Memory is divided into a long-term memory system and a working memory system. Research has demonstrated that children with developmental language disorder (DLD; also referred to as specific language impairment) have poor working memory which means they have difficulty holding and manipulating information in mind that they have just received. There has been less research examining the long-term memory system in children with DLD. The long-term memory system has two types of memory; procedural and declarative memory. Procedural long-term memory is our knowledge of how to do something such as ride a bike or tie our shoes and declarative memory is a type of long-term memory used for recalling facts, knowledge, events, and words.
The present study examined the role of declarative memory in children with DLD. The researchers assessed both immediate learning (10-minute delay) and retention (1-day delay) using nonverbal stimuli (seeing pictures of objects) and verbal stimuli (hearing words). Children who were typically developing and children with DLD were asked to complete a recognition task that was used to assess declarative memory. The recognition task was a judgement task where the participants had to indicate if they had seen or heard the item before. Participants first completed an encoding phase where they were presented with 32 real and 32 novel items. This was completed for both nonverbal and verbal stimuli. They completed the judgement task 10-minutes after the encoding phase and again 1-day after the encoding phase.
The researchers found that for nonverbal stimuli the typically developing children showed no change in accuracy between the 10- minute delay and the 1-day delay but children with DLD were significantly more accurate at the 1-day delay compared to the 10-minute delay. The typically developing children performed significantly better than the children with DLD when tested after the 10-minute delay but there was no difference between groups at the 1-day delay. This result indicates that after some consolidation the children with DLD were more accurately able to identify nonverbal items seen before. For verbal items, typically developing children performed better than children with DLD and they did not find the same trend of better performance in the DLD group at the 1-day delay. This result was not surprising since children with DLD are known to have difficulty with word learning.
These results would suggest that children with DLD have consolidation strengths in declarative memory, specifically for non-verbal items. This finding demonstrates the importance of consolidation and sleep for learning new objects. It would suggest that time for consolidation might be important when determining what a child with DLD has learned.
Blogger: Meghan Vollebregt is a student in the combined SLP MClSc/PhD program working under the supervision of Dr. Lisa Archibald.