Photosensitive ganglion cells: A diminutive, yet essential population.

Our visual system has evolved to provide us with an image of the scene that surrounds us, informing us of its texture, colour, movement, and depth with an enormous spatial and temporal resolution, and for this purpose, the image formation (IF) dedicates the vast majority of our retinal ganglion cell (RGC) population and much of our cerebral cortex. On the other hand, a minuscule proportion of RGCs, in addition to receiving information from classic cone and rod photoreceptors, express melanopsin and are intrinsically photosensitive (ipRGC). These ipRGC are dedicated to non-image-forming (NIF) visual functions, of which we are unaware, but which are essential for aspects related to our daily physiology, such as the timing of our circadian rhythms and our pupillary light reflex, among many others. Before the discovery of ipRGCs, it was thought that the IF and NIF functions were distinct compartments regulated by different RGCs, but this concept has evolved in recent years with the discovery of new types of ipRGCs that innervate subcortical IF regions, and therefore have IF visual functions. Six different types of ipRGCs are currently known. These are termed M1-M6, and differ in their morphological, functional, molecular properties, central projections, and visual behaviour responsibilities. A review is presented on the melanopsin visual system, the most active field of research in vision, for which knowledge has grown exponentially during the last two decades, when RGCs giving rise to this pathway were first discovered.

Células ganglionares fotosensibles: una población diminuta pero esencial / Photosensitive ganglion cells: A diminutive, yet essential population

Nuestro sistema visual ha evolucionado para proveernos una imagen de la escena que nos rodea informándonos de su textura, color, movimiento y profundidad con una enorme capacidad de resolución tanto espacial como temporal, y a esta finalidad la formación de imágenes (FI) dedica la inmensa mayoría de nuestras células ganglionares de la retina (CGR) y gran parte de nuestra corteza cerebral. Por otra parte, una proporción minúscula de las CGR, además de recibir información de fotorreceptores clásicos conos y bastones, expresan melanopsina y son intrínsecamente fotosensibles (CGRif). Estas CGRif se dedican a funciones visuales no formadoras de imágenes (NFI), de las que somos inconscientes, pero que resultan imprescindibles para aspectos relacionados con nuestra fisiología cotidiana como la puesta en hora de nuestros ritmos circadianos y nuestro reflejo fotomotor, entre otras muchas. Desde el descubrimiento de las CGRif se pensó que las funciones FI y NFI eran compartimentos distintos regulados por diferentes CGR, pero este concepto ha evolucionado en los últimos años con el descubrimiento de nuevos tipos de CGRif que inervan regiones subcorticales FI y, por tanto, presentan funciones FI. Hoy se conocen 6 tipos diferentes de CGRif que se denominan M1-M6 y difieren en sus propiedades morfológicas, funcionales, moleculares, proyecciones centrales y responsabilidades en comportamientos visuales. En este trabajo revisamos el sistema visual melanopsínico, el campo de investigación más activo en visión y cuyo conocimiento ha crecido exponencialmente durante las últimas 2décadas, desde que se descubrieron por primera vez las CGR que dan origen a esta vía (AU)

Our visual system has evolved to provide us with an image of the scene that surrounds us, informing us of its texture, colour, movement, and depth with an enormous spatial and temporal resolution, and for this purpose, the image formation (IF) dedicates the vast majority of our retinal ganglion cell (RGC) population and much of our cerebral cortex. On the other hand, a minuscule proportion of RGCs, in addition to receiving information from classic cone and rod photoreceptors, express melanopsin and are intrinsically photosensitive (ipRGC). These ipRGC are dedicated to non-image-forming (NIF) visual functions, of which we are unaware, but which are essential for aspects related to our daily physiology, such as the timing of our circadian rhythms and our pupillary light reflex, among many others. Before the discovery of ipRGCs, it was thought that the IF and NIF functions were distinct compartments regulated by different RGCs, but this concept has evolved in recent years with the discovery of new types of ipRGCs that innervate subcortical IF regions, and therefore have IF visual functions. Six different types of ipRGCs are currently known. These are termed M1-M6, and differ in their morphological, functional, molecular properties, central projections, and visual behaviour responsibilities. A review is presented on the melanopsin visual system, the most active field of research in vision, for which knowledge has grown exponentially during the last 2decades, when RGCs giving rise to this pathway were first discovered (AU)