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  • Because cannabis use has an age of onset SAMHSA

    2018-11-07

    Because cannabis use has an age of onset (SAMHSA, 2014) that overlaps with continued PFC gyrification development (Su et al., 2013; Klein et al., 2014), examining the impact of cannabis use on gyrification remains an important area to investigate. The current study examined whether cannabis use status predicted PFC or parietal gyrification in a sample of adolescents and emerging adults. Surface morphology may be related to cortical thickness and volume (Alemán-Gómez et al., 2013). Given that both reductions in cortical thickness and volume (Lopez-Larson et al., 2011; Price et al., 2015) and reductions in PFC sulcal concavity (Mata et al., 2010) were previously found in young cannabis users, we predicted that cannabis users would demonstrate reduced gyrification and SA in PFC and parietal regions. Reduced SA and gyrification may be most pronounced in both inferior frontal and parietal regions that show reductions in volume (Churchwell et al., 2010; Price et al., 2015) Within regions that differed between cannabis users and controls, follow-up analyses examined brain–behavior relationships in both groups.
    Materials and methods
    Results
    Discussion Decreased gyrification in right medial, calcium sensing receptor medial, and frontal pole regions, were associated with poorer performance on complex attention in cannabis users, suggesting that reduced gyrification confers a functional deficit. This is consistent with previous studies suggesting increased gyrification is associated with better cognitive functioning (Wallace et al., 2013) and may reflect improved cognitive control (Luders et al., 2012). Present findings are consistent with prior research demonstrating unique PFC surface morphology characteristics in cannabis using youth (Mata et al., 2010). Specifically, Mata et al. (2010) found reduced sulcal concavity in the PFC of cannabis users in comparison to non-users and failed to find global hemispheric differences in SA. In the current study we found significantly reduced LGI in medial, ventral medial, and frontal poles in cannabis users compared to controls. We found no significant differences in inferior parietal LGI and marginal differences in SA, while in an overlapping sample we previously reported subtle volume abnormalities in this region (Price et al., 2015). Though we did not examine the relationship between either LGI or SA and other cortical measures in this study, surface area, gyrification, and cortical thickness appear have distinct patterns in neurodevelopment from ages 6 to 22 (Raznahan et al., 2011). We also found unique patterns in cannabis effects between two cortical morphometry measures; after controlling for covariates including age and gender, results from the current study suggest that frequent cannabis use may influence LGI in a more diffuse PFC distribution compared to SA since we found only marginal reductions of SA in two PFC regions (left: ventral lateral and ventral medial PFC) among cannabis users compared to controls. Therefore, while gyrification may be partially related to gray matter volume and SA, it likely reflects a novel measure of brain maturation (Klein et al., 2014). Though Mata et al. (2010) did not find global hemispheric group differences in SA, perhaps the influence of frequent cannabis use on SA is restricted to regions with later SA development. Changes in global SA during late adolescents may be primarily driven by reduced global gyrification index (Raznahan et al., 2011) and may differ from influences driving cortical thickness maturation (Wierenga et al., 2014). Future studies may want to examine how cannabis use impacts neurodevelopment utilizing multiple measures of cortical morphometry (LGI, cortical thickness, volume, and SA). Frequent cannabis-using youth report using cannabis to cope with stressors or relax (Boys et al., 2001; Mitchell et al., 2007; Bonn-Miller et al., 2007; Johnson et al., 2010; Benschop et al., 2015), although continued use may negatively impact regions underlying healthy affective processing (Etkin et al., 2011). For example, the medial portions of the PFC are implicated in self-referential thought, regulation of stress response, autonomic regulation, emotional processing, and social cognition (Urry et al., 2009; Somerville et al., 2013; Bado et al., 2014; for reviews see Uddin et al., 2007; Hänsel and von Känel, 2008). Ventral medial portions of the PFC play a role in regulating amygdala activity, contextual decision-making, fear response and extinction, anticipatory responses, and social processing (Aoki et al., 2014; Lonsdorf et al., 2014; Rudorf and Hare, 2014; Spoormaker et al., 2014; Motzkin et al., 2014, 2015). Animal studies suggest that the inferior frontal regions also play a vital role in insight or one\'s ability to imagine consequences of behavior in new situations (Lucantonio et al., 2012). The frontal pole underlies detecting contextual change, and reward-related decision-making (Pollmann and Manginelli, 2009; Kovach et al., 2012). Therefore, additional studies examining functional consequences of cannabis use in youth may focus on affective processing, reward processing, and mood symptomatology. In addition, given the potential impact of endocannabinoid signaling on PFC activation (Filbey et al., 2010), future studies may want to examine whether genotypes related to endocannabinoid signaling interact with cannabis exposure to predict frontolimbic structural integrity in youth.