Attention deficit/hyperactivity disorder (ADHD) is a childhood-onset psychiatric condition characterized by hyperactivity, impulsivity, and attention deficit. In addition to these core symptoms, accumulating evidence suggests that ADHD may also involve alterations in circadian rhythms, sleep disturbance, and time perception. The habenula is a brain region transmitting limbic information to the midbrain monoamine systems and is thereby involved in the regulation of monoamine release in such target brain areas as the striatum, where it is part of the biological substrates that process time perception. The habenula is additionally a part of the circadian rhythm network and is involved in sleep regulation. Our recent study provides a new insight that a habenula lesion created early in development produces behavioral and brain alterations resembling those observed in ADHD. We propose that the habenula may be a promising target for understanding the pathogenesis of ADHD. (C) 2013 Elsevier Ltd. All rights reserved.

Neuroscientists have long observed that brain activity is naturally variable from moment-to-moment, but neuroimaging research has largely ignored the potential importance of this phenomenon. An emerging research focus on within-person brain signal variability is providing novel insights, and offering highly predictive, complementary, and even orthogonal views of brain function in relation to human lifespan development, cognitive performance, and various clinical conditions. As a result, brain signal variability is evolving as a bona fide signal of interest, and should no longer be dismissed as meaningless noise when mapping the human brain. (C) 2013 Elsevier Ltd. All rights reserved.

Individuals carrying the *E4 allele of the apolipoprotein E gene (APOE) are at increased risk of developing Alzheimer's disease (AD). However, the biological mechanisms underlying this association are still unclear because of the complexity of the pathological processes that cause AD. Furthermore, the effect of APOE genotype on development, maintenance and aging of the normal brain is poorly understood because of the strong bias toward studying disease associations. In vivo techniques such as neuroimaging and cognitive testing offer valuable insights into the effects of APOE genotype on brain structure and function in healthy and clinical populations. We review the evidence from in vivo studies that APOE *E4, in addition to increasing the chance of age-related pathological events, is associated with age-independent non-pathological changes in brain physiology, some of which make the brain less resilient to neurodegenerative processes. We argue that the interaction between the APOE-dependent non-pathological vulnerabilities and age-related pathological changes is one mechanism that can trigger neurodegeneration, resulting in AD and other complex phenotypes. (C) 2013 Published by Elsevier Ltd.

Structural connections between brain regions are thought to influence neural processing within those regions. It follows that alterations to the quality of structural connections should influence the magnitude of neural activity. The quality of structural connections may also be expected to differentially influence activity in directly versus indirectly connected brain regions. To test these predictions, we reviewed studies that combined diffusion tensor imaging (DTI) and functional magnetic resonance imaging (fMRI) in younger and older adults. By surveying studies that examined relationships between DTI measures of white matter integrity and fMRI measures of neural activity, we identified variables that accounted for variability in these relationships. Results revealed that relationships between white matter integrity and neural activity varied with (1) aging (i.e., positive and negative DTI-fMRI relationships in younger and older adults, respectively) and (2) spatial proximity of the neural measures (i.e., positive and negative DTI-fMRI relationships when neural measures were extracted from adjacent and non-adjacent brain regions, respectively). Together, the studies reviewed here provided support for both of our predictions. (C) 2013 Elsevier Ltd. All rights reserved.

Tourette syndrome (TS) is a neuropsychiatric disorder involving multiple motor and phonic tics. Tics, which usually begin between the ages of 6 and 8, are sudden, rapid, stereotyped, and apparently purposeless movements or sounds that involve discrete muscle groups. Individuals with TS experience a variety of different sensory phenomena, including premonitory urges prior to tics and somatic hypersensitivity due to impaired sensorimotor gating. In addition to other conditions, stress, anxiety, fatigue, or other heightened emotional states tend to exacerbate tics, while relaxation, playing sports, and focused concentration on a specific task tend to alleviate tic symptoms. Ninety percent of children with TS also have comorbid conditions, such as attention deficit hyperactivity disorder (ADHD), obsessive-compulsive disorder (OCD), or an impulse control disorder. These disorders often cause more problems for the child both at home and at school than tics do alone. Proper diagnosis and treatment of TS involves appropriate evaluation and recognition, not only of tics, but also of these associated conditions. (C) 2013 Published by Elsevier Ltd.

Auditory verbal hallucinations (AVHs) are the experience of hearing voices in the absence of any speaker, often associated with a schizophrenia diagnosis. Prominent cognitive models of AVHs suggest they may be the result of inner speech being misattributed to an external or non-self source, due to atypical self- or reality monitoring. These arguments are supported by studies showing that people experiencing AVHs often show an externalising bias during monitoring tasks, and neuroimaging evidence which implicates superior temporal brain regions, both during AVHs and during tasks that measure verbal self-monitoring performance. Recently, efficacy of noninvasive neurostimulation techniques as a treatment option for AVHs has been tested. Meta-analyses show a moderate effect size in reduction of AVH frequency, but there has been little attempt to explain the therapeutic effect of neurostimulation in relation to existing cognitive models. This article reviews inner speech models of AVHs, and argues that a possible explanation for reduction in frequency following treatment may be modulation of activity in the brain regions involving the monitoring of inner speech. (C) 2013 The Authors. Published by Elsevier Ltd. All rights reserved.