Abstract: Background: Impulsivity is a characteristic feature of
adolescence. We previously reported in a large (n¼1,896)
sample of 14-year-olds that impulsivity phenotypes were
differentially related to particular brain networks active during
the Stop Signal Task (SST; Whelan et al., 2012). Here, we
investigated how individual differences in these networks at
age 14 relate to inhibitory control networks and impulsivity
phenotypes at age 18.
Methods: Participants completed the SST under fMRI at both
age 14 and age 18. Measures of behavioral impulsivity, substance
misuse and ADHD symptoms were also obtained at
both time points. A factor analysis on regions of interest was
applied to fMRI data. Changes in brain networks were
modelled using a linear mixed effects approach.
Results: Factor analysis with 31 brain regions of interest
(ROIs) revealed remarkably similar networks at age 14 and 18.
All six networks associated with failed inhibition were identical
at age 14 and 18, while successful inhibition trials revealed
minor changes in brain dynamics in a parietal network.
Notably, individual differences in brain activity in a right prefrontal
network at age 14 predicted activity in this network at
age 18 (p<10 ˇ
-10), as did activity in the default mode (p<10 ˇ
and a substantia nigra/subthalamic nucleus network (p<.005).
Changes over the four-year period in the basal ganglia network
during successful and failed inhibition were modulated by the
extent of cigarette use (p¼0.011 and p<0.001, respectively).
Conclusions: Individual differences in task-related brain activity
at age 14 are predictive of activity at age 18 in similar
Abstract: Moment-to-moment reaction time variability on tasks of attention, often quantified by intra-individual response variability (IRV), provides a good indication of the degree to which an individual is vulnerable to lapses in sustained attention. Increased IRV is a hallmark of several disorders of attention, including Attention-Deficit/Hyperactivity Disorder (ADHD). Here, task-based fMRI was used to provide the first examination of how average brain activation and functional connectivity patterns in adolescents are related to individual differences in sustained attention as measured by IRV. We computed IRV in a large sample of adolescents (n = 758) across 'Go' trials of a Stop Signal Task (SST). A data-driven, multi-step analysis approach was used to identify networks associated with low IRV (i.e., good sustained attention) and high IRV (i.e., poorer sustained attention). Low IRV was associated with greater functional segregation (i.e., stronger negative connectivity) amongst an array of brain networks, particularly between cerebellum and motor, cerebellum and prefrontal, and occipital and motor networks. In contrast, high IRV was associated with stronger positive connectivity within the motor network bilaterally and between motor and parietal, prefrontal, and limbic networks. Consistent with these observations, a separate sample of adolescents exhibiting elevated ADHD symptoms had increased fMRI activation and stronger positive connectivity within the same motor network denoting poorer sustained attention, compared to a matched asymptomatic control sample. With respect to the functional connectivity signature of low IRV, there were no statistically significant differences in networks denoting good sustained attention between the ADHD symptom group and asymptomatic control group. We propose that sustained attentional processes are facilitated by an array of neural networks working together, and provide an empirical account of how the functional role of the cerebellum extends to cognition in adolescents. This work highlights the involvement of motor cortex in the integrity of sustained attention, and suggests that atypically strong connectivity within motor networks characterizes poor attentional capacity in both typically developing and ADHD symptomatic adolescents.