Children with autism have memory problems that not only limit their ability to remember faces, but also their ability to retain other types of information, according to a new study from the Stanford School of Medicine. The study found that these deficits are represented by unique wiring patterns in children’s brains.
The research, which will be published in Biological Psychiatry: Cognitive Neuroscience and Neuroimaging, clarifies a debate about memory function in autistic children, showing that their memory difficulties exceed their ability to form social memories. The finding should prompt broader thinking about autism in children and treating the developmental disorder, according to the scientists who conducted the study.
“Many high-functioning children with autism go to mainstream schools and receive the same education as other children,” said lead author Jin Liu, PhD, postdoctoral researcher in psychiatry and behavioral sciences. Memory is a key predictor of academic achievement, Liu said, adding that memory problems can disadvantage autistic children.
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The study findings also raise a philosophical debate about the neural origins of autism, the researchers said. Social challenges are recognized as a core feature of autism, but it is possible that memory impairment contributes significantly to the ability to engage socially.
“Social cognition cannot occur without reliable memory,” said lead author Vinod Menon, PhD, Rachael L. and Walter F. Nichols, MD, professor and professor of psychiatry and behavioral sciences.
“Social behaviors are complex and involve multiple brain processes, including the association of faces and voices with particular contexts, which require robust episodic memory,” Menon said. “Disturbances in the formation of these associative memory traces could constitute one of the fundamental elements of autism.”
Comprehensive memory tests
Autism, which affects approximately one in 36 children, is characterized by social impairments and restricted and repetitive behaviors. The condition exists on a broad spectrum. Those most severely affected cannot speak or care for themselves, and about a third of people with autism have intellectual disabilities. At the other end of the spectrum, many people with high-functioning autism have normal or high IQs, complete college, and work in a variety of fields.
Research has shown that children with autism have difficulty remembering faces. Some research has also suggested that children with autism have broader memory difficulties, but these studies were small and did not comprehensively assess participants’ memory abilities. They included children with wide age and IQ ranges, both of which influence memory.
To clarify the impact of autism on memory, the new study included 25 high-functioning children with autism and normal IQs between the ages of 8 and 12, and a control group of 29 typically developing children with ages and Similar IQs.
All participants completed a comprehensive assessment of their memory abilities, including their ability to remember faces; written material; and non-social photographs, or photos without people. Scientists tested participants’ ability to accurately recognize information (by identifying whether they had seen an image or heard a word before) and to recall it (by describing or reproducing details of the information they had seen or heard before). The researchers tested the memory of the participants after more or less long delays. All participants also received functional magnetic resonance imaging scans of their brains to assess how regions known to be involved in memory are connected to each other.
Distinct brain networks lead to memory problems
Consistent with previous research, children with autism had more difficulty remembering faces than typically developing children, according to the study. Research has shown that they also have trouble remembering non-social information.
On tests of the sentences they read and the nonsocial photos they viewed, their scores for immediate and delayed verbal recall, immediate visual recall, and delayed verbal recognition were lower.
“Study participants with autism had quite high IQs, comparable to typically developing participants, but we still observed very evident general memory impairments in this group,” Liu said, adding that the research team had not anticipated such significant differences.
In typically developing children, memory abilities were consistent. If a child had a good memory for faces, he was also good at remembering non-social information. This was not the case in autistic children. “Among autistic children, some children appear to have both impairments and some have more severe impairment in one memory area or the other,” Liu said.
The researchers also did not expect this result.
“It was a surprising finding that these two dimensions of memory are both dysfunctional, in ways that appear to be unrelated – and this fits with our analysis of brain circuitry,” Menon said. Brain scans have shown that, among autistic children, distinct brain networks lead to different types of memory impairment.
For children with autism, the ability to retain non-social memories was predicted by connections in a network centered on the hippocampus – a small structure deep in the brain known to regulate memory. But facial memory in autistic children was predicted by a distinct set of connections centered on the posterior cingulate cortex, a key region of the brain’s default mode network, which plays a role in social cognition and stands apart from others.
“The results suggest that general and facial memory problems have two underlying sources in the brain that contribute to a broader profile of memory impairment in autism,” Menon said.
In both networks, the brains of autistic children showed over-connected circuits compared to typically developing children. Over-connectivity – likely due to too indiscriminate pruning of neural circuits – has been found in other studies of brain networks in autistic children.
New autism therapies should take into account the extent of memory difficulties uncovered by research, as well as how these challenges affect social skills, Menon said. “It’s important for functioning in the real world and for academia.”