Executive functions in individuals with intellectual disability

Abstract

581 83 Linköping, Sweden, or henrik.danielsson@liu.se. Telephone +46 13 28 21 99 and fax +46 13 28 21 45. Executive Functions in Intellectual Disability 2 AbstractThe aim of the present study was to investigate executive functions in adults with intellectual disability, and compare them to a closely matched control group longitudinally for 5 years. In the Betula database, a group of adults with intellectual disability (ID, n=46) was defined from measures of verbal and nonverbal IQ. A control group, with two people for every person with intellectual disability (n=92), was chosen by matching on the following criterion in order of priority: IQ higher than 85, age, sex, sample, level of education, and years of education. 3 types of tasks of executive functions were included on 2 occasions, with 5 years between testing sessions: The Tower of Hanoi, executively loaded dual task versions of word recall, and verbal fluency. Adults with ID showed significant impairments on verbal fluency and on the executively loaded dual task word recall task (at encoding but not at recall). There were no group differences on the Tower of Hanoi. No significant differences between the 2 test occasions were found. The results are interpreted in terms of individuals with ID having problems with speed of accessing lexical items and difficulties with working memory-related executive control at encoding, which includes shifting between tasks. There are, however, not necessarily problems with inhibition. The dual task results additionally imply that the adults with intellectual disability were more sensitive to strategy interruptions at encoding, but that dividing attention at recall did not have such detrimental effects.

Strengths and weaknesses in executive functioning in children with intellectual disability

“…Other studies have reported mental age appropriate performance on Tower tasks (Numminen, Lehto, Ruoppila, 2001). By contrast, in a recent study, no differences were found on the Tower of Hanoi or on dual tasks with retrieval demands between adults with ID and a group matched for chronological age (CA), sex, years of education and type of education (Danielsson, Henry, Rönnberg & Nilsson, 2010). Regarding executiveloaded working memory (ELWM) tasks, MA appropriate performance has been reported (Numminen et al, 2002), but see Carretti, Belacchi and Cornoldi, (2010) for an argument that difficulties in this area might be more apparent for 'high demand' ELWM tasks.…”

“…Regarding executiveloaded working memory (ELWM) tasks, MA appropriate performance has been reported (Numminen et al, 2002), but see Carretti, Belacchi and Cornoldi, (2010) for an argument that difficulties in this area might be more apparent for 'high demand' ELWM tasks. In relation to fluency tasks and dual tasks, Danielsson et al (2010) reported lower performance for adults with ID compared to adults matched for CA and other attributes (see earlier).…”

Executive functions and processing speed in children with mild to borderline intellectual disabilities and externalizing behavior problems

“…In contrast, no inhibition differences were found for adults with ID versus control participants with average intelligence (Danielsson, Henry, Rönnberg, & Nilsson, 2010). In children, EF impairments comprised difficulties in cognitive flexibility (Danielsson, Henry, Messer, & Rönnberg, 2012) and working memory (Danielsson et al, 2010;Schuchardt, Gebhardt, & Mäehler, 2010). The results of other studies also show individuals with MBID to perform worse on cognitive flexibility and working memory when compared to same-aged participants with average intelligence, but not when matched with regard to mental age (Danielsson et al, 2012;Henry & MacLean, 2002).…”

“…It is certainly possible that impaired working memory may be more strongly associated with externalizing behavior in children with MBID than in preschool children with externalizing behavior from the general population, simply because a minimal level of working memory is required to process social information adequately. As children with MBID tend to already perform poorly in working memory, they may not attain this minimum level (Danielsson et al, 2010;Van der Molen et al, 2007), which may lead to inadequate processing of social information and externalizing behavior problems.…”

“…A meta-analysis showed that children with ID performed poorer than average intelligent controls on inhibition (Bexkens, Ruzzano, Collot d'Escury-Koenings, Van der Molen, & Huizinga, 2013). In contrast, no inhibition differences were found for adults with ID versus control participants with average intelligence (Danielsson, Henry, Rönnberg, & Nilsson, 2010). In children, EF impairments comprised difficulties in cognitive flexibility (Danielsson, Henry, Messer, & Rönnberg, 2012) and working memory (Danielsson et al, 2010;Schuchardt, Gebhardt, & Mäehler, 2010).…”