Objective-To investigate microstructure of white matter fiber tracts in pediatric bipolar disorder (PBD) and attention deficit hyperactivity disorder (ADHD).Methods-A diffusion tensor imaging (DTI) study was conducted at 3 Tesla on age and IQ-matched children and adolescents with PBD (n=13), ADHD (n=13), and healthy controls (HC) (n=15). Three DTI parameters, fractional anisotropy (FA), apparent diffusion coefficient (ADC), and regional fiber coherence index (r-FCI), were examined in eight fiber tracts: Anterior corona radiata (ACR); anterior limb of the internal capsule (ALIC); superior region of the internal capsule (SRI); posterior limb of the internal capsule (PLIC); superior longitudinal fasciculus (SLF); inferior longitudinal fasciculus (ILF); cingulum (CG); splenium (SP).Results-Significantly lower FA was observed in ACR in both PBD and ADHD relative to HC. In addition, FA and r-FCI values were significantly lower in ADHD relative to PBD and HC in both the ALIC and the SRI. Further, ADC was significantly greater in ADHD relative to both the PBD and HC in ACR, ALIC, PLIC, SRI, CG, ILF, and SLF. Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Conclusions-Decreased FA in ACR implies an impaired fiber density or reduced myelination in both PBD and ADHD in this prefrontal tract. These abnormalities, together with the reduced fiber coherence, extended to cortico-bulbar tracts in ADHD. Increased ADC across multiple white matter tracts in ADHD indicates extensive cellular abnormalities with less diffusion restriction in ADHD relative to PBD. NIH Public Access

Objective-This fMRI study examined how working memory circuits are affected by face emotion processing in pediatric bipolar disorder (PBD) and attention-deficit hyperactivity disorder (ADHD).Methods-Twenty-three patients with bipolar disorder, 14 patients with ADHD and 19 healthy controls (HC) (mean age = 13.36 ± 2.55) underwent an affective 2-back fMRI task with blocks of happy, angry and neutral faces.Results-For angry vs neutral faces PBD patients, relative to ADHD patients, exhibited increased activation in subgenual anterior cingulate cortex (ACC) and orbitofrontal cortex, and reduced activation in dorsolateral prefrontal cortex (DLPFC) and premotor cortex. Relative to HC the PBD group showed no increased activation and reduced activation at the junction of DLPFC and ventrolateral prefrontal cortex (VLPFC). Relative to HC the ADHD patients exhibited greater activation in DLPFC and reduced activation in ventral and medial PFC, pregenual ACC, striatum and temporo-parietal regions. For happy vs neutral faces, relative to ADHD the PBD group exhibited greater activation in bilateral caudate, and relative to HC it showed increased activation in DLPFC, striatal and parietal regions, and no reduced activation. The ADHD group, compared to HC, showed no reduced activation and increased activation in regions that were under-active for the angry face condition.Conclusions-Relative to the ADHD group the PBD group exhibited greater deployment of the emotion processing circuitry and reduced deployment of working memory circuitry. Commonalities across PBD and ADHD patients, relative to HC, entailed cortico-subcortical activity that is reduced under negative emotional challenge, and increased under positive emotional challenge.

Impulsivity, inattention and poor behavioral inhibition are common deficits in PBD (Pediatric Bipolar Disorder) and ADHD (Attention Deficit Hyperactivity Disorder). This study aimed to identify similarities and differences in the neural substrate of response inhibition deficits that are associated with these disorders. A functional magnetic resonance imaging (fMRI) study was conducted on 15 un-medicated PBD patients (Type I, manic/mixed), 11 un-medicated ADHD patients, and 15 healthy controls (HC) (mean age = 13.5 years; S.D. = 3.5). A Response Inhibition Task examined the ability to inhibit a motor response to a target when a stop cue appeared shortly after. The PBD and ADHD group did not differ on behavioral performance, although both groups were less accurate than the HC group. fMRI findings showed that for trials requiring response inhibition, the ADHD group, relative to the PBD and HC groups, demonstrated reduced activation in both ventrolateral (VLPFC) and dorsolateral (DLPFC) prefrontal cortex, and increased bilateral caudate activation compared to HC. The PBD group, relative to HC, showed decreased activation in left VLPFC, at the junction of inferior and middle frontal gyri, and in right anterior cingulate cortex (ACC). Prefrontal dysfunction was observed in both the ADHD and PBD groups relative to HC, although it was more extensive and accompanied by sub-cortical over activity in ADHD.

Although a few developmental fMRI studies have shed some light on the neurological development of either object or spatial processing we still know very little about the development of the 'what' and 'where' processing systems. The present study is the first to address this issue by comparing, concurrently and within the same behavioral paradigm, patterns of functional activation for face processing and location processing in 12 children (10-12 years old) and 16 adults. For both tasks this study found a developmental shift from a more distributed pattern of activation in children to a more focused pattern of activation in adults. Furthermore, the type of developmental redistribution of activation in children varied depending on the task. The present findings have important implications for theories of visuospatial development. They suggest that the neural systems involved in face and location processing may undergo development and fine-tuning well into late childhood.