Biomedical subjects

I E Sommer

Publications and source records attributed to I E Sommer.

7 recordsLinked to original sources

PubMed2001

Language lateralization in schizophrenia, an fMRI study.

Anatomical studies have shown that cerebral asymmetry is reduced in schizophrenia. Functional asymmetry appears to be reduced also, as was shown with dichotic listening studies. These studies, however, have not revealed whether reduced lateralization is the result of decreased language activity of the left hemisphere or whether it is the consequence of increased language-related activity in the right hemisphere. To elucidate this, we examined hemispheric dominance for language processing by means of functional MRI. Twelve schizophrenic patients and twelve healthy controls were scanned while they were engaged in a verb-generation and a semantic decision task. Activation was measured bilaterally in the frontal, temporal and temporo-parietal language areas, and a laterality index was derived from activity in these regions of interest in the left and the right hemispheres. Clinical symptoms were rated at the time of scanning. The results indicate that language processing is less lateralized in patients than in controls (a mean laterality index of 0.35 versus 0.63, respectively, difference p<0.01). Analysis of variance of the extent of activity, i.e. numbers of active voxels, revealed a significant hemisphere by group interaction (F(1,22)=11.2, p<0.001), which was due to increased activation in the right hemisphere of the patients (post hoc t-test p<0.05). We found no evidence of reduced activity in the left hemisphere. Further analysis of clinical symptoms rated prior to scanning revealed that decreased language lateralization was associated with more severe hallucinations (r=-0.54, p<0.05). We postulate that decreased language lateralization in schizophrenia may result from failure to inhibit the right hemisphere.

Adult↗

PubMed2001

Combined analysis of language tasks in fMRI improves assessment of hemispheric dominance for language functions in individual subjects.

Recent advances in functional neuroimaging techniques have prompted an increase in the number of studies investigating lateralization of language functions. One of the problems in relating findings of various studies to one another is the diversity of reported results. This may be due to differences in the tasks that are used to stimulate language processing regions and in the control tasks, as well as differences in the way imaging data are analyzed,in particular the threshold for significance of signal change. We present a simple method to assess language lateralization that allows for some variation of tasks and statistical thresholding, but at the same time yields reliable and reproducible results. Images acquired during a set of word-comprehension and -production tasks are analyzed conjointly. As opposed to the use of any one particular task, this combined task analysis (CTA) approach is geared toward identifying language regions that are involved in generic language functions rather than regions that are involved in functions that are specific to a single task. In two experiments CTA is compared to single-task analysis in healthy right-handed males. In a third experiment left-handed males were examined. Results indicate that CTA: (1) improves detection of language-related brain activity in individual subjects and (2) yields a high language laterality index (LI) in right-handed males with a small variance across subjects. The high LI matches the strong left-hemisphere dominance for language that is typical for these subjects as reported in neuropsychological and clinical tests in other studies. In the left-handed subjects dominance was found either in the left (n = 4) or the right (n = 1) hemisphere or was absent (n = 3). The LI derived from CTA is more consistent across statistical thresholds for significance of signal change in fMRI analysis than in individual-task analysis. Also, the CTA results are very similar to those obtained with conjunction analysis of the same data.

Adult↗

PubMed1999

Cerebral mirror-imaging in a monozygotic twin.

A healthy monozygotic twin of discordant handedness was scanned with functional magnetic resonance imaging during a language and a mental rotation task. Mirror-imaging was found for both cerebral functions.

Brain Mapping↗

PubMed1999

Lack of association between depression and loss of neurons in the locus coeruleus in Alzheimer disease.

BACKGROUND: Depression, one of the most frequent psychiatric disturbances in Alzheimer disease (AD), is proposed to have its neurobiological basis in neuron loss in the noradrenergic locus coeruleus, although this is not the case in idiopathic depression. METHODS: We performed image analyzer-assisted morphometry of the locus coeruleus in 6 depressed, 6 transiently depressed, and 6 nondepressed patients with AD and in 8 control subjects, emphasizing longitudinal psychiatric evaluations and matching for the clinical and neuropathological severity of dementia. RESULTS: The mean (+/-SD) number of pigmented neurons in the locus coeruleus in controls (11 607+/-946) was higher than in patients with AD, regardless of being depressed (5165+/-928; P=.001), transiently depressed (5647+/-1163; P=.003), or nondepressed (3717+/-661; P=.001). No significant difference was found in the number of pigmented neurons between patients with AD who were depressed, transiently depressed, and nondepressed. Patients who had depression at the onset of AD had a higher pigmented neuron number than other patients with AD. CONCLUSIONS: We confirmed the loss of pigmented neurons in the locus coeruleus of patients with AD; however, no supplementary loss of pigmented neurons in the locus coeruleus was found in patients with depression and AD. This finding resembles the situation in idiopathic depression, but is in contrast with earlier studies on depression in AD.

Aged↗

PubMed1999

Increased activity of surviving locus ceruleus neurons in Alzheimer's disease.

In Alzheimer's disease (AD) there is neuronal loss in the locus ceruleus (LC), and the noradrenergic system may be even more affected in depressed AD patients. However, this neuronal loss may go together with an increase in activity of the remaining noradrenergic neurons. We prospectively evaluated 16 AD patients (6 depressed, 5 transiently depressed, and 5 nondepressed) and 10 controls. We determined norepinephrine and its metabolite 3-methoxy-4-hydroxyphenylglycol (MHPG) in various brain areas, and compared these data with previously established neuron numbers in the LC in the same patients. We could not confirm earlier studies reporting lower norepinephrine concentrations in depressed than in nondepressed dementia patients. The mean norepinephrine concentrations in AD patients were significantly lower than those in control patients, whereas the mean concentrations of MHPG were not different. Moreover, we found significant inverse relationships between the number of remaining pigmented LC neurons and the MHPG/norepinephrine ratio in the frontal cortex and LC. These data are the first to provide direct evidence for the hypothesis that remaining LC neurons are activated to compensate for decreased cerebral norepinephrine levels in AD, by demonstrating that the MHPG/norepinephrine ratio is significantly higher in AD, indicating increased metabolism.

3,4-Dihydroxyphenylacetic Acid↗

PubMed1997

Congenital supratentorial arachnoidal and giant cysts in children: a clinical study with arguments for a conservative approach.

Little is known about the natural course of arachnoidal cysts (AC) and the incidence of complications. This poses a problem in selection of patients for surgical interventions. The present authors report on 19 children with supratentorial AC of varying location and size. The mean follow-up time is 6 years. The evolution of presenting symptoms, the developmental course, the occurrence of complications, the surgical intervention performed and its outcome are described. Associated neurological disorders cannot always be attributed to the cyst. If surgery is being considered, a causal relationship between the symptom and the cyst should be plausible.

Adolescent↗

PubMedDate not supplied

Depression in Parkinson's disease. The impact of symptom overlap on prevalence.

The reported prevalence of depression concomitant with Parkinson's disease varies greatly in the literature, which may partly be explained by symptom overlap. To determine the impact of symptom overlap on the prevalence, the authors tested 100 Parkinson's disease patients for major depression (DSM-III-R) with both a standard, inclusive method and a diagnostic-etiologic, exclusive method. The authors found that the prevalence detected with the inclusive method (23%) decreased when the exclusive method was used (13%), which was mainly caused by lower scores on the item "loss of interest." The study's findings give empirical support for the relevance of the new category in DSM-IV "mood disorder due to a general medical condition."

Aged↗