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At least 37 records · Page 2Linked to original sources
PubMed2004

Visual binding through reentrant connectivity and dynamic synchronization in a brain-based device.

Effective visual object recognition requires mechanisms to bind object features (e.g. color, shape and motion) while distinguishing distinct objects. Synchronously active neuronal circuits among reentrantly connected cortical areas may provide a basis for visual binding. To assess the potential of this mechanism, we have constructed a mobile brain-based device, Darwin VIII, which is guided by simulated analogues of cortical and sub-cortical areas required for visual processing, decision-making, reward and motor responses. These simulated areas are reentrantly connected and each area contains neuronal units representing both the mean activity level and the relative timing of the activity of groups of neurons. Darwin VIII learns to discriminate among multiple objects with shared visual features and associates 'target' objects with innately preferred auditory cues. We observed the co-activation of globally distributed neuronal circuits that corresponded to distinct objects in Darwin VIII's visual field. These circuits, which are constrained by a reentrant neuroanatomy and modulated by behavior and synaptic plasticity, are necessary for successful discrimination. By situating Darwin VIII in a rich real-world environment involving continual changes in the size and location of visual stimuli due to self-generated movement, and by recording its behavioral and neuronal responses in detail, we were able to show that reentrant connectivity and dynamic synchronization provide an effective mechanism for binding the features of visual objects.

Acoustic Stimulation↗
PubMed1997

Diagnosis of Alzheimer's disease in a community hospital-based brain bank program.

Several studies in recent years have addressed the accuracy of the clinical diagnosis of Alzheimer's disease (AD). However, most large studies have been done in university centers specializing in dementia. The purpose of this study was to assess the diagnostic accuracy of dementia in a community-based brain bank program, using data from the Central Florida component of the State of Florida's Brain Bank Program. Since 1987, 261 cases of dementia have been assessed at antopsy, and the clinical and pathologic diagnoses were compared. Of 234 patients with a clinical diagnosis of AD, 181 (77%) had a pathologic diagnosis of AD, with or without other contributing disorders. Of 27 patients with a clinical diagnosis of non-AD dementia, 14 (52%) had a pathologic diagnosis of AD, with or without other contributing diagnoses. These findings are similar to those previously reported and emphasize the importance of autopsy for the accurate diagnosis of dementia for genetic counseling, assessment of diagnostic techniques or drug therapy, and epidemiologic studies.

Alzheimer Disease↗
PubMed2006

A cerebellar model for predictive motor control tested in a brain-based device.

The cerebellum is known to be critical for accurate adaptive control and motor learning. We propose here a mechanism by which the cerebellum may replace reflex control with predictive control. This mechanism is embedded in a learning rule (the delayed eligibility trace rule) in which synapses onto a Purkinje cell or onto a cell in the deep cerebellar nuclei become eligible for plasticity only after a fixed delay from the onset of suprathreshold presynaptic activity. To investigate the proposal that the cerebellum is a general-purpose predictive controller guided by a delayed eligibility trace rule, a computer model based on the anatomy and dynamics of the cerebellum was constructed. It contained components simulating cerebellar cortex and deep cerebellar nuclei, and it received input from a middle temporal visual area and the inferior olive. The model was incorporated in a real-world brain-based device (BBD) built on a Segway robotic platform that learned to traverse curved paths. The BBD learned which visual motion cues predicted impending collisions and used this experience to avoid path boundaries. During learning, the BBD adapted its velocity and turning rate to successfully traverse various curved paths. By examining neuronal activity and synaptic changes during this behavior, we found that the cerebellar circuit selectively responded to motion cues in specific receptive fields of simulated middle temporal visual areas. The system described here prompts several hypotheses about the relationship between perception and motor control and may be useful in the development of general-purpose motor learning systems for machines.

Cerebellum↗
PubMed1999

Detecting structural changes in whole brain based on nonlinear deformations-application to schizophrenia research.

This paper describes a new method for detecting structural brain differences based on the analysis of deformation fields. Deformations are obtained by an intensity-based nonlinear registration routine that transforms one brain onto another one. We present a general multivariate statistical approach to analyze deformation fields in different subjects. This method was applied to the brains of 85 schizophrenic patients and 75 healthy volunteers to examine whether low frequency deformations are sufficiently sensitive to detect regional deviations in the brains of both groups. We observed significant changes caused by volume reduction in brains of schizophrenics bilaterally in the thalamus and in the superior temporal gyrus. On the left side, the superior frontal gyrus and precentral gyrus are found to be changed, while on the right side, the middle frontal gyrus was altered. In addition, there were significant changes in the occipital lobe (left lingual gyrus) and in the left cerebellum. Volume enlargement in brains of schizophrenics was observed in the right putamen and in the adjacent white matter of the thalamic region. Our data suggest a disturbance in the nodes of a prefrontal-thalamic-cerebellar circuitry. This provides further support for the model of "cognitive dysmetria," which postulates a disruption in these nodes. We have demonstrated the application of deformation-based morphometry by detecting structural changes in the whole brain. This technique is fully automatic, thus allowing for the inclusion of large samples, with no user bias or a priori-defined regions of interest.

Adult↗
PubMed2002

Architectural changes in the developing human brain based on the matrix cell theory.

Architectural changes in the developing human brain are discussed based on the matrix cell theory. Neural stem cells/matrix cells with self-renewing ability and multipotency exist in the developing human brain in vivo. The brain development is divided into three stages and the cell differentiation is time regulated. Immunohistochemical distribution of various markers for brain development is summarized and categorized along with differentiation lineages. Particularly, the existence of glial fibrillary acidic protein is re-evaluated in the developing human brain. The commonly used terms and concepts "radial glial fiber" or "subventricular zone" are also re-evaluated.

Biomarkers↗
PubMed2003

A multimodal brain-based feedback and communication system.

The Thought Translation Device (TTD) is a brain-computer interface based on the self-regulation of slow cortical potentials (SCPs) and enables completely paralyzed patients to communicate using their brain potentials. Here, an extended version of the TTD is presented that has an auditory and a combined visual and auditory feedback modality added to the standard visual feedback. This feature is necessary for locked-in patients who are no longer able to focus their gaze. In order to test performance of physiological regulation with auditory feedback 54 healthy participants were randomly assigned to visual, auditory or combined visual-auditory feedback of slow cortical potentials. The training consisted of three sessions with 500 trials per session with random assignment of required cortical positivity or negativity in half of the trials. The data show that physiological regulation of SCPs can be learned with auditory and combined auditory and visual feedback although the performance of auditory feedback alone was significantly worse than with visual feedback alone.

Acoustic Stimulation↗
PubMed1983

Single neuron cultivation of embryonic and perinatal rabbit or rat brains based on plasma clot technique.

Isolated neuronal cells dissociated from the brain of embryonic rabbits on the sixteenth day of gestation and of perinatal rats (eighteenth embryonic day, to E18, thirteenth day postnatum, p.n. 13) were selectively cultured using a plasma clot technique. The cells grown were shown to be neurons by means of the neuron-specific synaptosomal plasma membrane antibody (SPM). They differentiated at a very high frequency from rounded cells lacking processes into different shapes characteristic for several neuronal cell types. Morphological differences could be distinguished even after 24 h in culture. The neurons differentiated in vitro for up to 11 days, apparently without need of any direct intercellular contact. Cells caught inside the plasma clot were prevented from decreasing in number. This provides the opportunity to culture few neurons even from an extremely small area of a single brain. As an example, different cell types are shown originating from rat cerebella aged E18 to p.n. 13. Their appearance apparently corresponds to the genesis of cerebellar cell types, as is known from the in vivo situation. The high degree of characteristic neuronal differentiation and the prevention of direct intercellular contacts indicate that this culture method may serve as an in vitro assay for genetically fixed properties acquired in vivo.

Animals↗
PubMed2005

[Segmentation of the white matter in the brain based on MR-DTI fiber directions].

MR diffusion tensor imaging (DTI) allows the visualization of location and course of brain fiber bundles. To obtain these results, however, special evaluation techniques are necessary in addition to image acquisition and reconstruction. These include first the calculation of a preferential diffusional direction of water molecules in each voxel and then the tracking of brain fibers or segmentation of regions with similar fiber directions. In both cases, the procedures available thus far require the interactive definition of seed points. In this paper, we propose a method to segment voxel groups of connected data points without the need of setting seed points. This method is based first on the identification of all voxels of a brain volume with a sufficiently unique preferential diffusional direction and with interconnection. For each selected voxel, neighboring voxels are then identified that have a small deviation from the chosen preferential direction and can therefore be grouped with this point. Finally, the largest partial volumes determined in this way are marked and color-coded to present them as three-dimensional structures. The present method resulting in a largely automatic subdivision of the white matter in the brain in a number of bilateral partial volumes.

Brain↗