Working memory training improves cognitive function in VLBW preschoolers

Publication: Pediatrics

Institution: Norwegian University of Science and Technology, St. Olav University Hospital, Sørlandet Hospital

Investigator(s): Kristine Hermansen Grunewaldt, M.D., Gro Christine Løhaugen, Ph.D., Dordi Austeng, M.D., Ph.D., Ann- Mari Brubakk, M.D., Ph.D., & John Skranes, M.D., Ph.D.

Program: Cogmed JM

Background & Aim: Children born early can be characterized by as preterm (gestational age <37 weeks), very preterm (gestational age <32 weeks), or extremely preterm (gestational age <28 weeks). They can also be categorized as low birth weight (<2500 grams), very low birth weight (<1500 grams), or extremely low birth weight (<1000 grams). Several studies have shown that perinatal brain injury in very low birth weight (VLBW) preterms includes both grey and white matter damage, and that this may affect the ongoing brain development, not only at time of the incident, but throughout development. Due to advances in medical treatment in the past few decades, there is increased survival of children born at VLBW. Unfortunately, the number of children with brain pathology and neuro-impairments is still very high. Cognitive deficits, including poor attention and executive functioning, and behavioral problems in these children are reported to last into adolescence and early adulthood and may therefore impact academic achievement. The purpose of this research was therefore to determine whether a group of preterm born VLBW preschoolers would benefit from working memory (WM) training (Cogmed JM), as well as whether the training would have generalized benefits on memory, learning, behavior, attention, and anxiety. Preschoolers were randomly assigned to two groups and tested prior to any intervention. Then, group 1 began WM training while the other group did no intervention. When group1 completed training, both groups were tested again. Then, group 2 began training and was tested again post-training. The purpose of this stepped wedge design was to compare group 1 to a group of VLBW preschoolers that had only been exposed to assessments and thus, to control for test-retest effects. Population & Sample Size: N = 20 preschoolers born preterm with VLBW, ages 5 -6 years

• n = 9 preschoolers in adaptive Cogmed training group 1
• n = 11 preschoolers in adaptive Cogmed training group 2

Design: Randomized, Stepped-wedge, test-retest

T1 = baseline, T2 = post-test (group 1), T3 = post-test (group 2)

Results:

I. Children in both groups improved significantly on the tasks completed during training (Cogmed Training Index and on a non-trained measure of visuo-spatial WM (Span Board). There was no significant improvement on the measure of verbal WM (Digit Span). *Digit Span total score excluded due to test-retest effects.

II. Children in both groups improved significantly from pre to post-test on the following measures from the NESPY-II battery:

1) Auditory attention and response set
2) Phonological awareness (phonological processing and repetition of non-sense words)
3) Visual memory (memory for faces)
4) Verbal memory (narrative memory)
5) Verbal learning (sentence repetition)

* Visual attention total score and Statue measure excluded due to test-retest effects.

III. Children in both groups demonstrated normal scores on the ADHD rating scale (DSM-IV) prior to training. A slight reduction in hyperactivity/impulsivity scores post-training was observed but, no significant change post training on the attention score.

IV. Parents reported significantly decreased separation anxiety and total anxiety (Preschool Anxiety Scale).

Summary and Implications: This study was the first investigation of the impact of Cogmed Working Memory Training on the cognitive functioning and behavior of preterm born VLBW preschoolers. Compliance to the intervention protocol was 100%. Using a stepped wedge design, researchers found that children in both training groups improved on trained and non-trained measures of WM, as well as transfer measures of auditory attention, phonological awareness, and visual and verbal memory. Significant improvement on a measure of visual WM (Span Board) was observed in 75% of children and 70 – 80% improved significantly on auditory attention, phonological processing, and repetition of nonsense words assessing phonological awareness. Interestingly, phonological awareness is core to pre-reading linguistic ability and is important for development of math skills. Due to test-retest effects, as demonstrated by improvements in group 2 at T2, led the researchers to exclude the visual attention total points and statue measure (NEPSY-II) and the Digit Span total score from the analysis. Contrary to some of the Cogmed literature, there was no significant improvement from pre- to pos-training on the measure of verbal WM (digit span forward or backward). The researchers posited that this lack of significance may be due to the purely visuo-spatial nature of the Cogmed JM preschool program.

Children in the study did not demonstrate significant improvement on the DSM-IV ADHD parent rating scale, except for a slight improvement in hyperactivity/impulsivity. It is possible that this lack of change in inattention symptoms is due to the group having normal behavior scores prior to training. VLBW children did however demonstrate significantly decreased separation and total anxiety scores on the Preschool Anxiety Scale. Although it may be possible that children experienced increased maturity and decreased separation anxiety due to natural development over the course of the study or that their increased WM enabled the child to better understand complex explanations and thus the world around them. More research on the impact of WM training on anxiety in VLBW would be needed to further explore this question.

In a previous study, adolescents born at extremely low birth weight (ELBW) improved WM, as well as verbal and visual memory and learning (Løhaugen et al., 2010). The findings of the current study with VLBW preschoolers are thus consistent with the extant research regarding the impact of WM training on preterm born young people. The researchers speculated that because the improved functions were all those utilized in the school environment, that preschool training may have a positive impact on later academic ability and school performance. Although larger studies are needed to confirm the findings of the current research, this study demonstrated that WM training may be an effective tool for improving educational and functional outcomes in preterm children.

Funding: This study was supported by the Norwegian University of Science and Technology (NTNU) and Liaison Committee between the Central Norway Regional Health Authority and NTNU.