Biomedical subjects
Publications and source records attributed to M Spitzer.
A case of late onset metachromatic leukodystrophy with a clinical picture of paranoid hallucinatory psychosis and severe dyskinesia is described. The problem of diagnostic recognition is discussed. In the case, diagnostic procedures were initiated after atypical clinical course, and established on the basis of MRI and specific biochemical tests.
Functional magnetic resonance imaging was used to identify cortical regions activated by a working memory task involving letter detection. Twenty four normal subjects were scanned with a conventional 1.5-T magnet while performing one of two tasks: In the activation task, subjects responded by pressing a button whenever any presented letter was the same as the second last in the sequence. In the control condition, subjects had to respond to a single predefined letter without memory update requirements. The activation task and the control condition were identical with regard to perceptual input and motor output. They were different only regarding the task demand. Movement artifacts were minimized in a two way strategy and eight subjects were excluded from further analysis. Functional MR data from the remaining 16 subjects were analyzed on the basis of anatomical regions-of-interest which were manually defined in each subject. The engagement of working memory produced significant activation in the dorsolateral prefrontal cortex (Brodmann's areas 9, 10, 46, and 47) in both hemispheres. Results demonstrate the applicability of the paradigm within a clinical MRI setup and corroborate previous findings of non-lateralized dorsolateral prefrontal activation during continuous context updating and active maintenance.
Recent findings on frontal and subcortical circuitry provide an uniform and integral view of numerous neurological and psychiatric disorders. Frontal cortical areas, the basal ganglia and the thalamus are linked in parallel circuits, which can be related to specific mental and motor functions and pathologies. In particular, five such circuits can be distinguished: (1) motor, (2) oculomotor, (3) dorsolateral-pre-frontal, (4) lateral orbitofrontal, and (5) mediofrontal limbic. The anatomy of these circuits as well as the involved neurotransmitters provide a comprehensive framework for understanding the symptoms of neurological diseases such as frontal lobe infarctions, Parkinson's, Huntington's, and Binswanger's disease, as well as psychiatric diseases such as schizophrenic, affective, and obsessive-compulsive disorder.
The experimental association psychology approach to mental associations has been the conceptual background for the concept of schizophrenia. Cognitive neuroscience methods and concepts can be used to study various forms of schizophrenic thought disorder. In particular, the concepts of semantic associative and working memory can be applied fruitfully to schizophrenia research. Semantic associative networks can be simulated with self-organizing feature maps. Dysfunctional lexical access can be modeled in terms of low signal-to-noise ratio in intra- or between-network information processing. Evidence for the crucial role of dopamine in this function is presented, and a general neurocomputational model of schizophrenic thought disorder is developed. This model capitalizes on basic aspects of neural information processing (i.e., neuromodulation and neuroplasticity) and allows a parsimonious explanation of a number of otherwise inexplicable or unrelated clinical phenomena and experimental results.
The reports of a person suffering from loose associations and disordered behavior serve as the basis for a phenomenology of some central components of psychotic experience. Especially salient are "the expansion of the horizon of meanings," "the emergence of explicit experiences from implicit ones," and "the reduction of complexity." The phenomenological concepts thus developed supplement recent discoveries in neuroscience and experimental psychopathology. Cognitive neuroscientists have depicted the surface of the brain as a repository of self-organizing cortical maps of mental life. Furthermore, experimental psychopathologists have characterized semantic associative networks in normal experience and in psychosis. The authors conclude by joining the phenomenology of psychotic consciousness with the findings of these neuroscientists and experimental psychopathologists.
The purpose of this study was to explore dangerousness and fire setting recidivism of mentally disordered firesetters in comparison with mentally healthy arsonists. In Germany, all trials are registered centrally by the Federal Central Register. The records of this Register for the three year period from 1983 until 1985 were used in this follow-up study of arsonists to identify three samples of subjects: (1) All persons convicted of arson who have been found not guilty by reasons of insanity (n = 186), (2) all person convicted of arson who have been found guilty of diminished responsibility (n = 97), and (3) a random selection from all persons convicted of arson who have had no psychiatric examination in their trial (n = 187). The follow-up ended in 1994, providing a period of, on average, ten years. Mentally disordered arsonists differed from non-mentally disordered arsonists in the following ways: They were more likely, first, to have a history of arson before 1983, and secondly, to be convicted of arson again (11% relapse compared to 4%). Mentally disordered arsonists had fewer registrations of common offenses, such as theft as well as traffic violations and alcohol-related offenses. Based on the present sample, mentally disordered firesetters have a higher rate of recurrence of firesetting than non-mentally disordered firesetters and commit fewer common offenses other than firesetting.
Schizophrenic patients (n = 44) and normal controls (n = 50) performed a computerized version of the Stroop color-word interference task. Schizophrenic patients generally showed more Stroop interference than normal subjects. The effect was neither related to demographic variables, nor to actual psychopathology. However, the course of the disorder was related to the Stroop effect, in that acute, chronic, and schizoaffective patients displayed a larger interference effect than patients with a recurrent episode. From a methodological perspective, the computerized version of the Stroop task proved to be more sensitive to interference effects in the patient group. The finding of enhanced reverse Stroop interference in patients strongly preoccupied with colors is discussed within the framework of MacLeod and Dunbar's (MacLeod and Dunbar, 1988) theory of Stroop interference involving differential practice effects.
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In order to examine the effect of dopamine on semantic processing, we performed a double-blind, placebo-controlled study. Healthy volunteers (n = 31) were tested in a lexical decision paradigm after ingestion of either L-dopa 100 mg with benserazide 25 mg or placebo. While direct semantic priming was influenced only marginally by L-dopa, the indirect priming effects was reduced significantly. These data support the hypothesis that dopamine increases the signal-to-noise ratio in semantic networks by reducing the spread of semantic processing, thereby leading to a focussing of activation.
We documented and quantified Monsel's solution-related artifacts after cervical biopsies. All loop electrosurgical cone biopsy specimens over a 3-month period were reviewed for necrosis artifact of the surface epithelium. The degree of change was quantified and correlated with the antecedent use of Monsel's solution. Twenty-four cone biopsy specimens were evaluated. Three of the eight cone biopsy specimens obtained fewer than 10 days after the use of Monsel's solution showed definite changes. Between 10 and 18 days after the use of Monsel's solution, four of eight specimens showed change. After 18 days, none of eight specimens showed change. One specimen at 18 days showed focal changes that seemed to be related to the use of an unusually large amount of Monsel's solution, because the patient had had six biopsies within 2 days. The routine use of Monsel's solution may interfere with the ability to recognize and characterize disease process in cone biopsy specimens when the cone procedure is done within 3 weeks after the use of Monsel's solution.
Functional magnetic resonance imaging (fMRI), in conjunction with carefully designed, psychometrically optimized stimulation procedures, was used to investigate the relation between brain activation and the processing of word associations. A semantic discrimination task of word-pair similarity was performed by normal subjects (n = 17) within a clinical 1.5-Tesla whole-body MRI system. A color similarity task of psychometrically equivalent difficulty, as indicated by behavioral data acquired online during fMRI, served as active control condition. Comparisons between tasks dramatically improved results compared to comparisons between task and resting condition. The language paradigm selectively activated left frontal and left fronto-temporal areas. Cortical activation during the semantic task decreased significantly over three runs of the same word list and was paralleled by decreased reaction times. No such changes were observed in the active control condition indicating selective learning of the language task only. When combined with psychological activation schemes and the acquisition of behavioral data, fMRI represents a powerful tool for the study of brain-behavior interaction.
Operative laparoscopic techniques requiring placement of large-bore cannulas through the abdominal wall lateral to the midline result in increased numbers of injuries to abdominal wall vessels. Five cases of inferior epigastric artery hemorrhage were controlled by percutaneous transabdominal placement of polypropylene sutures, allowing the procedure to be completed with the cannula in place. In two patients the sutures were left in place for 72 to 96 hours, and cutaneous necrosis occurred requiring debridement and delayed primary closure. In the other three women, removal of the sutures less than 24 hours postoperatively resulted in satisfactory hemostasis and primary healing of the abdominal wound. Percutaneous placement of polypropylene sutures may provide effective hemostasis after inferior epigastric artery hemorrhage due to cannula injury. Early suture removal may avoid potential cutaneous necrosis.
AIMS: Functional magnetic resonance imaging was used in conjunction with a letter detection task for the study of working memory in 16 normal subjects. Because of movement artifacts, data from only 9 subjects were analysed. METHODS: In the activation task, subjects responded by pressing a button whenever any presented letter was the same as the second last in the sequence. In the control condition, the subjects had to respond to a fixed letter. Hence, the activation condition and the control condition differed only subjectively, i.e., regarding the task demand, whereas the stimuli and the type and frequency of response were identical. RESULTS: The activation condition produced significant activation in the dorsolateral prefrontal cortex (Brodmann's areas 10, 46, and 9). CONCLUSIONS: In contrast to experimental tasks previously used rather extensively to study the prefrontal cortex, the present paradigm is characterized by its simplicity, interpretability, and its ties to known neurophysiology of the frontal cortex.
Transcranial magnetic stimulation (TMS) can be triggered and thereby allows the reversible manipulation of cortical information processing. A magnetic field is induced by a coil which produces a current which has an excitatory or inhibitory effect on the underlying cortex. Triggered TMS has been used to assess the visual system and lately the method was also applied to higher cognitive functions. The method has good spatial and temporal resolution and it can be combined with other neuroscience and experimental psychological methods. We provide an overview on TMS research and present the results of a study. Possible applications and limitations of the method are discussed with respect to basic research as well as diagnostic and therapeutic implications.
The concepts of intoxication, intoxication psychosis, and drug-induced psychosis are frequently used to refer to psychopathological states caused by the intake of hallucinogenic substances. The considerable increase of intoxications with substances of the chemical class of amphetamines (in particular, "Ecstasy") in western countries should cause major concern. Moreover, the number of schizophrenic patients who also use hallucinogenic drugs is increasing. High incidence and comorbidity cause clinical problems and call for detailed knowledge of the drug related acute and chronic effects of the various agents currently in use. Clinical findings and subjective reports from research in experimental psychoses are used to discuss differential diagnosis and types of drug-induced mental disorders within the framework of present day classificatory systems, such as DSM-IV and ICD-10.
The concept of noise has only recently been applied to modelling neuropsychiatric disorders. Two examples of such models are presented. 1. A phantom limb is a neurological condition after the amputation of an extremity. It consists of sensations of the presence of the lost limb and has been attributed to cortical as well as non-cortical mechanisms. A neural network model of phantom limbs is proposed which can parsimoniously account for a large number of clinical features and recent findings of cortical map plasticity after deafferentation. In trained self-organizing feature maps, deafferentation was simulated. Reorganization is shown to be driven by input noise. According to the model, the production of input noise by the deafferented primary sensory neuron drives cortical reorganization in amputees. No such noise is generated and/or conducted to the cortex in paraplegics. 2. Several clinical features of schizophrenia have been related to the ratio of signal to noise in neuronal information processing. In particular, dopamine--which has been implicated in the causation of schizophrenia for decades--has been proposed to modulate signal-to-noise ratio. Data are presented which suggest that schizophrenic thought disorder is the result of a hypodopaminergic state and concomitant increased effects of noise in semantic information processing. Possible functions of noise in the nervous systems are discussed.
Neuropsychological, computational, and psycholinguistic data suggest the existence of semantic maps, i.e. localized representations of semantic information in the brain. Using functional magnetic resonance imaging, this hypothesis was directly tested with a picture naming task involving items from four different semantic categories. Small left lateralized fronto-temporal cortical sites of category-specific activation were found when brain activation signals were averaged. Data suggest the existence of multiple maps coding high-level representations of objects, such that meaningful distinctions, at least in part, govern the physical distribution of cortical semantic storage.