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Query: UMLS:C0036341 (schizophrenia)
 60,220 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Auditory hallucinations (AH), the perception of sounds and voices in the absence of external stimuli, remain a serious problem for a large subgroup of patients with schizophrenia. Functional imaging of brain activity associated with AH is difficult, since the target event is involuntary and its timing cannot be predicted. Prior efforts to image the patterns of cortical activity during AH have yielded conflicting results. In this study, MEG was used to directly image the brain electrophysiological events associated with AH in schizophrenia. We observed an increase in theta rhythm, as sporadic bursts, in the left superior temporal area during the AH states, whereas there was steady theta band activity in the resting state. The present finding suggests strong association of the left superior temporal cortex with the experience of AH in this patient. This is consistent with the hypothesis that AH arises from areas of auditory cortex subserving receptive language processing.
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PMID:Theta rhythm increases in left superior temporal cortex during auditory hallucinations in schizophrenia: a case report. 1104 65

Auditory sensory processing in the human cerebral cortex is disturbed in several neurological and neuropsychiatric disorders, ranging from devastating perceptual deficits in neuropsychological syndromes such as cortical deafness and auditory agnosia to the problem of involuntary hallucinatory perception in schizophrenia. With modern non-invasive functional imaging techniques (e.g., PET, fMRI, and MEG), the normal auditory cortical functional anatomy can now be studied in humans in vivo, as well as its disruption in pathological conditions. This article will summarize current knowledge on human central auditory perception in health and disease, with an emphasis on recent functional neuroimaging studies, in the context of clinical and basic neuroscientific knowledge. New strategies include a focus on the role of other, non-temporal brain areas for auditory processing, particularly in the frontal lobes, and the combined use of techniques offering both precise spatial and temporal resolution. One step towards this goal has been the recent development of a silent, event-related fMRI scanning technique.
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PMID:Functional neuroimaging of human central auditory processing in normal subjects and patients with neurological and neuropsychiatric disorders. 1132 Apr 47

A 2* 37 channel biomagnetic system (Magnes II) was used to record spontaneous magnetic activity for the frequency ranges 2-6 Hz and 12.5-30 Hz in 30 patients with schizophrenia (23 men and 17 women) and 30 healthy volunteers in both hemispheres during a resting condition. The dipole localization was calculated by the dipole density plot (DDP) method, which is a spatial averaging in order to decrease the influence of the nonfocal activity. The quantified DDP results were superimposed to T2-weighted MR-images of each patient's head as isocontour lines. To superimpose the MEG results to 3-D MRI data, the scanned head data set was fitted to the reconstructed MRI head shape using a surface fit programme developed by our department. The absolute dipole values were correlated with the psychopathological findings and the cumulative neuroleptic dosage for each patient. The group of patients with schizophrenia differed overall from the healthy subjects in the elevation of absolute dipole values measured in both hemispheres. For the region of slow dipole activity (2-6 Hz), a high correlation was found between the intensity of dipole concentration and productive psychotic symptoms (PANSS, P1-P7). Dipole localization (for both frequency ranges) showed a concentration effect (DCE) in the temporoparietal region in patients with schizophrenia.
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PMID:Spontaneous, slow and fast magnetoencephalographic activity in patients with schizophrenia. 1240 58

When slow waves in the EEG delta and theta frequency range appear in the waking state, they may indicate pathological conditions including psychopathology. The generators of focal slow waves can be mapped using magnetic source imaging. The resulting brain maps may possibly characterize dysfunctional brain areas. The present study examined the stability of the density and distribution of MEG slow waves during three conditions-rest, mental arithmetic and imagery-in 30 schizophrenic patients and 17 healthy controls. Schizophrenic patients displayed a higher density of delta and theta generators primarily in temporal and parietal areas. The group difference was not affected by the particular conditions. The focal concentration of delta and theta slow waves did not differ between patients with and without neuroleptic medication, whereas the prominence of theta dipoles in the temporal area correlated with neuroleptic dosage. The relative amount of temporal slow waves was correlated with the negative symptoms score (PANSS-N) suggesting that temporal dysfunction may be related to negative symptomatology.Results suggest that the distribution of slow-wave activity, measured in a standardized setting, might add diagnostic information about brain abnormalities in schizophrenia.
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PMID:Source distribution of neuromagnetic slow-wave activity in schizophrenic patients--effects of activation. 1289 59

Auditory hallucinations are one the most enigmatic and hampering symptoms associated with schizophrenia. Non-invasive functional imaging techniques have begun to delineate the underlying neuronal basis. We investigated the spontaneous magnetoencephalographic activity in a 33-year-old male schizophrenic patient and compared the results to those obtained from 13 healthy controls. Despite current neuroleptic medication (clozapine) the patient was still suffering from auditory hallucinations. Using the dipole density method, we were able to demonstrate an increase of fast MEG activity (12.5-30 Hz) in the left auditory cortex associated with hallucinations. This activity was absent in healthy controls. We conclude that an increase in fast MEG activity in the auditory cortex is a neurophysiologic correlate for auditory hallucinations in schizophrenia.
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PMID:Cortical activity associated with auditory hallucinations. 1509 16

The cerebellum has traditionally been associated with motor movements but recent studies suggest its involvement with fine timing, sensory analysis and cognition. Much of the new data comes from neuroimaging techniques such as fMRI and PET, which have high spatial resolution and show that for even simple stimuli many cerebellar and cortical areas are involved. We use examples from recent studies to demonstrate that magnetic field tomography (MFT) offers a new and powerful tool for studying cerebellar function through real time localization of cortical, brainstem and cerebellar activations over timescales ranging from a fraction of a millisecond to seconds, minutes and hours. The examples include demonstration of cerebellar activations along well-established anatomical pathways during saccades and the visualization of the ascending medullar volley after median nerve stimulation. MFT analysis of single trial MEG signals elicited by the presentation of faces in emotion and object recognition tasks, show changes in cerebellar activation between schizophrenics and normal subjects in agreement with proposals for disturbed cerebellar function in schizophrenia. The ability of MFT to identify cerebellar, brainstem and cortical activations in real time can add new insights about dynamics of brain activity to the recent findings about cerebellar function from PET and fMRI.
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PMID:Imaging cerebellum activity in real time with magnetoencephalographic data. 1566 Nov 87

Both an EEG P50 sensory gating deficit and abnormalities of the temporal lobe structure are considered characteristic of schizophrenia. The standard P50 sensory gating measure does not foster differential assessment of left- and right-hemisphere contributions, but its analogous MEG M50 component may be used to measure gating of distinct auditory source dipoles localizing to left- and right-hemisphere primary auditory cortex. The present study sought to determine how sensory gating ratio may relate to cortical thickness at the site of the auditory dipole localization. A standard auditory paired-click paradigm was used during MEG for patients (n=22) and normal controls (n=11). Sensory gating ratios were determined by measuring the strength of the 50 ms response to the second click divided by that of the first click (S2/S1). Cortical thickness was assessed by two reliable raters using 3D sMRI. Results showed that: (1) patients had a P50 and left M50 sensory gating deficit relative to controls; (2) cortex in both hemispheres was thicker in the control group; (3) in schizophrenia, poorer left-hemisphere M50 sensory gating correlated with thinner left-hemisphere auditory cortical thickness; and (4) poorer right-hemisphere M50 auditory sensory gating ratio correlated with thinner right-hemisphere auditory cortical thickness in patients. The MEG-assessed hemisphere-specific auditory sensory gating ratio may be driven by this structural abnormality in auditory cortex.
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PMID:Auditory sensory gating deficit and cortical thickness in schizophrenia. 1601 89

Multimodal imaging, the combination of several brain imaging techniques in one subject, provides a wealth of parameters and favours the interpretation of complex models in schizophrenia research. Moreover, new imaging tools allow the investigation of distinct neurotransmitter systems and their modulation by pharmacological intervention. An important feature of multimodal imaging is the possibility to characterize the activation dependencies of different neurotransmitters and provide the experimental tool to test system models of brain function and dysfunction. The combination of measurement techniques with high temporal resolution (e. g. MEG, EEG) and high spatial resolution (e. g. fMRI) facilitate the understanding of local and global systems as well as time characteristics. Moreover, the association of imaging parameters with genetic variations of neurotransmitter systems allows the investigation of neurotransmitter activity and its role in the pathophysiology of schizophrenia. To overcome the limitations of standard statistical methods, new approaches in machine learning have to be adapted to handle multiple parameters obtained from brain imaging and genetic measurements.
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PMID:Combination of multimodal imaging and molecular genetic information to investigate complex psychiatric disorders. 1650 2

Schizophrenia is typically associated with cognitive deficits, but symptoms also point to alterations in the processing of affective material, with potential impact on behavioral performance. This impact may unfold on multiple time scales, but initial processing of rapidly unfolding social cues may be particularly important. MEG-assessed regional brain activity associated with the capacity to process the emotional content of rapid visual stimuli (3/s) was examined in 12 individuals with schizophrenia and 12 matched controls. Patients showed less differentiation of emotional versus neutral stimuli 90-300 ms following picture onset. Together with group differences in the lateral topography of valence effects, these results are discussed as evidence of deficient automatic processing of emotionally potent stimuli in schizophrenia.
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PMID:Electromagnetic brain activity evoked by affective stimuli in schizophrenia. 1696 4

Used to study filtering abnormalities in schizophrenia, the paired-click paradigm suffers from poor test-retest reliability of the gating ratio, calculated from the P50 component of the ERP recorded at Cz approximately 50 ms following each of two stimuli. This study sought to improve reliability by assessing 50-ms gating at primary auditory cortices (PAC), the main generators of the P50 Cz component. MEG source modeling was used, taking advantage of the tangentially oriented PAC sources. Ten healthy subjects underwent three sessions, during which Cz-based and PAC-derived gating was measured. Unlike Cz P50, gating ratios at bilateral PACs achieved an intraclass coefficient of .8 or greater. Variability of gating within the same subject was also significantly smaller for bilateral PACs than for Cz P50. Paired-click gating ratio reliability can be improved by examining the individual PACs rather than composite scalp-recorded activity.
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PMID:Improved test-retest reliability of 50-ms paired-click auditory gating using magnetoencephalography source modeling. 1724 Nov 43


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