Seguimento de 5 anos de acuidade visual de pacientes com degeneração macular relacionada à idade exudativa (ÚMIDA) tratada com radioterapia e medicamentos antiangiogênicos / 5 years follow-up of visual acuity from patients with exudative (WET) age-related macular degeneration, treated with radiotherapy and antiangiogenic drugs

Objetivo: a degeneração macular relacionada à idade (DMRI) é atualmente uma das principais causas de deficiência visual grave em pacientes com mais de 55 anos. Existem aproximadamente 170 milhões de pessoas com alguma forma da doença em todo o mundo. Os tratamentos atuais da forma exsudativa ainda apresentam limitações, principalmente relacionadas à necessidade de inúmeras injeções intravítreas de antiangiogênicos ao longo do seguimento. O objetivo deste estudo é avaliar a acuidade visual e estabilidade de pacientes tratados com radioterapia intraocular com estrôncio 90 e duas injeções intravítreas de bevacizumabe nos 16 pacientes do grupo I, e uma aplicação de radioterapia intraocular com estrôncio 90 e duas injeções intravítreas de ranibizumabe em 13 pacientes no grupo II durante um acompanhamento de 5 anos.Métodos: Todos os 29 pacientes apresentaram neovascularização de coróide secundária à DMRI e foram acompanhados com exame oftalmológico completo, angiografia de fluorescência e tomografia de coerência óptica.Resultados: 87,5% dos pacientes do grupo I e 53,84% do grupo II mantiveram boa acuidade visual ao final dos 60 meses de seguimento. A média da melhor acuidade visual corrigida apresentou ganho de + 10,4 letras e + 5,23 letras, respectivamente, em tabela específica. O grupo bevacizumabe manteve-se estável ao longo do acompanhamento, além de um maior número de pacientes que alcançou acuidade visual ? 20/40.Conclusão: A radioterapia intraocular combinada com antiangiogênicos se enquadra no arsenal terapêutico disponível para DMRI neovascular como uma opção segura, especialmente nos casos que ocorrem com injeções intravítreas repetidas.

Early cross-modal interactions and adult human visual cortical plasticity revealed by binocular rivalry

In this research binocular rivalry is used as a tool to investigate different aspects of visual and multisensory perception. Several experiments presented here demonstrated that touch specifically interacts with vision during binocular rivalry and that the interaction likely occurs at early stages of visual processing, probably V1 or V2. Another line of research also presented here demonstrated that human adult visual cortex retains an unexpected high degree of experience-dependent plasticity by showing that a brief period of monocular deprivation produced important perceptual consequences on the dynamics of binocular rivalry, reflecting a homeostatic plasticity. In summary, this work shows that binocular rivalry is a powerful tool to investigate different aspects of visual perception and can be used to reveal unexpected properties of early visual cortex

Neural modulation of the human visual cortex

Neuroplasticity is a phenomenon that refers to the brain’s ability to reorganize, strengthen, and form neural connections, a process that becomes increasingly more difficult with age. Gamma amino-butyric acid (GABA), the primary inhibitory neurotransmitter in the brain, is thought to gate neuroplasticity, with increasing concentrations related to the closure of the critical period of development. As a result, the modulation of neuroplasticity and GABA concentration may have implications in the recovery and rehabilitation of neural functions. This research addresses neuroplasticity in the visual cortex by applying rapid visual stimulation and non-invasive brain stimulation using both physiological and psychophysical outcome measures. One fundamental mechanism of neuroplasticity is known as long-term potentiation (LTP), a synaptic strengthening mechanism characterized by changes in cortical physiology and underlies the processes of learning and memory formation. While LTP can be induced in animal models of the brain through invasive electrical stimulation, recent studies have demonstrated LTP-like effects induced by rapid visual stimulation. Another technique that modulates neuroplasticity is non-invasive brain stimulation. Anodal transcranial direct current stimulation (a-tDCS) has been reported to decrease GABA concentration in the motor cortex, while a form of magnetic stimulation, continuous theta-burst stimulation (cTBS) has the opposite effect. Cortical GABA concentration is measured directly using magnetic resonance spectroscopy (MRS) an imaging technique that quantifies neural metabolites within a small region of interest. Binocular rivalry—a phenomenon wherein perception alternates stochastically when two different images are shown to each eye—has been directly and indirectly associated with visual cortex GABA concentration, which poses the question of whether binocular rivalry dynamics can be used as an indirect measure of GABA concentration. First, we tested the hypothesis that rapid monocular visual stimulation would increase the dominance of the stimulated eye during a binocular rivalry task. Unexpectedly, we found that rapid monocular visual stimulation strengthens the non-stimulated eye, a result which was not explained by adaptation, suggesting that the shift in dominance towards the non-stimulated eye may result from a homeostatic gain control mechanism. Secondly, we investigated the effects of two opposing forms of non-invasive brain stimulation, a-tDCS and cTBS, on binocular rivalry dynamics. We hypothesized that a reduction of GABA using a-tDCS would result in an increase in binocular rivalry alternation rates, while cTBS would have the opposite effect. Although binocular rivalry alternation rates did not change with either stimulation method, duration of mixed perception increased significantly following cTBS. An increase in the inhibitory neurotransmitter GABA may translate to a reduction in neural noise, a complement to the phenomenon of stochastic resonance where increased neural noise may increase the detection of weak signals. Finally, we investigated the effects of a-tDCS on visual cortex GABA and glutamate concentration. Although many studies report a reduction in motor cortex GABA concentration following a-tDCS, our results showed that visual cortex GABA concentration remained the same. Unexpectedly, we found a trend for an increase in glutamate following active a-tDCS, supporting the possibility that a-tDCS effects the visual cortex and motor cortex differently. It is evident that there are many complex mechanisms that gate plasticity, and that modulating neuroplasticity is not as simple as we may have thought. Understanding these mechanisms, however, and the effects of modulatory techniques such as rapid visual stimulation and non-invasive brain stimulation on visual cortex plasticity, will provide a foundation for improving the recovery and rehabilitation potential of neurodevelopmental disorders and brain damage