Association of Copy Number Variation of the 15q11.2 BP1-BP2 Region With Cortical and Subcortical Morphology and Cognition

Importance

Recurrent microdeletions and duplications in the genomic region 15q11.2 between breakpoints 1 (BP1) and 2 (BP2) are associated with neurodevelopmental disorders. These structural variants are present in 0.5% to 1.0% of the population, making 15q11.2 BP1-BP2 the site of the most prevalent known pathogenic copy number variation (CNV). It is unknown to what extent this CNV influences brain structure and affects cognitive abilities.

Objective

To determine the association of the 15q11.2 BP1-BP2 deletion and duplication CNVs with cortical and subcortical brain morphology and cognitive task performance.

Design, Setting, and Participants

In this genetic association study, T1-weighted brain magnetic resonance imaging were combined with genetic data from the ENIGMA-CNV consortium and the UK Biobank, with a replication cohort from Iceland. In total, 203 deletion carriers, 45 247 noncarriers, and 306 duplication carriers were included. Data were collected from August 2015 to April 2019, and data were analyzed from September 2018 to September 2019.

Main Outcomes and Measures

The associations of the CNV with global and regional measures of surface area and cortical thickness as well as subcortical volumes were investigated, correcting for age, age2, sex, scanner, and intracranial volume. Additionally, measures of cognitive ability were analyzed in the full UK Biobank cohort.

Results

Of 45 756 included individuals, the mean (SD) age was 55.8 (18.3) years, and 23 754 (51.9%) were female. Compared with noncarriers, deletion carriers had a lower surface area (Cohen d = -0.41; SE, 0.08; P = 4.9 × 10-8), thicker cortex (Cohen d = 0.36; SE, 0.07; P = 1.3 × 10-7), and a smaller nucleus accumbens (Cohen d = -0.27; SE, 0.07; P = 7.3 × 10-5). There was also a significant negative dose response on cortical thickness (β = -0.24; SE, 0.05; P = 6.8 × 10-7). Regional cortical analyses showed a localization of the effects to the frontal, cingulate, and parietal lobes. Further, cognitive ability was lower for deletion carriers compared with noncarriers on 5 of 7 tasks.

Conclusions and Relevance

These findings, from the largest CNV neuroimaging study to date, provide evidence that 15q11.2 BP1-BP2 structural variation is associated with brain morphology and cognition, with deletion carriers being particularly affected. The pattern of results fits with known molecular functions of genes in the 15q11.2 BP1-BP2 region and suggests involvement of these genes in neuronal plasticity. These neurobiological effects likely contribute to the association of this CNV with neurodevelopmental disorders.

Dose response of the 16p11.2 distal copy number variant on intracranial volume and basal ganglia

Carriers of large recurrent copy number variants (CNVs) have a higher risk of developing neurodevelopmental disorders. The 16p11.2 distal CNV predisposes carriers to e.g., autism spectrum disorder and schizophrenia. We compared subcortical brain volumes of 12 16p11.2 distal deletion and 12 duplication carriers to 6882 non-carriers from the large-scale brain Magnetic Resonance Imaging collaboration, ENIGMA-CNV. After stringent CNV calling procedures, and standardized FreeSurfer image analysis, we found negative dose-response associations with copy number on intracranial volume and on regional caudate, pallidum and putamen volumes (β = -0.71 to -1.37; P < 0.0005). In an independent sample, consistent results were obtained, with significant effects in the pallidum (β = -0.95, P = 0.0042). The two data sets combined showed significant negative dose-response for the accumbens, caudate, pallidum, putamen and ICV (P = 0.0032, 8.9 × 10-6, 1.7 × 10-9, 3.5 × 10-12 and 1.0 × 10-4, respectively). Full scale IQ was lower in both deletion and duplication carriers compared to non-carriers. This is the first brain MRI study of the impact of the 16p11.2 distal CNV, and we demonstrate a specific effect on subcortical brain structures, suggesting a neuropathological pattern underlying the neurodevelopmental syndromes.

Income inequality, gene expression, and brain maturation during adolescence

Income inequality is associated with poor health and social outcomes. Negative social comparisons and competition may involve the hypothalamic-pituitary-adrenal (HPA) and hypothalamic-pituitary-gonadal (HPG) axes in underlying some of these complex inter-relationships. Here we investigate brain maturation, indexed by age-related decreases in cortical thickness, in adolescents living in neighborhoods with differing levels of income inequality and household income. We examine whether inter-regional variations relate to those in glucocorticoid receptor (HPA) and androgen receptor (HPG) gene expression. For each sex, we used a median split of income inequality and household income (income-to-needs ratio) to create four subgroups. In female adolescents, the high-inequality low-income group displayed the greatest age-related decreases in cortical thickness. In this group, expression of glucocorticoid and androgen receptor genes explained the most variance in these age-related decreases in thickness across the cortex. We speculate that female adolescents living in high-inequality neighborhoods and low-income households may experience greater HPA and HPG activity, leading to steeper decreases in cortical thickness with age.

Apparent intravoxel fibre population dispersion (FPD) using spherical harmonics

The vast majority of High Angular Resolution Diffusion Imaging (HARDI) modeling methods recover networks of neuronal fibres, using a heuristic extraction of their local orientation. In this paper, we present a method for computing the apparent intravoxel Fibre Population Dispersion (FPD), which conveys the manner in which distinct fibre populations are partitioned within the same voxel. We provide a statistical analysis, without any prior assumptions on the number or size of these fibre populations, using an analytical formulation of the diffusion signal autocorrelation function in the spherical harmonics basis. We also propose to extract features of the FPD obtained in the group of rotations, using several metrics based on unit quaternions. We show results on simulated data and on physical phantoms, that demonstrate the effectiveness of the FPD to reveal regions with crossing tracts, in contrast to the standard anisotropy measures.

Informed consent for MRI and fMRI research: analysis of a sample of Canadian consent documents

Background

Research ethics and the measures deployed to ensure ethical oversight of research (e.g., informed consent forms, ethics review) are vested with extremely important ethical and practical goals. Accordingly, these measures need to function effectively in real-world research and to follow high level standards.

Methods

We examined approved consent forms for Magnetic Resonance Imaging (MRI) and functional Magnetic Resonance Imaging (fMRI) studies approved by Canadian research ethics boards (REBs).

Results

We found evidence of variability in consent forms in matters of physical and psychological risk reporting. Approaches used to tackle the emerging issue of incidental findings exposed extensive variability between and within research sites.

Conclusion

The causes of variability in approved consent forms and studies need to be better understood. However, mounting evidence of administrative and practical hurdles within current ethics governance systems combined with potential sub-optimal provision of information to and protection of research subjects support other calls for more scrutiny of research ethics practices and applicable revisions.

Perspectives of Canadian Researchers on Ethics Review of Neuroimaging Research

The current and potential uses of neuroimaging in healthcare and beyond have spurred discussion about the ethical issues related to neuroimaging and neuroimaging research. This study examined the perspectives of neuroimagers on ethical issues in their research and on the ethics review process. One hundred neuroimagers from 13 Canadian neuroscience centers completed an online survey and 35 semi-structured interviews were conducted. Neuroimagers felt that most ethical and social issues identified in the literature were dealt with adequately, well, and even very well by research ethics boards (REBs), but some issues such as incidental findings and transfer of knowledge were problematic. Neuroimagers reported a range of practical problems in the ethics review process. We aimed to gather perspectives from REB on the ethics review process, but insufficient participation by REBs prevented us from reporting their perspectives. Given shortcomings identified by neuroimagers as well as longstanding issues in Canadian ethics governance, we believe that substantial challenges exist in Canadian research ethics governance that jeopardize trust, communication, and the overall soundness of research ethics governance. Neuroimagers and REBs should consider their shared responsibilities in developing guidance to handle issues such as incidental findings, risk assessment, and knowledge transfer.

Handedness, motor skills and maturation of the corticospinal tract in the adolescent brain

With anatomical magnetic resonance imaging, the signal intensity of the corticospinal tract (CST) at the level of the internal capsule is often paradoxically similar to that of grey matter. As shown previously in histological studies, this is likely due to the presence of very large axons. We measured the apparent grey-matter density (aGMd) of the putative CST (pCST) in a large cohort of adolescents (n = 409, aged 12-18 years). We tested the following hypotheses: (1) The aGMd in the pCST shows a hemispheric asymmetry that is, in turn, related to hand preference; (2) the maturation of the CST during adolescence differs between both sexes, due to the influence of testosterone; (3) variations in aGMd in the pCST reflect inter-individual differences in manual skills. We confirmed the first two predictions. Thus, we found a strong left > right hemispheric asymmetry in aGMd that was, on average, less marked in the 40 left-handed subjects. Apparent GMd in the pCST increased with age in adolescent males but not females, and this was particularly related to rising plasma levels of testosterone in male adolescents. This finding is compatible with the idea that testosterone influences axonal calibre rather than myelination. The third prediction, namely that of a relationship between age-related changes in manual skills and maturation of the pCST, was not confirmed. We conclude that the leftward asymmetry of the pCST may reflect an early established asymmetry in the number of large corticomotoneuronal fibres in the pCST.

Orbitofrontal cortex and drug use during adolescence: role of prenatal exposure to maternal smoking and BDNF genotype

CONTEXT

Prenatal exposure to maternal cigarette smoking (PEMCS) may affect brain development and behavior in adolescent offspring.

OBJECTIVE

To evaluate the involvement of the orbitofrontal cortex (OFC) in mediating the relationship between PEMCS and substance use.

DESIGN

Cross-sectional analyses from the Saguenay Youth Study aimed at evaluating the effects of PEMCS on brain development and behavior among adolescents. Nonexposed adolescents were matched with adolescents exposed prenatally to cigarette smoking by maternal educational level.

PARTICIPANTS AND SETTING

A French Canadian founder population of the Saguenay-Lac-Saint-Jean region of Quebec, Canada. The behavioral data set included 597 adolescents (275 sibships; 12-18 years of age), half of whom were exposed in utero to maternal cigarette smoking. Analysis of cortical thickness and genotyping were performed using available data from 314 adolescents.

MAIN OUTCOME MEASURES

The likelihood of substance use was assessed with the Diagnostic Interview Schedule for Children Predictive Scales. The number of different drugs tried by each adolescent was assessed using another questionnaire. Thickness of the OFC was estimated from T1-weighted magnetic resonance images using FreeSurfer software.

RESULTS

Prenatal exposure to maternal cigarette smoking is associated with an increased likelihood of substance use. Among exposed adolescents, the likelihood of drug experimentation correlates with the degree of OFC thinning. In nonexposed adolescents, the thickness of the OFC increases as a function of the number of drugs tried. The latter effect is moderated by a brain-derived neurotrophic factor (BDNF) genotype (Val66Met).

CONCLUSIONS

We speculate that PEMCS interferes with the development of the OFC and, in turn, increases the likelihood of drug use among adolescents. In contrast, we suggest that, among nonexposed adolescents, drug experimentation influences the OFC thickness via processes akin to experience-induced plasticity.

Brain size and folding of the human cerebral cortex

During evolution, the mammalian cerebral cortex has expanded disproportionately to brain volume. As a consequence, most mammals with large brains have profusely convoluted cortices. The human cortex is a good example of this trend, however, given the large variability in human brain size, it is not clear how cortical folding varies from the smallest to the largest brains. We analyzed cortical folding in a large cohort of human subjects exhibiting a 1.7-fold variation in brain volume. We show that the same disproportionate increase of cortical surface relative to brain volume observed across species can be also observed across human brains: the largest brains can have up to 20% more surface than a scaled-up small brain. We introduce next a novel local measure of cortical folding, and we show that the correlation between cortical folding and size varies along a rostro-caudal gradient, being especially significant in the prefrontal cortex. The expansion of the cerebral cortex, and in particular that of its prefrontal region, is a major evolutionary landmark in the emergence of human cognition. Our results suggest that this may be, at least in part, a natural outcome of increasing brain size.

Genes, maternal smoking, and the offspring brain and body during adolescence: design of the Saguenay Youth Study

The search for genes of complex traits is aided by the availability of multiple quantitative phenotypes collected in geographically isolated populations. Here we provide rationale for a large-scale study of gene-environment interactions influencing brain and behavior and cardiovascular and metabolic health in adolescence, namely the Saguenay Youth Study (SYS). The SYS is a retrospective study of long-term consequences of prenatal exposure to maternal cigarette smoking (PEMCS) in which multiple quantitative phenotypes are acquired over five sessions (telephone interview, home, hospital, laboratory, and school). To facilitate the search for genes that modify an individual's response to an in utero environment (i.e. PEMCS), the study is family-based (adolescent sibships) and is carried out in a relatively geographically isolated population of the Saguenay Lac-Saint-Jean (SLSJ) region in Quebec, Canada. DNA is acquired in both biological parents and in adolescent siblings. A genome-wide scan will be carried out with sib-pair linkage analyses, and fine mapping of identified loci will be done with family-based association analyses. Adolescent sibships (12-18 years of age; two or more siblings per family) are recruited in high schools throughout the SLSJ region; only children of French-Canadian origin are included. Based on a telephone interview, potential participants are classified as exposed or nonexposed prenatally to maternal cigarette smoking; the two groups are matched for the level of maternal education and the attended school. A total of 500 adolescent participants in each group will be recruited and phenotyped. The following types of datasets are collected in all adolescent participants: (1) magnetic resonance images of brain, abdominal fat, and kidneys, (2) standardized and computer-based neuropsychological tests, (3) hospital-based cardiovascular, body-composition and metabolic assessments, and (4) questionnaire-derived measures (e.g. life habits such as eating and physical activity; drug, alcohol use and delinquency; psychiatric symptoms; personality; home and school environment; academic and vocational attitudes). Parents complete a medical questionnaire, home-environment questionnaire, a handedness questionnaire, and a questionnaire about their current alcohol and drug use, depression, anxiety, and current and past antisocial behavior. To date, we have fully phenotyped a total of 408 adolescent participants. Here we provide the description of the SYS and, using the initial sample, we present information on ascertainment, demographics of the exposed and nonexposed adolescents and their parents, and the initial MRI-based assessment of familiality in the brain size and the volumes of grey and white matter.

Hippocampal volume is as variable in young as in older adults: implications for the notion of hippocampal atrophy in humans

Previous studies in humans have shown the presence of an age-related reduction of hippocampal (HC) volume, as well as the presence of reduced HC volume in psychiatric populations suffering from schizophrenia, depression or post-traumatic stress disorder. Altogether, these data suggested that aging or psychiatric disease can have neurotoxic effects on the hippocampus, and lead to HC atrophy. However, these two sets of findings imply that HC volume in young healthy adults should present less variability than HC volume in older adults and psychiatric populations. In the present study, we assessed HC volume in 177 healthy men and women aged from 18 to 85 years of age. We show that the dispersion around the mean of HC volume is not different in young and older adults, so that 25% of young healthy adults present HC volume as small as the average participants aged 60 to 75 years. This shows that HC volume is as variable in young as in older adults and suggests that smaller HC volume attributed to the aging process in previous studies could in fact represent HC volume determined early in life. We also report that within similar age groups, the percentage of difference in HC volume between the individuals with the smallest HC volume (smallest quartile) and the group average is greater than the percentage of difference reported to exist between psychiatric populations and normal control in recent meta-analyses. Taken together, these results confront the notion of hippocampal atrophy in humans and raise the possibility that pre-determined inter-individual differences in HC volume in humans may determine the vulnerability for age-related cognitive impairments or psychopathology throughout the lifetime.

Automated analysis of multi site MRI phantom data for the NIHPD project

In large multi-center studies it is important to quantify data variations due to differences between sites and over time. Here we investigate inter-site variability in signal to noise ratio (SNR), percent integral uniformity (PIU), width and height using the American College of Radiology (ACR) phantom scans from the NIHPD project. Longitudinal variations are also analyzed. All measurements are fully automated. Our results show that the mean SNR, PIU and the 2 metric values were statistically different across sites. The maximum mean difference in diameter across sites was 2 mm (1.1%), and the maximum mean difference in height was 2.5 mm (1.7%). Over time, an average drift of 0.4 mm per year was observed for the diameter while a drift of 0.5 mm per year was observed for the height. Trends observed over time often depended not only on site, but also on modality and scanner manufacturer.

Community structure and its dynamics of pest, predatory and neutral insects in a jujube ecosystem

An investigation on the insects in the jujube ecosystem in Taigu District of Shanxi Province, Northern China showed that more species and individual numbers of pest, predatory and neutral insects were found on the tree than on the ground. The ratio of the species and individual numbers of predatory and neutral insects to those of pest insects fluctuated from year to year. Homoptera, Coleoptera and Lepidoptera were the dominant groups of pest insects, while those of predatory insects were Coleopteran, Hemiptera, Diptera and Hymenoptera. The vertical distribution of the community structure of the same or different subcommunity was different in different seasons, as was the case of the same or different subcommunity in the same season. The diversity indexes of pest, predatory and neutral insects fluctuated with seasons, and the populations of predatory and neutral insects had a significant correlation (r = 0.9833, P <0.05) with the fluctuation of pest insects. There was also a significant correlation between the pest, predatory and neutral insects in different stratums of tree canopy, especially in the middle stratum of tree canopy (r = 0.9887, P <0.01).

Imaging speech production using fMRI

Human speech is a well-learned, sensorimotor, and ecological behavior ideal for the study of neural processes and brain-behavior relations. With the advent of modern neuroimaging techniques such as positron emission tomography (PET) and functional magnetic resonance imaging (fMRI), the potential for investigating neural mechanisms of speech motor control, speech motor disorders, and speech motor development has increased. However, a practical issue has limited the application of fMRI to issues in spoken language production and other related behaviors (singing, swallowing). Producing these behaviors during volume acquisition introduces motion-induced signal changes that confound the activation signals of interest. A number of approaches, ranging from signal processing to using silent or covert speech, have attempted to remove or prevent the effects of motion-induced artefact. However, these approaches are flawed for a variety of reasons. An alternative approach, that has only recently been applied to study single-word production, uses pauses in volume acquisition during the production of natural speech motion. Here we present some representative data illustrating the problems associated with motion artefacts and some qualitative results acquired from subjects producing short sentences and orofacial nonspeech movements in the scanner. Using pauses or silent intervals in volume acquisition and block designs, results from individual subjects result in robust activation without motion-induced signal artefact. This approach is an efficient method for studying the neural basis of spoken language production and the effects of speech and language disorders using fMRI.

fMRI Activation in Continuous and Spike-triggered EEG-fMRI Studies of Epileptic Spikes

PURPOSE

To evaluate functional magnetic resonance imaging (fMRI) with simultaneous EEG for finding metabolic sources of epileptic spikes. To find the localizing value of activated regions and factors influencing fMRI responses.

METHODS

Patients with focal epilepsy and frequent spikes were subjected to spike-triggered or continuous fMRI with simultaneous EEG. Results were analyzed in terms of fMRI activation, concordance with the location of EEG spiking and anatomic MRI abnormalities, and other EEG and clinical variables. In four patients, results also were compared with those of intracerebral EEG.

RESULTS

Forty-eight studies were performed on 38 patients. Seventeen studies were not analyzed, primarily because no spikes occurred during scanning. Activation was obtained in 39% of 31 studies, with an activation volume of 2.55 +/- 4.84 cc. Activated regions were concordant with EEG localization in almost all studies and confirmed by intracerebral EEG in four patients. Forty percent of patients without an MRI lesion showed activation; 37.5% of patients with a lesion had an activation; the activation was near or inside the lesion. Bursts of spikes were more likely to generate an fMRI response than were isolated spikes (76 vs. 11%; p < 0.05).

CONCLUSIONS

Combining EEG and fMRI in focal epilepsy yields regions of activation that are presumably the source of spiking activity. These regions are highly linked with epileptic foci and epileptogenic lesions in a significant number of patients. Activation also is found in patients with no visible MRI lesion. Intracerebral recordings largely confirm that these activation regions represent epileptogenic areas. It is still unclear why many patients show no activation.

Cognitive strategies dependent on the hippocampus and caudate nucleus in human navigation: variability and change with practice

The human brain activity related to strategies for navigating in space and how it changes with practice was investigated with functional magnetic resonance imaging. Subjects used two different strategies to solve a place-learning task in a computer-generated virtual environment. One-half of the subjects used spatial landmarks to navigate in the early phase of training, and these subjects showed increased activation of the right hippocampus. The other half used a nonspatial strategy and showed, with practice, sustained increased activity within the caudate nucleus during navigation. Activation common to both groups was observed in the posterior parietal and frontal cortex. These results provide the first evidence for spontaneous variability and shift in neural mechanisms during navigation in humans.

The BOLD response to interictal epileptiform discharges

We studied single-event and average BOLD responses to EEG interictal epileptic discharges (IEDs) in four patients with focal epilepsy, using continuous EEG-fMRI during 80-min sessions. The detection of activated areas was performed by comparing the BOLD signal at each voxel to a model of the expected signal. Since little is known about the BOLD response to IEDs, we modeled it with the response to brief auditory events (G. H., NeuroImage 9, 416-429). For each activated area, we then obtained the time course of the BOLD signal for the complete session and computed the actual average hemodynamic response function (HRF) to IEDs. In two of four patients, we observed clear BOLD responses to single IEDs. The average response was composed of a positive lobe peaking between 6 and 7 s in all patients and a negative undershoot in three patients. There were important variations in amplitude and shape between average HRFs across patients. The average HRF presented a wider positive lobe than the Glover model in three patients and a longer undershoot in two. There was a remarkable similarity in the shape of the HRF across areas for patients presenting multiple activation sites. There was no clear correlation between the amplitude of individual BOLD responses and the amplitude of the corresponding EEG spike. The possibility of a longer HRF could be used to improve statistical detection of activation in simultaneous EEG-fMRI. The variability in average HRFs across patients could reflect in part different pathophysiological mechanisms.

Differentiating noxious- and innocuous-related activation of human somatosensory cortices using temporal analysis of fMRI

The role of the somatosensory cortices (SI and SII) in pain perception has long been in dispute. Human imaging studies demonstrate activation of SI and SII associated with painful stimuli, but results have been variable, and the functional relevance of any such activation is uncertain. The present study addresses this issue by testing whether the time course of somatosensory activation, evoked by painful heat and nonpainful tactile stimuli, is sufficient to discriminate temporal differences that characterize the perception of these stimulus modalities. Four normal subjects each participated in three functional magnetic resonance imaging (fMRI) sessions, in which painful (noxious heat 45-46 degrees C) and nonpainful test stimuli (brushing at 2 Hz) were applied repeatedly (9-s stimulus duration) to the left leg in separate experiments. Activation maps were generated comparing painful to neutral heat (35 degrees C) and nonpainful brushing to rest. Directed searches were performed in SI and SII for sites reliably activated by noxious heat and brush stimuli, and stimulus-dependent regions of interest (ROI) were then constructed for each subject. The time course, per stimulus cycle, was extracted from these ROIs and compared across subjects, stimulus modalities, and cortical regions. Both innocuous brushing and noxious heat produced significant activation within contralateral SI and SII. The time course of brush-evoked responses revealed a consistent single peak of activity, approximately 10 s after the onset of the stimulus, which rapidly diminished upon stimulus withdrawal. In contrast, the response to heat pain in both SI and SII was characterized by a double-peaked time course in which the maximum response (the 2nd peak) was consistently observed approximately 17 s after the onset of the stimulus (8 s following termination of the stimulus). This prolonged period of activation paralleled the perception of increasing pain intensity that persists even after stimulus offset. On the other hand, the temporal profile of the initial minor peak in pain-related activation closely matched that of the brush-evoked activity, suggesting a possible relationship to tactile components of the thermal stimulation procedure. These data indicate that both SI and SII cortices are involved in the processing of nociceptive information and are consistent with a role for these structures in the perception of temporal aspects of pain intensity.

A four-dimensional probabilistic atlas of the human brain

The authors describe the development of a four-dimensional atlas and reference system that includes both macroscopic and microscopic information on structure and function of the human brain in persons between the ages of 18 and 90 years. Given the presumed large but previously unquantified degree of structural and functional variance among normal persons in the human population, the basis for this atlas and reference system is probabilistic. Through the efforts of the International Consortium for Brain Mapping (ICBM), 7,000 subjects will be included in the initial phase of database and atlas development. For each subject, detailed demographic, clinical, behavioral, and imaging information is being collected. In addition, 5,800 subjects will contribute DNA for the purpose of determining genotype- phenotype-behavioral correlations. The process of developing the strategies, algorithms, data collection methods, validation approaches, database structures, and distribution of results is described in this report. Examples of applications of the approach are described for the normal brain in both adults and children as well as in patients with schizophrenia. This project should provide new insights into the relationship between microscopic and macroscopic structure and function in the human brain and should have important implications in basic neuroscience, clinical diagnostics, and cerebral disorders.

A probabilistic atlas and reference system for the human brain: International Consortium for Brain Mapping (ICBM)

Motivated by the vast amount of information that is rapidly accumulating about the human brain in digital form, we embarked upon a program in 1992 to develop a four-dimensional probabilistic atlas and reference system for the human brain. Through an International Consortium for Brain Mapping (ICBM) a dataset is being collected that includes 7000 subjects between the ages of eighteen and ninety years and including 342 mono- and dizygotic twins. Data on each subject includes detailed demographic, clinical, behavioural and imaging information. DNA has been collected for genotyping from 5800 subjects. A component of the programme uses post-mortem tissue to determine the probabilistic distribution of microscopic cyto- and chemoarchitectural regions in the human brain. This, combined with macroscopic information about structure and function derived from subjects in vivo, provides the first large scale opportunity to gain meaningful insights into the concordance or discordance in micro- and macroscopic structure and function. The philosophy, strategy, algorithm development, data acquisition techniques and validation methods are described in this report along with database structures. Examples of results are described for the normal adult human brain as well as examples in patients with Alzheimer's disease and multiple sclerosis. The ability to quantify the variance of the human brain as a function of age in a large population of subjects for whom data is also available about their genetic composition and behaviour will allow for the first assessment of cerebral genotype-phenotype-behavioural correlations in humans to take place in a population this large. This approach and its application should provide new insights and opportunities for investigators interested in basic neuroscience, clinical diagnostics and the evaluation of neuropsychiatric disorders in patients.

Maturation of white matter in the human brain: a review of magnetic resonance studies

This review focuses on the maturation of brain white-matter, as revealed by magnetic resonance (MR) imaging carried out in healthy subjects. The review begins with a brief description of the nature of the MR signal and its possible biological underpinnings, and proceeds with a description of MR findings obtained in newborns, infants, children and adolescents. On MR images, a significant decrease in water content leads to a decrease of longitudinal relaxation times (T1) and transverse relaxation times (T2) and consequent "adult-like" appearance of T1-weighted and T2-weighted images becomes evident towards the end of the first year of life. Owing to the onset of myelination and the related increase of lipid content, MR images gradually acquire an exquisite grey-white matter contrast in a temporal sequence reflecting the time course of myelination. Albeit less pronounced, age-related changes in white matter continue during childhood and adolescence; white matter increases its overall volume and becomes more myelinated in a region-specific fashion. Detection of more subtle changes during this "late" phase of brain development is greatly aided by computational analyses of MR images. The review also briefly outlines future directions, including the use of novel MR techniques such as diffusion tensor imaging and magnetization transfer, as well as the suggestion for the concurrent use of experimental behavioral test-batteries, with structural MR imaging, to study developmental changes in structure-function relationships.

Voice-selective areas in human auditory cortex

The human voice contains in its acoustic structure a wealth of information on the speaker's identity and emotional state which we perceive with remarkable ease and accuracy. Although the perception of speaker-related features of voice plays a major role in human communication, little is known about its neural basis. Here we show, using functional magnetic resonance imaging in human volunteers, that voice-selective regions can be found bilaterally along the upper bank of the superior temporal sulcus (STS). These regions showed greater neuronal activity when subjects listened passively to vocal sounds, whether speech or non-speech, than to non-vocal environmental sounds. Central STS regions also displayed a high degree of selectivity by responding significantly more to vocal sounds than to matched control stimuli, including scrambled voices and amplitude-modulated noise. Moreover, their response to stimuli degraded by frequency filtering paralleled the subjects' behavioural performance in voice-perception tasks that used these stimuli. The voice-selective areas in the STS may represent the counterpart of the face-selective areas in human visual cortex; their existence sheds new light on the functional architecture of the human auditory cortex.

Event-related fMRI of the auditory cortex

An event-related protocol was designed to permit auditory fMRI studies minimally affected by the echo-planar noise artifact; a long time interval (TR = 10 s) between each cerebral volume acquisition was combined with stroboscopic data acquisition, and event-related curves were reconstructed with a 1-s resolution. The cerebral hemodynamic-response time course to a target auditory stimulus was measured in five individual subjects using this method. Clear bell-shaped event-related responses were observed bilaterally in all individuals in primary auditory cortex (A1) as well as in laterally extending secondary cortical fields. Group-average event-related curves attained their maxima (0.5-0.7%) 3 s after stimulus onset in A1 (4 s for more anterior and lateral regions of auditory cortex), and signal had returned to near-baseline level 6 s after stimulus onset. The stroboscopic event-related method appeared effective in minimizing effects of the interaction between scanning noise and experimental auditory stimulation; it adds useful temporal information to the spatial resolution afforded by fMRI in studies of human auditory function, while allowing presentation of auditory stimuli on a silent background.

Reovirus-induced apoptosis is preceded by increased cellular calpain activity and is blocked by calpain inhibitors

The cellular pathways of apoptosis have not been fully characterized; however, calpain, a cytosolic calcium-activated cysteine protease, has been implicated in several forms of programmed cell death. Reoviruses induce apoptosis both in vitro and in vivo and serve as a model for studying virus-induced cell death. We investigated the potential role of calpain in reovirus-induced apoptosis in vitro by measuring calpain activity as well as evaluating the effects of calpain inhibitors. L929 cells were infected with reovirus type 3 Abney (T3A), and calpain activity, measured as cleavage of the fluorogenic calpain substrate Suc-Leu-Leu-Val-Tyr-AMC, was monitored. There was a 1.6-fold increase in calpain activity in T3A-infected cells compared to mock-infected cells; this increase was completely inhibited by preincubation with calpain inhibitor I (N-acetyl-leucyl-leucyl-norleucinal [aLLN]), an active-site inhibitor. Both aLLN and PD150606, a specific calpain inhibitor that interacts with the calcium-binding site, inhibited reovirus-induced apoptosis in L929 cells by 54 to 93%. Apoptosis induced by UV-inactivated reovirus was also reduced 65 to 69% by aLLN, indicating that inhibition of apoptosis by calpain inhibitors is independent of effects on viral replication. We conclude that calpain activation is a component of the regulatory cascade in reovirus-induced apoptosis.

Contig map of the Parkinson's disease region on 4q21-q23

We have constructed a yeast artificial chromosome contig (YAC) map of human chromosome 4q21-q23 across the Parkinson's disease region by combining molecular and fluorescence in situ hybridization techniques. This map contains 55 YACs and 51 molecular markers, including 23 polymorphic markers. We have also isolated one P1 and 33 bacterial artificial chromosomes located within this contig. Plasmid libraries were generated from 11 of these BAC and P1 clones, and 614 random plasmid clones were sequenced for a total of about 200 kb. This contig allowed us to precisely determine the location of 18 transcripts within the D4S2460-D4S2986 interval, including the alpha-synuclein gene found to be mutated in some families with Parkinson's disease.

Mutation in the alpha-synuclein gene identified in families with Parkinson's disease

Parkinson's disease (PD) is a common neurodegenerative disorder with a lifetime incidence of approximately 2 percent. A pattern of familial aggregation has been documented for the disorder, and it was recently reported that a PD susceptibility gene in a large Italian kindred is located on the long arm of human chromosome 4. A mutation was identified in the alpha-synuclein gene, which codes for a presynaptic protein thought to be involved in neuronal plasticity, in the Italian kindred and in three unrelated families of Greek origin with autosomal dominant inheritance for the PD phenotype. This finding of a specific molecular alteration associated with PD will facilitate the detailed understanding of the pathophysiology of the disorder.

Mutation in the alpha-synuclein gene identified in families with Parkinson's disease

Parkinson's disease (PD) is a common neurodegenerative disorder with a lifetime incidence of approximately 2 percent. A pattern of familial aggregation has been documented for the disorder, and it was recently reported that a PD susceptibility gene in a large Italian kindred is located on the long arm of human chromosome 4. A mutation was identified in the alpha-synuclein gene, which codes for a presynaptic protein thought to be involved in neuronal plasticity, in the Italian kindred and in three unrelated families of Greek origin with autosomal dominant inheritance for the PD phenotype. This finding of a specific molecular alteration associated with PD will facilitate the detailed understanding of the pathophysiology of the disorder.

Reovirus-induced apoptosis of MDCK cells is not linked to viral yield and is blocked by Bcl-2

In this study, we investigated the relationship between reovirus-induced apoptosis and viral growth. Madin-Darby canine kidney (MDCK) epithelial cells infected with prototype reovirus strains type 1 Lang (T1L) or type 3 Dearing (T3D) were found to undergo apoptosis, and T3D induced apoptosis of MDCK cells to a substantially greater extent than T1L. By using T1L x T3D reassortant viruses, we found that differences in the capacities of these strains to induce apoptosis are determined by the viral S1 and M2 gene segments. These genes encode viral outer-capsid proteins that play important roles in viral entry into cells. T1L grew significantly better in MDCK cells than T3D, and these differences in growth segregated with the viral L1 and M1 gene segments. The L1 and M1 genes encode viral core proteins involved in viral RNA synthesis. Bcl-2 overexpression in MDCK cells inhibited reovirus-induced apoptosis but did not substantially affect reovirus growth. These findings indicate that differences in the capacities of reovirus strains to induce apoptosis and grow in MDCK cells are determined by different viral genes and that premature cell death by apoptosis does not limit reovirus growth in MDCK cells.

Linkage between reovirus-induced apoptosis and inhibition of cellular DNA synthesis: role of the S1 and M2 genes

The mammalian reoviruses are capable of inhibiting cellular DNA synthesis and inducing apoptosis. Reovirus strains type 3 Abney (T3A) and type 3 Dearing (T3D) inhibit cellular DNA synthesis and induce apoptosis to a substantially greater extent than strain type 1 Lang (T1L). We used T1L x T3A and T1L x T3D reassortant viruses to identify viral genes associated with differences in the capacities of reovirus strains to elicit these cellular responses to viral infection. We found that the S1 and M2 genome segments determine differences in the capacities of both T1L x T3A and T1L x T3D reassortant viruses to inhibit cellular DNA synthesis and to induce apoptosis. These genes encode viral outer-capsid proteins that play important roles in viral attachment and disassembly. To extend these findings, we used field isolate strains of reovirus to determine whether the strain-specific differences in inhibition of cellular DNA synthesis and induction of apoptosis are also associated with viral serotype, a property determined by the S1 gene. In these experiments, type 3 field isolate strains were found to inhibit cellular DNA synthesis and to induce apoptosis to a greater extent than type 1 field isolate strains. Statistical analysis of these data indicate a significant correlation between the capacity of T1L x T3A and T1L x T3D reassortant viruses and field isolate strains to inhibit cellular DNA synthesis and to induce apoptosis. These findings suggest that reovirus-induced inhibition of cellular DNA synthesis and induction of apoptosis are linked and that both phenomena are induced by early steps in the viral replication cycle.

Induction of diabetes with islet-specific T-cell clones is age dependent

To investigate the effects of recipient age on the induction of diabetes by CD4+ islet-specific T-cell clones, we tested four different clones in non-obese diabetic (NOD) mice of different ages. Transfer of each of the T-cell clones resulted in insulitis and full development of diabetes in unirradiated 8-18-day-old NOD mice within 2-3 weeks. A small gender bias in disease susceptibility was seen in 8-14-day-old female NOD mice, which showed a twofold increase in disease incidence over both age-matched males and slightly older (15-18-day-old) females. In contrast, both male and female NOD mice, 19 days or older, were highly resistant to T-cell clone-induced insulitis and completely resistant to the development of diabetes. In mice of an intermediate age range (15-18 days old), two of the clones showed a three- to fourfold reduction in transfer of overt diabetes regardless of gender. These results suggest that an important developmental event occurs in both male and female NOD mice between the age of 15 and 19 days, leading to the inhibition of disease induced by T-cell clones.

Islet-specific T cell clones transfer diabetes to nonobese diabetic (NOD) F1 mice

To investigate diabetes resistance to T cell-mediated disease transfer, we administered islet-specific T cell clones to the F1 progeny of nonobese diabetic (NOD) mice that were crossed with various nondiabetes-prone inbred mouse strains. We investigated four diabetogenic CD4+ T cell clones and all induced insulitis and full development of diabetes in (SWR x NOD)F1, (SJL x NOD)F1, and (C57BL/6 x NOD)F1 mice. In contrast, (BALB/c x NOD)F1 and (CBA x NOD)F1 mice were susceptible to disease transfer by some T cell clones but not others, and (C57/L x NOD)F1 mice seemed to be resistant to both insulitis and disease transfer by all of the clones tested. Disease induced by the T cell clones in susceptible F1 strains was age dependent and could only be observed in recipients younger than 13 days old. Full or partial disease resistance did not correlate with the presence or absence of I-E, different levels of Ag expression in islet cells, or differences in APC function. The results from this study suggest that there may be multiple factors contributing to susceptibility of F1 mice to T cell clone-mediated induction of diabetes, including non-MHC-related genetic background, the immunologic maturity of the recipient, and individual characteristics of the T cell clones.

Islet-specific T cell clones transfer diabetes to nonobese diabetic (NOD) F1 mice

To investigate diabetes resistance to T cell-mediated disease transfer, we administered islet-specific T cell clones to the F1 progeny of nonobese diabetic (NOD) mice that were crossed with various nondiabetes-prone inbred mouse strains. We investigated four diabetogenic CD4+ T cell clones and all induced insulitis and full development of diabetes in (SWR x NOD)F1, (SJL x NOD)F1, and (C57BL/6 x NOD)F1 mice. In contrast, (BALB/c x NOD)F1 and (CBA x NOD)F1 mice were susceptible to disease transfer by some T cell clones but not others, and (C57/L x NOD)F1 mice seemed to be resistant to both insulitis and disease transfer by all of the clones tested. Disease induced by the T cell clones in susceptible F1 strains was age dependent and could only be observed in recipients younger than 13 days old. Full or partial disease resistance did not correlate with the presence or absence of I-E, different levels of Ag expression in islet cells, or differences in APC function. The results from this study suggest that there may be multiple factors contributing to susceptibility of F1 mice to T cell clone-mediated induction of diabetes, including non-MHC-related genetic background, the immunologic maturity of the recipient, and individual characteristics of the T cell clones.

Experimental hepatic tumor necrosis. Comparison of spin-echo and pulsed magnetization transfer contrast magnetic resonance imaging

RATIONALE AND OBJECTIVES

We compared the effectiveness of pulsed magnetization transfer contrast (MTC) magnetic resonance imaging (MRI) and spin-echo MRI in detecting tumor necrosis.

METHODS

Adenocarcinoma cells were transplanted in the livers of 12 syngenic BDIX rats. To induce various degrees of tumor necrosis, the rats were randomly assigned to the following groups: 1) control; 2) localized hyperthermia; 3) intralesional cisplatin; and 4) hyperthermia plus intralesional cisplatin. At day 7 after treatment, the rats were imaged using a 1.5-T imager with 1) multiplanar gradient-recalled echo sequence (MPGR) 500/8/20 degrees with and without magnetization transfer contrast (MTC); 2) spin-echo 2500/20,80, and 3) spin-echo 300/20 pulse sequences. The rats were then sacrificed and pathologic specimens were prepared using MR images as guidance. T2 and ratios of signal intensity after saturation to signal intensity before saturation (Ms/Mo ratios) of the necrotic and granulation tissues and viable tumors were determined in 10 rats.

RESULTS

Compared with standard MPGR images, MPGR images with MTC provided better contrast between the pathologic tissues and normal liver. However, T2 values were more useful than Ms/Mo ratios in distinguishing necrotic areas from viable tumor. The T2 values of coagulative necrosis and granulation tissue were significantly different from that of viable tumor. No significant difference between the Ms/Mo ratios of the different pathologic tissues and normal liver was found.

CONCLUSION

Pulsed magnetization transfer contrast MRI was inferior to spin-echo MRI in distinguishing necrotic from viable tumors in rat livers using the pulse sequences described, and none of the sequences studied was thought to be reliable enough for this purpose.

Multiple intracerebral cavernous angiomas

Eight patients (seven women and one man) with multiple intracerebral cavernous angiomas (cavernomas), also known as angiomatosis cerebri, were examined with high-field magnetic resonance imaging (MRI). Although previous articles have referred to such cases, a series similar to the one reported here has apparently not been described in the radiology literature. The patients presented with seizures, progressive neurologic deficit or cerebral hemorrhage. In all eight cases the multiplicity of the lesions was an incidental finding in the magnetic resonance images. The MRI appearance of the cavernomas, although characteristic, is similar to that of other angiographically occult intracranial vascular malformations, in particular thrombosed arteriovenous malformations and mixed vascular malformations, as well as that of hemorrhagic metastases. Additional criteria, such as the absence of edema, the presence of calcifications and the temporal evolution of the cavernomas on serial scans, should allow cavernomas to be differentiated from hemorrhagic metastases. The exquisite sensitivity in detecting angiomatosis cerebri and the ability to show the evolution of internal hemorrhage in individual lesions make MRI the method of choice for diagnosing and following this condition.

Clinical applications of integrated 3-D stereoscopic imaging in neurosurgery

Stereotactic neurosurgery planning, an intrinsically three-dimensional procedure, is generally performed on the basis of two-dimensional tomographic or projection images. We present extensions to these conventional approaches that use stereoscopic digital subtraction angiography, three-dimensional volume rendered computed tomography or magnetic resonance images, or a combination of these modalities. The stereoscopic DSA images are analysed interactively on a 3-D workstation. This system employs a liquid-crystal polarizing shutter to display alternate left- and right-eye views to a user wearing polarized glasses. Quantitative planning operations may be performed on the basis of the angiograms alone, or in conjunction with tomographic images of the anatomy. We also describe the procedures used to produce volume-rendered three-dimensional images from MR and CT data-sets, as well as the methodology for combining the stereoscopic angiograms with the volumetric anatomical images.

Dose distributions in dynamic stereotactic radiosurgery

A treatment planning technique for calculation of dose distributions in dynamic stereotactic "radiosurgery" with a 10-MV isocentrically mounted linear accelerator is presented. The treatment planning for dynamic radiosurgery is a three-dimensional problem, since during treatment both the gantry and the couch rotate simultaneously, the gantry from 30 degrees to 330 degrees and the couch from 75 degrees to - 75 degrees. The patient surface and anatomical information is obtained from a family of computed tomography or magnetic resonance scans, and a stereotactic frame is used for target localization, treatment setup, and patient immobilization during the treatment. The dose calculational algorithm follows the gantry and couch rotation in an incremental fashion, and relies on measured stationary beam central axis percentage depth doses and dose profiles to calculate the normalized tissue-maximum-ratio distributions over a matrix of points defined on one of three orthogonal planes (transverse, sagittal, or coronal). The dose calculation algorithm is discussed in detail and calculated dose distributions for single plane and dynamic radiosurgery compared with measured data.

Physical aspects of dynamic stereotactic radiosurgery

Dynamic stereotactic radiosurgery is a radiosurgical technique based on a medium-energy isocentric linear accelerator and a stereotactic frame. The technique uses concurrent and continuous rotations of both the gantry (300 degrees, from 30 to 330 degrees) and the couch (150 degrees, from 75 to -75 degrees). It gives a uniform dose (+/- 5%) within the target volume and dose fall-offs outside the target volume comparable to those obtained from presently known radiosurgical techniques.

Combined use of digital subtraction angiography and MRI for radiosurgery and stereoencephalography

The authors report their experience with the combined use of digital subtraction angiography (DSA) and magnetic resonance imaging (MRI) for the stereotactic placement of intracerebral electrodes in epilepsy and for the radiosurgical treatment of otherwise inoperable arteriovenous malformations of the brain. Both imaging techniques, when used in conjunction, have been found most useful and complementary. For deep electrode placement, they permit optimal visualization of the cerebral structures to be reached by the electrode array while allowing the avoidance of vessels in the vicinity. For radiosurgery of arteriovenous malformations, DSA provides optimal visualization of the feeders and of the malformation itself, while the MRI reveals the cerebral structures to be spared by the photon beam of the linear accelerator. A discussion of their respective roles is presented, with the specific question as to whether MRI alone could be used for both procedures.