SELECTED STUDIES

Section Editor: Prof. Talaat I. Farag


Cognitive Changes in Adults with Down Syndrome
 
Safa Elgamal1; Sadika Al-Awadi2; Leila Bastaki2; Makia Marafie2; Talaat I. Farag3
1University  of Waterloo; 2Kuwait Genetic Center; 3Dalhousie University
 
Presented as a poster in the 2nd International Kuwait Medical Genetics Conference
 
Abstract

With the improvement of health care and longer lifespan of Down Syndrome persons, neuroscientists are studying the neuropathological and neurochemical basis of cognition in Down syndrome, and are interested in avoiding the decline of cognitive skills at older age.

It is well known that modalities for cognitive retraining may help patients to overcome their cognitive deficit. Rehearsal training can be used to improve working memory, and learning abilities in Down syndrome. Anti-Alzheimer medication may be a potential treatment for cognitive decline; however, further studies are required to confirm their usefulness. Here we present the profile of possible cognitive deficit in Downs syndrome, and briefly discusses both the medicinal and rehabilitative therapies.


Background
 
Patients with Down syndrome show evidence of verbal short-term and working memory deficit. In contrast to the explicit memory deficit, patients with Down syndrome have normal implicit memory. Expressive language deficit in Down syndrome is associated with a range of individual variability.
 

Moreover, patients with Down syndrome have potential risk of developing cognitive deterioration that starts after the age of 35 years. The neuropathological and neurochemical changes with age in DS are  indistinguishable from Alzheimer disease. The type,  and distribution of senile plaques and neurofibrillary tangles, and the pattern of atrophy of the neuronal systems are qualitatively, but not quantitatively the same as those of Alzheimer disease (Mann, 1988).

Cognitive Profile in Down Syndrome
 
Explicit Memory in Down Syndrome
 

Explicit memory is defined as conscious recollection of information:

• Verbal short term memory deficit (Jarrold and Baddeley, 2001)
• Intact Short term visual memory (Jarrold and Baddeley, 2001)
• Intact long term verbal memory (Jarrold et al, 2007).
• Mild long-term visual memory deficit (Jarrold et al, 2007).
•
 

Explicit  Memory can be classified as shown in the following Scheme

•

Implicit /Procedural Memory in Downs Syndrome

Implicit memory is defined as unconscious recollection of information. Implicit memory processes are involved in training. Persons with Down syndrome have intact implicit memory (Vicari, 2001).
 
Language in Down Syndrome
•Complex sentence production is intact in Downs syndrome (Chapman and Hesketh, 2001).
•Comprehension skills are preserved in Downs syndrome (Boudreau and Chapman, 2000).
•Sentence structure, verbs are more often omitted (Chapman et al, 1998).
 
Brain Aging in Down Syndrome
The neuro-pathological and neuro-chemical basis of aging brain in Down syndrome is indistinguishable from that seen in Alzheimer disease. Enhanced brain aging is represented by  earlier development of senile plaques and neurofibrillary tangles (Mann, 1988).
 
Treatment Modalities

• Cognitive retraining: rehearsal training and adopting active rehearsal strategies improve working memory in Down syndrome (Conners et al, 2001).
 
• Drug therapy: Anti Alzheimer medication such as donepezil improved cognitive deterioration in Down syndrome (Spiridigliozzi et al, 2007).
 
• Physical activity: improve overall health of Down syndrome patients, however, effect on cognition was not studied.

• Music therapy: recent research suggested an effect for music on verbal learning ( Peterson and Thaut, 2007), However, no recent data in Down syndrome, few old studies tested the effect of music in this group (Stratford and Ching, 1989).

Recommendation for Future Studies

Randomized controlled trials should be initiated to test the effect of exercise, music, and
acetylcholinesterase inhibitors among patients with Down syndrome.

 

References
 
••Mann DM. Alzheimer's disease and Down's syndrome. Histopathology. 1988 Aug;13(2):125-37.
•Jarrold C, Baddeley AD, Phillips C. Long-term memory for verbal and visual information in
Down syndrome and Williams syndrome: performance on the Doors and People test.
Cortex. 2007 Feb; 43(2):233-47.
•Jarrold C, Baddeley AD.nShort-term memory in Down syndrome: applying the working memory model.
Downs Syndr Res Pract. 2001 Oct;7(1):17-23.
•Vicari S. Implicit versus explicit memory function in children with Down and Williams syndrome.
Downs Syndr Res Pract. 2001 Oct;7(1):35-40.
•Boudreau DM, Chapman RS. The relationship between event representation and linguistic skill in narratives
of children and adolescents with Down syndrome. J Speech Lang Hear Res. 2000 Oct;43(5):1146-59
•Chapman RS, Seung HK, Schwartz SE, Kay-Raining Bird E. Language skills of children and adolescents with
Down syndrome: II. Production deficits. J Speech Lang Hear Res. 1998 Aug;41(4):861-73.
•Chapman RS, Hesketh LJ. Language, cognition, and short-term memory in individuals with Down syndrome.
Downs Syndr Res Pract. 2001 Oct;7(1):1-7.
•Mann DM, Yates PO, Marcyniuk B, Ravindra CR. Pathological evidence for neurotransmitter deficits in
Down syndrome of middle age. J Ment Defic Res. 1985; 29:125-135.
•Spiridigliozzi GA, Heller JH, Crissman BG, Sullivan-Saarela JA, Eells R, Dawson D, Li J. Kishnani PS.
Preliminary study of the safety and efficacy of donepezil hydrochloride in children with Down syndrome:
a clinical report series. Am J Med Genet A. 2007 Jul 1;143(13):1408-13.
•Conners FA, Rosenquist CJ, Taylor LA. Memory training for children with Down syndrome.
Downs Syndr Res Pract. 2001 Oct;7(1):25-33.
•Peterson DA, Thaut MH. Music increases frontal EEG coherence during verbal learning.
Neurosci Lett. 2007 Feb 2;412(3):217-21.
•Stratford B, Ching EY. Responses to music and movement in the development of children with Down's syndrome.
J Ment Defic Res.1989 Feb;33 ( Pt 1):13-24.
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Dr. Safa Elgamal, MD, MSc, PhD is the Schlegel Research Chair on Aging and Assistant Professor University of Waterloo, Canada. Her email is safa_elgamal@yahoo.com


 


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