Neuro-physiological correlates of sluggish cognitive tempo (SCT) symptoms in school-aged children.

This study was the first to examine the relationship between neurophysiological abnormalities and symptoms of sluggish cognitive tempo (SCT) in children. Thirty children aged 6-12 years were recruited. Their heart rate variability (HRV) was measured under resting and warning signal conditions. At rest, the children's SCT symptoms were found to be positively associated with their HRV (indicated by the standard deviation of the Poincaré plot along the line of identity in normalized units, SD2 nu). SCT symptoms were also positively associated with a change in SD2 nu between the resting and warning signal conditions. When controlling for symptoms of attention deficit hyperactivity disorder, the children's SCT symptoms were significantly predicted by their resting SD2 nu and by changes in SD2 nu and the percentage of successive RR intervals that differ by more than 50 ms (pNN50) between the resting and warning signal conditions. These findings suggest that the readiness and regulation of the autonomic nervous system may contribute to symptoms of SCT. Specifically, disturbances in the internal neurophysiological system may explain the difficulties experienced by children when exposed to environmental stimulation. These initial data support the hypothesis that SCT results from deficiencies in arousal.