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    • To elucidate the development of neural mechanisms mediating

    2018-11-07

    To elucidate the development of neural mechanisms mediating age-related changes in behavior, it diindolylmethane is important to map brain-behavior associations across age (Pfeifer and Allen, 2012). Poldrack has emphasized the importance of quantifying such associations precisely (Poldrack, 2014). However, most developmental studies examine the relationship between activation and neural responses averaged over time (Poldrack, 2014), rather than at the level of specific trials. ISVRT is a particularly well-suited construct with which to delineate the development of brain-behavior associations in a precise fashion because 1) ISVRT has been shown to change with age, 2) RT varies at the level of specific trials, and 3) RT can be measured easily. One approach to directly mapping brain-behavior relationships employs functional magnetic resonance imaging (fMRI) to link trial-specific changes in RT to trial-specific changes in the BOLD signal (Weissman et al., 2006). Using this approach in adults, several researchers have reported robust “RT-BOLD relationships” in frontal and parietal regions during executive function tasks (Weissman et al., 2006; Chee and Tan, 2010; Prado and Weissman, 2011; Yarkoni et al., 2009). Moreover, some researchers have reported that the size of the RT-BOLD relationship varies across populations who differ in their attentional abilities. For example, in frontal and parietal regions crucial for attention, stronger RT-BOLD relationships manifest in individuals who exhibit minimal, relative to marked, effects of sleep deprivation on attention (Chee and Tan, 2010; Chee et al., 2008). Similarly, investigating developmental differences in the RT-BOLD relationship may help to reveal which neural processes underlie developmental differences in executive functioning (Plude et al., 1994; Anderson et al., 2001; Rueda et al., 2004; Ridderinkhof and van der Stelt, 2000). Along these lines, it is presently unclear whether children and adolescents show similar RT-BOLD relationships to adults. Carp and colleagues found weak or absent RT-BOLD associations in a relatively small sample of children and adolescents (n=18) as compared to a group of young adults (n=21) (Carp et al., 2012). Analogous to the above-noted findings on sleep deprivation, weaker RT-BOLD associations in children and adolescents compared to adults could reflect reduced attentional capacity early in development (Plude et al., 1994; Rueda et al., 2004; Ridderinkhof and van der Stelt, 2000). However, Kim and colleagues identified strong, linear RT-BOLD relationships in a larger (n=28) sample of children (Kim et al., 2013), thereby raising the possibility that the first study was underpowered. Further, neither study employed age as a continuous variable to investigate more specifically how the RT-BOLD relationship varies cross-sectionally with age. Finally, both studies modeled RT-BOLD relationships using a canonical hemodynamic response function, which precludes the ability to distinguish between RT-BOLD relationships that occur “early” versus “late” in the average time-locked BOLD response to a trial type. Nonetheless, these “early” and “late” relationships can be quite different, possibly in ways that relate to early lapses of attention and later compensatory effects (Weissman et al., 2006). For all of these reasons, resolution remains unclear whether and when in the course of a neural response the RT-BOLD relationship differs between children and adults. The goal of the present study was to answer these questions using methods that characterize RT-BOLD relationships throughout the course of each trial during the performance of a selective attention task that requires the engagement of executive function (Weissman et al., 2006). To this end, we used a finite impulse response (FIR) model to derive empirically the average event-related BOLD response to target stimuli in a selective attention task (Ollinger et al., 2001). We then compared both “early” and “late” time points of the RT-BOLD relationship in healthy children and adults. Finally, we employed age as a continuous variable to investigate more specifically how the RT-BOLD relationship varies across development.