Though generally considered to be a technique that is difficult to apply in younger populations, MRI has been used at an increasing rate over the last few decades to study brain development in typically developing children and children with neurodevelopmental disorders (1). The onset of many neurodevelopmental disorders, such as dyslexia (2–4), attention-deficit/ hyperactivity disorder ([ADHD]; 5), specific language impairment ([SLI]; 6), autism spectrum disorders ([ASD]; 7), intellectual disability (8), and developmental stuttering (9, 10) occurs at preschool-age or earlier. The ability to detect subtle neural differences near symptom onset can be greatly enhanced by the acquisition of whole-brain measures using functional magnetic resonance imaging (fMRI), which is crucial to extract both localized and network-level information to expand our understanding of the nature of these neurodevelopmental disorders. Early detection of brain network-level changes associated with childhood neurodevelopmental disorders might pave the way for developing assessments, interventions, and better prognostic markers for these disorders; however, this requires acquiring MRI data from very young children.
Collecting high-quality MRI data from preschool-age children is challenging. Notably, age is an important factor that influences data quality across various data collection methods in terms of compliance, active participation, and reliability of measurement (11, 12). For MRI in particular, it is difficult for young children to remain still for the 30 to 60 minute scanning period required for most research scans (11, 12). In addition, young children may exhibit fear or anxiety associated with the scanning environment, which can lead to increased movement during scanning. Previous research has shown that for neuroimaging studies in children 4–6 years of age, researchers may need to increase recruitment for data collection by 20–40% to obtain sufficient useable data without movement artifacts (12). Malisza and colleagues (11) indicated that children 2–3 years of age have a significantly lower rate of successful MRI completion than children 6–7 years of age. These authors also suggest that researchers should anticipate a failure rate of at least 50% if a study includes children 2–7 years of age (11). Age is consistently found to influence the “success” of MRI data collection in children. Success of MRI data collection in this study is defined as data that are relatively free of movement artifacts and are thus of sufficient quality to be included in data analysis. In preschool-age children, success rates are especially low (11, 12). Given the challenges researchers face in acquiring MRI data in young children, it is vital to understand factors that may interact with the age of the child that could lead to excessive movement during scanning.
Previous research has suggested that scan duration, movement restrictions, being placed within a confined space, and the excessive noise produced by MRI gradient coils may contribute to a child having difficulty completing a scan (13–15). Potential modulatory factors that have been investigated in clinical disorders and typically developing children include age and sex; however, the contribution of these variables is understudied and thus poorly understood (11, 16). Some studies have found that age did not predict willingness to participate in MRI but did predict scanning success (11). The sample sizes in this study differed across age groups however, potentially influencing their results. Additionally, 2–5 year-olds had a failure rate of 50%, while 6–7 year-olds only had a failure rate of 35%. There is no strong evidence for an effect of sex (11, 16); however, not all studies explicitly examined sex as a factor (12). These studies importantly did not examine the differences between sexes within clinical populations, despite a large body of evidence suggesting that different behaviors and developmental patterns are present among boys and girls diagnosed with neurodevelopmental disorders (e.g., 17–20).
Still, some young children seem to be able to tolerate scanning better than much older children. This observation suggests that interactions with variables other than age may predispose some children to tolerate scanning better than others. One such factor that may influence pediatric scanning success is temperament, or one’s innate behavioral dispositions. For example, temperament affects a child’s tolerance to many clinical environments such as doctor and dental visits (e.g., 21–23). To date, few studies have directly investigated temperament as it relates to the successful completion of MRI scanning in children (16, 24). From these studies, the best predictors of movement during scanning were poor attention and adaptability skills (i.e., ability to handle novel experiences) among preschool- and school-age children (16, 24). Children with neurodevelopmental disorders may display decreased attention regulation and adaptability, which might further compromise their ability to tolerate scanning (25–33). While some studies have shown that children with neurodevelopmental disorders such as ADHD, and ASD, or developmental delays tend to have fewer successful scans than controls, the reasons for this have not been clarified, especially in preschool-age children (12, 16).
Moreover, temperament factors such as adaptability and attentional control develop differently between the sexes, even in typically developing children. Preschool-age girls tend to have more advanced skills related to effortful control than their age-matched male peers (34). If temperamental factors associated with poor attention and adaptability skills influence scanning tolerance in children, those with neurodevelopmental disorders may already be at a greater disadvantage and have a lower probability of success, leading to spurious group differences that may be erroneously attributed to the core clinical condition. If temperament factors that influence MRI scanning develop more slowly in boys than girls, boys with neurodevelopmental disorders may have an even more challenging time tolerating MRI scanning.
Several studies to date have reported that children who stutter (CWS) and children who do not stutter differ in some temperament dimensions. For example, CWS have been shown to demonstrate decreases in inhibition (35–38), attentional shifting (35, 36), attentional focusing (36, 37, 39), and attentional regulation (36, 40). They also exhibit increased difficulty adapting to change (41–42), present with greater negative affect (35, 42, 43), display increased emotional reactivity (40), show higher activity levels (37, 42), demonstrate more anger and frustration (35, 39), and exhibit more impulsivity (37). Because these factors may contribute to tolerance of the scanning procedures in clinical populations, information that further elucidates relationships between temperament, presence of a clinical condition (in this case, stuttering), and head movement during scanning, could help develop strategies to increase chances of collecting usable MRI data that is comparable across the clinical and control groups.
The current study investigated whether clinical condition (stuttering compared to children who do not stutter, hereafter referred to as “controls”), age, sex, and temperament as assessed by scores on the Child Behavior Questionnaire ([CBQ]; 44), could predict excessive head movement during resting-state fMRI scanning in a cohort of preschool-age children. We focused our temperament analyses on the three CBQ composite scores: effortful control, negative affectivity, and extraversion/surgency. Effortful control reflects a child’s ability to control attentional processes and regulate behaviors, such as their ability to maintain focus on a task. Negative affectivity measures children’s negative emotional responses, such as a negative response to an adverse, unique, or high-intensity event. Extraversion/surgency describes how extroverted or outgoing a child may be, for example, how willing a child may be open to new experiences (45). Guided by previous research reporting temperament differences between CWS and controls as well as the relationship between temperament and MRI tolerance in children, we tested the following hypotheses. First, we expected that CWS would exhibit significantly more movement during scanning than controls. Second, we expected that the groups would differ in temperament indices that may affect tolerance of MRI procedures, including effortful control and negative affectivity, because of their relationship to poor attention and adaptability skills (i.e., ability to handle novel experiences) that have been shown to be associated with increased tolerance of MRI scanning (16, 24). These factors are consistent with the effortful control scale on the CBQ that measures self-regulation of behavior and emotions. Our third hypothesis tested whether the extent of movement during MRI scanning is influenced by temperamental characteristics associated with lower adaptability skills and attentional control, such as low effortful control and negative affectivity scores. We predicted that these temperamental differences would be associated with the most movement artifacts in their scans and that this relationship would be modulated by age and sex.