Elevated unanticipated acoustic startle reactivity in dyslexia

Abstract

People with dyslexia, a neurodevelopmental disorder of reading, are highly attuned to the emotional world. Compared with their typically developing peers, children with dyslexia exhibit greater autonomic nervous system reactivity and facial behaviour to emotion- and empathy-inducing film clips. Affective symptoms, such as anxiety, are also more common in children with dyslexia than in those without. Here, we investigated whether the startle response, an automatic reaction that lies at the interface of emotion and reflex, is elevated in dyslexia. We measured facial behaviour, electrodermal reactivity (a sympathetic nervous system measure) and emotional experience in response to a 100 ms, 105 dB unanticipated acoustic startle task in 30 children with dyslexia and 20 comparison children without dyslexia (aged 7-13) who were matched on age, sex and nonverbal reasoning. Our results indicated that the children with dyslexia had greater total facial behaviour and electrodermal reactivity to the acoustic startle task than the children without dyslexia. Across the sample, greater electrodermal reactivity during the startle predicted greater parent-reported anxiety symptoms. These findings contribute to an emerging picture of heightened emotional reactivity in dyslexia and suggest accentuated sympathetic nervous system reactivity may contribute to the elevated anxiety that is often seen in this population.

Keywords: affective symptoms; autonomic nervous system; learning differences; reading; skin conductance.

Figure 1.. Group comparisons of facial behavior, electrodermal reactivity, and emotional experience to the unanticipated startle task.

Compared to children without dyslexia, children with dyslexia had (a) greater total facial behavior but (b) similar total emotional experience during the unanticipated startle task. On measures of electrodermal activity, children with dyslexia showed greater reactivity in (d) skin conductance response (SCR) and (e) skin conductance level (SCL) than children without dyslexia. The smoothed time-series of each group’s average (e) skin conductance response (SCR) and (f) skin conductance level (SCL) during the unanticipated startle task are provided (the line represents the mean, and the shaded area represents the standard error). Time-series were averaged and smoothed within each group using locally-fitted polynomial regression for visualization. The onset of the unanticipated acoustic startle stimulus is denoted with the dashed line; the period prior represents the 60-s pre-startle baseline, and the period subsequent represents the 60-s post-startle baseline. Asterisks indicate significant differences at p<.05.

Figure 2.. Relationship between electrodermal reactivity and anxiety.

Across the sample, greater anxiety was associated with greater reactivity in (a) skin conductance response and (b) skin conductance level during the unanticipated startle task.