Children With Angelman Recognize Words, Struggle to Assign Meaning
Study of electrical activity suggests differences in left and mid-brain responses
In children with Angelman syndrome, the parts of the brain that recognize words show activity similar to that of children with typical development, but lesser activity is seen in brain regions needed to assign meaning to words, a study suggested.
The study, “Typical and atypical neural mechanisms support spoken word processing in Angelman syndrome,” was published in the journal Brain and Language.
Most children with Angelman syndrome are unable to communicate through spoken language, though some are able to vocalize single words or simple sentences. Generally, children with this condition have better receptive communication than expressive communication — meaning they are generally able to understand more than they can communicate.
Differing activity in brain regions for word recognition vs. assigned meaning
The human brain has evolved exquisitely specialized systems that allow it to rapidly process and comprehend language using electrical signals sent among nerve cells. Scientists have recently begun to delve into the details of these bioelectrical processes, and to understand how they may be dysregulated in conditions like Angelman where speech development is abnormal.
Researchers at Vanderbilt University, in Tennessee, conducted a word versus pseudoword assessment to examine language-related brain activity in children with Angelman. Put simply, this involves measuring brain electrical activity with electrodes placed on the scalp while a person listens to either known words or pseudowords, or word-like sounds that do not have any meaning in the language being spoken.
“The use of the word-pseudoword contrast reduced attentional demands (i.e., compared to a picture-word matching paradigm), making the assessment suitable for individuals across a wide range of functioning,” the researchers noted.
Their study included 24 children with Angelman syndrome alongside 30 typically developing children of a similar age range. Seven adults with Angelman also participated in the study.
Marked differences were seen for known words compared with pseudowords in the electrical activity of certain brain regions with typically developing children. This activity, which reflects the children’s ability to recognize and understand the known word but not the pseudoword, was mainly localized in specific portions on the left side of the brain, with some additional activity toward the middle of the brain.
Children with Angelman syndrome had similar differences in word-pseudoword activity in the left side of the brain, though the activity was generally more spread out and less efficiently organized than in the other children. The researchers noted that this spread in activity is similar to what has been reported in typically developing toddlers who are still learning to speak.
“Our results indicated that both participant groups demonstrated neural specialization for known words processing reflected by more negative left-hemisphere [electrical activity] to words than pseudowords,” the researchers wrote.
The fact that children with Angelman syndrome show electrical activity that’s comparable to typically developing children “suggests the possibility of greater expressive communication abilities that are obscured by other difficulties” for these patients, they added.
Language-processing brain activity also was similar among adults and children with Angelman, which “indicates that their developmental course of neural specialization for spoken word processing may proceed at a slower than typical rate and/or derive less benefit from continuous exposure to language, resulting in slower vocabulary acquisition,” the researchers wrote.
Whereas language-recognizing brain activity was comparable, electrical activity in the middle of the brain — which, the researchers said, is associated with memory and assigning meaning to words — was substantially reduced or absent in children with Angelman. This suggests that, even when they can recognize words they have heard before, the ability to make associations between words and their meanings may be impaired in children with the condition.
Notably, results indicated that Angelman patients with more activity in this brain region tended to report more behavioral issues like hyperactivity. This suggests “that less neurologically disrupted individuals may find their expressive communication difficulties more frustrating,” the researchers wrote.
They suggested that future research test whether these individuals may benefit from assistive communication strategies.