The structure and function of semantic memory in children with attention-deficit/hyperactivity disorder

Semantic memory, the organized knowledge network an individual possesses about words, objects, facts and concepts and the relationships among them, emerges from direct experience with the environment. The network is constructed and refined over the course of development as the individual encounters new stimuli in the environment and relates them to representations of previously encountered material. This process is highly dependent on attentional processes and executive functions as the individual must select which aspects of the stimulus to attend to and what to relate it to in the long-term memory stores. Previous research has demonstrated that children with ADHD perform more poorly than their normal peers on measures tapping attention and executive function, thus they may also demonstrate deficits in measures tapping semantic memory abilities. The present study set out to investigate whether children with ADHD demonstrate differential patterns of development of the semantic memory network compared to age- matched controls. The sample included 19 children with ADHD combined type, 29 children with ADHD inattentive type and 25 normal control children. Structure of the semantic memory system was investigated using a priming task where relationship between target and prime word were varied for degree of abstraction in the relationship (semantic vs. functional) and for strength of association (high vs. low). It was hypothesized that children with ADHD would demonstrate less priming in the semantic low association strength condition as creating such relationships in the semantic network is more cognitively demanding. Function of the semantic memory was investigated using two list learning tasks, one in which subjects were cued to use semantic clustering as an aid in encoding and one in which these cues were absent. It was hypothesized children with ADHD would be less likely to utilize strategies such as semantic clustering if not cued to do so. Data were subjected to analysis of variance. The results indicated that children with ADHD do demonstrate less priming for words that are more abstractly related to one another. Children with ADHD did not differ from controls, however, in their use of semantic clustering as an encoding strategy or their recall ability.