The human brain follows a distinct

The human GW 610 cost follows a distinct spatial and temporal pattern of maturation that begins with phylogenetically older posterior and inferior regions and then progressively extends to more anterior and superior regions (for reviews, see ). Postmortem (), MRI (), and diffusion tensor imaging (DTI) studies () suggest that concurrent changes in gray and white matter are two important events that follow distinct developmental trajectories that significantly contribute to brain maturation. The increase in global gray matter volume during development follows an inverted U-shaped curve that increases and peaks during adolescence and then decreases until early adulthood, whereas global white matter increases steadily throughout childhood into adulthood (). If maturational changes are examined over the course of the entire lifespan, global white matter volume also follows an inverted U-shaped trajectory, with white matter volume reaching its peak around 40 years of age (). It is believed that the function of cortical regions is based on the intrinsic properties and extrinsic pattern of white matter input and output and that the information transmission properties of a given white matter tract can be predicted by the functions of the cortical regions it connects (). Although the function of the (UF) is still largely unclear, its location and connectivity often associate it with the limbic system and its functions (e.g., emotion, episodic memory, etc.), making it a likely candidate for disruption in disorders affecting personality, emotion, and episodic memory. The extended development of this white matter tract into the third decade of life might also make it more susceptible to disruptions in function and could help explain why the UF has been implicated in several developmental and psychiatric disorders. We previously reviewed the human adult and non-human primate literature on the UF (). The purpose of the present literature review is to integrate current knowledge about the UF\'s developmental trajectory with the relevant literature on developmental disorders, while placing them in the theoretical context of our findings on the adult UF. We believe that this review will be of interest to both clinicians and cognitive scientists, and we aim to link the UF to clinical disorders, as well as to normal cognition, as we believe that one informs the other. Anatomy and maturation of the uncinate fasciculus We described the anatomy of the uncinate fasciculus previously (Von Der Heide et al., 2013). In brief, it is a long-range association pathway that creates a monosynaptic pathway between the anterior temporal lobes (BA 38 including perirhinal cortex and portions of the anterior parahippocampal gyrus) and amygdala to the lateral orbitofrontal cortex (OFC; BA 11, 47/12) and BA 10. It has a distinctive hook shape, arcing around the Sylvian fissure into the frontal lobe (see Fig. 1; Schmahmann & Pandya, 2006; Thiebaut de Schotten et al., 2012). It is frequently damaged in epilepsy resection surgery, as well as blunt-force trauma affecting the frontal lobes. The UF is one of the last white matter tracts to reach its maturational peak, with its developmental time course extending throughout adolescence, young adulthood, and peaking beyond the age of 30 (see Fig. 2; Lebel et al., 2012; Lebel et al., 2008). Although the basic characteristics of UF macrostructure (e.g., volume, length, shape) have been reported in adult studies (Hasan et al., 2009; Malykhin et al., 2008; Taoka et al., 2006; Wakana et al., 2007), little is known about the trajectories of these characteristics across development. Until recently, when developmental DTI studies began to fill in gaps of knowledge, relatively little has also been known about maturational changes in the microstructural characteristics of the UF. Recent developmental DTI studies report that from childhood to adulthood, fractional anisotropy (FA) values, which are thought to reflect myelination, white matter organization, and the density of the fiber tracts, continue to increase with age (Giorgio et al., 2010), whereas measures of local diffusion such as mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD) of the UF significantly decrease (Eluvathingal et al., 2007). A similar pattern of development has also been documented for other white matter tracts (see Lebel et al., 2012; L. T. Westlye et al., 2010). However, unlike other white matter association tracts, the FA values of the UF are some of the last to reach their peak maturity between 28 and 35 years of age. UF measures of axial and radial diffusivity are also slow to reach their minima during this developmental time frame (Lebel et al., 2012).