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Purpose: To explore the retinal functions in healthy volunteers during acute hypoxic exposure, applying a set of electrophysiological tests., Methods: Standard electroretinograms (ERGs) of the retina (rod-(scotopic) ERGs, cone-(photopic) ERGs, maximal responses and oscillatory potentials (OPs)) and 30-Hz flicker ERGs were recorded according to ISCEV (International Society of Clinical Electrophysiology of Vision) recommendations in 14 healthy volunteers during a 15-min exposure to a simulated altitude of 5500 m., Results: The mean arterial oxygen saturation level was significantly reduced (P < 0.001) during the hypobaric challenge. It returned to the normal level very shortly after the end of the hypoxic exposure. No significant change in the latency or amplitude of the slow components of the ERG was found in any recording. The OPs of the ERG, however, revealed a significant decrease in amplitude during hypoxic exposure. Both OP1 and OP2 amplitudes were significantly different (P < 0.05) from the baseline values during hypoxia. Partial recovery of these waves occurred after termination of the hypoxia., Conclusions: These results appear to support the notion that the inner layers of the retina presumed to be the main source of the OPs, display the highest sensitivity towards circulatory and/or hypoxic challenges.

B. F. O'Donnell et al. found impaired discrimination performances at low and medium spatial frequencies in patients with schizophrenia. In this study, the authors replicated this finding in a group of remitted, unmedicated, and highly functioning outpatients with spared IQ and attentional functions. However, the deficit was restricted to low spatial frequencies (0.5 cycles/degree), which suggests that this deficit is a trait marker of schizophrenia., (Copyright 2006 APA, all rights reserved.)

This is a survey on the function of parallel visual pathway with a special emphasis on its clinical implications. It is based on data in the literature and own results of our group. The paper primarily deals with the X, Y, W pathways and by the magnocellular, parvocellular and koniocellular visual pathways characterized by cells of various size as well as by nerve fibers of various thickness. Electrophysiological, microelectrode recording of single-unit activity makes the distinction between the pathways available in animal model. Much more difficulties arise if we intend to characterize the pathways in humans or to detect the selective damage of one of these pathways in patients. The non-invasive diagnostic methods that could be used in the diagnosis are detailed here, too. Finally, the neurological, ophthalmological and psychological diseases are discussed in which a selective damage of any visual pathway is suspected. Summing it up, the survey provides evidences for the introduction of the novel concept of parallel pathways into the diagnostic aspects of ophthalmology, neurology and psychiatry.

The "dorsal-stream vulnerability" hypothesis claims that motion-sensitive areas in the dorsal occipito-parietal visual system are vulnerable to genetic and environmental factors which affect brain maturation and development. The aim of this study was to investigate the possibility that developmental anomalies of directional motion perception can be detected in children of mothers with schizophrenia and bipolar disorder. Motion and form coherence thresholds were measured in 36 children of mothers with schizophrenia, 28 children of mothers with bipolar disorder, and 30 children with negative family history at 7, 8-9, and 10-11 years of age. These tasks require the detection of direction of coherently moving dots embedded among randomly oscillating dots (motion task) and the detection of tangentially oriented line-segments embedded among randomly oriented segments (form task). Results revealed that the rate of development in the motion task was less pronounced in children of mothers with schizophrenia than that in children of mothers with bipolar disorder and in age-matched controls. The development of form perception was spared. Children of mothers with bipolar disorder showed an intact development in both motion and form perception tasks. These results suggest that the progressive developmental abnormality of motion-sensitive visual areas may be a characteristic feature of schizophrenia-vulnerability.

The article presents an overview on the peripheral and central neural mechanisms underlying pain in the orofacial area. First a definition of pain and a description of general aspects of orofacial pain are presented. Characteristics of acute and chronic pain are also described. The study highlights the sense organs, the molecular mechanisms and categories of primary afferents involved in peripheral events of orofacial pain. After describing the brain-stem nuclei participating in trigeminal pain and their functional role, primary afferents involved in nociceptive sensation from the tooth pulp, explanations of dentinal sensitivity and differences between the brain-stem endings of primary afferents among different species are discussed in details. The role of higher brain centres, with a special emphasis on the thalamus and somatosensory cortex in the development of orofacial pain sensation is considered. The last section provides a review about how the activities of nociceptive neurons are controlled by higher brain centres and neurochemicals involved in pain transmission.

Background: Schizophrenia is associated with impaired visual information processing. The aim of this study was to investigate the relationship between anomalous perceptual experiences, positive and negative symptoms, perceptual organization, rapid categorization of natural images and magnocellular (M) and parvocellular (P) visual pathway functioning., Method: Thirty-five unmedicated patients with schizophrenia and 20 matched healthy control volunteers participated. Anomalous perceptual experiences were assessed with the Bonn Scale for the Assessment Basic Symptoms (BSABS). General intellectual functions were evaluated with the revised version of the Wechsler Adult Intelligence Scale. The 1-9 version of the Continuous Performance Test (CPT) was used to investigate sustained attention. The following psychophysical tests were used: detection of Gabor patches with collinear and orthogonal flankers (perceptual organization), categorization of briefly presented natural scenes (rapid visual processing), low-contrast and frequency-doubling vernier threshold (M pathway functioning), isoluminant colour vernier threshold and high spatial frequency discrimination (P pathway functioning)., Results: The patients with schizophrenia were impaired on test of perceptual organization, rapid visual processing and M pathway functioning. There was a significant correlation between BSABS scores, negative symptoms, perceptual organization, rapid visual processing and M pathway functioning. Positive symptoms, IQ, CPT and P pathway measures did not correlate with these parameters. The best predictor of the BSABS score was the perceptual organization deficit., Conclusions: These results raise the possibility that multiple facets of visual information processing deficits can be explained by M pathway dysfunctions in schizophrenia, resulting in impaired attentional modulation of perceptual organization and of natural image categorization.

Background: Schizophrenia is associated with perceptual organization deficits and abnormal neuronal connectivity has been described in early visual areas. The purpose of this study was to investigate the functional integrity of lateral connections in early visual areas of patients with schizophrenia and type I bipolar disorder with a history of psychosis., Method: Twenty-four out-patients with schizophrenia, 22 out-patients with bipolar disorder, and 20 healthy control subjects participated in the study. Using a computer-assisted psychophysical test, contrast thresholds were measured for centrally presented target stimuli (Gabor patches), which were surrounded by two collinear flankers. Target-to-flanker distances were 0, 1, 2, 3, 4, 6, 9 and 122. Psychophysical measures were contrast threshold changes at each target-to-flanker distance compared with baseline thresholds determined for isolated targets with no flankers. Clinical measures included IQ, positive, negative, and depressive symptoms. Results. In patients with schizophrenia, flankers did not facilitate contrast detection for target stimuli at 2-6 lambda distances compared to controls [effect size (Cohen's d): 1.25-1.42]. The inhibitory effect of flankers (0 and 1lambda) and contrast thresholds in the absence of flankers were spared. Patients with bipolar disorder did not differ from the controls. Medicated and non-medicated patients displayed similar performances. Positive and negative symptoms and depression did not correlate with contrast threshold values., Conclusions: Excitatory lateral connections in early visual cortex are specifically impaired in patients with schizophrenia, which may contribute to perceptual disorders such as unclear seeing, partial or skewed sight, disrupted rectilinearity, and abnormal figure-ground segregation.

This study investigated the relationship between theory of mind (ToM) deficits and visual perception in patients with schizophrenia (N=52; 17 remitted and unmedicated) compared with healthy controls (N=30). ToM was assessed with the Eyes Test, which asked participants to choose which of 4 words best described the mental state of a person whose eyes were depicted in a photograph. Visual perception was evaluated with form and motion coherence threshold measurements. Results revealed that patients with schizophrenia (both remitted and nonremitted) showed deficits on the Eyes Test and the motion coherence task. ToM dysfunctions were associated with higher motion coherence thresholds and more severe negative symptoms. This suggests that ToM deficits are related to motion perception dysfunctions, which indicates a possible role of motion-sensitive areas in the pathophysiology of schizophrenia., (((c) 2005 APA, all rights reserved).)

In this study, the authors investigated the relationship between the Ser9Gly (SG) polymorphism of the dopamine D3 receptor (DRD3) and striatal habit learning in healthy controls and patients with schizophrenia. Participants were given the weather prediction task, during which probabilistic cue-response associations were learned for tarot cards and weather outcomes (rain or sunshine). In both healthy controls and patients with schizophrenia, participants with Ser9Ser (SS) genotype did not learn during the early phase of the task (1-50 trials), whereas participants with SG genotype did so. During the late phase of the task (51-100 trials), both participants with SS and SG genotype exhibited significant learning. Learning rate was normal in patients with schizophrenia. These results suggest that the DRD3 variant containing glycine is associated with more efficient striatal habit learning in healthy controls and patients with schizophrenia., ((c) 2005 APA, all rights reserved.)

The multifocal visual evoked potentials are the evoked responses over the visual cortex in response to the stimulation of circumscribed small areas in the central 30 degree region of the retina. The recording of multifocal visual evoked potentials was made possible by the computer algorhythm elaborated by Sutter in 1991. Multifocal electroretinography, developed upon the same theoretical principles, is already an routine clinical examination method for the topographic analysis of functional damages in the central part of the retina and for the differential diagnostics in neuro-ophthalmology. The multifocal visual evoked potential, however, has not been introduced into the clinical practice, although it displays the function of ganglion cells in a given region of the retina in a more detailed way than the sensitivity threshold in the perimetry. This examination makes the objective verification of defects possible in the visual pathway, too. In our department the recording of multifocal visual evoked potentials was started in 2002. In this paper we present the basics of this method and also deal with the problems concerning its application and its status in the history of visual evoked potentials.

The aim of this study was to investigate lateral connectivity in early visual cortex of schizophrenia patients. Contrast thresholds were measured for centrally presented Gabor patches which were surrounded by two collinear or orthogonal flankers. The healthy subjects (n = 15) showed lower contrast thresholds for central Gabor patches when collinear flankers were presented. This effect was significantly reduced in unmedicated highly functioning schizophrenia patients (n = 20) who performed normally on the continuous performance test. The performance of the patients did not correlate with the positive and negative symptoms. The facilitation effect of collinear flankers is believed to reflect lateral interactions between feature-specific units in early visual cortex (V1). Our results therefore suggest abnormal lateral interactions in early visual cortex of schizophrenia patients.

Unlabelled: Recently, a series of endogenous ligands related to inhibition of sensory transduction of noxious stimuli at the spinal level has been described, including endomorphins, agmatine, and adenosine, which act on different receptors; however, little data exist concerning their effect during continuous administration or their interactions. In this study, we investigated the antinociceptive properties of continuously administered (for 60 min) adenosine and agmatine on carrageenan-induced thermal hyperalgesia by means of a thermal paw withdrawal test in awake rats. The possible interaction between endomorphin-1 and adenosine or agmatine was also determined. Continuous administration of adenosine (0.3-3 microg/min) did not influence the paw withdrawal latencies of the normal or inflamed paws during the infusion but in larger doses it resulted in a significant increase in latencies after the cessation of the infusion. Agmatine (0.3-3 microg/min) dose-dependently decreased the hyperalgesia, but the largest dose caused a temporary excitation in 50% of animals. The continuous administration of adenosine or agmatine (3 micro g/min) potentiated and prolonged the antinociceptive effect of endomorphin-1 (1 microg/min). Our results revealed that adenosine and agmatine have a small antinociceptive efficacy during continuous intrathecal administration but that both potentiate the effect of endomorphin-1. These data suggest that the combination of these endogenous ligands might represent novel targets for the therapeutic modulation of pain; however, the systematic examination of side effects is essential., Implications: Adenosine and agmatine have little antinociceptive efficacy during continuous intrathecal administration, as shown by the inflammatory pain test in rats, but both potentiate the effect of endomorphin-1. These data suggest that the combination of these endogenous ligands might represent novel targets for the therapeutic modulation of pain; however, the systematic examination of side effects is essential.

The extract of Sempervivum tectorum L. (Crassulaceae) containing several flavonoids is widely used as an antiinflammatory agent in folk medicine. Previous studies have demonstrated that various flavonoids or flavonoid-containing plant extracts produce significant antinociception, but no data are available concerning their antinociceptive effect especially at the spinal level. The purpose of the present study was to investigate the antinociceptive activity of Sempervivum tectorum L. extract on acute and inflammatory pain sensitivity in awake rats. The pain sensitivity was assessed by the acute tail- flick test in intact rats and by the paw withdrawal test after carrageenan-induced inflammation using heat stimulus. The plant extract was administered intraperitoneally and intrathecally in rats. The intraperitoneal injection of a high dose of the extract (1000 mg/kg) significantly (p < 0.05) increased the paw withdrawal latency of the inflamed paw. The intrathecal administration (30-300 micro g) caused a small, but significant increase (10%-15%) in tail- flick latency. In the carrageenan-induced inflammatory model, the intrathecally applied extract (30-1000 micro g) significantly decreased, but did not relieve the thermal hyperalgesia. The results suggest that the spinal cord does not seem to play an important role in the antinociceptive effects of this plant extract., (Copyright 2003 John Wiley & Sons, Ltd.)

The aim of the study was to investigate spatiotemporal visual functions under scotopic and photopic conditions in order to acquire human psychophysical and electrophysiological data that are comparable with contrast sensitivities based on single-unit recordings in animal experiments. Static and dynamic contrast sensitivities (CSs) and steady-state visual evoked potentials (VEPs) were measured under photopic and scotopic conditions in healthy volunteers. The results from the CS experiment indicated that the inclusion of temporal modulation and the application of scotopic luminance levels uniformly resulted in a relatively increased sensitivity for low spatial frequencies. Similarly, analysis of the second harmonic component of the VEPs demonstrated a shift from band-pass to low-pass functions. These results suggest that, under scotopic conditions, human visuospatial processing is characteristically predominated by the functional activity of the magnocellular pathways.