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Biomedical subjects

Z Janka

Publications and source records attributed to Z Janka.

At least 19 recordsLinked to original sources
PubMed2002

Codon 311 (Cys --> Ser) polymorphism of paraoxonase-2 gene is associated with apolipoprotein E4 allele in both Alzheimer's and vascular dementias.

The gene of an esterase enzyme, called paraoxonase (PON, EC.3.1.8.1.) is a member of a multigene family that comprises three related genes PON1, PON2, and PON3 with structural homology clustering on the chromosome 7.(1,2) The PON1 activity and the polymorphism of the PON1 and PON2 genes have been found to be associated with risk of cardiovascular diseases such as hypercholesterolaemia, non-insulin-dependent diabetes, coronary heart disease (CHD) and myocardial infaction.(3-8) The importance of cardiovascular risk factors in the pathomechanism of Alzheimer's disease (AD) and vascular dementia (VD)(9-13) prompted us to examine the genetic effect of PON2 gene codon 311 (Cys-->Ser; PON2*S) polymorphism and the relationship between the PON2*S allele and the other dementia risk factor, the apoE polymorphism in these dementias. The PON2*C and PON2*S allele frequencies were similar in both AD (25% and 75%) and VD groups (23% and 77%), respectively, compared with the controls (27% and 73%). The ratio of the PON2*S carriers was significantly higher among the apoE4 allele carrier AD (27%) and VD (25%) groups than in the control (12%). Our results indicate that the PON2*S and apoE4 alleles have interactive effect on the development of the two most common forms of dementias AD and VD, and further support the hypothesis that cardiovascular factors contribute to the development of AD.

Aged↗
PubMed2001

Intact prototype learning in schizophrenia.

In this study, we examined executive functions and visual prototype learning in patients with schizophrenia (n=22) and matched healthy control subjects (n=20). The patients demonstrated marked perseveration in the Wisconsin Card Sorting Test (WCST), whereas they successfully learned prototypes of dot-pattern category exemplars. These findings are against the hypothesis of a pure generalized cognitive dysfunction in schizophrenia, providing preliminary evidence for intact neocortical mechanisms related to perceptual classification functions.

Adult↗
PubMed2001

[Impaired visual information processing in unaffected siblings of schizophrenia patients].

Recent research has provided evidence that certain psychophysiological dysfunctions are present in non-psychotic biological relatives of schizophrenia patients. A new candidate for such studies is the visual backward masking (VBM) dysfunction. In this study, the authors compared the VBM and Wisconsin Card Sorting Test (WCST) performances of unaffected siblings of schizophrenia patients with that of normal volunteers with a negative family history. In the BM test, a briefly presented target letter must be recognized, which is followed by an irrelevant stimulus (mask). The WCST assesses higher-level cognitive (prefrontal) functions of categorization and attentional set-shifting. Despite their intact psychosocial and general intellectual functions, the unaffected relatives of schizophrenia patients showed lower BM performances in comparison with the controls, which was restricted to short interstimulus intervals (< 60 ms). In the controls, there was a non-linear (N-shaped) masking function, whereas in the relatives no similar effects were found. There was no significant difference in the WCST performances. These results suggest that the dysfunction of early sensory-perceptual processes is a trait marker of schizophrenia.

Adolescent↗
PubMed2001

Remitted schizophrenia-spectrum patients with spared working memory show information processing abnormalities.

Working memory and information processing abnormalities are often reported in schizophrenia. The aim of this study was to examine visual backward masking (BM) functions in remitted schizophrenia-spectrum patients with spared working memory functions. Seventy-two patients with DSM-IV schizophrenia-spectrum disorders were screened using the Wisconsin Card Sorting Test (WCST) and the digit span forward/backward tasks. Patients with spared WCST and digit span performances were selected and administered a spatial working memory test and two BM procedures (target identification and location). The schizophrenia-spectrum group with spared WCST and digit span performances included individuals with schizophreniform disorder (N=11), schizophrenia (N=2), and schizoaffective disorder (N=2). These patients were clinically remitted and demonstrated spared IQ, normal spatial working memory, and relatively high psychosocial functioning. However, there was a significant impairment in the BM procedure, most prominently in the target location task and at short interstimulus intervals. These results suggest that the BM dysfunction is a trait marker of schizophrenia-spectrum disorders and may be present in the absence of working memory abnormalities.

Adult↗
PubMed2001

Are Alzheimer's disease patients able to learn visual prototypes?

Recently, controversial results emerged regarding visual prototype learning in Alzheimer's disease (AD). The aim of this study was to elucidate this issue in a larger population of AD patients. The AD patients (N=72) and age-matched healthy control subjects (N=25) learned to recognize and to categorize visual dot patterns. In comparison with the control subjects, the AD patients as a group showed dysfunctions in the recognition task, whereas categorization was relatively spared in their case. Recognition was impaired in patients with mild AD (Mini-Mental score: 18-23) and moderate AD (Mini-Mental score<18), whereas categorization was impaired only in patients with moderate AD. These results suggest that while the medio-temporal/diencephalic explicit memory system is markedly affected even in early AD, the sensory neocortical areas mediating implicit category learning display a sufficient degree of functional capacity until later stages of the disease.

Aged↗
PubMed2001

Event-related potentials from a visual categorization task.

Investigation of the neural bases of human perceptual categorization is a continuously growing territory of visual sciences. Recently, several papers appeared on the cortical bases of human categorization performance, using functional brain imaging techniques such as positron emission tomography (PET) or functional magnetic resonance imaging (fMRI). However, the cheaper commercially available laboratory tests are not always the best methods to study multiple aspects of visual categorization. In this study, we describe the electrophysiological correlates of natural scene categorization in humans. The subject's task was to decide whether briefly presented natural scenes contained animal or non-animal items. Analysis of event-related potentials (ERPs) recorded during the categorization task, revealed more negative potentials for non-animal stimuli (NAS) in the time windows of 150-250 ms (N1) and 350-500 ms (N2), and more positive potentials for animal stimuli (AS) in the time window of 250-350 ms (P2). Our work provides an inexpensive noninvasive method to study both early perceptual and late phases of semantic information processing by recording ERPs during the categorization of natural scenes.

Evoked Potentials, Visual↗
PubMed2001

Different trait markers for schizophrenia and bipolar disorder: a neurocognitive approach.

BACKGROUND: The aim of this study was to assess visual information processing and cognitive functions in unaffected siblings of patients with schizophrenia, bipolar disorder and control subjects with a negative family history. METHODS: The siblings of patients with schizophrenia (N = 25), bipolar disorder (N = 20) and the controls subjects (N = 20) were matched for age, education, IQ, and psychosocial functioning, as indexed by the Global Assessment of Functioning scale. Visual information processing was measured using two visual backward masking (VBM) tests (target location and target identification). The evaluation of higher cognitive functions included spatial and verbal working memory, Wisconsin Card Sorting Test, letter fluency, short/long delay verbal recall and recognition. RESULTS: The relatives of schizophrenia patients were impaired in the VBM procedure, more pronouncedly at short interstimulus intervals (14, 28, 42 ms) and in the target location task. Marked dysfunctions were also found in the spatial working memory task and in the long delay verbal recall test. In contrast, the siblings of patients with bipolar disorder exhibited spared performances with the exception of a deficit in the long delay recall task. CONCLUSIONS: Dysfunctions of sensory-perceptual analysis (VBM) and working memory for spatial information distinguished the siblings of schizophrenia patients from the siblings of individuals with bipolar disorder. Verbal recall deficit was present in both groups, suggesting a common impairment of the fronto-hippocampal system.

Adult↗
PubMed2001

Comparative studies on [Ca2+]i-level of fibroblasts from Alzheimer patients and control individuals.

The accumulation of the beta-amyloid peptide (betaAP) in the brain, produced from the ubiquitously expressed amyloid precursor protein (APP) is a defining feature of Alzheimer's disease (AD). Consistent with studies demonstrating the importance of skin biopsy in the diagnosis of neurodegenerative disorders, we investigated whether differences in intracellular free calcium levels ([Ca2+]i) of cultured cutaneous fibroblasts derived from sporadic AD patients and from age-matched control individuals might be present. [Ca2+]i was measured in Fura-2AM-loaded human fibroblasts by dual wavelength spectrofluorimetry. AD cells exhibited lower [Ca2+]i as compared to the control cultures. Exposure of fibroblasts to betaAP resulted in increased [Ca2+]i of the control cells, but not of AD fibroblasts. Our test could prove useful in supporting the diagnosis of (sporadic) AD in patients suspected of suffering from the disease.

Aged↗
PubMed2000

Visual information processing in patients with schizophrenia: evidence for the impairment of central mechanisms.

Patients with schizophrenia are especially impaired in the detection of spatial location if the briefly presented target stimulus is followed by a mask in a close temporal proximity (target location backward masking (BM) paradigm). It has been suggested that this phenomenon is related to the impairment of low spatial and high temporal frequency-sensitive transient (magnocellular) visual channels. To test this hypothesis, we measured target location BM and visual contrast sensitivity (CS) in clinically remitted patients with schizophrenia. In the BM task, subjects were asked to indicate the position of letters appearing at four possible spatial locations. In the CS test, a two-alternative forced choice method was used to measure the minimal contrast level required for the detection of horizontal gratings set at low spatial and high temporal frequencies (0.5 cycle/degree and 8 Hz, respectively). We found that the schizophrenia patients with normal CSs (spared transient channel functions) showed a marked deficit in the target location BM task. This suggests that the abnormality of subcortical transient channels does not explain some visual information processing dysfunctions in schizophrenia. Instead, deficient cortical interactions of rapidly changing environmental signals may be involved.

Adult↗
PubMed2000

P300 component of visual event-related potentials distinguishes patients with idiopathic parkinson's disease from patients with essential tremor.

A considerable rate of misdiagnosis has recently been reported in movement disorders. One of the most difficult clinical problems is the differentiation of Parkinson's disease and essential tremor. In this study, we have examined whether event-related potentials (ERPs) could aid in the solution of this differential diagnostic problem. Visual ERPs were obtained by using an "oddball" paradigm in 20 patients with idiopathic Parkinson's disease (IPD), 20 patients with essential tremor (ET), and 20 age-matched control subjects. We found that the P300 amplitudes were selectively reduced in the IPD group at the midline (Fz, Cz, Pz) electrode sites, whereas the ET group exhibited selectively elevated P300 amplitudes at the left parietal and frontal (F3, P3) recording sites. The patients with IPD, but not ET, showed a significant prolongation of the P300 latency at each electrode site. Similarly, only the IPD patients were significantly slower in responding to the target stimulus. The primary visual evoked potential (P100) did not distinguish among the IPD, ET, and control subjects. These results suggest that visual ERPs might provide a useful diagnostic method for differentiating IPD from ET.

Aged↗
PubMed2000

Early and late components of visual categorization: an event-related potential study.

We examined the characteristics of early and late components of event-related potentials (ERPs) accompanying the visual categorization of natural scenes. In the first experiment, ERPs were recorded in an animal-non-animal categorization task (CT), whereas the second experiment included a spatial frequency discrimination task (DT). In the CT, there were more negative potentials for non-animals in the time windows of 150-250 ms (N1) and 350-500 ms (N2), and a more positive potential for animals in the time window of 250-350 ms (P2). In the DT, spatial frequency gratings evoked only a short-duration difference N1 at the frontal sites. Our results suggest that N1 may be related to higher-level categorization processes.

Adult↗
PubMed2000

Schizophrenics know more than they can tell: probabilistic classification learning in schizophrenia.

BACKGROUND: Previous studies have demonstrated impaired explicit and preserved implicit memory functions in schizophrenia. However, it is less clear whether schizophrenics can learn complex information (e.g. probabilistic stimulus response associations) with or without access for conscious recollection. In this study we applied a classification learning task to assess explicit and implicit processes concurrently. METHODS: Two test procedures were administered to 40 schizophrenic subjects and 20 healthy volunteers: a probabilistic classification learning (PCL) task to evaluate implicit memory functions; and a category cue recognition test to investigate the explicit memory system. The PCL task included feedback guided category learning of geometrical shapes. These shapes were called category cues, predicting class membership with certain probabilities. The gradual increase of categorization performance during the feedback learning was a potentially implicit process, whereas the subsequent recognition of category cues required explicit memory functions. RESULTS: The schizophrenic patients improved their categorization performance to a similar extent to the controls, but they failed to recognize the category cues. Memory performances were independent of the positive and negative symptoms. CONCLUSIONS: Patients with schizophrenia were able to establish representations of complex categories, but these remained unconscious. This is consistent with earlier reports, suggesting damaged explicit and spared implicit memory in schizophrenia.

Adult↗
PubMed2000

Serum and cerebrospinal fluid cystatin C levels in vascular and Alzheimer's dementia.

INTRODUCTION: Cystatin C, a cysteine protease inhibitor, has been implicated in the neurodegenerative and repair processes of the nervous system, and the deposition of the same protein together with beta amyloid peptide was found as cerebral amyloid angiopathy (CAA) in different types of dementias. OBJECTIVE AND METHODS: Because of the differential diagnostic importance, serum and cerebrospinal fluid (CSF) cystatin C levels of 24 late onset Alzheimer's demented (AD) and 16 ischemic type of vascular demented (VD) probands were compared with 17 aged control (AC) persons. RESULTS: The serum and CSF cystatin levels were found in the normal range in all groups. The ischemic VD probands had the tendency to have higher cystatin C levels than the AD. No correlation has been found with the severity and duration of dementia and with the other measured parameters. CONCLUSION: These results indicate that lower than normal CSF cystatin C level is not a diagnostic marker in ischemic VD and CAA related to AD.

Aged↗
PubMed1999

[Regional cerebral blood flow changes in schizophrenic patients detected by SPECT studies under resting and active conditions].

Brain SPECT studies in schizophrenia revealed changes in regional cerebral blood flow (rCBF). The rCBF changes can be detected more accurate by activating tests. The aim of this study was to assess rCBF changes under resting and activation condition by the Raven test. Four control patients (2 male, 2 female, average age 45 years, 26-57 years) and 11 chronic, treated schizophrenic patients (4 male, 7 female, average age: 46 years, 33-56 years) were studied in two HMPAO brain SPECT sessions, 48 hours apart, both resting and during activation task. The images were evaluated visually and semiquantitatively. Under resting condition in the control group, there were no significant rCBF changes. In the Raven activation test, a significantly higher blood flow in the prefrontal region was seen (p < 0.05). The schizophrenic group had a significantly lower rCBF in the temporal region under resting condition (p < 0.05): four patients displayed left, 4 right temporal hypoperfusion and 3 exhibited no rCBF abnormality. In the Raven activation tests 5 patients had prefrontal hyperperfusion, and the remaining 6 patients had no such activation answer. Five patients had hypoperfusion in the temporal region. In our sample, patients with chronic schizophrenia displayed significant temporal hypoperfusion. Moreover the chronic schizophrenic group exhibited a poor response to prefrontal activation compared to the control group.

Adult↗
PubMed1999

Early visual impairment is independent of the visuocognitive and memory disturbances in Alzheimer's disease.

Static and dynamic contrast sensitivity (SCS and DCS), semantic object identification, and verbal recall functions were evaluated in 20 Alzheimer's disease (AD) patients and in 20 control subjects. We found general SCS and DCS loss in the 0.48-14.34 c deg-1 spatial frequency range. In relation to the cognitive functions, semantic object identification was intact, whereas explicit memory was markedly impaired in the AD group. There was no significant correlation between the CS and the memory disturbances. The results suggest that early visual impairment and higher-level cognitive disturbances are independent in AD.

Aged↗
PubMed1999

Classification learning in Alzheimer's disease.

Previous research has demonstrated that explicit recognition of dot patterns is impaired in amnesic patients with damage to the limbic-diencephalic memory system, while implicit categorization of the same kind of stimuli is preserved. The aim of the present study was to investigate the relationship between recognition and categorization performances in patients with Alzheimer's disease. Consistent with the findings in amnesic subjects, our results revealed that the explicit recognition of dot patterns was significantly impaired in Alzheimer's disease. However, implicit categorization functions were also disrupted. This was selective for the prototype stimuli; the categorization of non-prototype dot patterns was spared. The impaired category learning is likely to reflect the damage of modality-specific neocortical areas in Alzheimer's disease.

Aged↗