This, That, and the Background

"The attached image is of a horizontal interneuron taken from the retina of a catfish. The cell is stained with the pH-sensitive fluorescent dye HAF to indicate changes in the relative H+ ion concentration within the intracellular compartment. The image was obtained using a Zeiss LSM-510 Laser Scanning Meta-Confocal Microscope at the Marine Biological Laboratory in Woods Hole, Massachusetts. The most useful information in a visual scene is contained in patterns of contrast. Our retina creates receptive fields as an adaptation for detecting this useful information in order to craft our visual experience. I have set out to explore the molecular and cellular mechanisms that modulate our visual signal in the outer vertebrate retina in order to process contrast. A light stimulus starts a signaling process in the photoreceptors and ultimately leads to visual information being sent to the brain for higher processing via the optic nerve. During this time, the signal initiated by the light stimulus undergoes a myriad of modifications by interneurons in order to “finely tune” the visual signal through a series of both excitatory and inhibitory synaptic connections. This complex meshwork of nerve cells in the retina modulates signal transduction in order to create the center-surround receptive fields that are so essential to producing contrast between an object and its background."