Brain blood flow changes measured by positron emission tomography during an auditory cognitive task in healthy volunteers and in schizophrenic patients.

OBJECTIVE: Cognitive deficit is an essential feature of schizophrenia. One of the generally used simple cognitive tasks to characterize specific cognitive dysfunctions is the auditory "oddball" paradigm. During this task, two different tones are presented with different repetition frequencies and the subject is asked to pay attention and to respond to the less frequent tone. The aim of the present study was to apply positron emission tomography (PET) to measure the regional brain blood flow changes induced by an auditory oddball task in healthy volunteers and in stable schizophrenic patients in order to detect activation differences between the two groups. METHOD: Eight healthy volunteers and 11 schizophrenic patients were studied. The subjects carried out a specific auditory oddball task, while cerebral activation measured via the regional distribution of [15O]-butanol activity changes in the PET camera was recorded. RESULTS AND DISCUSSION: Task-related activation differed significantly across the patients and controls. The healthy volunteers displayed significant activation in the anterior cingulate area (Brodman Area - BA32), while in the schizophrenic patients the area was wider, including the mediofrontal regions (BA32 and BA10). The distance between the locations of maximal activation of the two populations were 33 mm and the cluster size was about twice as large in the patient group. CONCLUSIONS: The present results demonstrate that the perfusion changes induced in the schizophrenic patients by this cognitive task extends over a larger part of the mediofrontal cortex than in the healthy volunteers. The different pattern of activation observed during the auditory oddball task in the schizophrenic patients suggests that a larger cortical area - and consequently a larger variety of neuronal networks--is involved in the cognitive processes in these patients. The dispersion of stimulus processing during a cognitive task requiring sustained attention and stimulus discrimination may play an important role in the pathomechanism of the disorder.

[Cognitive functions in prepsychotic and negative-symptom schizophrenic patients]. / Kognitív funkciók prepszichotikus és negatív tünetes szkizofrén betegekben.

BACKGROUND: Relationship between schizophrenia and cognitive functions has been reported by several studies. Our work group examined the changes of cognitive functions in prepsychotic patients without any relevant psychiatric disorder in their anamnesis, and also in schizophrenic patients with predominantly negative symptoms. METHODS: Measures were carried out by Cambridge Neuropsychological Test Automated Battery (CANTAB), a complex computer-based test battery of 13 tests covering a wide range of cognitive functions. 11 prepsychotic (9 male, 2 female) and 14 negative-symptom schizophrenic patients (all male) took part in the study. RESULTS: Prepsychotic patients showed significant (p < 0.05) impairment in the tests of visual memory, spatial recognition memory, spatial working memory and sustained attention. In patients with negative-symptoms significant deficits were also found (p < 0.05) in the delayed matching to sample, the working memory test, and in the intra-extradimensional shift--an analogue of Wisconsin Card Sorting Test. CONCLUSION: The present results show CANTAB may be a useful tool to detect the emergence of psychosis in an early phase, and also it has been found that in schizophrenic patients with predominantly negative symptoms further areas of cognition are also affected. The results may provide a better understanding about the background of the disorder, and the early recognition of the cognitive deficits may help to initiate a specific therapy in proper time. This could result in the slowing of the progression and an improved chance of recovery.

[Spatial standardization of [15O]-butanol PET images using T1-weighted MRI data]. / [15O]-butanol PET-vizsgálatok térbeli standardizálása szegmentált, T1-súlyozott MRI-felvételek segítségével.

Population averaged brain activation studies require the spatial standardization of the individual perfusion PET images. This procedure is usually supported by T1-weighted MRI images. The authors developed a segmentation technique to improve the automatized transformation of the individual MRI images into Talairach space. It was for the first time in Hungary that population averages of standardized T1-weighted MRI and [15O]-butanol PET images of the brain were created after validation of the procedure using data from 23 healthy volunteers. The newly developed method offers a solution for the automatized processing of primary data from brain activation experiments prior to statistical analysis.

[Use of positron emission tomography in psychiatry]. / A pozitronemissziós tomográfia pszichiátriai alkalmazása.

For the past years, substantial amount of experimental data has been published on the use of positron emission tomography in different psychiatric disorders. The different PET methods, which evaluate the whole-brain or regional metabolism, tissue perfusion or receptor density may help to identify the disorder specific changes in brain function and also better understand the underlying pathophysiology. In the clinical practice, PET plays an important role in the diagnosis and differential diagnosis of dementias and, presumably, in the near future the PET technique will be also extensively used in the clinical examination of other psychiatric disorders.

[Auditory event related potential and PET scan: a possibility for the comprehensive evaluation of cognition]. / Auditoros eseményhez kötött potenciál és PET: lehetóség a kogníció folyamatának komplex megközelítésére.

The authors studied the parallel use of event related potential (ERP) and brain activation PET in nine healthy volunteers. The presence of P300 wave in the EEG recording was accompanied by a parallel increase in the blood perfusion of the anterior cingulate gyrus. Furthermore, the functional connectivity between cortical and subcortical structures was also present during the task. This method combines the fine temporal-resolution of ERP and spatial-resolution of PET, which allows for the complex examination of fast cognitive processes. This approach may be useful in the investigation of psychiatric disorders.