Advanced techniques in magnetic resonance imaging of the brain in children with ADHD

Identifying ADHD Individuals From Resting-State Functional Connectivity Using Subspace Clustering and Binary Hypothesis Testing

Objective: This study focused on the ADHD classification through functional connectivity (FC) analysis. Method: An ADHD classification method was proposed with subspace clustering and binary hypothesis testing, wherein partial information of test data was adopted for training. By hypothesizing the binary label (ADHD or control) for the test data, two feature sets of training FC data were generated during the feature selection procedure that employed both training and test data. Then, a multi-affinity subspace clustering approach was performed to obtain the corresponding subspace-projected feature sets. With the energy comparison of projected feature sets, we finally identified ADHD individuals for the test data. Results: Our method outperformed several state-of-the-art methods with the above 90% average identification accuracy. By the discriminative FC contribution analysis, it also proved the reliability of our method. Conclusion: Results demonstrate the remarkable classification performance of our method and reveal some useful brain circuits to identify ADHD.

The impact of ADHD persistence, recent cannabis use, and age of regular cannabis use onset on subcortical volume and cortical thickness in young adults

BACKGROUND

Both Attention Deficit Hyperactivity Disorder (ADHD) and chronic cannabis (CAN) use have been associated with brain structural abnormalities, although little is known about the effects of both in young adults.

METHODS

Participants included: those with a childhood diagnosis of ADHD who were CAN users (ADHD_CAN; n=37) and non-users (NU) (ADHD_NU; n=44) and a local normative comparison group (LNCG) who did (LNCG_CAN; n=18) and did not (LNCG_NU; n=21) use CAN regularly. Multiple regressions and MANCOVAs were used to examine the independent and interactive effects of a childhood ADHD diagnosis and CAN group status and age of onset (CUO) on subcortical volumes and cortical thickness.

RESULTS

After controlling for age, gender, total brain volume, nicotine use, and past-year binge drinking, childhood ADHD diagnosis did not predict brain structure; however, persistence of ADHD was associated with smaller left precentral/postcentral cortical thickness. Compared to all non-users, CAN users had decreased cortical thickness in right hemisphere superior frontal sulcus, anterior cingulate, and isthmus of cingulate gyrus regions and left hemisphere superior frontal sulcus and precentral gyrus regions. Early cannabis use age of onset (CUO) in those with ADHD predicted greater right hemisphere superior frontal and postcentral cortical thickness.

DISCUSSION

Young adults with persistent ADHD demonstrated brain structure abnormalities in regions underlying motor control, working memory and inhibitory control. Further, CAN use was linked with abnormal brain structure in regions with high concentrations of cannabinoid receptors. Additional large-scale longitudinal studies are needed to clarify how substance use impacts neurodevelopment in youth with and without ADHD.

Have we been ignoring the elephant in the room? Seven arguments for considering the cerebellum as part of addiction circuitry

Addiction involves alterations in multiple brain regions that are associated with functions such as memory, motivation and executive control. Indeed, it is now well accepted that addictive drugs produce long-lasting molecular and structural plasticity changes in corticostriatal-limbic loops. However, there are brain regions that might be relevant to addiction other than the prefrontal cortex, amygdala, hippocampus and basal ganglia. In addition to these circuits, a growing amount of data suggests the involvement of the cerebellum in many of the brain functions affected in addicts, though this region has been overlooked, traditionally, in the addiction field. Therefore, in the present review we provide seven arguments as to why we should consider the cerebellum in drug addiction. We present and discuss compelling evidence about the effects of drugs of abuse on cerebellar plasticity, the involvement of the cerebellum in drug-induced cue-related memories, and several findings showing that the instrumental memory and executive functions also recruit the cerebellar circuitry. In addition, a hypothetical model of the cerebellum's role relative to other areas within corticostriatal-limbic networks is also provided. Our goal is not to review animal and human studies exhaustively but to support the inclusion of cerebellar alterations as a part of the physiopathology of addiction disorder.

Sex differences in white matter integrity in youths with attention-deficit/hyperactivity disorder: a pilot study

Widespread disparities in white matter (WM) microstructure and organization have been found in adolescents with attention-deficit/hyperactivity disorder (ADHD); however, little is known about the role sex plays in these differences. The present diffusion tensor imaging (DTI) study performed whole-brain, tract-based, voxel-wise, and region of interest (ROI) analyses to investigate WM microstructure differences between ADHD and healthy control (HC) adolescents to examine the impact of sex on measures of fractional anisotropy (FA). Eighteen adolescents with ADHD and 24 HC were included in this study. All participants received a 64-direction DTI scan on a 3 Tesla Siemens scanner. FSL's TBSS was used to perform whole-brain, tract-based, voxel-wise analyses. Tracts demonstrating significant sex-by-diagnosis interactions were further evaluated using univariate analyses performed on mean FA data that were extracted from ROIs using the Johns Hopkins University WM tractography atlas. TBSS analyses between diagnostic groups revealed significantly increased FA in HC relative to ADHD in the bilateral superior longitudinal fasciculus (SLF), forceps major, left cingulum, and bilateral callosal regions. In addition, both TBSS and separate ROI analyses revealed significant sex-by-diagnosis interactions for the corticospinal tract (CST), inferior longitudinal fasciculus (ILF) and SLF. In the HC group, FA was increased in males relative to females for all analyses. In WM regions demonstrating a significant sex-by-diagnosis, FA was increased in females relative to males in the ADHD group. Our findings suggest that WM microstructure in several major WM tracts differs between males and females with ADHD. These differences in WM microstructure may account for some of the differences in ADHD subtypes and comorbidities seen between the sexes. Additional studies in ADHD, examining sex differences in phenotypic expression, treatment response and brain network trajectories are warranted.

Microstructural abnormalities in the combined and inattentive subtypes of attention deficit hyperactivity disorder: a diffusion tensor imaging study

Previous research has demonstrated that there are specific white matter abnormalities in patients with attention deficit/hyperactivity disorder (ADHD). However, the results of these studies are not consistent, and one of the most important factors that affects the inconsistency of previous studies maybe the ADHD subtype. Different ADHD subtypes may have some overlapping microstructural damage, but they may also have unique microstructural abnormalities. The objective of this study was to investigate the microstructural abnormalities associated with two subtypes of ADHD: combined (ADHD-C) and inattentive (ADHD-I). Twenty-eight children with ADHD-C, 28 children with ADHD-I and 28 healthy children participated in this study. Fractional anisotropy (FA), radial diffusivity (RD) and axial diffusivity (AD) were used to analyze diffusion tensor imaging (DTI) data to provide specific information regarding abnormal brain areas. Our results demonstrated that ADHD-I is related to abnormalities in the temporo-occipital areas, while the combined subtype (ADHD-C) is related to abnormalities in the frontal-subcortical circuit, the fronto-limbic pathway, and the temporo-occipital areas. Moreover, an abnormality in the motor circuit may represent the main difference between the ADHD-I and ADHD-C subtypes.

Neuroimaging and psychiatry: the long road from bench to bedside

Advances in neuroscience have revolutionized our understanding of the central nervous system. Neuroimaging technologies, in particular, have begun to reveal the complex anatomical, physiological, biochemical, genetic, and molecular organizational structure of the organ at the center of that system: the human brain. More recently, neuroimaging technologies have enabled the investigation of normal brain function and are being used to gain important new insights into the mechanisms behind many neuropsychiatric disorders. This research has implications for psychiatric diagnosis, treatment, and risk assessment. However, with some exceptions, neuroimaging is still a research tool, not ready for use in clinical psychiatry.

The cerebellum and neuropsychiatric disorders

Relative to non-human primates, in humans the cerebellum, and prefrontal cortex are brain regions which have undergone major evolutionary changes. In recent decades, progress in molecular biology and advances in the development of functional neuroimaging analysis have shown that the evolution of the human cerebellum was accompanied by the acquisition of more functions than were previously deduced from human post-mortem studies and animal experimentation. These new cerebellar functions included the control of attention and other cognitive functions, emotions and mood, and social behavior, which were all thought to represent cortical functions. The importance of this new view of cerebellar physiology has been confirmed by the frequency of neuropsychiatric disorders in individuals with cerebellar abnormalities. The information collected in this review emphasizes the importance of cerebellar studies in establishing the physiological substrate of mental diseases.