Neuropediatrics 2006; 37 - TP98
DOI: 10.1055/s-2006-945691

IMPLICIT MEMORY FUNCTION IN CHILDREN WITH DEVELOPMENTAL DISORDERS

M Inagaki 1, A Gunji 1, N Kokubo 1, M Kaga 1
  • 1National Institute of Mental Health, NCNP, Kodaira, Tokyo, Japan

Objectives: It has been reported that adults with mental retardation have a deficit in implicit memory. In this study, we evaluated the implicit memory performance in control and young patients with developmental disorders (DD) such as mental retardation (MR), autistic disorder (AD), dyslexia and ADHD using picture fragment completion task (PFCT).

Methods: We made a modified PFCT, a perceptual identification task, in which the stimuli consisted of 20 images (10 at priming and 10 at novel testing) of familiar objects and animals. Each image was presented on CRT monitor as degraded fragmentation of 8 levels to control and DD children aged 5 to 15 years. They were encouraged to name each visual stimulus during the priming and the test phase. The fragmentation level (level 1; several dots, level 8; complete figure) at which the image was correctly named was recorded.

Results: Age-related change of identification threshold (IT) levels was observed in control children. Mean (±SD) acceleration of IT for 1 hour was -21 (±5.5) in normal adults (n=14). However, there was little acceleration of IT in mild MR children (n=7; -8.6±5.7; 6y–14y,). Children with autistic disorder and reading disorder showed almost intact implicit memory (n=10; -18±6.7, n=7; -23±4.7). Many errors of picture naming were observed during both phases in ADHD children.

Conclusion: Developmental changes of implicit memory could be determined using the modified PFCT. Children with DD might have characteristic pattern of implicit memory function. In MR, there is a dysfunction of implicit processes even in childhood.