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

In addition to the existence of complex memory (similar to the implicit nondeclarative memory of Squire), the existence of a phylogenetically old apparatus of a memory of situations (SMA) is supposed, which is to some extent comparable with the declarative memory of Squire. During actual sensory information the SMA generates a general frame and forms a general 'mark', indicating whether a given information has its origin inside or outside the body, and whether it is new or known. The procedure of this marking process can be explained as the time-depending arrest of a copy of the actual original information-transporting signal 'shower'; this copy must last until the feedback from thalamocortical centers indicates the termination of the processing of the original signal showers. The arrest of the shower copies is the performance of neuronal networks of the entorhinal cortex (EC) and the gyrus dentatus (GD). The psychopathological and biochemical analyses of experimental dibenamine psychosis show a different effect of dibenamine on the noradrenaline (NA) receptors of the EC and GD, respectively: these effects are responsible for the repeated perception cycles of a single situation. N,N-Dibencylamine blocks the postsynaptic alpha(1)-receptors of the EC without influencing the beta-receptors of the GD. Thus the interaction between EC and GD is changed: instead of new scenes, perceptions that have just been experienced get repeated presence and the quality of familiarity. The prolonged arrest of shower copies simultaneously blocks the entrance of new signal showers from the EC to the GD. No information-transporting signal showers can come in as long as the arrest lasts. In case of a disturbance in NA-dependent actions within the EC and the GD, the duration of arrest of information-transporting signal showers is shortened. Thus the formal frame of experience receives the quality of novelty instead of familiarity, and in addition the qualities of uncertainty, vagueness, and alienity. These very changes in perception and experience represent the basic disturbance of schizophrenia. All the symptoms of schizophrenia may be explained by this basic disturbance. The analysis of biochemical aspects turns attention to the energetic situation of NA and N-methyl-D-aspartate systems. These considerations suggest a genetic background of the basic disturbance of schizophrenia: transmitter effects on membranes of neurons and possibly also on glial cells, and energy supply of these effects may be predetermined genetically. It may be assumed that the compensation of such membrane-dependent disturbances will be possible within wide areas of the neural network, except for the 'bottleneck' of the overlapping region of the iso- and allocortex.
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PMID:Schizophrenia - A disturbance of signal interaction between the entorhinal cortex and the dentate gyrus? The contribution of experimental dibenamine psychosis to the pathogenesis of schizophrenia: A hypothesis. 1042 98

The purpose of the present study was to evaluate the cortical response to motor stimulation in neuroleptic-naive first episode schizophrenics in comparison to matched controls using a high speed functional magnetic resonance imaging technique (fMRI). Twelve patients satisfying ICD 10 criteria (F20.0) for schizophrenia (paranoid subtype) as well as sex- and age-matched healthy volunteers participated in this study. All subjects underwent fMRI examination on a conventional 1.5 T MR unit equipped with an echo-planar imaging booster. The blood oxygen level dependent (BOLD) response of the sensorimotor cortex and the higher order SMA region was evaluated during performance of a left hand sequential finger opposition task. Special care was taken to minimize performance and motion artifacts. Patients and controls showed no notable difference with respect to laterality, changes of signal intensity or spatial extent of activation within the primary and higher order motor regions. Using high speed fMRI no fundamental motor cortical dysfunction was evident in a group of paranoid neuroleptic-naive first episode schizophrenic patients. In contrast to data previously reported for chronic disorganized medicated patients, these results suggest that motor dysfunction is not part of the phenomenology of acute paranoid first episode patients.
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PMID:Cortical response to motor stimulation in neuroleptic-naive first episode schizophrenics. 1082 97

The present study used functional MRI to clarify the brain regions activated during a series of motor sequencing tasks in healthy volunteers. Ten subjects were scanned while performing three soft signs tasks ranging from simple (PT: palm tapping), moderate (PS: pronation/supination) to complex movements (FEP: fist-edge-palm). The FEP task induced significant activations within the cortical networks including bilateral sensorimotor, SMA, left parietal, and right cerebellum, but no activation in the prefrontal area. Moreover, the percentage signal changes within the left sensorimotor, left thalamus and right cerebellum showed an increase in activation with task complexity. The present findings challenge the traditional belief that FEP was a task for frontal lobe function but suggest that successful performance of more complex neurological soft sign tasks like FEP requires the participation of more brain areas than simple motor sequencing and coordination task like PS and PT. These also provide the empirical data on the neural basis of neurological soft signs for further study in other clinical group like schizophrenia in the near future.
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PMID:The neural basis of motor sequencing: an fMRI study of healthy subjects. 1646 46

Increasing evidence suggests that schizophrenia is associated with various morphological and functional abnormalities of the frontal cortex. So far research has concentrated on the dorsolateral and orbitofrontal cortex. Behavioral evidence suggests however that regions responsible for higher motor control are compromised in schizophrenia as well. The current study assessed volumes of the anterior supplementary motor area (pre-SMA) and implicit motor sequence learning in 15 subjects with first-episode schizophrenia and 15 healthy matched controls. Pre-SMA volumes were assessed by three-dimensional structural magnetic resonance imaging (3D-MRI) and manual parcellation according to an established protocol. Implicit motor sequence learning was assessed using the Serial Reaction-Time Task (SRTT). Compared with control subjects, schizophrenia subjects had significantly smaller volumes of the left pre-SMA (16%). Subjects with schizophrenia were severely impaired on sequence-specific implicit motor learning. Size of the left pre-SMA of schizophrenia subjects was significantly related to impaired implicit learning. We conclude that subjects with first-episode schizophrenia have a morphological abnormality of the left pre-SMA that might predispose them to develop disturbances of higher motor control during acute episodes of psychosis. These structural and behavioral abnormalities might be conceptualized within a broader model that views schizophrenia as a disorder of disturbed coordination of thought and action.
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PMID:Reduced size of the pre-supplementary motor cortex and impaired motor sequence learning in first-episode schizophrenia. 1662 28

The recall of an object from features is a specific operation in semantic memory in which the thalamus and pre-supplementary motor area (pre-SMA) are integrally involved. Other higher-order semantic cortices are also likely to be involved. We used the object-recall-from-features paradigm, with more sensitive scanning techniques and larger sample size, to replicate and extend our previous results. Eighteen right-handed healthy participants performed an object-recall task and an association semantic task, while undergoing functional magnetic resonance imaging. During object-recall, subjects determined whether words pairs describing object features combined to recall an object; during the association task they decided if two words were related. Of brain areas specifically involved in object recall, in addition to the thalamus and pre-SMA, other regions included the left dorsolateral prefrontal cortex, inferior parietal lobule, and middle temporal gyrus, and bilateral rostral anterior cingulate and inferior frontal gyri. These regions are involved in semantic processing, verbal working memory and response-conflict detection and monitoring. The thalamus likely helps to coordinate activity of these different brain areas. Understanding the circuit that normally mediates this process is relevant for schizophrenia, where many regions in this circuit are functionally abnormal and semantic memory is impaired.
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PMID:Neural correlates of the object-recall process in semantic memory. 1693 39

The present study assessed 25 patients with unipolar major depression and 34 patients with schizophrenia along with 50 healthy, non-psychiatric controls for the presence of serum antinuclear (ANA), smooth muscle (SMA), anti-endothelial (AEA), anti-sarcolemma (ASA), thyroid gland (TGA) and parietal cell (PCA) antibodies. In the group of patients with major depression, the frequency of elevated ANA, TGA and PCA was significantly higher than in the control group. In addition, the group of patients with schizophrenia significantly more often showed increased levels of ANA and SMA than the control group of healthy volunteers. When the two psychiatric groups were compared, PCA serum titers in major depression and SMA values in schizophrenia were significantly more frequently elevated, whereas values of AEA and ASA showed no difference. These results point towards the existence of an unspecific (auto) immune disposition or reaction in at least a subgroup of patients with major depression and schizophrenia.
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PMID:Autoantibody reactivity in serum of patients with major depression, schizophrenia and healthy controls. 1809 44

Acupuncture therapy has been applied to various psychiatric diseases and chronic pain since acupuncture stimulation might affect brain activity. From this point of view, we investigated the effects of acupuncture on autonomic nervous system and brain hemodynamics in human subjects using ECGs, EEGs and near-infrared spectroscopy (NIRS). Our previous studies reported that changes in parasympathetic nervous activity were correlated with number of de-qi sensations during acupuncture manipulation. Furthermore, these autonomic changes were correlated with EEG spectral changes. These results are consistent with the suggestion that autonomic changes induced by needle manipulation inducing specific de-qi sensations might be mediated through the central nervous system, especially through the forebrain as shown in EEG changes, and are beneficial to relieve chronic pain by inhibiting sympathetic nervous activity. The NIRS results indicated that acupuncture stimulation with de-qi sensation significantly decreased activity in the supplementary motor complex (SMC) and dorsomedial prefrontal cortex (DMPFC). Based on these results, we review that hyperactivity in the SMC is associated with dystonia and chronic pain, and that in the DMPFC is associated with various psychiatric diseases with socio-emotional disturbances such as schizophrenia, attention deficit hyperactive disorder, etc. These findings along with the previous studies suggest that acupuncture with de-qi sensation might be effective to treat the various diseases in which hyperactivity in the SMA and DMPFC is suspected of playing a role.
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PMID:Effects of acupuncture on the brain hemodynamics. 2060 14

Deficits in executive functioning have been described as a core feature of schizophrenia and have been linked to patterns of fronto-temporo-limbic brain alterations. To date, such structure-cognition relationships have not been explored in a clinically defined at-risk mental state (ARMS) for psychosis using whole-brain neuroimaging techniques. Therefore, we used voxel-based morphometry in 40 ARMS and 30 matched healthy control (HC) individuals to investigate whether gray and white matter volumes (1) correlated with the performance in the Trail-Making Test B (TMT-B), an established measure of executive functioning, and (2) were volumetrically linked to the ventromedial prefrontal cortex (VMPFC), found to be associated with TMT-B in the ARMS during the first analysis step. We found the ARMS subjects to be specifically impaired in their TMT-B performance versus HC. Brain-cognition associations involving the insular cortices were observed in the HC, but not in the ARMS individuals. Conversely, TMT-B correlations in the VMPFC, the cerebellum, the fronto-callosal white matter were detected in the ARMS, but not the HC group. The VMPFC was linked to the temporo-limbic cortices in HC, whereas the connectivity pattern in the ARMS involved the left temporal and dorsolateral prefrontal cortex, the cerebellum, the right SMA and extended portions of the fronto-callosal white matter. These findings suggest that executive deficits are already present in the ARMS for psychosis and may be subserved by structurally altered networks of interconnected cortical and subcortical brain regions in line with the disconnectivity hypothesis of schizophrenia.
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PMID:Neuroanatomical correlates of executive dysfunction in the at-risk mental state for psychosis. 2082 78

Little is known about the neurobiology of hypokinesia in schizophrenia. Therefore, the aim of this study was to investigate alterations of white matter motor pathways in schizophrenia and to relate our findings to objectively measured motor activity. We examined 21 schizophrenia patients and 21 healthy controls using diffusion tensor imaging and actigraphy. We applied a probabilistic fibre tracking approach to investigate pathways connecting the dorsolateral prefrontal cortex (dlPFC), the rostral anterior cingulate cortex (rACC), the pre-supplementary motor area (pre-SMA), the supplementary motor area proper (SMA-proper), the primary motor cortex (M1), the caudate nucleus, the striatum, the pallidum and the thalamus. Schizophrenia patients had lower activity levels than controls. In schizophrenia we found higher probability indices forming part of a bundle of interest (PIBI) in pathways connecting rACC, pre-SMA and SMA-proper as well as in pathways connecting M1 and pre-SMA with caudate nucleus, putamen, pallidum and thalamus and a reduced spatial extension of motor pathways in schizophrenia. There was a positive correlation between PIBI and activity level in the right pre-SMA-pallidum and the left M1-thalamus connection in healthy controls, and in the left pre-SMA-SMA-proper pathway in schizophrenia. Our results point to reduced volitional motor activity and altered motor pathway organisation in schizophrenia. The identified associations between the amount of movement and structural connectivity of motor pathways suggest dysfunction of cortico-basal ganglia pathways in the pathophysiology of hypokinesia in schizophrenia. Schizophrenia patients may use cortical pathways involving the supplementary motor area to compensate for basal ganglia dysfunction.
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PMID:Altered cortico-basal ganglia motor pathways reflect reduced volitional motor activity in schizophrenia. 2327 79

Abnormalities in both time processing and dopamine (DA) neurotransmission have been observed in schizophrenia. Time processing seems to be linked to DA neurotransmission. The cognitive dysmetria hypothesis postulates that psychosis might be a manifestation of the loss of coordination of mental processes due to impaired timing. The objective of the present study was to analyze timing abilities and their corresponding functional neuroanatomy in schizophrenia. We performed a functional magnetic resonance imaging (fMRI) study using a predictive motor timing paradigm in 28 schizophrenia patients and 27 matched healthy controls (HC). The schizophrenia patients showed accelerated time processing compared to HC; the amount of the acceleration positively correlated with the degree of positive psychotic symptoms and negatively correlated with antipsychotic dose. This dysfunctional predictive timing was associated with BOLD signal activity alterations in several brain networks, especially those previously described as timing networks (basal ganglia, cerebellum, SMA, and insula) and reward networks (hippocampus, amygdala, and NAcc). BOLD signal activity in the cerebellar vermis was negatively associated with accelerated time processing. Several lines of evidence suggest a direct link between DA transmission and the cerebellar vermis that could explain their relevance for the neurobiology of schizophrenia.
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PMID:Predictive Motor Timing and the Cerebellar Vermis in Schizophrenia: An fMRI Study. 2719 Feb 80


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