THE EFFECTIVENESS OF INTERVENTION PROGRAM ON SHORT-TERM MEMORY IN DOWN SYNDROME

Transcription

1 Man In India, 96 (1-2) : Serials Publications THE EFFECTIVENESS OF INTERVENTION PROGRAM ON SHORT-TERM MEMORY IN DOWN SYNDROME Shaznee Iryana Bt Yusoff and Yeo Kee Jiar Individuals with Down syndrome or Trisomy 21 are individuals who have an extra chromosome on the 21 st pair. It is one of the most common genetic causes of severe intellectual disability (ID). They are known to have significant deficits in short-term memory. They need to be taught repetitively in order for them to finally grasp the information. This reflects a limited capability in their memory span. Short-term memory (STM) is a short-term storage of information that holds both verbal and visual information that eventually will shift them to the working memory. The objective of this study is to determine the effectiveness of intervention program by looking at the rankings of verbal short-term memory and visuo-spatial short-term memory scores before and after the intervention in experimental and control groups. This intervention was tested using quasi- experimental design on 40 Down syndrome children and adolescent aged between 6-14 years in 5 primary schools for 8 weeks. A cognitive- based measurement of working memory called the Automated Working Memory Assessment (AWMA) was used to measure the level of short- term memory in children and adolescents with DS before and after intervention. The treatment group showed positive significant changes in all Verbal Short-Term Memory subtests and all Visuo-Spatial Short-Term Memory subtests after the intervention. Keywords: Down syndrome, short-term memory, intervention, Automated Working Memory Assessment (AWMA) Introduction The Down Syndrome (DS) is a frequent chromosomal disorder which has extra copies of genes on chromosome 21. DS is also known as Trisomy 21. Due to these extra copies of genes, researchers believe that the course of normal development will be interfered causing the characteristic features of Down syndrome, impairments and limitations in intellectual abilities and the risk of health problems associated with this condition. Some physical characteristics that often seen in individuals with DS include small chin, slanted eyes, poor muscle tone (hypotonia), and a flat nasal bridge, Mongoloid- like facial and numerous deformities. According to Christianson et al. (2006), more than 200,000 cases of incidence with DS were recorded each year worldwide. In western countries, there are approximately 1 in 700 to 800 live births that showed the incidence of Down syndrome (Sherman et al., 2007; Centers for Disease Control & Prevention, 2006). On the other hand, based on a study done in a Maternity Hospital, Kuala Lumpur showed that the incidence of Down syndrome was 1:959 live births. With an IQ ranging from mild (IQ 50-70) to moderate (IQ 35-50) (Naess et al., 2011), they are under the category of slow learners. Since they have limitations in intellectual abilities, impairments Address for communication: Shaznee Iryana Bt Yusoff, Faculty of Education, Universiti Teknologi Malaysia, shazneeyusoff@gmail.com

2 538 MAN IN INDIA in the growth of cognitive development are certain. A brain disorder that is called Alzheimer disease is also believed to be related to them. This disease results in a gradual loss of memory, judgment, and ability to function. One of the main features of handicaps in cognitive development is the memory. Their ability to store and manipulate information over short duration of time (shortterm memory and working memory) are rather poor than other people. Based on past research, individuals with DS showed more limitation in STM (STM) capability than typically developing people of the same age. The STM and the peripheral systems of articulatory rehearsal had been determined to have several deficits; so as the central systems that direct the information processing (Hulme and Mackenzie, 1992). Based on Jarrold et al. (2008), individuals with DS face a more complicated situation in storing and retrieving verbal information than with the visual information. Moreover, according to Byrne et al. (1995), deficiencies in memory span particularly in processing verbal information will produce a poor language and learning outcome. Short-term memory (STM) or the primary memory is the capability to hold a small sum of information in an active state for a short period of time. Unlike the working memory, STM only deals with the short-term storage of information, and it does not include the manipulation of material hold in memory. Based on the Baddeley s 1986 model of working memory, two short-term storage mechanisms exist. There are the phonological loop (verbal) and the visuo-spatial sketchpad (visual). It is believed that the duration of time of STM is between 15 and 30 seconds (Atkinson and Shiffrin, 1971). Significant deficiencies in STM are known to be common among individuals with DS. Memory span is the capacity to recollect the longest list of items in the right order. Memory span tasks that usually being used to assess short-term or working memory span include random numbers, letters or words that have to be repeated in a similar order. Hulme and Mackenzie (1992) stated that adolescents with DS have a memory span of only 3 or 4 digits while typically developing adolescents have 7 or 8. According to Kay- Raining Bird and Chapman (1994), individuals with DS showed lower STM spans in contrast of their general level of intellectual function. This study showed that even though individuals with DS are being paralleled to the typically developing children in terms of their level of intellectual functioning, they still showed a lower performance in their digit span. Past studies that had proved the deficiency in this area of functioning in individuals with DS include (Bower & Hayes, 1994; Broadley & MacDonald, 1993; Byrne, Buckley, MacDonald, & Bird, 1995; Comblain A., 1999; Jarrold & Baddeley, 2001; Jarrold, Baddeley, & Phillips, 1999; Jarrold, Purser, & Brock, 2006; Laws, MacDonald, & Buckley, 1996; Marcell & Armstrong, 1982; Marcell & Weeks, 1988). However, Vallar and Papagno (1993) showed otherwise. A young woman with DS was reported to be fluent in 3 languages and had a perfectly normal verbal.

3 THE EFFECTIVENESS OF INTERVENTION PROGRAM On the other hand, a handful of studies that used the contrasted digit (verbal) and Corsi span (visual) to measure both the verbal STM and visuo- spatial STM have shown that individuals with DS are impeded only on digit span (Azari et al., 1999; Jarrold & Baddeley, 1997; Jarrold, Baddeley & Hewes, 1999; Wang & Bellugi, 1994; Vicari, Carlesimo & Caltagirone, 1995). These ultimately show that the visuo- spatial STM of individuals with DS is relatively unaffected. Past studies showed the use of visual (picture) and verbal rehearsal techniques in memory training for young people with DS. The limitation of STM can be overcome by rehearsing the items verbally, either by saying it out loud or by mentally emulate it. The information will be re-entering the short-term storage and can be kept for a longer time. As proven by Conners et. al (2008), memory training using entirely in verbal mode is possible in giving positive outcome using the rehearsal strategy. They were trained for 10 minutes, 5 times a week for 3 months. Result showed that there is a small but significant increase in digit span. Earlier, Broadley et al. (1994) have used the rehearsal and organization strategies while incorporating it with the visual aids. In the rehearsal training, children were taught to remember a list of items by practising them aloud and in order with the use of picture materials. Meanwhile, during organization training, children were taught to assemble items into categories to help in remembering them. Furthermore, a study by C. P. Duarte et al. (2011) found that visuo- spatial support can make up for verbal STM deficiencies in individuals with DS. It shows that with the addition of a spatial component, it can improve verbal STM in individuals with DS. On the contrary, Broadley, MacDonald & Buckley (1995), as well as Marcell, Harvey & Cothran (1988) showed that even when they use visual support when presenting digits or words, the deficits in verbal STM in individuals with DS remained stagnant. Additionally, Brock & Jarrold (2005) and Marcell & Weeks (1988) also showed that even when they eliminate the need to response verbally, the deficits in the verbal STM in individuals with DS still prevail. Hence, in order to improve educational outcomes, training or intervention must be given to enhance the short term and working memory function. The main objective of this study is to determine the effectiveness of intervention program by looking at the rankings of verbal STM and visuo-spatial STM scores before and after the intervention in experimental and control groups in children and adolescents with DS. Methodology Participant A group of 6-14 years old children and adolescents with DS in the Kuala Lumpur district were gathered as the sample for this study. In the initial stage, prerequisite requirements of having no physical and sensory impairment were met no matter

4 540 MAN IN INDIA what their gender is. As a result, a total of 40 DS children and adolescents who scores at or below the 15 th centile on listening recall and backward digit recall (two subtests from AWMA) (Holmes et al., 2009) were selected for this study. Next, they were split by half into a control group and an experimental group. A cognitivebased measurement of working memory called the Automated Working Memory Assessment (AWMA) was used to measure the level of STM in children and adolescents with DS before and after intervention. An intervention program which was based on the Working Memory Model (Baddeley, 1974) and Children s Memory Scales Assessment (CMS) were given to the children and adolescents in the experimental group to enhance their level of STM. Measures A cognitive- based assessment tool that was developed by Alloway (2007) was used to measure the level of STM in children and adolescents with DS. The Automated Working Memory Assessment (AWMA) is a computer- based assessment that has a very user- friendly interface which assesses working memory skills. This culture-fair tool would come in handy to educational professionals in screening individuals for significant working memory problems as it is very practical and convenient. It can be use on individuals from early childhood as young as 4 years old to adulthood (22 years). The AWMA is made up by measures on both verbal and visuo- spatial aspects of STM and working memory. Each component of memory has three subtests. Subtests that are used to measure the verbal STM include digit recall, word recall and non-words recall while subtests such as dot matrix, mazes memory and block recall are used to measure the visuo-spatial STM domain. On the contrary, tasks that associated with simultaneous storage and processing of information are used to measure the verbal and visuo-spatial working memory. Additionally, subtests such as listening recall, counting recall and backwards digit recall are being used to measure the verbal working memory while subtests such as odd one out, spatial recall and Mister X are being used to measure the visuo-spatial working memory. In order to measure the central executive aspect of working memory, more complex tasks have been made. It includes the counting recall where the participant counts the number of target items in each of a series of consecutive line-ups and then recalls the totals for each line-up in the original sequence (Case, Kurland, and Goldberg, 1982). Procedure A 30-minute classroom intervention program is being conducted four times a week for 12 weeks on experimental group while the control group did not receive any training. The intervention program comprises of four domains, each based on the working memory component; the visuo-spatial domain, the phonological loop domain, the episodic domain and the attention and organization domain. An activity

5 THE EFFECTIVENESS OF INTERVENTION PROGRAM of each domain is being conducted every week within the school hour. All domains except for the attention and organization domain consist of two activities that cover both STM and working memory. A fixed activity that covers on the central executive is being added regularly weekly. The visuo-spatial domain consists of family pictures and picture location; the phonological loop domain consists of counting and numbers ; the episodic domain consists of the same activity but with different medium, which is using the flashcard and cartoon; and last but not least the attention and organization domain which centralized on themes. Sustained attention is believed to be the foundation of all learning and memory, thus the reason why the same activity in the attention and organization is conducted every week. Results In this section, descriptive statistics and Wilcoxon signed-rank test of verbal STM and visuo-spatial STM subtests scores before and after the intervention in experimental and control groups are presented in Table 1.1 and Table 1.2. These scores showed the difference the between the pretest and posttest results. TABLE 1.1: DESCRIPTIVE STATISTIC AND WILCOXON SIGNED-RANK TEST RESULTS FOR VERBAL SHORT-TERM MEMORY SUBTESTS Subtests Group Time Mdn Z Asym. Sig. (2-tailed) Digit Recall Experimental Pre a* 0.47 Post 65.0 Control Pre a.592 Post 65.0 Word Recall Experimental Pre a*.026 Post 67.9 Control Pre b.972 Post 62.0 Non-Word Recall Experimental Pre a**.001 Post Control Pre b.687 Post 84.3 a based on negative ranks. b based on positive ranks. c The sum of negative ranks equals the sum of positive ranks * p<.05. ** p<.01. *** p<.001. The results of Wilcoxon signed-rank test analysis indicated that there were positive changes in all subtests of Verbal STM for experimental group after the intervention. Table 1.1 showed that Non-Word Recall has the highest positive changes with the median of 96.0 to (Z= 3.315, p=.001), followed by Word Recall with the median of 64.0 to 67.9 (Z= 2.229, p=.026) and Digit Recall with the median of 64.0 to 65.0 (Z= 1.988, p=.047). On the contrary, there were no positive changes in all subtests of Verbal STM for control group after the

6 542 MAN IN INDIA intervention. In fact, there were negative changes in Word Recall (median from 64.0 to 62.0) and Non- Word Recall (median from 86.0 to 84.3) for the control group except for Digit Recall which remained the same. TABLE 1.2: DESCRIPTIVE STATISTIC AND WILCOXON SIGNED-RANK TEST RESULTS FOR VISUO-SPATIAL SHORT-TERM MEMORY SUBTESTS Subtests Group Time Mdn Z Asym. Sig. (2-tailed) Dot Matrix Experimental Pre a*.033 Post Control Pre a.266 Post Mazes Memory Experimental Pre a*.023 Post 66.8 Control Pre b.717 Post Block Recall Experimental Pre a*.031 Post Control Pre b.732 Post a based on negative ranks. b based on positive ranks. c The sum of negative ranks equals the sum of positive ranks * p<.05. ** p<.01. *** p<.001. The results of Wilcoxon signed-rank test analysis indicated that there were positive changes in all subtests of Visuo-Spatial STM for experimental group after the intervention. Table 1.2 showed that Dot Matrix has the highest positive changes with the median of to (Z= 2.133, p=.033), followed by Mazes Memory with the median of to (Z= 2.227, p=.023) and Block Recall with the median of to (Z= 2.157, p=.031). On the other hand, there were no positive changes for the subtests in the control group after the intervention except for Block recall with a slight change of median from to (Z= 0.342, p=.732). The Dot Matrix showed negative changes with the median of to (Z= 1.113, p=.266) while the Mazes Memory remained unchanged. Discussion and Conclusion This study showed the effectiveness of intervention program in individuals with DS. It is shown by looking at the rankings of verbal STM and visuo-spatial STM scores before and after the intervention in experimental and control groups in children and adolescents with DS. The findings showed that there are positive changes in all subtests of Verbal STM for experimental group after the intervention. On the contrary, there were no positive changes in all subtests of Verbal STM for control group after the intervention. In the mean time, positive changes can also be seen in all subtests of Visuo-Spatial STM for experimental group after the

7 THE EFFECTIVENESS OF INTERVENTION PROGRAM intervention as opposed to all subtests of Visuo-Spatial STM within the control group. Results are consistent with the previous study such as Broadley et al. (1994) whom had used the rehearsal and organization strategies while incorporating it with the visual aids. In addition, Gathercole SE (2008) reported positive outcomes as the results of using computer training programs with children with ADHD and with children with poor working memory. Comblain A (1994) also showed that there is significant improvement in memory span after the rehearsal training had been implemented on individuals with DS. In a nutshell, children and adolescents with DS of the treatment group in this study showed positive significant changes in all Verbal STM subtests and all Visuo- Spatial STM subtests after the intervention. For future study, in order to see the effectiveness of this intervention program; it is best to do a study on other individuals with mental disability using the intervention program. References Alloway, T. P. (2007). Working memory, reading and mathematical skills in children with developmental coordination disorder. Journal of Experimental Child Psychology, 96: Atkinson, R. C., and Shiffrin, R. M. (1971). The control processes of short-term memory. Institute for Mathematical Studies in the Social Sciences, Stanford University. Azari, N.P., Horwitz, B., Pettigrew, K. D., Grady, C. L., Haxby, J.V., Giacometti, K. R. & Schapiro, M. B. (1994). Abnormal pattern of cerebral glucose metabolic rates involving language areas in young adults with Down syndrome. Brain and Language, 46: Baddeley A. D. and Hitch, G. J. (1974). Working memory. In G. Bower (Ed.), The Psychology of Learning and Motivation, Vol. VIII, (pp ). New York: Academic Press. Bower, A. & Hayes, A. (1994). Short- term memory deficits and Down s syndrome: A comparative study. Down s Syndrome Research and Practice, 2: Broadley, I. and MacDonald, J. (1994). Teaching short- term memory skills to children with Down s syndrome. Down s Syndrome Research and Practice, 1: Broadley, I., MacDonald, J. and Buckley, S. (1994). Are children with Down s syndrome able to maintain skills learned from a short- term memory training programme? Down s Syndrome Research and Practice, 2: Brock, J. & Jarrold, C. (2005). Serial order reconstruction in Down syndrome: Evidence for a selective deficit in verbal short- term memory. Journal of Child Psychology and Psychiatry, 46 (3): Byrne, A., Buckley, S., MacDonald, J. and Bird, G. (1995). Investigating the literacy, language and memory skills of children with Down s syndrome. Down Syndrome Research and Practice, 3(2): Case, R. Kurland, D. M., and Goldberg, J. (1982). Working memory capacity as long term activation: An individual differences approach. Journal of Experimental Psychology: Learning, Memory and Cognition, 19:

8 544 MAN IN INDIA Christianson, A., Howson, C. P. and Modell, B. (2006). March of Dimes Global Report on Birth Defects: the hidden toll of dying and disabled children, March of Dimes birth Defects Foundation, White Plains, NY, pp. 98. Comblain, A. (1994). Working Memory in Down Syndrome: Training the Rehearsal Strategy. Down Syndrome Research and Practice, 2(3): Conners, F. A., Rosenquist, C. J., Arnett, L., Moore, M. S., Hume, L. E. (2008). Improving memory span in children with Down syndrome. Journal of Intellectual Disability Research, 52 (3): Duarte, C. P., Covre, P., Braga, A. C. & De Macedo, E. C. (2011). Visuospatial support for verbal short-term memory in individuals with Down syndrome. Research in Developmental Disabilities, 32: Gathercole, S.E. (2008). Working memory in the classroom. The Psychologist, 21 (5): Holmes et al. (2009). Adaptive training leads to sustained enhancement of poor working memory in children. Journal of Developmental Science, 12(4): Hulme, C. & Mackenzie, S. (1992). Working memory and severe learning difficulties. Lawrence Erlbaum Associates Ltd. Hove, UK. Jarrold, C., and Baddeley, A. (1997). Short-term memory for verbal and visuo-spatial information in Down s syndrome. Cognitive Neuropsychiatry, 2: Jarrold, C., Baddeley, A. D., and Hewes, A. K. (1999). Verbal Short-Term Memory Deficits in Down Syndrome: A Consequence of Problems in Rehearsal? Journal of Child Psychology and Psychiatry, 40(20): Jarrold, C., and Baddeley, A. D. & Phillips, C. (1999). Down syndrome and the phonological loop: The evidence for, and importance of, a specific verbal short- term memory deficit. Down Syndrome Research and Practice, 6: Jarrold, C., and Baddeley, A. D. (2001). Short-term memory in Down Syndrome: Applying the working memory model, Down Syndrome Research and Practice, 7(1): Jarrold, C., Purser, H. R. M., & Brock, J. (2006). Short-term memory in Down syndrome. In T. P. Alloway & S. E. Gathercole (Eds.), Working memory and neurodevelopmental conditions, (pp ). Hove, East Sussex, UK: Psychology Press. Jarrold, C., Nadel, L. & Vicari, S. (2008). Memory and Neuropsychology in Down syndrome. Down Syndrome Research and Practice, Kay- Raining Bird, E., & Chapman, R. S. (1994). Sequential recall in individuals with Down syndrome. Journal of Speech and Hearing Research, 37: Laws, G., MacDonald, J. & Buckley, S. (1996). The effects of a short training in the use of a rehearsal strategy on memory for words and pictures in children with Down syndrome. Down s syndrome: Research and Practice, 4: Marcell, M. M. and Armstrong, V. (1982). Auditory and visual sequential memory of Down Syndrome and non-retarded children. American Journal of Mental Deficiency, 52: Marcell, M. M. and Weeks S. L. (1988). Short-term memory difficulties and Down s syndrome. J Ment Defic Res, 32: Marcell, M. M., Harvey, C. F. and Cothran, L. P. (1988). An attempt to improve auditory shortterm memory in Down s syndrome individuals through reducing distractions. Res Dev Disabil, 9:

9 THE EFFECTIVENESS OF INTERVENTION PROGRAM Naess K-A. B., S-A. H. Lyster, C. and Hulme, M. Melby- Lerva (2011, November-December). Language and verbal short- term memory skills in children with Down syndrome: A Meta Analytic Review. Research in Developmental Disabilities, 32(6): Sherman, S. L., Allen, E. G., Bean, L. H. and Freeman, S. B. (2007). Epidemiology of Down Syndrome. Mental Retardation and Developmental Disabilities Research Reviews, 13: Vallar, G. & Papagno, C. (1993). Preserved vocabulary acquisition in Down s syndrome: The role of phonological short- term memory. Cortex, 29: Vicari, S., Carlesimo, A. and Caltagirone, C. (1995). Short-term memory in persons with intellectual disabilities and Down s syndrome. J Intellect Disabil Res, 39: Wang, P. P. & Bellugi, U. (1994). Evidence from two genetic syndromes for a dissociation between verbal and visual- spatial short- term memory. Journal of Clinical and Experimental Neuropsychology, 16: