Schizophrenia is a severe mental disorder that has a strong genetic basis. Converging evidence suggests that schizophrenia is a progressive neurodevelopmental disorder, with earlier onset cases resulting in more profound brain abnormalities. Siblings of patients with schizophrenia provide an invaluable resource for differentiating between trait and state markers, thus highlighting possible endophenotypes for ongoing research. However, findings from sibling studies have not been systematically put together in a coherent story across the broader age span. We review here the cortical grey matter abnormalities in siblings of patients with schizophrenia from childhood to adulthood, by reviewing sibling studies from both childhood-onset schizophrenia, and the more common adult-onset schizophrenia. When reviewed together, studies suggest that siblings of patients with schizophrenia display significant brain abnormalities that highlight both similarities and differences between the adult and childhood populations, with shared developmental risk patterns, and segregating trajectories. Based on current research it appears that the cortical grey matter abnormalities in siblings are likely to be an age-dependent endophenotype, which normalize by the typical age of onset of schizophrenia unless there has been more genetic or symptom burdening. With increased genetic burdening (e.g. discordant twins of patients) the grey matter abnormalities in (twin) siblings are progressive in adulthood. This synthesis of the literature clarifies the importance of brain plasticity in the pathophysiology of the illness, indicating that probands may lack protective factors critical for healthy development.

Neurodegenerative disorders with high iron in the basal ganglia encompass an expanding collection of single gene disorders collectively known as neurodegeneration with brain iron accumulation. These disorders can largely be distinguished from one another by their associated clinical and neuroimaging features. The aim of this study was to define the phenotype that is associated with mutations in WDR45, a new causative gene for neurodegeneration with brain iron accumulation located on the X chromosome. The study subjects consisted of WDR45 mutation-positive individuals identified after screening a large international cohort of patients with idiopathic neurodegeneration with brain iron accumulation. Their records were reviewed, including longitudinal clinical, laboratory and imaging data. Twenty-three mutation-positive subjects were identified (20 females). The natural history of their disease was remarkably uniform: global developmental delay in childhood and further regression in early adulthood with progressive dystonia, parkinsonism and dementia. Common early comorbidities included seizures, spasticity and disordered sleep. The symptoms of parkinsonism improved with l-DOPA; however, nearly all patients experienced early motor fluctuations that quickly progressed to disabling dyskinesias, warranting discontinuation of l-DOPA. Brain magnetic resonance imaging showed iron in the substantia nigra and globus pallidus, with a 'halo' of T1 hyperintense signal in the substantia nigra. All patients harboured de novo mutations in WDR45, encoding a beta-propeller protein postulated to play a role in autophagy. Beta-propeller protein-associated neurodegeneration, the only X-linked disorder of neurodegeneration with brain iron accumulation, is associated with de novo mutations in WDR45 and is recognizable by a unique combination of clinical, natural history and neuroimaging features.

Cortical lesions constitute an important part of multiple sclerosis pathology. Although inflammation appears to play a role in their formation, the mechanisms leading to demyelination and neurodegeneration are poorly understood. We aimed to identify some of these mechanisms by combining gene expression studies with neuropathological analysis. In our study, we showed that the combination of inflammation, plaque-like primary demyelination and neurodegeneration in the cortex is specific for multiple sclerosis and is not seen in other chronic inflammatory diseases mediated by CD8-positive T cells (Rasmussen's encephalitis), B cells (B cell lymphoma) or complex chronic inflammation (tuberculous meningitis, luetic meningitis or chronic purulent meningitis). In addition, we performed genome-wide microarray analysis comparing micro-dissected active cortical multiple sclerosis lesions with those of tuberculous meningitis (inflammatory control), Alzheimer's disease (neurodegenerative control) and with cortices of age-matched controls. More than 80% of the identified multiple sclerosis-specific genes were related to T cell-mediated inflammation, microglia activation, oxidative injury, DNA damage and repair, remyelination and regenerative processes. Finally, we confirmed by immunohistochemistry that oxidative damage in cortical multiple sclerosis lesions is associated with oligodendrocyte and neuronal injury, the latter also affecting axons and dendrites. Our study provides new insights into the complex mechanisms of neurodegeneration and regeneration in the cortex of patients with multiple sclerosis.

Mutations in the gene superoxide dismutase 1 (SOD1) are causative for familial forms of the neurodegenerative disease amyotrophic lateral sclerosis. When the first SOD1 mutations were identified they were postulated to give rise to amyotrophic lateral sclerosis through a loss of function mechanism, but experimental data soon showed that the disease arises from a-still unknown-toxic gain of function, and the possibility that loss of function plays a role in amyotrophic lateral sclerosis pathogenesis was abandoned. Although loss of function is not causative for amyotrophic lateral sclerosis, here we re-examine two decades of evidence regarding whether loss of function may play a modifying role in SOD1-amyotrophic lateral sclerosis. From analysing published data from patients with SOD1-amyotrophic lateral sclerosis, we find a marked loss of SOD1 enzyme activity arising from almost all mutations. We continue to examine functional data from all Sod1 knockout mice and we find obvious detrimental effects within the nervous system with, interestingly, some specificity for the motor system. Here, we bring together historical and recent experimental findings to conclude that there is a possibility that SOD1 loss of function may play a modifying role in amyotrophic lateral sclerosis. This likelihood has implications for some current therapies aimed at knocking down the level of mutant protein in patients with SOD1-amyotrophic lateral sclerosis. Finally, the wide-ranging phenotypes that result from loss of function indicate that SOD1 gene sequences should be screened in diseases other than amyotrophic lateral sclerosis.

Inflammatory perivascular cuffs are comprised of leucocytes that accumulate in the perivascular space around post-capillary venules before their infiltration into the parenchyma of the central nervous system. Inflammatory perivascular cuffs are commonly found in the central nervous system of patients with multiple sclerosis and in the animal model experimental autoimmune encephalomyelitis. Leucocytes that accumulate in the perivascular space secrete matrix metalloproteinases that aid their transmigration into the neural parenchyma. We described previously that the upstream inducer of matrix metalloproteinase expression, extracellular matrix metalloproteinase inducer (CD147), was elevated in experimental autoimmune encephalomyelitis, and that its inhibition reduced leucocyte entry into the central nervous system. Here we investigated whether the expression of extracellular matrix metalloproteinase inducer varies with the temporal evolution of lesions in murine experimental autoimmune encephalomyelitis, whether it was uniformly upregulated across multiple sclerosis specimens, and whether it was a feature of inflammatory perivascular cuffs in multiple sclerosis lesions. In experimental autoimmune encephalomyelitis, elevation of extracellular matrix metalloproteinase inducer was correlated with the appearance and persistence of clinical signs of disease. In both murine and human samples, extracellular matrix metalloproteinase inducer was detected on endothelium in healthy and disease states but was dramatically increased in and around inflammatory perivascular cuffs on leucocytes, associated with matrix metalloproteinase expression, and on resident cells including microglia. Leucocyte populations that express extracellular matrix metalloproteinase inducer in multiple sclerosis lesions included CD4+ and CD8+ T lymphocytes, B lymphocytes and monocyte/macrophages. The extra-endothelial expression of extracellular matrix metalloproteinase inducer was a marker of the activity of lesions in multiple sclerosis, being present on leucocyte-containing perivascular cuffs but not in inactive lesions. By using a function-blocking antibody, we implicate extracellular matrix metalloproteinase inducer in the adhesion of leucocytes to endothelial cells and determined that its activity was more crucial on leucocytes than on endothelium in leucocyte-endothelial cell engagement in vitro. Extracellular matrix metalloproteinase inducer activity regulated the level of alpha 4 integrin on leucocytes through a mechanism associated with nuclear factor κB signalling. Blocking extracellular matrix metalloproteinase inducer attenuated the transmigration of monocytes and B lymphocytes across a model of the blood-brain barrier in culture. In summary, we describe the prominence of extracellular matrix metalloproteinase inducer in central nervous system inflammatory perivascular cuffs, emphasize its dual role in matrix metalloproteinase induction and leucocyte adhesion, and highlight the elevation of extracellular matrix metalloproteinase inducer as an orchestrator of the infiltration of leucocytes into the central nervous system parenchyma.

Neuroimaging techniques, such as positron emission tomography and functional magnetic resonance imaging are essential tools for the analysis of organized neural systems in working and resting states, both in physiological and pathological conditions. They provide evidence of coupled metabolic and cerebral local blood flow changes that strictly depend upon cellular activity. In 1890, Charles Smart Roy and Charles Scott Sherrington suggested a link between brain circulation and metabolism. In the same year William James, in his introduction of the concept of brain blood flow variations during mental activities, briefly reported the studies of the Italian physiologist Angelo Mosso, a multifaceted researcher interested in the human circulatory system. James focused on Mosso's recordings of brain pulsations in patients with skull breaches, and in the process only briefly referred to another invention of Mosso's, the 'human circulation balance', which could non-invasively measure the redistribution of blood during emotional and intellectual activity. However, the details and precise workings of this instrument and the experiments Mosso performed with it have remained largely unknown. Having found Mosso's original manuscripts in the archives, we remind the scientific community of his experiments with the 'human circulation balance' and of his establishment of the conceptual basis of non-invasive functional neuroimaging techniques. Mosso unearthed and investigated several critical variables that are still relevant in modern neuroimaging such as the 'signal-to-noise ratio', the appropriate choice of the experimental paradigm and the need for the simultaneous recording of differing physiological parameters.

After stroke, penumbral salvage determines clinical recovery. However, the rescued penumbra may be affected by selective neuronal loss, as documented both histopathologically in animals and using the validated in vivo positron emission tomography marker (11)C-flumazenil in humans. However, whether the non-infarcted penumbra is capable of neuronal activation, and how selective neuronal loss may interfere, is unknown. Here we prospectively mapped the topographical relationships between functional magnetic resonance imaging responses and non-infarcted penumbra, and tested the hypothesis that the former do take place in the latter, but only in its subsets spared selective neuronal loss. Seven patients (mean age 74 years; three thrombolysed) with first-ever acute anterior circulation stroke, presence of penumbra on computed tomography perfusion performed within 6 h of onset, and substantial deficit on admission but good outcome at 1-3 months (National Institute of Health Stroke Score range 6-13 and 0-1, respectively, P = 0.001), were studied. At follow-up, patients underwent structural magnetic resonance imaging to map the infarct, functional magnetic resonance imaging (three tasks selected to probe the right or left hemisphere), and (11)C-flumazenil positron emission tomography generating binding potential maps. Patients with significant carotid or middle-cerebral artery disease or impaired vasoreactivity were excluded. Following image coregistration, the non-infarcted penumbra comprised all acutely ischaemic voxels (identified on acute computed tomography perfusion using previously validated thresholds) not part of the final infarct. To test our hypotheses, the overlap between functional magnetic resonance imaging activation clusters and non-infarcted penumbra was mapped, and binding potential values then computed both within and outside this overlap. In addition, the overlap between functional magnetic resonance imaging activation clusters and areas of significantly reduced binding potential (determined using Statistical Parametric Mapping against 16 age-matched control subjects) was assessed in each patient. An overlap between non-infarcted penumbra and functional magnetic resonance imaging clusters was present in seven of seven patients, substantial in four. Binding potential was significantly reduced in the whole non-infarcted penumbra (P < 0.01) but not within the functional magnetic resonance imaging overlap. Clusters with significantly reduced binding potential showed virtually no overlap with functional magnetic resonance imaging activation compared with 12 age-matched controls (P = 0.04).The results from this proof of principle study suggest that 1-3 months after stroke the non-infarcted penumbra is capable of neuronal activation, consistent with its established role in recovery of neurological functions. However, although the non-infarcted penumbra as a whole was affected by selective neuronal loss, activations tended to occur within portions spared selective neuronal loss, suggesting the latter impedes neuronal activation. Although its clinical correlates are still elusive, selective neuronal loss may represent a novel therapeutic target in the aftermath of ischaemic stroke.

Functional magnetic resonance imaging has demonstrated reorganization of memory encoding networks within the temporal lobe in temporal lobe epilepsy, but little is known of the extra-temporal networks in these patients. We investigated the temporal and extra-temporal reorganization of memory encoding networks in refractory temporal lobe epilepsy and the neural correlates of successful subsequent memory formation. We studied 44 patients with unilateral temporal lobe epilepsy and hippocampal sclerosis (24 left) and 26 healthy control subjects. All participants performed a functional magnetic resonance imaging memory encoding paradigm of faces and words with subsequent out-of-scanner recognition assessments. A blocked analysis was used to investigate activations during encoding and neural correlates of subsequent memory were investigated using an event-related analysis. Event-related activations were then correlated with out-of-scanner verbal and visual memory scores. During word encoding, control subjects activated the left prefrontal cortex and left hippocampus whereas patients with left hippocampal sclerosis showed significant additional right temporal and extra-temporal activations. Control subjects displayed subsequent verbal memory effects within left parahippocampal gyrus, left orbitofrontal cortex and fusiform gyrus whereas patients with left hippocampal sclerosis activated only right posterior hippocampus, parahippocampus and fusiform gyrus. Correlational analysis showed that patients with left hippocampal sclerosis with better verbal memory additionally activated left orbitofrontal cortex, anterior cingulate cortex and left posterior hippocampus. During face encoding, control subjects showed right lateralized prefrontal cortex and bilateral hippocampal activations. Patients with right hippocampal sclerosis showed increased temporal activations within the superior temporal gyri bilaterally and no increased extra-temporal areas of activation compared with control subjects. Control subjects showed subsequent visual memory effects within right amygdala, hippocampus, fusiform gyrus and orbitofrontal cortex. Patients with right hippocampal sclerosis showed subsequent visual memory effects within right posterior hippocampus, parahippocampal and fusiform gyri, and predominantly left hemisphere extra-temporal activations within the insula and orbitofrontal cortex. Correlational analysis showed that patients with right hippocampal sclerosis with better visual memory activated the amygdala bilaterally, right anterior parahippocampal gyrus and left insula. Right sided extra-temporal areas of reorganization observed in patients with left hippocampal sclerosis during word encoding and bilateral lateral temporal reorganization in patients with right hippocampal sclerosis during face encoding were not associated with subsequent memory formation. Reorganization within the medial temporal lobe, however, is an efficient process. The orbitofrontal cortex is critical to subsequent memory formation in control subjects and patients. Activations within anterior cingulum and insula correlated with better verbal and visual subsequent memory in patients with left and right hippocampal sclerosis, respectively, representing effective extra-temporal recruitment.