Biomedical subjects

Josef Zihl

Publications and source records attributed to Josef Zihl.

8 recordsLinked to original sources

PubMed2006

Persistent cognitive impairment in depression: the role of psychopathology and altered hypothalamic-pituitary-adrenocortical (HPA) system regulation.

BACKGROUND: Dysregulation of the hypothalamic-pituitary-adrenocortical (HPA) system and cognitive impairment are consistent findings in depression. This study examines the associations between HPA system regulation, cognitive functioning, and psychopathology in depressed inpatients on admission and at discharge. METHODS: The HPA system dysregulation was evaluated with the dexamethasone (DEX)/corticotropin-releasing hormone (CRH) test. Cognitive assessment included speed of information processing, divided and selective attention, as well as short-term and working memory. Psychopathology was evaluated with the Hamilton Rating Scale for Depression (HAMD). Data from 75 depressed inpatients are reported, 51 (68%) of them achieved remission. RESULTS: Despite a significant reduction of depressive symptoms between admission and discharge, a high rate of patients remained cognitively impaired. Selective attention improved significantly in remitters and nonremitters, while speed of information processing increased only in remitters. The cortisol response to the DEX/CRH test decreased significantly only in remitters, which was uncorrelated with cognitive performance. In nonremitters, severity of depression was significantly correlated with information processing time while improvement in short-term memory was negatively associated with the cortisol response at discharge. CONCLUSIONS: Our data support the assumption that psychopathological symptoms and the HPA system dysregulation can be dissociated in their impact on cognitive functioning in depressed patients.

Adult↗

PubMed2006

Attention and memory deficits in schizophrenia: the role of symptoms of depression.

BACKGROUND: Schizophrenic patients suffer from neuropsychologic impairments in several cognitive domains, that is, attention and memory. Similar impairments have been observed in patients with depression. Therefore, the question arises whether and how the symptoms of depression seen in many patients with schizophrenia are linked to their neuropsychologic functioning. METHODS: Seventeen schizophrenic in-patients (after attenuation of acute psychosis) and 17 healthy control subjects matched for sex, age, and education were investigated by use of an neuropsychologic test battery targeting at attention and memory. Symptoms of depression were evaluated by use of 3 self-rating scales and the Hamilton Depression Rating Scale. RESULTS: Patients performed significantly worse in all neuropsychologic tests applied, except in digit span. Additionally, patients exhibited significantly higher levels of depression according to all 3 self-rating scales and moderate depression severity according to the Hamilton Depression Rating Scale (mean: 13.1). By taking the proportion of variance explained by the self-ratings of depression statistically into account, significant group differences disappeared in half of the attention measures and in all memory measures. CONCLUSIONS: These results suggest that part of the neuropsychologic impairments seen in schizophrenia is linked with symptoms of depression. This seems to be especially true for attention and memory disturbances.

Adult↗

PubMed2005

Visual spatial and visual pattern working memory: neuropsychological evidence for a differential role of left and right dorsal visual brain.

According to neurophysiological, neuroimaging, and behavioural evidence, visual working memory (WM) can be separated into a "what" and a "where" component, reflecting the duality of visual processing. Whereas a wealth of empirical data suggests a right-sided fronto-parietal network critical for the maintenance of spatial information, the cortical structures underlying maintenance of object information have remained controversial. Although visual object processing depends on ventral, inferior temporal areas, recent neuroimaging results suggest that maintenance of visual object information involves a left-sided or bilateral fronto-parietal network. The aim of the present study is to further clarify the role of the left and right parietal lobes for pattern and spatial visual WM. Seven patients with left-sided, seven with right-sided parietal brain injury, and two age-matched healthy control groups performed a delayed-matching-to-sample task using either pattern (shape) or spatial (location) information or both. In addition, eight patients with left-sided injury sparing parietal areas were tested to further examine the specific role of the left parietal cortex in pattern WM. Left parietal injury resulted in pattern WM impairment, only, while right parietal injury was associated with pattern and spatial WM deficits. Non-parietal injury was not associated with comparable deficits. These results suggest that visual spatial WM depends critically on right parietal areas; in contrast, pattern WM depends on both, left and right parietal areas.

Adult↗

PubMed2005

Effect of repeated gaboxadol administration on night sleep and next-day performance in healthy elderly subjects.

Aging is associated with dramatic reductions in sleep continuity and sleep intensity. Since gaboxadol, a selective GABA(A) receptor agonist, has been demonstrated to improve sleep consolidation and promote deep sleep, it may be an effective hypnotic, particularly for elderly patients with insomnia. In the present study, we investigated the effects of subchronic gaboxadol administration on nocturnal sleep and its residual effects during the next days in elderly subjects. This was a randomized, double-blind, placebo-controlled, balanced crossover study in 10 healthy elderly subjects without sleep complaints. The subjects were administered either placebo or 15 mg gaboxadol hydrochloride at bedtime on three consecutive nights. Sleep was recorded during each night from 2300 to 0700 h and tests assessing attention (target detection, stroop test) and memory function (visual form recognition, immediate word recall, digit span) were applied at 0900, 1400, and 1700 h during the following days. Compared with placebo, gaboxadol significantly shortened subjective sleep onset latency and increased self-rated sleep intensity and quality. Polysomnographic recordings showed that it significantly decreased the number of awakenings, the amount of intermittent wakefulness, and stage 1, and increased slow wave sleep and stage 2. These effects were stable over the three nights. None of the subjects reported side effects. Next-day cognitive performance was not affected by gaboxadol. Gaboxadol persistently improved subjective and objective sleep quality and was devoid of residual effects. Thus, at the employed dose, it seems an effective hypnotic in elderly subjects.

Activities of Daily Living↗

PubMed2004

A biased competition based neurodynamical model of visual neglect.

On the computational basis of a neurodynamical cortical model, we investigate a specific top-down visual cognitive impairment in brain-damaged patients known as visual spatial neglect. The computational cortical model accounts the neurodynamics underlying selective visual attention, is based on the "biased competition hypothesis" and structured in several network modules which can be related with the different areas of the dorsal and ventral path of the visual cortex. Spatial and object attention are accomplished by a multiplicative gain control that emerges dynamically through intercortical mutual biased coupling. By damaging the model in different ways, a variety of dysfunctions associated with visual neglect can be simulated and explained as disruption of specific subsystems. Essentially, the damage destabilizes the underlying intra- and intermodular mutually biased neurodynamical competition that macroscopically yields the functional deficits observed in visual neglect patients. In particular, we are able to explain the asymmetrical effect of spatial cueing on neglect, and the phenomenon of extinction in the framework of visual search.

Animals↗

PubMed2003

The use of visual feedback and on-line target information in catching and grasping.

Although visual feedback (i.e. seeing our hand while we move it) improves the accuracy and efficiency of grasping movements, these positive effects of visual feedback are not consistently found for catching. It was the aim of our study to compare the efficiency of the use of visual feedback in grasping and catching and to explore possible reasons why visual feedback effects have been found less consistently in catching than in grasping. The first reason might be technical. Less sensitive measurement methods have been used in catching; this might explain why some catching studies did not find visual feedback effects. This problem was avoided in our study by using the same methods for both the catching and the grasping task. The effects of visual feedback were examined under standard conditions and under conditions where subjects wore prismatic glasses. Nevertheless, visual feedback effects were obtained for grasping but not for catching movements. This confirms that the difference in the use of visual feedback is real and not due to technical differences between grasping and catching studies. The second reason relates to the different temporal demands of grasping and catching. During a catching task, subjects have less time to respond, and therefore might not have sufficient time to use visual feedback. We tested this explanation with a task that required subjects to reach for a stationary object (i.e. grasping) as quickly as they had for the moving object in the catching task. However, even in this time-constrained grasping task, significant visual feedback effects were found, suggesting that time constraints do not explain the lack of visual feedback effects in catching. In our last explanation, we suggest that possibly the mode of motor control is different for catching and grasping, more particularly while grasping allows for on-line corrections, such corrections might not be possible for catching movements. We tested this explanation with a catching task that contained perturbation trials. During those perturbation trials, the target trajectory was shifted, after the subject had already started to move. We found that subjects responded to the target shifts with an appropriate shift of their catching response. This shows that on-line corrections are possible in the case of catching movements. We conclude that neither differences in the temporal demands nor in the capacity to make on-line modifications explain why visual feedback is used less effectively in the catching than in the grasping task.

Adult↗

PubMed2003

Clinical and neurobiological effects of tianeptine and paroxetine in major depression.

Selective serotonin reuptake inhibitors (SSRIs) are widely used as effective pharmacological agents to treat depressive disorders. In contrast to the SSRIs, which block the presynaptic serotonin (5-HT) transporter and by this route increase the concentration of serotonin in the synaptic cleft, the antidepressant tianeptine enhances the presynaptic neuronal reuptake of 5-HT and thus decreases serotonergic neurotransmission. Both SSRIs and tianeptine are clinically effective; however, their opposite modes of action challenge the prevailing concepts on the need of enhancement of serotonergic neurotransmission. To better understand the differences between these two opposite pharmacological modes of action, we compared the changes induced by tianeptine and paroxetine on psychopathology, the hypothalamic-pituitary-adrenocortical (HPA) system, and cognitive functions in a double-blind, randomized, controlled trial including 44 depressed inpatients over a period of 42 days. Depressive symptomatology significantly improved in all efficacy measures, with no significant differences between tianeptine and paroxetine. There was a trend toward better response to the SSRI among women. Assessment of the HPA system showed marked hyperactivity before the beginning of treatment, which then normalized in most of the patients, without significant differences between the two antidepressants. Cognitive assessments showed no significant differences between the two drugs investigated. The results of the current study suggest that the initial effect, i.e., enhancement or decrease of 5-HT release, is only indirectly responsible for antidepressant efficacy, and they support the notion that downstream adaptations within and between nerve cells are crucial. The normalization of the HPA system as a common mode of action of different antidepressants seems to be of special interest.

Adult↗

PubMed2002

The time course of selective visual attention: theory and experiments.

Historically, the psychophysical evidence for "selective attention" originated mainly from visual search experiments. A first important distinction in the processing of information in visual search tasks is its separation in two stages. The first, early "preattentive" stage operates in parallel across the entire visual field extracting single "primitive features" without integrating them. The second "attentive" stage corresponds to the specialized integration of information from a limited part of the field at any one time, i.e. serially. So far, models based on the above mentioned two-stage processes have been able to distinguish features from conjunction search conditions based on the observed slopes of the linear relation between reaction time (i.e., search time) and the number of items in the stimulus array. We propose a neuroscience based model for visual attention that works across the visual field in parallel, but due to its intrinsic dynamics can show the two experimentally observed modes of visual attention, namely: the serial focal attention and the parallel spread of attention over space. The model demonstrates that neither explicit serial focal search nor saliency maps need to be assumed. In the present model the focus of attention is not included in the system but only emerges after convergence of the dynamical behaviour of the neural networks. Furthermore, existing models have not been able to explain the variation of slopes observed in different kinds of conjunction search modes. We hypothesize that the different slopes can be explained by assuming that selective attention is guided by an independent mechanism which corresponds to the independent search for each feature. The model consistently integrates the different neuroscience levels by considering the microscopic neurodynamical mechanism that underlies visual attention, the different brain areas of the dorsal or "where" and ventral or "what" paths of the visual cortex, and behavioural data.

Adult↗