Biomedical subjects

J Chmielowska

Publications and source records attributed to J Chmielowska.

13 recordsLinked to original sources

PubMed1999

Comparison of PET [15O]water studies with 6-minute and 10-minute interscan intervals: single-subject and group analyses.

The authors recently showed that [15O]water PET data obtained with a short interscan interval (6 minutes) produced similar results whether or not the residual background from the previous scan is subtracted. The purpose of the present study was to compare scans obtained during motor activation using a short (6-minute) interscan interval protocol with those obtained with a standard (10-minute) protocol in the same scanning session. Single-subject and group analyses were performed using Worsley's method, which uses a pooled variance estimate and statistical parametric mapping with a local variance estimate. High consistency in both the activation maps, i.e., the number of activated motor brain structures and the Talairach coordinates of peak intensities of the activated regions, was obtained in the 6- and 10-minute studies in both single-subject and group analyses. However, in comparison to the 6-minute studies, a larger cluster size of activated brain regions and an approximately 20% higher peak activation in these regions were observed in the 10-minute studies with the same number of replicates. Analysis of these results suggests that using a 6-minute interval with an increased number of replications, i.e., without changing the subject's total study duration, should produce comparable statistical power to that of the 10-minute interval for group analysis and increased statistical power for single-subject analyses that use a local variance estimate because of increased degrees of freedom. Alternatively, with a small increase in the number of scans and the use of a 6-minute interscan interval, a comparable level of statistical significance may be achieved for single-subject experiments that use a local variance estimate, with an overall shortening of the study duration.

Adult↗

PubMed1998

Positron emission tomography [15O]water studies with short interscan interval for single-subject and group analysis: influence of background subtraction.

Use of short interscan interval [15O]water positron emission tomography (PET) studies reduces the overall study duration and may allow an increased number of scans for single-subject analysis of unique cases (e.g., stroke). The purpose of this study was to examine how subtraction of residual radioactivity from the previous injection (corrected scan) compared to nonsubtraction (uncorrected scan) in a PET short interscan interval (6 minutes) study affects single-subject and group data analysis using a motor activation task. Two currently widely used analytic strategies, Worsley's method and the SPM technique, were applied. Excellent agreement between activation maps obtained from corrected and uncorrected data sets was obtained both in single-subject analyses performed on data sets from the six normal subjects and three stroke (subcortical infarct) patients, and in group analysis (six normal subjects) within a particular statistical method. The corrected and uncorrected data were very similar in the (1) number of activated brain regions; (2) size of clusters of activated brain voxels; (3) Talairach coordinates of the activated region; and (4) t or Z value of the peak intensity for every significantly activated motor brain structure (both for large activations such as in motor cortex and small activations such as in putamen and thalamus). [15O]Water PET data obtained with a short interscan interval (6 minutes) produce similar results whether or not the background is subtracted. Thus, if injection dose and timing are constant, one can achieve the advantage of a short interscan interval without the added complexity of correcting for background radioactivity.

Adult↗

PubMed1998

An efficient method for correcting the edge artifact due to smoothing.

Spatial smoothing is a common pre-processing step in the analysis of functional brain imaging data. It can increase sensitivity to signals of specific shapes and sizes (Rosenfeld and Kak [1982]: Digital Picture Processing, vol. 2. Orlando, Fla.: Academic; Worsley et al. [1996]: Hum Brain Mapping 4:74-90). Also, some amount of spatial smoothness is required if methods from the theory of Gaussian random fields are to be used (Holmes [1994]: Statistical Issues in Functional Brain Mapping. PhD thesis, University of Glasgow). Smoothing is most often implemented as a convolution of the imaging data with a smoothing kernel, and convolution is most efficiently performed using the Convolution Theorem and the Fast Fourier Transform (Cooley and Tukey [1965]: Math Comput 19:297-301; Priestly [1981]: Spectral Analysis and Time Series. San Diego: Academic; Press et al. [1992]: Numerical Recipes in C: The Art of Scientific Computing, 2nd ed. Cambridge: Cambridge University Press). An undesirable side effect of smoothing is an artifact along the edges of the brain, where brain voxels become smoothed with non-brain voxels. This results in a dark rim which might be mistaken for hypoactivity. In this short methodological paper, we present a method for correcting functional brain images for the edge artifact due to smoothing, while retaining the use of the Convolution Theorem and the Fast Fourier Transform for efficient calculation of convolutions.

Artifacts↗

PubMed1995

Patterns of thalamocortical degeneration after ablation of somatosensory cortex in monkeys.

We examined the pattern of cytochrome oxidase (CO), Nissl staining, and gamma-amino butyric acid (GABA) immunoreactivity in the ventroposterior lateral nucleus (VPL) of the thalamus in monkeys that received no, total, or subtotal, ablation of the hand representations in postcentral somatosensory cortex. In unoperated animals, the region of VPL representing the hand was characterized by relatively dense and homogeneous CO staining throughout the rostral-caudal extent of VPL. Counts of neurons in the VPL hand representation from adjacent thalamic sections processed for Nissl and GABA immunostaining indicated that there were approximately 261.4 neurons/mm2 of which 78.4/mm2 stained positive for GABA. GABA(+) puncta-like terminals were readily apparent throughout the VPL. By contrast, animals that received total removals of the postcentral hand representations showed a dramatic reduction in CO staining in the VPL, which was confined to the expected location of the thalamic hand representation. Counts of neurons in the affected region from adjacent sections that underwent Nissl staining and GABA immunostaining also revealed a dramatic reduction of Nissl-stained neurons, with a smaller reduction in the number of neurons staining positive for GABA. Specifically, large to medium-sized (> 180 microns 2) GABA(-) neurons were virtually eliminated in the affected portion of the VPL, and the numbers of GABA(+) neurons were significantly reduced. The remaining population of GABA(+) neurons was typically shrunken, and no GABA(+) puncta-like terminals were observed in the affected region. The results obtained after subtotal ablation of the postcentral hand representations (only one postcentral area spared, 3b or 3a) differed from those obtained when total removals were made. Instead of virtually complete degeneration of medium-sized to large neurons throughout the hand representation in VPL, as was the case with total removals, after partial removals, we found alternating regions in the VPL hand representation that appeared qualitatively normal, or dramatically degenerated. Thalamic sections stained with CO revealed light, moderate, and darkly stained patches of label within the hand representation in VP, depending on the type of cortical ablation. The most dramatic reduction of Nissl-stained neurons coincided precisely with the lightest staining CO patches. Interestingly, the only statistically significant reduction in the number of GABA(+) neurons occurred in the light CO patches. In the thalamic regions coincident with the dark and moderately stained CO patches, the number of medium-sized and large neurons decreased, but the number of GABA(+) neurons was comparable to normal. Optical density measurements of the dark patches also indicated a statistically significant difference from normal CO staining in this region.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1989

Spatial organization of thalamocortical and corticothalamic projection systems in the rat SmI barrel cortex.

Axonal tracing techniques were used to examine the distribution of corticothalamic projection neurons in relation to the organization of the thalamocortical recipient zones in the whisker representation of the rat first somatic sensory cortex. Following injection of horseradish peroxidase into the physiologically defined vibrissa area in the ventrobasal complex of the thalamus, labeling in the cortex had a columnar appearance. Dense patches of anterograde labeling were located within the centers of the layer IV barrels and extended superficially through lamina III; the septa between barrels contained considerably less reaction product. Retrogradely labeled neurons were observed in lower layer V and layer VI where they were concentrated preferentially deep to the barrel centers. Regions deep to the septa displayed less overall labeling and a lower relative number of thalamic projecting neurons. Zones having the larger numbers of retrogradely labeled cells also contained terminallike labeling of either corticothalamic or thalamocortical origin. Following an injection that included the posterior group medial to the ventrobasal complex, anterograde labeling in layer IV was located largely in the septa. In conjunction with previous findings concerning the origin and termination of other projection systems in the barrel cortex, these results suggest that a vibrissal column contains a central core zone intimately linked with the ventrobasal thalamus that is bounded by narrower regions of more diverse inputs and outputs that form an interface between adjacent cortical columns.

Animals↗

PubMed1988

Quantitative autoradiographic analysis of the distribution of [3H]muscimol binding to GABA receptors in chick brain.

Quantitative receptor autoradiography was used to investigate the distribution of high-affinity GABA receptors (GABAA) in left and right hemispheres of the brains of 3-week-old chicks. The receptors were labelled with the potent GABA agonist [3H]muscimol. High levels of [3H]muscimol labelling were found throughout the fore-, mid-, and hindbrain, though considerable variation was found in different regions. In the telencephalon the highest concentration of specific binding was found in the hyperstriatum ventrale followed by the neostriatum, and then the lobus parolfactorius of the paleostriatal complex, whilst in the diencephalon highest levels of labelling were present in the infundibulum. In the midbrain distinct lamination was observed in the high levels of [3H]muscimol binding in the optic tectum and in the hind brain the highest density of labelling occurred in the granular layers of the cerebellum. Levels of labelling were generally low in the brainstem regions. The distribution of [3H]muscimol binding in the optic tectum and in the hind brain the highest density of labelling occurred in the granular layers of the cerebellum. Levels of labelling were generally low in the brainstem regions. The distribution of [3H]muscimol binding sites is in good agreement with our previous work on the distribution of GABA-immunoreactivity in the chick brain.

Animals↗

PubMed1988

gamma-Aminobutyric acid (GABA) immunoreactivity in mouse and rat first somatosensory (SI) cortex: description and comparison.

The location and morphological characteristics of gamma-aminobutyric acid (GABA)-immunopositive cells and their processes were studied in rat and mouse first somatosensory (SI) cortex (including 'barrels') in layer IV, and layers above (I-III), and below (V and VI). In coronal sections of SI cortex of both species GABA-immunopositive cells and punctate profiles were found in each of layers I-VI. The cells were of various sizes; the largest, located in layers III and V of each species, resemble the large basket cells seen in Golgi-impregnated material. Most of the immunopositive cells were multipolar and circular or ellipsoidal in shape, but occasionally bipolar cells with fusiform perikarya were also seen. In coronal sections, immunopositive cells did not form a characteristic pattern. GABA-immunopositive cells were observed to be most numerous in the supragranular layers whereas GABA-positive punctate profiles were more numerous in layer IV. In tangential sections from layer IV of SI cortex of both species, GABA-immunopositive cells, processes and punctate profiles were visible throughout the entire barrel field. The pattern of distribution of immunopositive cells was similar (a) in two different morphological groups--i.e. the posteromedial barrel subfield (PMBSF) and the anterolateral barrel subfield (ALBSF) in rat barrel field, and (b) in PMBSF barrels of both rat and mouse (excluding differences due to structural dissimilarities between rat and mouse barrels). GABA-immunopositive neurons were grouped mainly in the barrel side and septum and were visible frequently in small clusters. In barrels of both species GABA-immunopositive cells were of a variety of sizes and ranged in shape from ellipsoidal to circular.

Animals↗

PubMed1987

Autoradiographic localization of gamma-aminobutyric acid receptors in mouse barrel field.

The distribution of high-affinity gamma-aminobutyric acid (GABA) receptors in mouse posteromedial barrel subfield (PMBSF) in layer IV of the somatosensory (SI) cortex was studied using [3H]muscimol autoradiography in vitro. A qualitative study revealed a heterogeneous distribution in the density of [3H]muscimol binding in the barrel field. In the barrel sides and septum between the barrels [3H]muscimol binding exhibits the lowest level of labelling in the entire tissue. In comparison, [3H]muscimol binding in the hollows is considerably higher than in the barrel sides although the level is not homogeneous. These findings suggest that the barrel hollows are much richer in GABA receptors than the surrounding barrel sides and septa.

Animals↗

PubMed1986

gamma-Aminobutyric acid immunoreactivity in mouse barrel field: a light microscopical study.

The barrel field of the mouse somatosensory cortex (SmI) was investigated immunocytochemically using an antiserum against the inhibitory neurotransmitter gamma-aminobutyric acid (GABA). GABA-immunopositive cells and processes are grouped largely in the barrel side, whereas the barrel hollow is only weakly immunostained. The GABA-immunopositive cells have an ellipsoidal appearance similar to that of non-pyramidal class II barrel neurones described previously in Golgi impregnation studies of the mouse and rat barrel field.

Animals↗

PubMed1986

Single vibrissal cortical column in the mouse labeled with 2-deoxyglucose.

Columnar labeling was found in the primary somatosensory cortex of mice after stimulation of a single mystacial vibrissa following 2-deoxyglucose injection. The cortical vibrissal column had a cylindrical shape, passing through all layers of the cortex and was centered upon the appropriate vibrisal barrel. Columnar labeling extended beyond this barrel onto parts of neighbouring barrels, particularly within the same row. The densest labeling was found in layer IV in the barrel hollow. Removal of the non-stimulated vibrissae resulted in a subsequent lowering of 2DG uptake in the barrelfield surrounding the activated column, but did not affect the dimension of the activated column.

Animals↗

PubMed1984

A single vibrissal column in the first somatosensory cortex of the mouse demonstrated with 2-deoxyglucose.

Single functional column activated by stimulation of C3 vibrissa was visualized in the mouse somatosensory cortex with 2-deo-xyglucose autoradiography. The column was cylindrical in shape and extended through the entire cortical thickness. The darkest labeling was found in layer IV, over the anatomical C3 vibrissal barrel. The functional column stretched horizontally over parts of adjacent barrels. A zone of low 2-deoxyglucose uptake surrounded the densly labeled area and covered the rest of the postero medial barrel subfield.

Afferent Pathways↗

PubMed1984

Crosscorrelation analysis of intracolumnar neuronal connectivity in area 17 of binocularly deprived cats.

Eight cats were binocularly deprived of pattern vision by rearing in masks from the time of eye opening. Twenty five groups of 3 neurons and 28 neuronal pairs were studied in visual orientation columns of their striate cortices. The crosscorrelograms of neuronal discharges were analyzed and the inference of underlying interneuronal connectivity was made. The results were compared with the normal cats data obtained earlier in an identical experiment. Total number of existing interactions was only slightly reduced: from 95010 of analyzed pairs in normal cats to 90 percent in deprived animals. The most pronounced effect of visual deprivation was the reduction of the percentage of neuronal pairs that shared the same source of input from 61 to 34 percent. The proportion of direct excitatory connections was not affected, while an increase in the number of inhibitory correlations was found.

Animals↗

PubMed1983

Responses of area 17 neurons in cats binocularly deprived by rearing in hoods.

Responses of single units of area 17 were recorded in cats binocularly deprived by rearing in hoods. Neurons were recorded in pairs or in three-neuron groups with multichannel microelectrodes. Of 131 units recorded 22 percent were not visually excitable. The rest were predominantly monocularly driven. Response strength defined as the PST peak-to-background ratio was lower than 10 in 90 percent of cells. The orientation selectivity defined as the ratio of response strengths for the preferred and null stimulus orientations was lower than 5 in 79 percent of neurons. Directional selectivity was detected in 22 percent of units. The aim of this paper is to show that, considering the electrophysiological effects in cortica1 area 17, rearing in hoods can be used instead of eyelid suturing. This paper describes the standard parameters of units that were subsequently used for the analysis of interneuronal connectivity in visually deprived cortex (10).

Adaptation, Physiological↗