Further evidence for a reversed crossing of foveal projections in schizophrenic vulnerability

The possible role of retinal dopaminergic system in visual performance

It is a well-known fact that the retina is one of the tissues in the body, which is richest in dopamine (DA), yet the role of this system in various visual functions remains unclear. We have identified 13 types of DA retinal pathologies, and 15 visual functions. The pathologies were arranged in this review on a net grid, where one axis was "age" (i.e., from infancy to old age) and the other axis the level of retinal DA (i.e., from DA deficiency to DA excess, from Parkinson disorder to Schizophrenia). The available data on visual dysfunction(s) is critically presented for each of the DA pathologies. Special effort was made to evaluate whether the site of DA malfunction in the different DA pathologies and visual function is at retinal level or in higher brain centers. The mapping of DA and visual pathologies demonstrate the pivot role of retinal DA in mediating visual functions and also indicate the "missing links" in our understanding of the mechanisms underlying these relationships.

From genes to brain oscillations: Is the visual pathway the epigenetic clue to schizophrenia?

Molecular data and gene expression data and recently mitochondrial genes and possible epigenetic regulation by non-coding genes is revolutionizing our views on schizophrenia. Genes and epigenetic mechanisms are triggered by cell-cell interaction and by external stimuli. A number of recent clinical and molecular observations indicate that epigenetic factors may be operational in the origin of the illness. Based on the molecular insights, gene expression profiles and epigenetic regulation of gene, we went back to the neurophysiology (brain oscillations) and found a putative role of the visual experiences (i.e. visual stimuli) as epigenetic factor. The functional evidences provided here, establish a direct link between the striate and extrastriate unimodal visual cortex and the neurobiology of the schizophrenia. This result support the hypothesis that 'visual experience' has a potential role as epigenetic factor and contribute to trigger and/or to maintain the progression of the schizophrenia. In this case, candidate genes sensible for the visual 'insult' may be located within the visual cortex including associative areas, while the integrity of the visual pathway before reaching the primary visual cortex is preserved. The same effect can be perceived if target genes are localised within the visual pathway, which actually, is more sensitive for 'insult' during the early life than the cortex per se. If this process affects gene expression at these sites a stably sensory specific 'insult', i.e. distorted visual information, is entering the visual system and expanded to fronto-temporo-parietal multimodal areas even from early maturation periods. The difference in the timing of postnatal neuroanatomical events between such areas and the primary visual cortex in humans (with the formers reaching the same development landmarks later in life than the latter) is 'optimal' to establish an abnormal 'cell- communication' mediated by the visual system that may further interfere with the local physiology. In this context the strategy to search target genes need to be rearrangement and redirected to visual-related genes. Otherwise, psychophysics studies combining functional neuroimage, and electrophysiology are strongly recommended, for the search of epigenetic clues that will allow to carrier gene association studies in schizophrenia.

Schizophrenia and eye movement – a new diagnostic and therapeutic concept

In the present article, conclusions are drawn from four papers on the genesis of schizophrenia, published in Medical Hypotheses between 1999 and 2002, knowledge of which is required to understand this paper in greater depth. For these, the author had developed two sight tests in which schizophrenic patients revealed a stronger fusional reactivity of the nasal than of the temporal foveal halves and a disconnection between peripheral and foveal vision. Both phenomena could be explained by a reversed crossing of foveal projections in the chiasma opticum constituting a genetic vulnerability which, in case of additional defects of binocular balance, could result in a foveal convergence stimulus being executed as a divergence movement by one of the eyes. The author has now succeeded in finding a very simple standardized method to discover the described vergence abnormality, the Hook test, part of the ZEISS Near Pola Test, which would therefore be suitable for detecting schizophrenic vulnerability in screening tests so that the outbreak of schizophrenia could be prevented by an early correction of the additional visual defects. The movement impulses resulting from the erraneous vergence are analyzed and explain the phenomenon of the schizophrenic's "mad look". The connection between the somatic component and the patient's psycho-social problems is shown and a detailed description given of non-neuroleptic methods of rectifying both.