatho-
logic abnormalities found in the frontal
lobe also may relate to other linguistic
impaiiments in Down syndrome (Jerni-
gan et al., 1993).
A second set of potentially related
findings is constituted by the impairments
in short-term auditory memory and the
neuropathologic abnormalities found in
the temporal lobe. Although the precise
anatomic locus for auditory short-term or
working memory has not been clearly
identified, it is hypothesized to reside in
the region of the superior temporal lobe
(Colombo et al., 1990).MRI studies and
postmortem neuropathologic results, re-
spectively, have elucidated hypoplasia
and cortical disorganization in nearby
temporal areas. A reasonable hypothesis
would be that these neuroanatomic
abnormalities preclude formation of the
normal cortical circuits that might sup-
port the temporary storage of auditory
information.
Perhaps the best documented brain-
behavior association among those dis-
cussed here is that between the basal
ganglia and performance on the rotor
pursuit task. Studies of adult patients with
Huntington’s Disease have demonstrated
that performance on this task deteriorates
in the early stages of that disease, before
the onset of dementia, when the only
neuropathologic changes are found in the
neostriatum. Studies with other adult
populations support this structure-func-
tion relationship (Heindelet al., 1989).In
individuals with Down syndrome the
coexistence of superior perfomiance on
the rotor pursuit task and the volumetric
preservation of the basal ganglia is there-
fore not surprising.
In Down syndrome, the relative
preservation of performance on visual-
motor tasks such as drawing and block
construction may relate to a neuroana-
toniic system that is distinct from the
striatal circuit underling rotor pursuit
performance. Specifically, it is hypoth-
esized that a dorsal parietal system may
mediate these visual-construction tasks
(Goodale and Milner, 1992). The relative
preservation of posterior cortical volume
found by Jernigan et al. may therefore be
related to the neuropsychological preser-
vation.
CONCLUSIONS
Any review of the history of
research on Down syndrome should
make it clear that there are multiple
motivations for such research. The two
most prominent motivations for neuro-
psychological research on the disorder are
theoretical testing of brain-behavior rela-
tionships and clinical elucidation of the
educational needs of those with Down
syndrome. zyxwvuts
Individualization o
f
educational plans remains
paramount, regardless of
the similarities that
children with Down
syndrome may share. Any
given child with this
disorder may show the
typical pro$le zyxw
o
f strengths
and weaknesses to a
greater or lesser degree,
or not at all.
In reviewing their own K-ABC
results and those of other investigators,
Hodapp and colleagues (1992) argue
strongly that sign language training should
be helpful in building the early communi-
cative skdl of children with Down syn-
drome. Indeed, the auditory STM defi-
cits found in Down syndrome would be
expected to hamper the acquisition of
oral vocabulary (Gathercole and Badde-
ley, 1993). The advantage of sign lan-
guage as an alternative mode of commu-
nication is enhanced by the relative
strength of these children in manual
expression. Goodman (1993) and Singer
et al. (in press) have reported that even
without formal sign language training,
children with Down syndrome showed
better use of gestural communication
than did a matched group of children
with Williams syndrome. Furthermore,
Miller (1992) has shown that there is no
foundation for parents’ fears that the use
ofsign language will prevent the develop-
ment of oral language. Therefore, sign
language instruction should be consid-
ered for all children with Down syn-
drome and, indeed, for any other children
with communicative impairments who
might benefit 6om it. Extensive clinical
experiencehas shown thebenefits ofimprov-
ing communicativeskills,both in preventing
the fiustrationthat accompaniesthe inability
to communicate and in permitting other
social and cognitive learning.
More generally, their relative
strength in visual-motor skills is a re-
source that can be exploited for children
with Down syndrome. When alternative
didactic methods exist, these children
might benefit most from hands-on, “just
do it” instruction rather than elaborate
verbal guidance. When verbal instruc-
tions are given, they should be kept short
and few in number. These guidelines
might also point to the vocations andjobs
for which young adults with Down
syndrome are best suited.
A more difficult question is whether
the impairnients in short-term auditory
memory in Down syndrome can be
remedied or only can be circumvented.
(As discussed earlier, auditory STM may
be an important resource for many other
cognitive operations.) Preliminary results
do suggest that some improvement in this
skdl is possible with intensive practice,
but it is not known just how far this skill
can advance (Hulme and Mackenzie,
1992). Until this skill can be effectively
remediated, strateges should be under-
taken to minimize the secondary impair-
ments that may result (see, for example,
Levine, 1994).
Individualization of educational
plans remains paramount, regardless of
the similarities that children with Down
syndrome may share. Any given child
with this disorder may show the typical
profile of strengths and weaknesses to a
greater or lesser degree, or not at all.
Given Korenberg’s view of Down syn-
drome as a contiguous gene deletion
syndrome, children whose syndrome
results from chromosomal translocation
may be those most likely to exhibit
atypical neuropsychological profiles. Fur-
thermore, genes residing on chromo-
somes other than number 21 will influ-
106 MRDD RESEARCH REVIEWS NEUROPSYCHOLOGICALPROFILE zyxw
OF DOWNSYNDROME WANC

6. ence the profile of neuropsychologcal
skills. Children with Down syndrome
will inherit these variable alleles from
their parents just as other children do. Of
course their neuropsychological skillsalso
may be influenced by the early environ-
ment their caretakers provide. However,
regardless of the source of such neuropsy-
chological variability, educators and other
cliniciansmust remain receptive to it, and
niust adapt their therapeutic efforts ac-
cordingly. zyxwvutsrqp
Future Directions
To date then, the profile of neuro-
psychological skills in Down syndrome
has been only partially elucidated. But
the results at hand are potentially very
valuable for use in planning future
research on both descriptive and prescrip-
tive levels. First, the basis of the deficit in
short-term auditory memory and its
implications beg for more complete
explication. What is the neurobiologcal
basis for the deficit? Does it result from an
auditory perceptual deficiency? Precisely
how does this deficit interfere with
language acquisition? How does it influ-
ence other cognitive processes and aca-
demic processes, such as reading compre-
hension and arithmetic calculation?
Researchers must address the ques-
tion of how this memory deficit can be
ameliorated. Are pharmacologic interven-
tions possible? O r must intervention be
done during the period of cortical
development?To what extent can behav-
ioral interventions improve short-term
memory? What educational and psycho-
logical strateges are effective in bypassing
this deficit? What processes do not
require short-term auditory memory, and
can thus be easily pronioted in people
with Down syndrome?What is the most
appropriate balance between attempting
to bypass and attempting to remediate
this impairment?
Other neuropsychological skills also
are impaired in Down syndrome,as many
previous authors have demonstrated. But
it appears that many of these deficits may
not be specific to this disorder, but occur
more generally in zyxwvutsr
all children with
mental retardation. For these impair-
ments, remediation may be more difficult
to target. Only further investigation will
demonstrate whether this is true. Future
investigation also will determine to what
extent the relative strengths of children
with Down syndrome, such as their
visual-motor skills, may be extended and
exploited to serve a broad range oftasks.
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