Biomedical subjects

S S Kindermann

Publications and source records attributed to S S Kindermann.

8 recordsLinked to original sources

PubMed2001

fMRI measurement of brain dysfunction in alcohol-dependent young women.

BACKGROUND: Studies of brain functioning in alcohol-dependent adults have produced varied results but generally suggest that alcohol affects brain functioning and that relatively short durations of heavy drinking may adversely affect women. It remains unclear when in the course of alcohol dependency and at which developmental stage these brain changes emerge. Our neuropsychological studies have indicated that drinking-related neurocognitive effects occur as early as adolescence (Brown et al., 2000; Tapert & Brown, 1999). This study seeks to characterize brain regions that subserve the affected neurocognitive functions. METHODS: Alcohol-dependent young women (n = 10) were recruited from a longitudinal study of alcohol- and drug-abusing youth, all of whom met criteria for alcohol dependence. Control participants (n = 10) had no history of alcohol or drug problems and were comparable with alcohol-dependent participants on age (18-25 years), family history of alcohol use disorders, and education. After a minimum of 72 hr of abstinence, functional magnetic resonance imaging, neuropsychological, alcohol/drug involvement, and mood data were collected. Participants performed spatial working memory and vigilance tasks during functional magnetic resonance imaging acquisition to probe brain response. RESULTS: Alcohol-dependent women demonstrated significantly less blood oxygen level-dependent response than controls during the spatial working memory task in the right superior and inferior parietal, right middle frontal, right postcentral, and left superior frontal cortex, after controlling for the baseline vigilance response. CONCLUSIONS: Working memory produces a larger neuronal response in some cortical regions than vigilance. Alcohol-dependent women showed less differential response to working memory than controls in frontal and parietal regions, especially in the right hemisphere. Heavy, chronic drinking appears to produce adverse neural effects that are detectable by functional magnetic resonance imaging.

Adolescent↗

PubMed2000

Executive functions and P300 latency in elderly depressed patients and control subjects.

The authors asked whether impaired executive functioning and long P300 latency are related dysfunctions and whether they are associated with geriatric depression. A group of 25 elderly depressed patients without dementia and 20 control subjects were assessed on tasks of fluency, initiation and perseveration, the Stroop task, the Wisconsin Card Sorting Test (WCST) perseverative error score, and P300 latency. The groups' performance differed significantly on these tasks and in P300 latency. Longer latency was associated with poorer performance in both groups on all measures except WCST perseverative errors. Regardless of patients' depression status, increased P300 latency predicts poorer performance on executive function tasks requiring speeded performance.

Aged↗

PubMed1999

Brain activation and pupil response during covert performance of the Stroop Color Word task.

Patterns of brain activation associated with covert performance of the Stroop Color-Word task were studied in young, healthy, adult volunteers using blood oxygen level dependent (BOLD) functional magnetic resonance imaging (fMRI). Comparisons of the incongruous Stroop condition were made with both color naming and word reading baselines. Areas of the left and right anterior cingulate, the right precuneus, and the left pars opercularis displayed larger BOLD signal responses during the incongruous Stroop condition than during baseline conditions. Activation of BOLD signals in these areas was highly repeatable. In a second experiment, pupil diameter was used to assess cognitive load in 7 individuals studied during overt and covert performance of both Stroop and color naming conditions. Cognitive load was similar in overt and covert response conditions. Results from the BOLD study indicate that brain regions participating in selective visual attention and in the selection of motor programs involved in speech were activated more by the Stroop task than by the baseline tasks. The neural substrate involved in the resolution of the perceptual and motor conflicts elicited by the Stroop Color-Word task does not appear to be a single brain region. Rather, a network of brain regions is implicated, with separate regions within this system supporting distinct functions.

Adult↗

PubMed1998

Spatially independent activity patterns in functional MRI data during the stroop color-naming task.

A method is given for determining the time course and spatial extent of consistently and transiently task-related activations from other physiological and artifactual components that contribute to functional MRI (fMRI) recordings. Independent component analysis (ICA) was used to analyze two fMRI data sets from a subject performing 6-min trials composed of alternating 40-sec Stroop color-naming and control task blocks. Each component consisted of a fixed three-dimensional spatial distribution of brain voxel values (a "map") and an associated time course of activation. For each trial, the algorithm detected, without a priori knowledge of their spatial or temporal structure, one consistently task-related component activated during each Stroop task block, plus several transiently task-related components activated at the onset of one or two of the Stroop task blocks only. Activation patterns occurring during only part of the fMRI trial are not observed with other techniques, because their time courses cannot easily be known in advance. Other ICA components were related to physiological pulsations, head movements, or machine noise. By using higher-order statistics to specify stricter criteria for spatial independence between component maps, ICA produced improved estimates of the temporal and spatial extent of task-related activation in our data compared with principal component analysis (PCA). ICA appears to be a promising tool for exploratory analysis of fMRI data, particularly when the time courses of activation are not known in advance.

Algorithms↗

PubMed1998

Neuropsychologic impairment in patients with nonepileptic seizures.

Patients with nonepileptic seizures (NES), those with epileptic seizures (ES), and normal controls were compared on a battery of neuropsychologic tests. Diagnoses were made after intensive electroencephalogram (EEG) monitoring. Excluded from the study were patients with both ES and NES, as well as patients with ES who had evidence of structural brain damage. On all neuropsychologic measures, the two seizure groups were significantly impaired relative to the controls, but there were no significant differences between the ES and NES group performances. Additional neuropsychologic measures were obtained on the two seizure groups but not controls, and again there were no significant differences between the two seizure groups. Further analyses suggested that the NES group's impairment was related to emotional factors. The Minnesota Multiphasic Personality Inventory (MMPI)/MMPI-2 and the Portland Digit Recognition Test were helpful in classifying patients by seizure group. Our results, which are consistent with those of previous studies, suggest that neuropsychologic abnormalities are not pathognomonic of brain dysfunction in this population. However, the Portland Digit Recognition Test (PDRT) and measures of personality are useful for classification purposes in the differential diagnosis of epileptic and nonepileptic seizures.

Journal Article↗

PubMed1998

Analysis of fMRI data by blind separation into independent spatial components.

Current analytical techniques applied to functional magnetic resonance imaging (fMRI) data require a priori knowledge or specific assumptions about the time courses of processes contributing to the measured signals. Here we describe a new method for analyzing fMRI data based on the independent component analysis (ICA) algorithm of Bell and Sejnowski ([1995]: Neural Comput 7:1129-1159). We decomposed eight fMRI data sets from 4 normal subjects performing Stroop color-naming, the Brown and Peterson work/number task, and control tasks into spatially independent components. Each component consisted of voxel values at fixed three-dimensional locations (a component "map"), and a unique associated time course of activation. Given data from 144 time points collected during a 6-min trial, ICA extracted an equal number of spatially independent components. In all eight trials, ICA derived one and only one component with a time course closely matching the time course of 40-sec alternations between experimental and control tasks. The regions of maximum activity in these consistently task-related components generally overlapped active regions detected by standard correlational analysis, but included frontal regions not detected by correlation. Time courses of other ICA components were transiently task-related, quasiperiodic, or slowly varying. By utilizing higher-order statistics to enforce successively stricter criteria for spatial independence between component maps, both the ICA algorithm and a related fourth-order decomposition technique (Comon [1994]: Signal Processing 36:11-20) were superior to principal component analysis (PCA) in determining the spatial and temporal extent of task-related activation. For each subject, the time courses and active regions of the task-related ICA components were consistent across trials and were robust to the addition of simulated noise. Simulated movement artifact and simulated task-related activations added to actual fMRI data were clearly separated by the algorithm. ICA can be used to distinguish between nontask-related signal components, movements, and other artifacts, as well as consistently or transiently task-related fMRI activations, based on only weak assumptions about their spatial distributions and without a priori assumptions about their time courses. ICA appears to be a highly promising method for the analysis of fMRI data from normal and clinical populations, especially for uncovering unpredictable transient patterns of brain activity associated with performance of psychomotor tasks.

Algorithms↗

PubMed1997

Review of functional magnetic resonance imaging in schizophrenia.

Functional magnetic resonance imaging (fMRI) holds great promise for assessing temporal changes in brain activity using various challenge paradigms. In this report, we review the 14 studies (eight of them abstracts) that comprise the fMRI literature available to date relating to schizophrenia. Twelve of the 14 investigations examined changes in blood-oxygen-level-dependent (BOLD) contrast: two examined blood volume. Eight of the 12 BOLD studies relied on lower-order cognitive processing to measure activation (involving sensory or motor areas), whereas four used higher-order tasks (word production, auditory processing, and subspan word recall involving multiple brain areas). Although the variability in tasks used, brain regions studied, imaging methods used, patient characteristics reported, and methods of reporting significance precluded a full meta-analysis, we re-analyzed these published data to compute effect sizes. In most studies, resting blood volume and BOLD changes, regardless of the complexity of the cognitive task, appeared to differ between patients with schizophrenia and control subjects.

Brain↗

PubMed1997

Depression and memory in the elderly: a meta-analysis.

A meta-analysis (N = 40) of the effects of depression on memory in the elderly (sample mean age > or = 55 years) examined variables potentially accounting for divergent findings in the literature. The distribution of effects was bimodal and the effect sizes were heterogeneous. Compared to controls, groups containing unipolar subjects only were significantly less impaired than were mixed unipolar-bipolar; five of six studies mixing depression subtype were associated with the more negative mode. Samples containing younger depressed subjects (< 45 years) were significantly more impaired and were associated with the more negative mode. Significant group differences were found between studies matching their comparison groups reasonably well on years of education and those that did not. Thoroughness of dementia screening yielded no group differences. Although correlated observations precluded significance tests, larger effects were found for (1) figural (vs. verbal) memory; (2) delayed (vs. immediate) memory; and (3) recognition (vs. free recall and incidental or cued recall; incidental and cued recall effects were nearly identical). Similar effects were found for composite memory scores versus constituent and for various presentation paradigms (e.g., single presentation, selective reminding). Effect sizes for these categories were in the moderate range. Difficulties synthesizing this literature are discussed as are suggested remedies and directions for future research.

Aged↗