Development of cortical surface area and gyrification in attention-deficit/hyperactivity disorder.

BACKGROUND: Delineation of the cortical anomalies underpinning attention-deficit/hyperactivity disorder (ADHD) can powerfully inform pathophysiological models. We previously found that ADHD is characterized by a delayed maturation of prefrontal cortical thickness. We now ask if this extends to the maturation of cortical surface area and gyrification.
METHODS: Two hundred thirty-four children with ADHD and 231 typically developing children participated in the study, with 837 neuroanatomic magnetic resonance images acquired longitudinally. We defined the developmental trajectories of cortical surfaces and gyrification and the sequence of cortical maturation, as indexed by the age at which each cortical vertex attained its peak surface area.
RESULTS: In both groups, the maturation of cortical surface area progressed in centripetal waves, both lateral (starting at the central sulcus and frontopolar regions, sweeping toward the mid and superior frontal gyrus) and medial (descending down the medial prefrontal cortex, toward the cingulate gyrus). However, the surface area developmental trajectory was delayed in ADHD. For the right prefrontal cortex, the median age by which 50% of cortical vertices attained peak area was 14.6 years (SE = .03) in ADHD, significantly later than in typically developing group at 12.7 years (SE = .03) [log-rank test χ(¹)² = 1300, p < .00001]. Similar, but less pronounced, delay was found in the left hemispheric lobes. There were no such diagnostic differences in the developmental trajectories of cortical gyrification.
CONCLUSIONS: The congruent delay in cortical thickness and surface area direct attention away from processes that selectively affect one cortical component toward mechanisms controlling the maturation of multiple cortical dimensions.