Brain dynamics predictive of response to psilocybin for treatment-resistant depression

Psilocybin therapy for depression has started to show promise, yet the underlying causal mechanisms are not currently known. Here, we leveraged the differential outcome in responders and non-responders to psilocybin (10 and 25 mg, 7 days apart) therapy for depression-to gain new insights into regions and networks implicated in the restoration of healthy brain dynamics. We used large-scale brain modelling to fit the spatiotemporal brain dynamics at rest in both responders and non-responders before treatment. Dynamic sensitivity analysis of systematic perturbation of these models enabled us to identify specific brain regions implicated in a transition from a depressive brain state to a healthy one. Binarizing the sample into treatment responders (>50% reduction in depressive symptoms) versus non-responders enabled us to identify a subset of regions implicated in this change. Interestingly, these regions correlate with in vivo density maps of serotonin receptors 5-hydroxytryptamine 2a and 5-hydroxytryptamine 1a, which psilocin, the active metabolite of psilocybin, has an appreciable affinity for, and where it acts as a full-to-partial agonist. Serotonergic transmission has long been associated with depression, and our findings provide causal mechanistic evidence for the role of brain regions in the recovery from depression via psilocybin.

Modulation of limbic resting-state networks by subthalamic nucleus deep brain stimulation

Beyond the established effects of subthalamic nucleus deep brain stimulation (STN-DBS) in reducing motor symptoms in Parkinson's disease, recent evidence has highlighted the effect on non-motor symptoms. However, the impact of STN-DBS on disseminated networks remains unclear. This study aimed to perform a quantitative evaluation of network-specific modulation induced by STN-DBS using Leading Eigenvector Dynamics Analysis (LEiDA). We calculated the occupancy of resting-state networks (RSNs) in functional MRI data from 10 patients with Parkinson's disease implanted with STN-DBS and statistically compared between ON and OFF conditions. STN-DBS was found to specifically modulate the occupancy of networks overlapping with limbic RSNs. STN-DBS significantly increased the occupancy of an orbitofrontal limbic subsystem with respect to both DBS OFF (p = 0.0057) and 49 age-matched healthy controls (p = 0.0033). Occupancy of a diffuse limbic RSN was increased with STN-DBS OFF when compared with healthy controls (p = 0.021), but not when STN-DBS was ON, which indicates rebalancing of this network. These results highlight the modulatory effect of STN-DBS on components of the limbic system, particularly within the orbitofrontal cortex, a structure associated with reward processing. These results reinforce the value of quantitative biomarkers of RSN activity in evaluating the disseminated impact of brain stimulation techniques and the personalization of therapeutic strategies.

On screen experiment showed that becoming a parent for the first time shifted people's priorities from themselves to their infant at 1 year of age

AIM

This study used a screen-based perceptual matching task to see how non-parents, people trying to get pregnant, and those who had given birth prioritised shapes and labels relating to self or infant conditions.

METHODS

The study took place at Aarhus University Hospital in Denmark from December 2016 to November 2021. Recruitment methods included family planning clinics, social media, online recruitment systems and local bulletin boards. The modified perceptual matching task linked five shapes to five labels, including self and infant.

RESULTS

We found that 67 males and females with a mean age of 24.4 ± 3 years, who had no plans to become parents in the near future, reacted faster and more accurately to self-shapes and labels (p < 0.001), which validated the experiment. The 56 participants aged 27.1 ± 4.4 years who were actively trying to become parents showed no statistically significant prioritisation. A subset of 21 participants aged 28.7 ± 4.4 years showed faster response times to infant than self-shapes and labels 1 year after giving birth (p < 0.001).

CONCLUSION

Healthy first-time parents showed faster reactions to infant than self-conditions 1 year after giving birth, in contrast to the other two groups.

A magnetoencephalography study of first-time mothers listening to infant cries

Studies using magnetoencephalography (MEG) have identified the orbitofrontal cortex (OFC) to be an important early hub for a “parental instinct” in the brain. This complements the finding from functional magnetic resonance imaging studies linking reward, emotion regulation, empathy, and mentalization networks to the “parental brain.” Here, we used MEG in 43 first-time mothers listening to infant and adult cry vocalizations to investigate the link with mother–infant postpartum bonding scores and their level of sleep deprivation (assessed using both actigraphy and sleep logs). When comparing brain responses to infant versus adult cry vocalizations, we found significant differences at around 800–1,000 ms after stimuli onset in the primary auditory cortex, superior temporal gyrus, hippocampal areas, insula, precuneus supramarginal gyrus, postcentral gyrus, and posterior cingulate gyrus. Importantly, mothers with weaker bonding scores showed decreased brain responses to infant cries in the auditory cortex, middle and superior temporal gyrus, OFC, hippocampal areas, supramarginal gyrus, and inferior frontal gyrus at around 100–300 ms after the stimulus onset. In contrast, we did not find correlations with sleep deprivation scores. The significant decreases in brain processing of an infant’s distress signals could potentially be a novel signature of weaker infant bonding in new mothers and should be investigated in vulnerable populations.

A novel method for estimating connectivity-based parcellation of the human brain from diffusion MRI: Application to an aging cohort

Connectivity‐based parcellation (CBP) methods are used to define homogenous and biologically meaningful parcels or nodes—the foundations of brain network fingerprinting—by grouping voxels with similar patterns of brain connectivity. However, we still lack a gold standard method and the use of CBPs to study the aging brain remains scarce. Our study proposes a novel CBP method from diffusion MRI data and shows its potential to produce a more accurate characterization of the longitudinal alterations in brain network topology occurring in aging. For this, we constructed whole‐brain connectivity maps from diffusion MRI data of two datasets: an aging cohort evaluated at two timepoints (mean interval time: 52.8 ± 7.24 months) and a normative adult cohort—MGH‐HCP. State‐of‐the‐art clustering techniques were used to identify the best performing technique. Furthermore, we developed a new metric (connectivity homogeneity fingerprint [CHF]) to evaluate the success of the final CBP in improving regional/global structural connectivity homogeneity. Our results show that our method successfully generates highly homogeneous parcels, as described by the significantly larger CHF score of the resulting parcellation, when compared to the original. Additionally, we demonstrated that the developed parcellation provides a robust anatomical framework to assess longitudinal changes in the aging brain. Our results reveal that aging is characterized by a reorganization of the brain's structural network involving the decrease of intra‐hemispheric, increase of inter‐hemispheric connectivity, and topological rearrangement. Overall, this study proposes a new methodology to perform accurate and robust evaluations of CBP of the human brain.

Habitual coffee drinkers display a distinct pattern of brain functional connectivity

Coffee is the most widely consumed source of caffeine worldwide, partly due to the psychoactive effects of this methylxanthine. Interestingly, the effects of its chronic consumption on the brain's intrinsic functional networks are still largely unknown. This study provides the first extended characterization of the effects of chronic coffee consumption on human brain networks. Subjects were recruited and divided into two groups: habitual coffee drinkers (CD) and non-coffee drinkers (NCD). Resting-state functional magnetic resonance imaging (fMRI) was acquired in these volunteers who were also assessed regarding stress, anxiety, and depression scores. In the neuroimaging evaluation, the CD group showed decreased functional connectivity in the somatosensory and limbic networks during resting state as assessed with independent component analysis. The CD group also showed decreased functional connectivity in a network comprising subcortical and posterior brain regions associated with somatosensory, motor, and emotional processing as assessed with network-based statistics; moreover, CD displayed longer lifetime of a functional network involving subcortical regions, the visual network and the cerebellum. Importantly, all these differences were dependent on the frequency of caffeine consumption, and were reproduced after NCD drank coffee. CD showed higher stress levels than NCD, and although no other group effects were observed in this psychological assessment, increased frequency of caffeine consumption was also associated with increased anxiety in males. In conclusion, higher consumption of coffee and caffeinated products has an impact in brain functional connectivity at rest with implications in emotionality, alertness, and readiness to action.

Breakdown of Whole-brain Dynamics in Preterm-born Children

The brain operates at a critical point that is balanced between order and disorder. Even during rest, unstable periods of random behavior are interspersed with stable periods of balanced activity patterns that support optimal information processing. Being born preterm may cause deviations from this normal pattern of development. We compared 33 extremely preterm (EPT) children born at < 27 weeks of gestation and 28 full-term controls. Two approaches were adopted in both groups, when they were 10 years of age, using structural and functional brain magnetic resonance imaging data. The first was using a novel intrinsic ignition analysis to study the ability of the areas of the brain to propagate neural activity. The second was a whole-brain Hopf model, to define the level of stability, desynchronization, or criticality of the brain. EPT-born children exhibited fewer intrinsic ignition events than controls; nodes were related to less sophisticated aspects of cognitive control, and there was a different hierarchy pattern in the propagation of information and suboptimal synchronicity and criticality. The largest differences were found in brain nodes belonging to the rich-club architecture. These results provide important insights into the neural substrates underlying brain reorganization and neurodevelopmental impairments related to prematurity.

Reorganization of brain structural networks in aging: A longitudinal study

Normal aging is characterized by structural and functional changes in the brain contributing to cognitive decline. Structural connectivity (SC) describes the anatomical backbone linking distinct functional subunits of the brain and disruption of this communication is thought to be one of the potential contributors for the age-related deterioration observed in cognition. Several studies already explored brain network's reorganization during aging, but most focused on average connectivity of the whole-brain or in specific networks, such as the resting-state networks. Here, we aimed to characterize longitudinal changes of white matter (WM) structural brain networks, through the identification of sub-networks with significantly altered connectivity along time. Then, we tested associations between longitudinal changes in network connectivity and cognition. We also assessed longitudinal changes in topological properties of the networks. For this, older adults were evaluated at two timepoints, with a mean interval time of 52.8 months (SD = 7.24). WM structural networks were derived from diffusion magnetic resonance imaging, and cognitive status from neurocognitive testing. Our results show age-related changes in brain SC, characterized by both decreases and increases in connectivity weight. Interestingly, decreases occur in intra-hemispheric connections formed mainly by association fibers, while increases occur mostly in inter-hemispheric connections and involve association, commissural, and projection fibers, supporting the last-in-first-out hypothesis. Regarding topology, two hubs were lost, alongside with a decrease in connector-hub inter-modular connectivity, reflecting reduced integration. Simultaneously, there was an increase in the number of provincial hubs, suggesting increased segregation. Overall, these results confirm that aging triggers a reorganization of the brain structural network.

Validation of Olfactory Network Based on Brain Structural Connectivity and Its Association With Olfactory Test Scores

Olfactory perception is a complicated process involving multiple cortical and subcortical regions, of which the underlying brain dynamics are still not adequately mapped. Even in the definition of the olfactory primary cortex, there is a large degree of variation in parcellation templates used for investigating olfaction in neuroimaging studies. This complicates comparison between human olfactory neuroimaging studies. The present study aims to validate an olfactory parcellation template derived from both functional and anatomical data that applies structural connectivity (SC) to ensure robust connectivity to key secondary olfactory regions. Furthermore, exploratory analyses investigate if different olfactory parameters are associated with differences in the strength of connectivity of this structural olfactory fingerprint. By combining diffusion data with an anatomical atlas and advanced probabilistic tractography, we found that the olfactory parcellation had a robust SC network to key secondary olfactory regions. Furthermore, the study indicates that higher ratings of olfactory significance were associated with increased intra- and inter-hemispheric SC of the primary olfactory cortex. Taken together, these results suggest that the patterns of SC between the primary olfactory cortex and key secondary olfactory regions has potential to be used for investigating the nature of olfactory significance, hence strengthening the theory that individual differences in olfactory behaviour are encoded in the structural network fingerprint of the olfactory cortex.

Signatures of white-matter microstructure degradation during aging and its association with cognitive status

Previous studies have shown an association between cognitive decline and white matter integrity in aging. This led to the formulation of a "disconnection hypothesis" in the aging-brain, which states that the disruption in cortical network communication may explain the cognitive decline during aging. Although some longitudinal studies have already investigated the changes occurring in white matter microstructure, most focused on specific white matter tracts. Our study aims to characterize the longitudinal whole-brain signatures of white matter microstructural change during aging. Furthermore, we assessed the relationship between distinct longitudinal alterations in white matter integrity and cognition. White matter microstructural properties were estimated from diffusion magnetic resonance imaging, and cognitive status characterized from extensive neurocognitive testing. The same individuals were evaluated at two timepoints, with a mean interval time of 52.8 months (SD = 7.24) between first and last assessment. Our results show that age is associated with a decline in cognitive performance and a degradation in white matter integrity. Additionally, significant associations were found between diffusion measures and different cognitive dimensions (memory, executive function and general cognition). Overall, these results suggest that age-related cognitive decline is related to white matter alterations, and thus give support to the "disconnected hypothesis" of the aging brain.

Chemosensory Sensitivity after Coffee Consumption Is Not Static: Short-Term Effects on Gustatory and Olfactory Sensitivity

Chemosensory sensitivity has great variation between individuals. This variation complicates the chemosensory diagnostics, as well as the creation of a meal with universally high hedonic value. To ensure accurate characterization of chemosensory function, a common rule of thumb is to avoid food/beverages one hour before chemosensory testing. However, the scientific foundation of this time of fast remains unclear. Furthermore, the role of coffee on immediate chemosensitivity is not known and may have implications for optimization of gastronomy and hedonia. The aim of this study is to investigate the modularity effects of coffee consumption on immediate gustatory and olfactory sensitivity. We included 155 participants. By applying tests for olfactory and gustatory sensitivity before and after coffee intake, we found no changes in olfactory sensitivity, but significantly altered sensitivity for some basic tastants. We repeated our experimental paradigm using decaffeinated coffee and found similar results. Our results demonstrate that coffee (regular and decaffeinated) alters the subsequent perception of taste, specifically by increasing the sensitivity to sweet and decreasing the sensitivity to bitter. Our findings provide the first evidence of how coffee impacts short-term taste sensitivity and consequently the way we sense and perceive food following coffee intake-an important insight in the context of gastronomy, as well as in chemosensory testing procedures.

Disrupted brain structural connectivity in Pediatric Bipolar Disorder with psychosis

Bipolar disorder (BD) has been linked to disrupted structural and functional connectivity between prefrontal networks and limbic brain regions. Studies of patients with pediatric bipolar disorder (PBD) can help elucidate the developmental origins of altered structural connectivity underlying BD and provide novel insights into the aetiology of BD. Here we compare the network properties of whole-brain structural connectomes of euthymic PBD patients with psychosis, a variant of PBD, and matched healthy controls. Our results show widespread changes in the structural connectivity of PBD patients with psychosis in both cortical and subcortical networks, notably affecting the orbitofrontal cortex, frontal gyrus, amygdala, hippocampus and basal ganglia. Graph theoretical analysis revealed that PBD connectomes have fewer hubs, weaker rich club organization, different modular fingerprint and inter-modular communication, compared to healthy participants. The relationship between network features and neurocognitive and psychotic scores was also assessed, revealing trends of association between patients’ IQ and affective psychotic symptoms with the local efficiency of the orbitofrontal cortex. Our findings reveal that PBD with psychosis is associated with significant widespread changes in structural network topology, thus strengthening the hypothesis of a reduced capacity for integrative processing of information across brain regions. Localised network changes involve core regions for emotional processing and regulation, as well as memory and executive function, some of which show trends of association with neurocognitive faculties and symptoms. Together, our findings provide the first comprehensive characterisation of the alterations in local and global structural brain connectivity and network topology, which may contribute to the deficits in cognition and emotion processing and regulation found in PBD.

Re-Test Reliability of Gustatory Testing and Introduction of the Sensitive Taste-Drop-Test

The sense of taste holds a key integrate role in assessing the flavor of food before swallowing is initiated. If the expectations for taste are not met, palatability and pleasure of the food can decrease. In patients suffering from taste disorders, this may impair appetite and nutritional state. Testing gustatory function can be important for diagnostics and assessment of treatment effects. However, the gustatory tests applied are required to be both sensitive and reliable. In this study, we investigate the re-test validity of popular Taste Strips gustatory test for gustatory screening. Furthermore, we introduce a new sensitive Taste-Drop-Test, which was found to be superior for detecting a more accurate measure of tastant sensitivity.

Uncovering the underlying mechanisms and whole-brain dynamics of deep brain stimulation for Parkinson's disease

Deep brain stimulation (DBS) for Parkinson’s disease is a highly effective treatment in controlling otherwise debilitating symptoms. Yet the underlying brain mechanisms are currently not well understood. Whole-brain computational modeling was used to disclose the effects of DBS during resting-state functional Magnetic Resonance Imaging in ten patients with Parkinson’s disease. Specifically, we explored the local and global impact that DBS has in creating asynchronous, stable or critical oscillatory conditions using a supercritical bifurcation model. We found that DBS shifts global brain dynamics of patients towards a Healthy regime. This effect was more pronounced in very specific brain areas such as the thalamus, globus pallidus and orbitofrontal regions of the right hemisphere (with the left hemisphere not analyzed given artifacts arising from the electrode lead). Global aspects of integration and synchronization were also rebalanced. Empirically, we found higher communicability and coherence brain measures during DBS-ON compared to DBS-OFF. Finally, using our model as a framework, artificial in silico DBS was applied to find potential alternative target areas for stimulation and whole-brain rebalancing. These results offer important insights into the underlying large-scale effects of DBS as well as in finding novel stimulation targets, which may offer a route to more efficacious treatments.

How structure sculpts function: Unveiling the contribution of anatomical connectivity to the brain's spontaneous correlation structure

Intrinsic brain activity is characterized by highly organized co-activations between different regions, forming clustered spatial patterns referred to as resting-state networks. The observed co-activation patterns are sustained by the intricate fabric of millions of interconnected neurons constituting the brain's wiring diagram. However, as for other real networks, the relationship between the connectional structure and the emergent collective dynamics still evades complete understanding. Here, we show that it is possible to estimate the expected pair-wise correlations that a network tends to generate thanks to the underlying path structure. We start from the assumption that in order for two nodes to exhibit correlated activity, they must be exposed to similar input patterns from the entire network. We then acknowledge that information rarely spreads only along a unique route but rather travels along all possible paths. In real networks, the strength of local perturbations tends to decay as they propagate away from the sources, leading to a progressive attenuation of the original information content and, thus, of their influence. Accordingly, we define a novel graph measure, topological similarity, which quantifies the propensity of two nodes to dynamically correlate as a function of the resemblance of the overall influences they are expected to receive due to the underlying structure of the network. Applied to the human brain, we find that the similarity of whole-network inputs, estimated from the topology of the anatomical connectome, plays an important role in sculpting the backbone pattern of time-average correlations observed at rest.

Insights into Brain Architectures from the Homological Scaffolds of Functional Connectivity Networks

In recent years, the application of network analysis to neuroimaging data has provided useful insights about the brain's functional and structural organization in both health and disease. This has proven a significant paradigm shift from the study of individual brain regions in isolation. Graph-based models of the brain consist of vertices, which represent distinct brain areas, and edges which encode the presence (or absence) of a structural or functional relationship between each pair of vertices. By definition, any graph metric will be defined upon this dyadic representation of the brain activity. It is however unclear to what extent these dyadic relationships can capture the brain's complex functional architecture and the encoding of information in distributed networks. Moreover, because network representations of global brain activity are derived from measures that have a continuous response (i.e., interregional BOLD signals), it is methodologically complex to characterize the architecture of functional networks using traditional graph-based approaches. In the present study, we investigate the relationship between standard network metrics computed from dyadic interactions in a functional network, and a metric defined on the persistence homological scaffold of the network, which is a summary of the persistent homology structure of resting-state fMRI data. The persistence homological scaffold is a summary network that differs in important ways from the standard network representations of functional neuroimaging data: (i) it is constructed using the information from all edge weights comprised in the original network without applying an ad hoc threshold and (ii) as a summary of persistent homology, it considers the contributions of simplicial structures to the network organization rather than dyadic edge-vertices interactions. We investigated the information domain captured by the persistence homological scaffold by computing the strength of each node in the scaffold and comparing it to local graph metrics traditionally employed in neuroimaging studies. We conclude that the persistence scaffold enables the identification of network elements that may support the functional integration of information across distributed brain networks.

Abnormal frontostriatal connectivity in adolescent-onset schizophrenia and its relationship to cognitive functioning

BACKGROUND

Adolescent-onset schizophrenia (AOS) is associated with cognitive impairment and poor clinical outcome. Cognitive dysfunction is hypothesised, in part, to reflect functional dysconnectivity between the frontal cortex and the striatum, although structural abnormalities consistent with this hypothesis have not yet been demonstrated in adolescence.

OBJECTIVE

To characterise frontostriatal white matter (WM) tracts in relation to cognition in AOS.

DESIGN

A MRI volumetric and diffusion tensor imaging study.

PARTICIPANTS

Thirty-seven AOS subjects and 24 age and sex-matched healthy subjects.

OUTCOME MEASURES

Using probabilistic tractography, cortical regions with the highest connection probability for each striatal voxel were determined, and correlated with IQ and specific cognitive functions after co-varying for age and sex. Fractional anisotropy (FA) from individual tracts was a secondary measure.

RESULTS

Bayesian Structural Equation modeling of FA from 12 frontostriatal tracts showed processing speed to be an intermediary variable for cognition. AOS patients demonstrated generalised cognitive impairment with specific deficits in verbal learning and memory and in processing speed after correction for IQ. Dorsolateral prefrontal cortex connectivity with the striatum correlated positively with these measures and with IQ. DTI voxel-wise comparisons showed lower connectivity between striatum and the motor and lateral orbitofrontal cortices bilaterally, the left amygdalohippocampal complex, right anterior cingulate cortex, left medial orbitofrontal cortex and right dorsolateral prefrontal cortex.

CONCLUSIONS

Frontostriatal dysconnectivity in large WM tracts that can explain core cognitive deficits are evident during adolescence. Processing speed, which is affected by alterations in WM connectivity, appears an intermediary variable in the cognitive deficits seen in schizophrenia.

Tractography Study of Deep Brain Stimulation of the Anterior Cingulate Cortex in Chronic Pain: Key to Improve the Targeting

BACKGROUND

Deep brain stimulation (DBS) of the anterior cingulate cortex (ACC) is a new treatment for alleviating intractable neuropathic pain. However, it fails to help some patients. The large size of the ACC and the intersubject variability make it difficult to determine the optimal site to position DBS electrodes. The aim of this work was therefore to compare the ACC connectivity of patients with successful versus unsuccessful DBS outcomes to help guide future electrode placement.

METHODS

Diffusion magnetic resonance imaging (dMRI) and probabilistic tractography were performed preoperatively in 8 chronic pain patients (age 53.4 ± 6.1 years, 2 females) with ACC DBS, of whom 6 had successful (SO) and 2 unsuccessful outcomes (UOs) during a period of trialing.

RESULTS

The number of patients was too small to demonstrate any statistically significant differences. Nevertheless, we observed differences between patients with successful and unsuccessful outcomes in the fiber tract projections emanating from the volume of activated tissue around the electrodes. A strong connectivity to the precuneus area seems to predict unsuccessful outcomes in our patients (UO: 160n/SO: 27n), with (n), the number of streamlines per nonzero voxel. On the other hand, connectivity to the thalamus and brainstem through the medial forebrain bundle (MFB) was only observed in SO patients.

CONCLUSIONS

These findings could help improve presurgical planning by optimizing electrode placement, to selectively target the tracts that help to relieve patients' pain and to avoid those leading to unwanted effects.

Structural connectivity in schizophrenia and its impact on the dynamics of spontaneous functional networks

The neuropathology of schizophrenia remains unclear. Some insight has come from modern neuroimaging techniques, which offer an unparalleled opportunity to explore in vivo the structure and function of the brain. Using functional magnetic resonance imaging, it has been found that the large-scale resting-state functional connectivity (rsFC) in schizophrenia--measured as the temporal correlations of the blood-oxygen-level-dependent (BOLD) signal--exhibit altered network topology, with lower small-world index. The origin of these rsFC alterations and link with the underlying structural connectivity remain unclear. In this work, we used a computational model of spontaneous large-scale brain activity to explore the role of the structural connectivity in the large-scale dynamics of the brain in health and schizophrenia. The structural connectomes from 15 adolescent patients with early-onset schizophrenia and 15 age- and gender-matched controls were built from diffusion tensor imaging data to detect the white matter tracts between 90 brain areas. Brain areas, simulated using a reduced dynamic mean-field model, receive excitatory input from other areas in proportion to the number of fibre tracts between them. The simulated mean field activity was transformed into BOLD signal, and the properties of the simulated functional networks were analyzed. Our results suggest that the functional alterations observed in schizophrenia are not directly linked to alterations in the structural topology. Instead, subtly randomized and less small-world functional networks appear when the brain operates with lower global coupling, which shifts the dynamics from the optimal healthy regime.

A comparative assessment of heavy metal accumulation in soft parts and byssus of mussels from subarctic, temperate, subtropical and tropical marine environments

Existing data on metal concentrations in mussels from subarctic, temperate, subtropical and tropical waters were analyzed using multivariate statistics in order to assess regional variations in metal contamination. Potential errors were reduced by only analyzing data from surveys that employed the same protocols, analytical methodologies and analysts. Factor analysis demonstrated that mussels inhabiting extremely contaminated areas (e.g. from Japanese and Swedish metallurgy sources) could be separated from mussels from other contaminated areas, and that metals such as Cd, Pb, Cu and Zn could be used to identify heavily contaminated samples while Co, Fe, Cr and Ni concentrations were good markers for exposure to inputs from different industrial sources. Furthermore byssus, like soft tissue, selectively and sensitively reflects variations of certain metal concentrations in ambient waters and thus serves as a reliable biomonitor for these contaminants in a variety of coastal and estuarine areas.

Considerations about TENORM: a study case on niobium facilities

Two niobium mining facilities located at two different geological settings were selected as case studies for assessing the radiological impacts associated with mining and milling activities. The impacts were assessed both for operational and post-operational (future unrestricted use of the area) scenarios. The work methodology encompassed sampling and analysis of different materials along the operational process, including wastes, effluents and by-products, mass balance calculations, and dose assessment. The exposure scenario considered during the operational phase included the land use by hypothetical groups of members of the general public. In the case of post-operational phase the possible occupation of contaminated areas was considered. The results pointed out that during the operational phase of the investigated industries no relevant impacts could be attributed to them. However, in the case of the potential occupation of the contaminated areas where the wastes are being deposited, the unrestricted use of these areas cannot be accepted in terms of the relevant radiation protection requirements.

Radon dynamics and reduction in an underground mine in Brazil. Implications for workers' exposure

This work was aimed at studying the behaviour of 222Rn in an experimental underground copper mine in Brazil with a single entrance. The 222Rn concentrations, meaured by using a dynamic radon measuring technique. varied between 30.5 Bq.m(-3), during ventilated conditions applied to the mine galleries, and 19.4 x 10(3) Bq.(-3) for non-ventilated conditions and when operational mining activities were conducted inside. High radon concentration surges were observed after blasting and drilling activities. In the cases of inadequate ventilation, it was estimated that workers could be subjected to exposures as high as 10 microSv.h(-1), only due to 222Rn and its short-lived progeny. The results show the importance of real-time measurements to evaluate radon dynamics during mining operations.

Environmental radiological impact associated with non-uranium mining industries: a proposal for screening criteria

Niobium, phosphate, coal and gold mining facilities have been selected as case studies with the aim of identifying possible sources of radiological impact during and after cessation of industrial operations. The results have shown that acid drainage, as well as chemical processing of mineral ores, constitute relevant impact indicators for present-day and future scenarios. The possible use of solid wastes abandoned at the end of the operations represents a long-term radiological concern. Therefore, it is necessary that Brazilian legislation for environmental licensing be revised taking into account the potential environmental and radiological impacts caused by these industries and establishing remedial procedures for waste storage areas in the existing sites. The indicators developed and procedures carried out can be used in screening for decisions on the adoption of regulatory requirements for practices at such types of installations.

Changes in cerebral blood flow as measured by HMPAO SPECT in patients following spontaneous intracerebral haemorrhage

Lack of an effective treatment for spontaneous intracerebral haemorrhage (ICH) is partly because the mechanism of neuronal damage in ICH is not fully understood. Animal experiments have shown that there is a zone of ischaemia and oedema around the haematoma which can be reduced by early evacuation of the mass lesion. We set out to study Cerebral Blood Flow (CBF) changes in patients with ICH. We present data on 13 patients (mean age 60). SPECT scans were performed within 48 hours of ictus and 4-7 days later. Four patients had surgical evacuation of the clot; 9 were managed conservatively. The ratio of uptake of the isotope in the cerebral hemisphere containing the haematoma to the isotope uptake in the contra-lateral (un-affected) cerebral hemisphere was taken as an index of perfusion of the affected cerebral hemisphere. The perfusion index of the affected hemisphere improved between the first and the second scans in all the surgically treated patients; in the conservatively managed group, it was worse in 6 patients, the same in 1 and very slightly better in 2. There was an overall mean improvement of 3.87% in the surgical group, and an overall mean deterioration of 3.61% in the medical group. This data suggests that surgical evacuation of the clot may improve perfusion in the ipsilateral cerebral hemisphere in ICH. It underlines the importance of a prospective randomised trial to assess the value of surgery in patients with ICH. The Surgical Trial in Intracerebral Haemorrhage (STICH) is currently underway worldwide. We also describe the application of Difference Based Region Growing (DBRG) to SPECT image analysis. This method overcomes the difficulties posed by 1) the presence of a mass lesion and 2) surgical evacuation of haematoma.

Continuous monitoring of ICP and CPP following ICH and its relationship to clinical, radiological and surgical parameters

Sixty-two patients with a spontaneous supratentorial haemorrhage had continuous Intracranial Pressure (ICP) and Cerebral Perfusion Pressure (CPP) monitoring. In addition to the recordings of physiological data their past medical history, presenting neurological state, Computed Tomograph (CT) findings, daily Glasgow Coma Score (GCS) and outcome were noted. The mean age was 57.6 years (sd 13.3). Onset of recording, after ictus was at a mean of 32.6 hours (sd 26.0). Average length of recording was 62.0 hours (sd 39.8). Thirty-one patients had evacuation of haematoma, 6 insertion of External Ventricular Drain (EVD). Preoperative measures of ICP were significantly related to delayed neurological deterioration, death within three days and Glasgow Outcome Scale (GOS) at neurosurgical discharge. No such relationships existed with preoperative measures of CPP and neither ICP nor CPP was related to outcome at 6 months. Post-operative measures of both ICP and CPP demonstrated a significant relationship with death within three days of ictus and GOS at neurosurgical discharge. Again no relationship existed with these parameters and outcome at six months. Surgical evacuation of haematoma acted to significantly reduce ICP and improve CPP. Given that these factors seem to be related to deterioration, death and early outcome, it would seem that surgery could play a role in reducing mortality and improving outcome following Intra cerebral Haemorrhage (ICH).

Assessment of acid rock drainage pollutants release in the uranium mining site of Poços de Caldas--Brazil

We compared three different techniques to assess acid drainage occurrence connected to pyritic waste rock piles at a uranium mining and milling site in Poços de Caldas--Brazil: (1) mass balance calculations, (2) column leaching experiments and (3) geochemical modelling. The study site was chosen because all the drainage coming from the pile is collected in one holding pond and a huge database (monitoring program) was available. The three independent methods predicted similar values for the intrinsic oxidation rate (IOR) (about 10(-9) kg m-3 s-1). We estimate the total time for consumption of all oxidizable material in the dump to be greater than 500 years. Geochemical model results showed a good agreement between predicted sulphate concentrations in relation to those found in the waste pile drainage, although the Al values were overestimated and pH values were underestimated.

Surgery in intracerebral hemorrhage. The uncertainty continues

BACKGROUND AND PURPOSE

Primary intracerebral hemorrhage (ICH) accounts for 10% to 20% of stroke but carries the highest rates of mortality and morbidity of all stroke subtypes. Current treatment, however, is varied and haphazard. The most recent Cochrane systematic review refers to 4 prospective, randomized controlled trials. We present a further meta-analysis to include 3 new trials. In addition, we review the trials of Chen et al and McKissock et al and discuss aspects of their quality that, we believe, prevent their inclusion in modern day meta-analysis.

METHODS

Literature databases and articles were searched from 1966 to October 1999. Using the end points of death and dependency, the results of the 7 identified randomized trials were expressed as odds ratios. All available data were then analyzed with meta-analysis techniques. Analysis of relevant subsets of trials was also carried out.

RESULTS

Meta-analysis of all 7 trials shows a trend toward a higher chance of death and dependency after surgery (OR 1.20; 95% CI 0.83 to 1.74). Meta-analysis was also carried out after exclusion of the Chen and McKissock trials for reasons discussed in the text. This meta-analysis suggests a benefit from surgery, with a reduction in the chances of death and dependency after surgical treatment by a factor of 0.63 (OR 0.63; 95% CI 0.35 to 1.14).

CONCLUSIONS

When meta-analysis is restricted to modern-day, post-CT, well-constructed, balanced trials, a trend for surgery to reduce the chances of death and dependency is found. Perhaps, then, in the modern era of CT, good neuroanesthesia, intensive care, and the operating microscope, surgery has a role in the treatment of supratentorial intracerebral hemorrhage. The results of a large, multicenter, randomized controlled trial are urgently needed, and the ongoing International Surgical Trial of Intracerebral Hemorrhage should fulfill this objective.

Spontaneous intracerebral haemorrhage: a surgical dilemma

The optimal management, surgical or otherwise, of a patient following a spontaneous intracerebral haemorrhage (ICH) remains controversial. A survey of British neurosurgeons was carried out to assess current attitudes and practice. Patient management was most consistently influenced by the depth (71% agreement), dominance (74.3% agreement) and site (44.7%) of the haematoma. Almost half of neurosurgeons said they would evacuate an ICH in a deteriorating patient, but management choice was very varied in stable patients. However, 80% of the same respondents felt evacuation was helpful in reducing mortality, and 71.3% morbidity. Fifteen per cent of respondents were not influenced by the size of an ICH, but 31% would readily operate on haematomas with volumes of between 50 and 80 ml. Over 30% felt that there was no optimal time for surgical evacuation, but 66.9% felt delayed evacuation was helpful. Premorbid dependency was a stronger influence than age on management choice. Despite these variations, over half felt that they were consistent in their treatment of ICH. However, 81% expressed surgical uncertainty. Furthermore, respondents demonstrated a significant tendency to intervene surgically more readily in ICH related to aneurysm or AVM. Results from a prospective randomized controlled trial to assess the role of surgery are urgently needed.

Clinical evaluation of the Codman microsensor intracranial pressure monitoring system

INTRODUCTION

The use of the Camino fibre-optic subdural device for measuring Intracranial Pressure (ICP) in patients, has been shown to correlate well with recordings from the "gold standard" intraventricular fluid filled catheter [1]. Following this work, its use has become standard in the clinical monitoring of patients. More recently, laboratory studies have demonstrated accuracy, acceptable drift and high fidelity for the new Codman Microsensor ICP Transducer, a miniature strain gauge mounted on a flexible nylon catheter [3]. Its performance in patients, however, has yet to be fully assessed, in comparative studies.

METHODS

Eight patients (5 head injured, 3 with an Intracerebral haematoma) had a Codman Microsensor inserted. A Camino Transducer was fitted immediately adjacent to it. A computerised system was used to continuously record both ICP readings.

RESULTS

In total 140,323 recordings were made over a wide range of ICP values. Study periods ranged from 0.5 to 116 hours. In one patient the Codman transducer tracing failed after several days, probably due to fracture of electrical cable close to the interface box. The readings from the two ICP transducers were compared on Time Series, logistic regression and Altman-Bland plots. Drift of the ICP recorded by the Codman microsensor, was noted in 2 patients, 1 in positive direction (maximum 30 mmHg), 1 negative (max. 20 mmHg). In both cases the Camino ICP recording was relatively stable. In 24% of the recordings the Codman microsensor recorded ICP as 5 or more mmHg greater than the Camino, this difference was 10 mmHg or greater in 9% of recordings. Conversely the Camino recording was 5 mmHg or more, than the Codman, in 5% of all recordings, and 10 mmHg or more in 3%.

CONCLUSION

These differences could in the majority of cases (excepting the negative drift) be explained by a constant offset of the Codman transducer, as described previously [6]. Further examination of this device is required.

Heavy metal distribution in sediments and ecological risk assessment: The role of diagenetic processes in reducing metal toxicity in bottom sediments

This paper describes the heavy metal distributions in river and lagoonal sediments of Jacarepaguá Basin, Rio de Janeiro, Brazil. The occurrence of metal phase translocation from the reducible to the oxidizable was observed for Fe, Mn and Ni, from the fluvial environment to the lagoonal. Cu was mainly associated with the oxidizable phase while Zn and Pb were mainly associated with the reducible phase in both environments. It has been demonstrated that metal sulfide formation and complexation by organic complexes are very important aspects in terms of toxicity reduction. By means of a risk assessment methodology, based on available sediment data, it was demonstrated that the lagoonal system is exposed to a low potential ecological risk and that Zn was the metal of greater concern with respect to the system pollution.

Anterior cervical discectomy: an improvement in donor site operative technique

Bone graft harvest from the iliac crest for anterior cervical discectomy is common surgical practice. Its rate of complication remains far higher than that of the cervical operation. We describe a method of harvest that we believe reduces post-operative complications and pain, facilitating early patient mobilization and discharge.

Heavy-metal pollution assessment in the coastal lagoons of Jacarepaguá, Rio de Janeiro, Brazil

The Jacarepaguá lagoon receives the waste from 239 industries and domestic sewage. Bottom sediment analysis revealed that metal pollution is not spread over the lagoons but restricted to the discharge areas of the main metal-carrier rivers. Metal concentrations in superficial water showed the following concentrations values in ng/ml: Zn, 9.63+/-3.59; Pb, 0.61+/-0.43; Cu, 0.94+/-0.45; Mn, 12.7+/-8.0. Metal concentration in fish (average of seven different species) presented the following results, in mg/kg wet weight: Cr, 0.08+/-0.01; Cu, 0.4+/-0.15; Zn, 4.6+/-3.4; Fe, 2.4+/-1.3; Mn, 0.4+/-0.3. These results imply, considering fish consumption rate and the RfD (USEPA Reference Dose), that the local population is not exposed to undue health risks. Metal concentrations in the water may, however, increase due to their dissolution induced by pH and redox changes in the sediments.