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    • br Developmental changes in executive systems

    2018-11-07


    Developmental changes in executive systems Executive functions (EFs), such as voluntary attention control, intentional response selection, or contextual framing of stimuli, serve to guide behavior, attention, and memory toward or away from predetermined goals. EFs interface with perceptual systems to enhance or blunt sensory processing of stimuli (Shi et al., 2014). EFs can also augment or diminish emotional experience and associated subcortical signals (Ochsner et al., 2004; Giuliani et al., 2008) Conversely, emotional activity can diminish efficacy of executive functions when they are irrelevant to task demands, or enhance functioning when they are congruent with them (Blair et al., 2007; Robinson et al., 2013). EFs have a protracted developmental trajectory. For example, improvements in working memory, selective attention, response inhibition, and flexible engagement of behavior occur from birth through the mid to late adolescent years (Luna et al., 2004; Crone, 2009; Luna, 2009; Diamond, 2013). This improvement is particularly marked in the social domain (Germine et al., 2011; Gur et al., 2012). A similar protracted and largely linear developmental pattern has been observed specifically in the ability to use EF to modulate emotional responses (McRae et al., 2012). EFs are instantiated in dorsal, medial, and ventrolateral regions of prefrontal opioid receptor antagonist (Miller and Cohen, 2001). However, the ventral region of PFC, which includes the orbitofrontal cortex, plays more of an intermediary role between “hot” functions, like subjective valuation, and “cold” executive functions like response selection (Rudebeck et al., 2013). Similarly the anterior cingulate cortex (ACC), while not traditionally viewed as a region directly involved in cold executive functions, plays an important role in cognitive control, particularly in the context of affective experiences, learning, and error monitoring (Totah et al., 2009; Medalla and Barbas, 2010; Shackman et al., 2011; Tamnes et al., 2013). A number of studies have indicated that the ACC and vPFC play an important role in various aspects of social interaction (Somerville et al., 2006; Guyer et al., 2008b; Masten et al., 2009, 2011; Somerville et al., 2013; Blakemore, 2014; Guyer et al., 2015; Jarcho et al., 2015a,b). These regions might play a particularly important role in integrating social behavior with more traditional (cold) EFs. Both structural and functional maturational changes in the PFC occur into late adolescence in humans (Gogtay et al., 2004; Crone, 2009; Luna et al., 2010; Mills et al., 2014). From a structural standpoint, the PFC matures in a manner similar to the social perception regions in the occipital and temporal lobe. In early life there is an increase in volume and gray matter, followed by a more protracted reduction in gray matter, and a linear increase in white matter. Functionally, however, there may be important differences in development between perceptual and executive mechanisms. As indicated above, while several “sensitive periods” have been identified for social perceptual processes, like face processing and language acquisition, no such windows have been identified for EFs in the social domain (but see Nelson et al. (2007) for a possible exception). Rather than develop in a pattern of rapid orienting and protracted narrowing and refining, EFs tend to develop in a manner suggesting slow linear improvement of function as the brain matures with age (Gur et al., 2012; Tamnes et al., 2013). This relatively slow improvement in EFs may help explain the protracted and gradual ability to match social behavior to specific goals and task demands (Cohen Kadosh et al., 2013b). It may also reflect the gradual transition of motivated behavior across different phases of development into individualized patterned circuits (Euston et al., 2012). Several models contrast the slow linear maturation of brain regions implicated in EF with the inverted-U shaped maturational pattern of brain regions implicated in affective processing in general (Ernst et al., 2006; Somerville et al., 2010), and affective processing in the social domain in particular (Steinberg, 2008; Smith et al., 2013). These models have generally highlighted the transition from adolescence to adulthood as a risky period when behavioral responses are strongly impacted by affective responses since EF systems reach full functional maturation in adulthood.