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The retina – the neuronal tissue located at the back of our eyes – is where all visual processing begins. Visual information splits into parallel channels, each served by different sets of cell types and each computing a specific modality of the visual scene, such as color, edge detection, or motion detection. These computations are carried to secondary visual structures by different types of retinal ganglion cells – the output neurons of the retina.

We have found that this organized system can be disrupted by short repetitive visual stimulation, resulting in a new form of adaptation that triggers a functional switch in retinal cells and changes the modality that they encode.

Our goal is to study the mechanisms involved in these dynamics and to resolve how computations performed by anatomically defined neuronal circuits are altered by external stimulation. In addition, we aim to establish how changes in retinal circuits are integrated and interpreted along the visual pathway, in the thalamus and in the visual cortex, and how this retinal plasticity affects our visual perception.

 

Using the retina for early diagnostic of neurodegenerative diseases

Parkinson’s disease is caused by death of dopaminergic neurons in the midbrain. The retina contains dopaminergic neurons as well, and there is evidence that retinal dopamine levels are decreased in Parkinsonian patients. We aim to determine how the responses of retinal neurons change as a function of dopamine levels. Our goal is to provide the first step to establishing of a simple visually-based method to diagnose Parkinson’s disease and determine its progression.

The cholinergic system is most severely affected in Alzheimer's disease. The reduction of acetylcholine, found in the cortex and certain subcortical areas, might also occur in the retina. Indeed, visual symptoms are often among the first complaints of patients suffering from Alzheimer's disease, and a substantial loss of retinal neurons is documented in Alzheimer's patients. While the retina is comprised of various types of neurons, it contains only one type of cholinergic neurons, the starburst amacrine cells (SACs). SACs belong to the direction selective circuit, which mediates the optokinetic reflex – a visual reflex involved in tracking motion in the visual field, and that can be easily measured in the lab/clinic. We aim to use direct measurements from retinal neurons, in order to evaluate Retina’s cholinergic levels via the visual reflex. These measurements from retinal neurons may be applied to the development of an early diagnose of Alzheimer disease based on a simple, non-invasive, visual test.