Magnetic Resonance Imaging of Neural Plasticity in the Visual Cortex of Patients with Central Vision Loss: Effects of Long-term Adaptation and Training

黄斑变性等视网膜疾病通常会导致中央视力丧失，使患者依赖于周围残余视力。通常，一种伪中央凹（首选视网膜轨迹，PRL）在外围视野中发育，然后在日常生活中用于固定物体或面部，以及阅读。这些长期的适应过程伴随着受影响患者视觉皮层的某些神经可塑性变化。此外，适当的训练方案，如视觉感知学习任务，可以帮助进一步提高周边视觉表现，甚至触发神经元可塑性。在这个计划中的项目中，我们的目标是研究这两个长期适应和训练的神经可塑性过程是如何共同作用的，并揭示两者之间可能的相互关系。为此，我们将应用外周视野的视觉知觉学习，并将检验中枢性视力丧失患者在PRL的学习成功与在相反视觉半球（OppPRL）的相当外周区域的学习成功在多大程度上不同于接受相同视觉任务训练的正常视力对照者的学习成功。训练措施将伴随着（功能性）磁共振成像（fMRI）来揭示视觉皮层中学习的神经关联。此外，由学习引起的生化变化将通过磁共振波谱（MRS）来确定。为了研究视觉皮层灰质和白质的宏观和微观结构可能发生的变化，将进行结构和扩散加权MRI。这些措施将为我们提供中枢视力丧失患者长期和短期神经可塑性适应过程的更全面的图景，从而有助于设计更有效的训练方案。

Retinal diseases such as macular degeneration usually lead to central vision loss, making the affected patients dependent on their peripheral residual vision. Often a kind of pseudo fovea (preferred retinal locus, PRL) develops in the peripheral visual field, which is then used in everyday life for the fixation of objects or faces, as well as for reading. These long-term adaptation processes are accompanied by certain neuroplastic changes in the visual cortex of the affected patients. Furthermore, appropriate training protocols, such as visual perceptual learning tasks, can help to further improve peripheral visual performance and even trigger neuronal plasticity. Our goal in this planned project is to investigate how these two neuroplastic processes of long-term adaptation and training act together and to uncover possible interrelations between the two. For this purpose, visual perceptual learning in the peripheral visual field will be applied, and it will be examined to what extent the learning success at the PRL of patients with central vision loss will be different from the learning success at a comparable peripheral site in the opposite visual hemifield (OppPRL) and from the learning success of normally sighted control persons, who are trained in the same visual task. The training measures will be accompanied by (functional) magnetic resonance imaging (fMRI) to reveal the neural correlates of learning in the visual cortex. Additionally, the biochemical changes caused by learning will be determined by magnetic resonance spectroscopy (MRS). To investigate possible changes in the cortical macro- and microstructure in grey and white matter of the visual cortex, structural and diffusion-weighted MRI will be performed. These measures will provide us with a more comprehensive picture of long and short term neuroplastic adaptation processes in patients with central vision loss and thus help to design even more efficient training protocols.