Invariant characterization of neural systems

It is shown that the invariant integral, viz., the Kolmogorov second entropy, is eminently suited to characterize EEG quantitatively. The estimation obtained for a "clinically normal" brain is compared with a previous result obtained from the EEG of a person under epileptic seizure.     

Induced coding strategies and hemispheric differences in matching letter pairs

The importance of task requirements in producing visual half-field asymmetries was investigated through manipulation of the criteria by which a central probe and a unilateral target letter were matched. Physical characteristics of the letters were emphasized (those made up of straight lines only vs those having at least one curved feature, e.g. F vs P). An interaction of visual field and type of judgment (match vs mismatch) was found for manual response time. Matching responses were faster to RVF than LVF probes and mismatches were faster to LVF than RVF probes. The significance of this interaction for models of hemispheric asymmetry is discussed.     

NTU‐DSI‐122: A diffusion spectrum imaging template with high anatomical matching to the ICBM‐152 space

A diffusion‐weighted (DW) template in a standard coordinate system is often necessary for the analysis of white matter (WM) structures using DW images. Although several DW templates have been constructed in the ICBM‐152 space, a template for diffusion spectrum imaging (DSI) is still lacking. In this study, we developed a DSI template in the ICBM‐152 space from 122 healthy adults. This high quality template, NTU‐DSI‐122, was built through incorporating the macroscopic anatomical information using high‐resolution T₁‐weighted images and the microscopic structural information obtained from DSI datasets. Two evaluations were conducted to examine the quality of NTU‐DSI‐122. The first evaluation examined the anatomical consistency of NTU‐DSI‐122 in matching to the ICBM‐152 coordinate system. The results showed that this template matched to the ICBM‐152 templates very well across the whole brain, not only in the deep white matter regions as other DW templates but also in the superficial white matter regions. In the second evaluation, a large number of independent diffusion tensor imaging (DTI) datasets were registered to the DTI template derived from NTU‐DSI‐122. The examination was performed by quantifying the anatomical consistency among the registered DTI datasets. The results showed that using NTU‐DSI‐122 as the registration template the registered DTI datasets can achieve high anatomical alignment. Both evaluations demonstrate that NTU‐DSI‐122 is a useful high quality DW template. Therefore, NTU‐DSI‐122 can serve as a representative DSI dataset for a healthy adult population, and will be of potential value for brain research and clinical applications. The NTU‐DSI‐122 template is available at http://www.nitrc.org/projects/ntu‐dsi‐122/ . Hum Brain Mapp 36:3528–3541, 2015. © 2015 Wiley Periodicals, Inc.     

Localizing gray matter deficits in late-onset depression using computational cortical pattern matching methods

OBJECTIVE: The authors used magnetic resonance imaging and an image analysis technique known as cortical pattern matching to map cortical gray matter deficits in elderly depressed patients with an illness onset after age 60 (late-onset depression). METHOD: Seventeen patients with late-onset depression (11 women and six men; mean age=75.24, SD=8.52) and 17 group-matched comparison subjects (11 women and six men; mean age=73.88, SD=7.61) were included. Detailed spatial analyses of gray matter were conducted across the entire cortex by measuring local proportions of gray matter at thousands of homologous cortical surface locations in each subject, and these patterns were matched across subjects by using elastic transformations to align sulcal topography. To visualize regional changes, statistical differences were mapped at each cortical surface location in three dimensions. RESULTS: The late-onset depression group exhibited significant gray matter deficits in the right lateral temporal cortex and the right parietal cortex, where decreases were most pronounced in sensorimotor regions. The statistical maps also showed gray matter deficits in the same regions of the left hemisphere that approached significance after permutation testing. No significant group differences were detected in frontal cortices or any other anatomical region. CONCLUSIONS: Regionally specific decreases of gray matter occur in late-onset depression, supporting the hypothesis that this subset of elderly patients with major depression presents with certain unique neuroanatomical abnormalities that may differ from patients with an earlier onset of illness.     

A study of the standard brain in Japanese children: Morphological comparison with the MNI template

Functional magnetic resonance imaging (MRI) studies involve normalization so that the brains of different subjects can be described using the same coordinate system. However, standard brain templates, including the Montreal Neurological Institute (MNI) template that is most frequently used at present, were created based on the brains of Western adults. Because morphological characteristics of the brain differ by race and ethnicity and between adults and children, errors are likely to occur when data from the brains of non-Western individuals are processed using these templates. Therefore, this study was conducted to collect basic data for the creation of a Japanese pediatric standard brain. Participants in this study were 45 healthy children (contributing 65 brain images) between the ages of 6 and 9 years, who had nothing notable in their perinatal and other histories and neurological findings, had normal physical findings and cognitive function, exhibited no behavioral abnormalities, and provided analyzable MR images. 3D-T1-weighted images were obtained using a 1.5-T MRI device, and images from each child were adjusted to the reference image by affine transformation using SPM8. The lengths were measured and compared with those of the MNI template. The Western adult standard brain and the Japanese pediatric standard brain obtained in this study differed greatly in size, particularly along the anteroposterior diameter and in height, suggesting that the correction rates are high, and that errors are likely to occur in the normalization of pediatric brain images. We propose that the use of the Japanese pediatric standard brain created in this study will improve the accuracy of identification of brain regions in functional brain imaging studies involving children.     

Atlantoaxial instability in adults with down syndrome: A clinical and radiological survey

A survey of 129 adults with Down syndrome was undertaken to determine the prevalence of atlantoaxial instability (AAI) and to establish a base line for long term prospective study. Clinical and radiological evaluations were performed to determine optimal screening methods for this condition. The findings indicate that radiological evidence of AAI was found in 40% with anterior atlanto-odontoid distance (AAOD) of 3 mm or more and in 10% with 5 mm or more. These findings are similar to those reported in the pediatric age group. A preponderance of females with symptomatic AAI is noted. Clinical evaluation suggested the presence of spinal cord compression, which was confirmed by CT scan of the atlantoaxial region. There were no false negative clinical results. Among the false positive clinical findings other explanations were present in some cases. A comparison with the literature is offered along with guidelines on screening and management.     

Anatomical standardization of small animal brain FDG-PET images using synthetic functional template: experimental comparison with anatomical template

Anatomical standardization (also called spatial normalization) of positron emission tomography (PET) small animal brain images is required to make statistical comparisons across individuals. Frequently, PET images are co-registered to an individual MR or CT image of the same subject in order to transform the functional images to an anatomical space. In the present work, we evaluate the normalization of synthetic PET (synPET) images to a synthetic PET template. To provide absolute error in terms of pixel misregistration, we created a synthetic PET image from the individual MR image through segmentation of the brain into gray and white matter which produced functional and anatomical images in the same space. When comparing spatial normalization of synPET images to a synPET template with the gold standard (MR images to an MR template), a mean translation error of 0.24mm (±0.20) and a maximal mean rotational error of 0.85° (±0.91) were found. Significant decrease in misregistration error was measured when achieving spatial normalization of functional images to a functional template instead of an anatomical template. This accuracy strengthens the use of standardization methods where individual PET images are registered to a customized PET template in order to statistically assess physiological changes in rat brains.     

A case of leukoencephalopathy with vanishing white matter

A 6-year old Turkish boy with a recently defined entity: "leukoencephalopathy with vanishing white matter" is described. He was born to consanguinous parents. His psychomotor development was normal till he first presented with fever and generalized tonic-clonic seizures at the age of 2.5, followed by rapid motor and mental deterioration. Decerebrate posture and marked spasticity subsequently developed. The initial MRI examination showed diffuse involvement of white matter, including subcortical U-fibers, with signal intensity parallel to CSF on all sequences. The white matter appeared swollen. The ventricles were slightly enlarged and there was cavum septi pellucidi et vergae. The posterior crus of the internal capsule, external and extreme capsules were affected. Cerebellar hemispheres and vermis showed atrophy. The involvement pattern of brainstem was noteworthy in that pontine tegmentum and cruri cerebri were affected. Follow-up MRI obtained after three years did not show any interval change. Brain biopsy showed thinned cortex with relatively preserved cortical layering and neuronal structure. There was rarefaction of the white matter with cystic degeneration. Fibrillary gliosis and increased number of oligodendroglial cells were observed within the cerebral white matter.     

A Japanese girl with leukoencephalopathy with vanishing white matter

A Japanese girl with peculiar leukoencephalopathy was reported. Following normal development until 1 year of age, she showed progressive neurological deterioration with ataxia, epilepsy, pyramidal tract signs and choreic movement. Serial brain computed tomographies (CTs) revealed markedly low density and progressive volume loss in whole white matter. In extensive laboratory investigations, the level of glycine in the urine was elevated. She died at the age of 4 years, and the neuropathological findings were comprised of severe extensive changes in cerebral and cerebellar white matter, such as marked rarefaction or cystic degeneration with axonal loss. The pontine central tegmental tracts were also affected. Neuronal loss was seen in the cerebellar cortex. These features were compatible with leukoencephalopathy with vanishing white matter, which was recently established as a clinical entity. To our knowledge, this is the first report of a non-Caucasian patient with this new type of leukoencephalopathy.     

A matter of time: internal delays in binaural processing

As an animal navigates its surroundings, the sounds reaching its two ears change in waveform similarity (interaural correlation) and in time of arrival (interaural time difference, ITD). Humans are exquisitely sensitive to these binaural cues, and it is generally agreed that this sensitivity involves coincidence detectors and internal delays that compensate for external acoustic delays (ITDs). Recent data show an unexpected relationship between the tuning of a neuron to frequency and to ITD, leading to several proposals for sources of internal delay and the neural coding of interaural temporal cues. We review the alternatives, and argue that an understanding of binaural mechanisms requires consideration of sensitivity not only to ITDs, but also to interaural correlation.     

New directions in multiple sclerosis therapy: matching therapy with pathogenesis

All currently approved therapies for multiple sclerosis (MS) modulate systemic immune components prior to their entry into the central nervous system (CNS). Available data indicate they lack impact on the progressive phases of disease; the more potent systemic immune-directed agents predispose to development of infectious or neoplastic disorders. Development of new agents that enhance disease stage related efficacy and limit systemic toxicity will need to consider the underlying mechanisms related to each phase of the clinical disorder, namely relapses, remission, and progression. This report focuses on disease related mechanisms ongoing within the CNS that contribute to the different phases of MS and how these may serve as potential therapeutic targets. Such mechanisms include CNS compartment specific immunologic properties especially as related to the innate immune system and neural cell-related properties that are determinants of the extent of actual tissue injury and repair (or lack thereof).     

Dimension change, coarse grained coding and pattern recognition in spatio-temporal nonlinear systems

Several research programs employing spatio-temporal recurrent dynamics and changes in dimensionality have extended the dialog on neural computation and coding beyond classical frameworks such as feed forward and attractor neural networks and feature detectors. Some have emphasized spiking networks, while others emphasize oscillations and synchronization as the locus of computation and coding. In this paper, the formalism of locally connected homogeneous coupled map lattices is described. Its deployment in an extended version of the dynamical recognizer framework is described, and is compared with density coding, computational mechanics, and liquid state machine frameworks for neural computation. A population coding strategy based on coarse graining the continuous valued distribution of all sites in the lattice is developed and examined as a form of dimension reduction. Results on recognition of 3-D objects are reported. In order to better understand the dynamics supporting recognition, measures suggested by these other research programs and computational frameworks were examined. Dynamics trajectories from object recognition trials were examined for correlation with recognition rates and measures of the distance of the representation space statistics between the target objects and noise initial conditions, and the intrinsic separation between different objects in the set to be classified were performed. These results raise questions about the efficacy of density coding as an explanation for the results, and on the validity of recent criticisms that chaotic systems cannot satisfy separation requirements required for real time computation.     

Molecular mechanisms of short-term plasticity as a basis of frequency coding: The role of proteolytic systems

During vital activities, synapses permanently receive afferent inflow followed by short-term modifications of transmission. These modifications play an important role in information processing, creating the basis for the formation of the temporal pattern of a response and frequency coding. A neuronal network with these properties may not only differentiate frequency features of input signals but can also form individual patterns of activity in each of the outputs. Here, we review the data on the dependence of the parameters of short-term plasticity on the molecular composition of synaptic compartments. The role of regulated proteolysis in the formation of a specific molecular composition in the pre- and postsynapses is discussed. The specific pattern of enzyme activation in each compartment coordinates proteolytic activity in accordance with input signals. We believe that the molecular composition in each synapse may depend on previous experience and represent the substrate of memory, which determines recall, not only the spatial pattern, but also the frequency-temporal pattern, which is required for adaptive behavior.     

Medical and legal problems in psychiatric coding under the DSM and ICD systems

The various diagnostic systems in psychiatry have differed in their terminology and associated numerical codes. Lack of attention to coding variations in the DSM and ICD systems during the review of patient records can lead to misinterpretation and confusion; reliance on historical or statistical studies that use differing systems may be questionable. Two cases illustrate the problems caused by lack of awareness of these factors. Specification by the psychiatrist of both the diagnostic system used and the appropriate revision or edition can lessen communication error or misunderstanding.     

Perceptual matching in patients with cerebral lesions

Tasks of perceptual matching, including three types of visual stimulus (slope of line, position of dot and size of gap in contour) were devised. Seventy-four patients with unilateral cortical lesions were tested. The right parietal group was impaired on the perceptual matching tasks. There was no association between performance on perceptual matching tasks and tachistoscopic threshold measurements or a test of picture recognition. The relationship between perceptual matching and performance on other more complex visual tasks is discussed.