Fear Potentiated Startle in Children With Autism Spectrum Disorder: Association With Anxiety Symptoms and Amygdala Volume.
Startle size alone is not an autism anxiety marker—only kids with bigger amygdalae show the link.
01Research in Context
What this study did
Mason et al. (2021) tested fear-potentiated startle in children with autism and typical kids. They paired a loud noise with a threat cue to see if the autism group startled harder.
All kids had their brain scanned to measure amygdala size. The team then checked whether bigger or smaller amygdalae changed the link between startle size and anxiety.
What they found
Both groups startled the same amount. Fear-potentiated startle alone did not flag autism or anxiety.
Inside the autism group only, kids with larger amygdalae showed a tighter match between big startles and high anxiety scores.
How this fits with other research
Bernier et al. (2005) and Castañe et al. (1993) also saw no autism-versus-typical difference in startle size. David’s work extends these older studies by adding brain volume as a key piece.
Chen et al. (2021) used fMRI and found special amygdala wiring in anxious autistic youths. David’s structural finding dovetails with that work: both show the amygdala matters for anxiety, just measured in different ways.
At first glance, South et al. (2017) seems to disagree. They reported lower skin-conductance reactivity to social threat in autism, while David found normal startle. The gap disappears when you note the tasks: social threat versus pure loud-noise fear, and different body signals (sweat versus blink).
Why it matters
Do not expect a single startle test to tell you which autistic client has anxiety. If you do use it, ask for the MRI report. A bigger amygdala means the child’s startle numbers are more likely to line up with real anxiety symptoms, guiding your next assessment steps.
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02At a glance
03Original abstract
Atypical responses to fearful stimuli and the presence of various forms of anxiety are commonly seen in children with autism spectrum disorder (ASD). The fear potentiated startle paradigm (FPS), which has been studied both in relation to anxiety and as a probe for amygdala function, was carried out in 97 children aged 9-14 years including 48 (12 female) with ASD and 49 (14 female) with typical development (TD). In addition, exploratory analyses were conducted examining the association between FPS and amygdala volume as assessed with magnetic resonance imaging in a subset of the children with ASD with or without an anxiety disorder with available MRI data. While the startle latency was increased in the children with ASD, there was no group difference in FPS. FPS was not significantly associated with traditional Diagnostic and Statistical Manual (DSM) or "autism distinct" forms of anxiety. Within the autism group, FPS was negatively correlated with amygdala volume. Multiple regression analyses revealed that the association between FPS and anxiety severity was significantly moderated by the size of the amygdala, such that the association between FPS and anxiety was significantly more positive in children with larger amygdalas than smaller amygdalas. These findings highlight the heterogeneity of emotional reactivity associated with ASD and the difficulties in establishing biologically meaningful probes of altered brain function. LAY SUMMARY: Many children with autism spectrum disorder (ASD) have additional problems such as anxiety that can greatly impact their lives. How these co-occurring symptoms develop is not well understood. We studied the amygdala, a region of the brain critical for processing fear and a laboratory method called fear potentiated startle for measuring fear conditioning, in children with ASD (with and without an anxiety disorder) and typically developing children. Results showed that the connection between fear conditioning and anxiety is dependent on the size of the amygdala in children with ASD.
Autism research : official journal of the International Society for Autism Research, 2021 · doi:10.1017/S0954579417001626