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At least 19 recordsLinked to original sources

[Neuroanatomical study of the internal structures of the brain based on brain fiber dissection].

From the beginning of the 17th Century, anatomists started to elucidate numerous tracts and fasciculi of the brain using fiber dissection techniques. Due to the complexities associated with tissue preparation and the time-consuming nature of traditional techniques the popularity of this method has gradually declined with the advent of modern neuroimaging techniques such as MRI. Many novel approaches to deep brain lesions have recently been devised following the development of skull base surgery. In comparison, the study of functional neuroanatomy has been relatively neglected. Understanding how neuronal fibers in the brain interconnect and communicate neuronal functions is critical when performing surgery for malignant glioma and epilepsy, as brain parenchyma has to be resected and neuronal fibers are interrupted. In the preoperative planning process we have applied anatomical studies using brain fiber dissection techniques. Brain fiber dissection offers the advantage of exposing association, commissural and projection fibers of cerebral white matter in three dimensions. Brain fiber dissection appears useful for assisting neurosurgeons to acquire neurosurgical skills and become familiar with neuroanatomical features. The techniques and significance of brain fiber dissection are described herein.

Brain↗

Machine psychology: autonomous behavior, perceptual categorization and conditioning in a brain-based device.

In studying brain activity during the behavior of living animals, it is not possible simultaneously to analyze all levels of control from molecular events to motor responses. To provide insights into how levels of control interact, we have carried out synthetic neural modeling using a brain-based real-world device. We describe here the design and performance of such a device, designated Darwin VII, which is guided by computer-simulated analogues of cortical and subcortical structures. All levels of Darwin VII's neural architecture can be examined simultaneously as the device behaves in a real environment. Analysis of its neural activity during perceptual categorization and conditioned behavior suggests neural mechanisms for invariant object recognition, experience-dependent perceptual categorization, first-order and second-order conditioning, and the effects of different learning rates on responses to appetitive and aversive events. While individual Darwin VII exemplars developed similar categorical responses that depended on exploration of the environment and sensorimotor adaptation, each showed highly individual patterns of changes in synaptic strengths. By allowing exhaustive analysis and manipulation of neuroanatomy and large-scale neural dynamics, such brain-based devices provide valuable heuristics for understanding cortical interactions. These devices also provide the groundwork for the development of intelligent machines that follow neurobiological rather than computational principles in their construction.

Animals↗

MRI-based brain volumetrics: emergence of a developmental brain science.

MRI-based brain volumetrics is an established methodology of great versatility and reliability with a broad range of potential applications in medicine and basic human brain science. We consider here, more theoretical implications of brain tissue volumes. Specifically, we suggest that volume is an evolutionarily and developmentally regulated fundamental property of tissue, in this instance the brain and its component structures. Within this framework (1), regularities in relative variation of volumes with respect to mean volume of a structure are viewed as systematic manifestations of the rules of histogenetic process (2), regularities in the relative strength of correlation of volumes of structures are suggested to reflect constraints which serve systematically the requirements of neural systems operation. These hypotheses, if supported by extensive observation, may guide the design of applications of MRI based volumetric analysis of the human brain.

Animals↗

Impact of endocrine manipulations on brain-based rat growth hormone.

Our laboratory has previously described the widespread distribution of an immunoreactive and bioactive rat growth hormone (rGH)-like protein in rat brain. It has also been demonstrated that regulation of pituitary rGH secretion is at least partly mediated by a short-loop negative feedback system. In such a system, increased levels of rGH, acting at a suprapituitary locus, would decrease pituitary GH secretion. Thus, the present study has dealt with attempts to further investigate the hypothesis that one function of brain-based rGH might be as a mediator of the short-loop negative feedback system controlling pituitary rGH release. If brain-based rGH were to function as a mediator of such a system, then in situations where serum rGH levels are decreased, brain rGH concentrations should increase, indicating activation of a negative feedback loop. In the present communication we report that significantly decreased serum GH levels in oophorectomized and in thyroidectomized rats were coupled with a significant increase in rGH concentrations in the hypothalamus and in the amygdala. By contrast, adrenalectomy, which was not associated with any changes in levels of GH in serum caused no perturbations in levels of rGH in the brain. These discordant changes in serum and brain-based rGH are findings compatible with the hypothesis that one function of brain-based rGH is as a mediator of the short-loop negative feedback system regulating the release of pituitary GH.

Adrenal Cortex Hormones↗

Automated histogram-based brain segmentation in T1-weighted three-dimensional magnetic resonance head images.

Current semiautomated magnetic resonance (MR)-based brain segmentation and volume measurement methods are complex and not sufficiently accurate for certain applications. We have developed a simpler, more accurate automated algorithm for whole-brain segmentation and volume measurement in T(1)-weighted, three-dimensional MR images. This histogram-based brain segmentation (HBRS) algorithm is based on histograms and simple morphological operations. The algorithm's three steps are foreground/background thresholding, disconnection of brain from skull, and removal of residue fragments (sinus, cerebrospinal fluid, dura, and marrow). Brain volume was measured by counting the number of brain voxels. Accuracy was determined by applying HBRS to both simulated and real MR data. Comparing the brain volume rendered by HBRS with the volume on which the simulation is based, the average error was 1.38%. By applying HBRS to 20 normal MR data sets downloaded from the Internet Brain Segmentation Repository and comparing them with expert segmented data, the average Jaccard similarity was 0.963 and the kappa index was 0.981. The reproducibility of brain volume measurements was assessed by comparing data from two sessions (four total data sets) with human volunteers. Intrasession variability of brain volumes for sessions 1 and 2 was 0.55 +/- 0.56 and 0.74 +/- 0.56%, respectively; the mean difference between the two sessions was 0.60 +/- 0.46%. These results show that the HBRS algorithm is a simple, fast, and accurate method to determine brain volume with high reproducibility. This algorithm may be applied to various research and clinical investigations in which brain segmentation and volume measurement involving MRI data are needed.

Adult↗

An organizational perspective on goal setting in community-based brain injury rehabilitation.

PURPOSE: To use a taxonomy of goal content, developed in community-based brain injury rehabilitation to examine and compare the content of goals set within two different service settings; and to further examine the potential of the taxonomy to be a reliable and comprehensive framework for classifying goals. METHOD: Qualitative analysis and categorization of 1492 goal statements extracted from a community-based brain injury rehabilitation service over two time periods (1996--97, 1998--99), and cross-organizational comparison of ratings of goal classifications using a random sample of 100 goal statements drawn from this data set and the original 1765 goal statements used in developing the taxonomy. RESULTS: Application of the taxonomy beyond the original service setting in which it was developed indicated a strong inter-rater reliability, with a high test-retest agreement reported over time. For both services, a small number of categories accounted for a substantial proportion of goals set within the two time periods, while considerable change was evident in goals between the two periods for one service. Further, both placed emphasis on individually focused goals rather than relationship or family-related goals. CONCLUSION: The taxonomy provides a reliable means for classifying goals and is a useful tool for exploration of the multiple influences on goal setting. Further application of the taxonomy to examine the relative influence on goal setting of client factors versus a range of organizational factors would be beneficial.

Activities of Daily Living↗

Cortical change in Alzheimer's disease detected with a disease-specific population-based brain atlas.

We report the first detailed population-based maps of cortical gray matter loss in Alzheimer's disease (AD), revealing prominent features of early structural change. New computational approaches were used to: (i) distinguish variations in gray matter distribution from variations in gyral patterns; (ii) encode these variations in a brain atlas (n = 46); (iii) create detailed maps localizing gray matter differences across groups. High resolution 3D magnetic resonance imaging (MRI) volumes were acquired from 26 subjects with mild to moderate AD (age 75.8+/-1.7 years, MMSE score 20.0+/-0.9) and 20 normal elderly controls (72.4+/-1.3 years) matched for age, sex, handedness and educational level. Image data were aligned into a standardized coordinate space specifically developed for an elderly population. Eighty-four anatomical models per brain, based on parametric surface meshes, were created for all 46 subjects. Structures modeled included: cortical surfaces, all major superficial and deep cortical sulci, callosal and hippocampal surfaces, 14 ventricular regions and 36 gyral boundaries. An elastic warping approach, driven by anatomical features, was then used to measure gyral pattern variations. Measures of gray matter distribution were made in corresponding regions of cortex across all 46 subjects. Statistical variations in cortical patterning, asymmetry, gray matter distribution and average gray matter loss were then encoded locally across the cortex. Maps of group differences were generated. Average maps revealed complex profiles of gray matter loss in disease. Greatest deficits (20-30% loss, P<0.001-0.0001) were mapped in the temporo-parietal cortices. The sensorimotor and occipital cortices were comparatively spared (0-5% loss, P>0.05). Gray matter loss was greater in the left hemisphere, with different patterns in the heteromodal and idiotypic cortex. Gyral pattern variability also differed in cortical regions appearing at different embryonic phases. 3D mapping revealed profiles of structural deficits consistent with the cognitive, metabolic and histological changes in early AD. These deficits can therefore be (i) charted in a living population and (ii) compared across individuals and groups, facilitating longitudinal, genetic and interventional studies of dementia.

Aged↗

Characterizing functional hippocampal pathways in a brain-based device as it solves a spatial memory task.

Analyzing neural dynamics underlying complex behavior is a major challenge in systems neurobiology. To meet this challenge through computational neuroscience, we have constructed a brain-based device (Darwin X) that interacts with a real environment, and whose behavior is guided by a simulated nervous system incorporating detailed aspects of the anatomy and physiology of the hippocampus and its surrounding regions. Darwin X integrates cues from its environment to solve a spatial memory task. Place-specific units, similar to place cells in the rodent, emerged by integrating visual and self-movement cues during exploration without prior assumptions in the model about environmental inputs. Because synthetic neural modeling using brain-based devices allows recording from all elements of the simulated nervous system during behavior, we were able to identify different functional hippocampal pathways. We did this by tracing back from reference neuronal units in the CA1 region of the simulated hippocampus to all of the synaptically connected units that were coactive during a particular exploratory behavior. Our analysis identified a number of different functional pathways within the simulated hippocampus that incorporate either the perforant path or the trisynaptic loop. Place fields, which were activated by the trisynaptic circuit, tended to be more selective and informative. However, place units that were activated by the perforant path were prevalent in the model and were crucial for generating appropriate exploratory behavior. Thus, in the model, different functional pathways influence place field activity and, hence, behavior during navigation.

Animals↗

Automatic morphology-based brain segmentation (MBRASE) from MRI-T1 data.

A method called morphology-based brain segmentation (MBRASE) has been developed for fully automatic segmentation of the brain from T1-weighted MR image data. The starting point is a supervised segmentation technique, which has proven highly effective and accurate for quantitation and visualization purposes. The proposed method automates the required user interaction, i.e., defining a seed point and a threshold range, and is based on the simple operations thresholding, erosion, and geodesic dilation. The thresholds are detected in a region growing process and are defined by connections of the brain to other tissues. The method is first evaluated on three computer simulated datasets by comparing the automated segmentations with the original distributions. The second evaluation is done on a total of 30 patient datasets, by comparing the automated segmentations with supervised segmentations carried out by a neuroanatomy expert. The comparison between two binary segmentations is performed both quantitatively and qualitatively. The automated segmentations are found to be accurate and robust. Consequently, the proposed method can be used as a default segmentation for quantitation and visualization of the human brain from T1-weighted MR images in routine clinical procedures.

Adolescent↗

Selection of electrode positions for an EEG-based brain computer interface (BCI).

One major question in designing an EEG-based Brain Computer Interface to bypass the normal motor pathways is the selection of proper electrode positions. This study investigates electrode selection with a Distinction Sensitive Learning Vector Quantizer (DSLVQ). DSLVQ is an extended Learning Vector Quantizer (LVQ) which employs a weighted distance function for dynamical scaling and feature selection. The data analysed and classified were 56-channel EEG recordings over sensorimotor areas during preparation for discrete left or right index finger flexions. Data from 3 subjects are reported. It was found by DSLVQ that the most important electrode positions for differentiation between planning of left and right finger movement overlie cortical finger/hand areas over both hemispheres.

Adult↗

The need for specialists in biologically-based brain diseases.

Because neuroscience research has documented that mental illnesses are biologically-based brain diseases, our country should start training programs to create BBBD specialists. The National Alliance for the Mentally Ill has proposed a 2-track training system for psychiatric professionals--(1) A BBBD track and (2) a "mental health" track.

Biological Psychiatry↗

Brain-based devices for the study of nervous systems and the development of intelligent machines.

The simultaneous study of brain function at all levels of organization is difficult to undertake with current experimental tools. Present day electrophysiology only allows the recording of at most hundreds of neurons while an animal is performing a behavioral task. Because of this limitation and the sheer complexity of the nervous system, computational modeling has become essential in developing theories of brain function. Accordingly, our group has constructed a series of brain-based devices (BBDs), that is, physical devices with simulated nervous systems that guide behavior, to serve as a heuristic for testing theories of brain function. Unlike animal models, BBDs permit analysis of activity at all levels of the nervous system as the device behaves in its environment. Although the principal focus of developing BBDs has been to test theories of brain function, this type of modeling may also provide a basis for robotic design and practical applications.

Artificial Intelligence↗

A systematic study of brain base arteries in the wild boar (Sus scrofa scrofa).

This study aimed at describing and systematizing the arteries of the base of the brain of the wild boar (Sus scrofa scrofa). Thirty-three heads were used, of which 30 were injected with latex, and three with acrylic dental resin through the common carotid arteries. The brain carotid artery arose from the rostral epidural rete mirabile, and divided into a rostral and a caudal branch. The rostral branch gave off the middle cerebral artery and then continued as rostral cerebral artery. The latter branched into lateral rhinal, internal ethmoidal and medial rhinal arteries. The rostral cerebral artery joined its contralateral homologue, becoming the single rostral inter-hemispheric artery. The caudal branch emitted the caudal cerebral artery and the tectal arteries, and then fused with the branch of the opposite antimere, joining the basilar artery. The rostral cerebellar arteries derived from this point. The basilar artery originated from the anastomosis between the arteries derived from the caudal epidural rete mirabile of each antimere. The basilar artery extended rostrally, giving off as main collateral branch the caudal cerebellar artery. The basilar artery presented a significant decrease in diameter before joining the caudal branches of the brain carotid arteries. The cerebral arterial circle was rostrally and caudally closed.

Animals↗

EEG-based brain computer interface (BCI). Search for optimal electrode positions and frequency components.

Several laboratories around the world have recently started to investigate EEG-based brain computer interface (BCI) systems in order to create a new communication channel for subjects with severe motor impairments. The present paper describes an initial evaluation of 64-channel EEG data recorded while subjects used one EEG channel over the left sensorimotor area to control on-line vertical cursor movement. Targets were given at the top or bottom of a computer screen. Data from 3 subjects in the early stages of training were analyzed by calculating band power time courses and maps for top and bottom targets separately. In addition, the Distinction Sensitive Learning Vector Quantizer (DSLVQ) was applied to single-trial EEG data. It was found that for each subject there exist optimal electrode positions and frequency components for on-line EEG-based cursor control.

Adult↗

Tryptophan hydroxylase activity in rat brain base arteries related to innervation originating from the dorsal raphe nucleus.

BACKGROUND AND PURPOSE: Tryptophan hydroxylase activity was assayed in cell-free extracts of rat brain base arteries as marker of a serotonergic innervation. METHODS: Estimation of the enzymatic activity was made in untreated male Sprague-Dawley rats (n = 53) and in those who underwent destruction of the dorsal and median raphe nuclei (n = 10). RESULTS: Tryptophan hydroxylase activity was measured in rat cerebral arteries. The time-dependent 5-hydroxytryptophan production was undetectable in the absence of tryptophan or 6-methyltetrahydropterine and in the presence of 6-fluorotryptophan, and it was significantly reduced in the presence of p-chlorophenylalanine. Destruction of the dorsal raphe nucleus but not the median raphe nucleus brought about a significant reduction in enzyme activity. CONCLUSIONS: These results suggest that rat cerebral arteries receive a serotonergic innervation arising from the dorsal raphe nucleus.

Animals↗

Evolutionary game theory in an agent-based brain tumor model: exploring the 'Genotype-Phenotype' link.

To investigate the genotype-phenotype link in a polyclonal cancer cell population, here we introduce evolutionary game theory into our previously developed agent-based brain tumor model. We model the heterogeneous cell population as a mixture of two distinct genotypes: the more proliferative Type A and the more migratory Type B. Our agent-based simulations reveal a phase transition in the tumor's velocity of spatial expansion linking the tumor fitness to genotypic composition. Specifically, velocity initially falls as rising payoffs reward the interactions among the more stationary Type A cells, but unexpectedly accelerates again when these A-A payoffs increase even further. At this latter accelerating stage, fewer migratory Type B cells appear to confer a competitive advantage in terms of the tumor's spatial aggression over the overall numerically dominating Type A cells, which in turn leads to an acceleration of the overall tumor dynamics while its surface roughness declines. We discuss potential implications of our findings for cancer research.

Brain Neoplasms↗

Cervical gangliectomy does not affect in vitro tryptophan hydroxylase activity in rat brain base arteries.

The presence of a serotonergic innervation in rat cerebral arteries of peripheral origin was explored. Superior cervical ganglia removal did not change tryptophan hydroxylase activity measured in cell-free extracts of brain base vessels. A low enzyme activity was detected in the ganglia. These results suggest that rat cerebral arteries do not receive a serotonergic innervation from the superior cervical ganglia.

Animals↗

Spatial navigation and causal analysis in a brain-based device modeling cortical-hippocampal interactions.

We describe Darwin X, a physical device that interacts with a real environment, whose behavior is guided by a simulated nervous system incorporating aspects of the detailed anatomy and physiology of the hippocampus and its surrounding regions. This brain-based device integrates cues from its environment and solves a spatial memory task. The responses of simulated neuronal units in the hippocampal areas during its exploratory behavior are comparable to place cells in the rodent hippocampus and emerged by associating sensory cues during exploration. To identify different functional hippocampal pathways and their influence on behavior, we employed a time series analysis that distinguishes causal interactions within and between simulated hippocampal and neocortical regions while the device is engaged in a spatial memory task. Our analysis identified different functional pathways within the neural simulation and prompts novel predictions about the influence of the perforant path, the trisynaptic loop and hippocampal-cortical interactions on place cell activity and behavior during navigation. Moreover, this causal time series analysis may be useful in analyzing networks in general.

Animals↗