Vision Science: Retinal Layers and Receptive Fields

The response of bipolar cells is proportional to the amount of glutamate released by photoreceptors, resulting in a graded potential. ON-centre bipolars are depolarised (excited) by an increase in luminance, whereas OFF-centre bipolars are inhibited by it.

Photoreceptors convert light into an electrical signal through phototransduction, and glutamate is released by photoreceptors as a neurotransmitter, which then responds to bipolar cells.

The inner nuclear layer (INL) contains bipolar, horizontal, and amacrine cell nuclei, whereas the outer nuclear layer (ONL) contains rod and cone nuclei.

<p>The RPE is a layer of cells that supports the photoreceptor layer, and it is adjacent to the photoreceptor layer.</p> Signup and view all the answers

<p>The ganglion cell layer contains the cell bodies of ganglion cells, which transmit visual information to the brain, and the nerve fibre layer contains the axons of these cells.</p> Signup and view all the answers

<p>Receptive fields are important for understanding the visual pathway, and they are crucial in perimetry, as they help to map the visual field.</p> Signup and view all the answers

<p>Retinal parasol cells have larger receptive fields than midget cells, and their receptive fields (and dendritic trees) get larger towards the periphery.</p> Signup and view all the answers

<p>K-cells have moderately slow conduction velocity and moderate spatial acuity, and they carry blue-yellow colour opponent information.</p> Signup and view all the answers

<p>Rods mainly contribute to the magnocellular pathway, while cones contribute to both magnocellular and parvocellular pathways.</p> Signup and view all the answers

<p>The rod system has larger receptive fields that are more diffuse, with less centre-surround antagonism, and no OFF pathway.</p> Signup and view all the answers

<p>The dual input allows parasol ganglion cells to receive information from both rod and cone systems, contributing to their sensitivity and spatial acuity.</p> Signup and view all the answers

<p>The three major channels are the parvocellular, magnocellular, and koniocellular pathways.</p> Signup and view all the answers

<p>Amacrine cells are interneurons that carry information laterally through the inner plexiform layer, and they synapse with bipolar, amacrine, and ganglion cells. They help 'sharpen up' the receptive fields of ganglion cells, and they have various functions and release various neurotransmitters.</p> Signup and view all the answers

<p>ON-centre bipolar cells depolarize in response to light stimuli, whereas OFF-centre bipolar cells hyperpolarize in response to light stimuli.</p> Signup and view all the answers

<p>The Dendritic Field (DF) of a ganglion cell is the physical area of the dendritic arbour, whereas the Receptive Field (RF) of a ganglion cell describes the area of photoreceptors that will ultimately contribute to the response of the ganglion cells (after relay by bipolar cells).</p> Signup and view all the answers

<p>Bipolar cells receive direct input from a group of photoreceptors and transmit visual information to ganglion cells.</p> Signup and view all the answers

<p>The receptive fields of bipolar cells are smaller and more localized than those of ganglion cells, which are larger and more complex.</p> Signup and view all the answers

<p>Receptive fields are the areas of the visual field that will produce a change in the response of a cell in the visual system, and they contribute to our perception of the visual world by allowing us to detect and respond to visual stimuli.</p> Signup and view all the answers

<p>They have better performance characteristics.</p> Signup and view all the answers

<p>By reducing the duration of the stimulus, currently 200ms, to uncover an important functional biomarker for the condition.</p> Signup and view all the answers

<p>Altered receptive fields may be an important biomarker for glaucoma; unanswered questions include whether receptive fields are altered, which cells are affected, and where in the visual pathway this alteration occurs.</p> Signup and view all the answers

<p>They are critical for identifying glaucomatous damage and may be improved by altering the current stimulus design.</p> Signup and view all the answers

<p>The visual pathway may be altered at the level of receptive fields, potentially masking important biomarkers for glaucoma; this has implications for the design of perimetry stimuli.</p> Signup and view all the answers

<p>It could lead to the development of more effective diagnostic tools and a better understanding of the underlying mechanisms of glaucoma.</p> Signup and view all the answers

<p>Responses A, B, and C are equal as long as the total amount of light falling on receptive fields is the same, resulting in the same perception.</p> Signup and view all the answers

<p>If we halve the luminance, we must double the duration to maintain visibility, and vice versa.</p> Signup and view all the answers

<p>The critical duration is up to 100ms, during which complete temporal summation occurs, and beyond which summation is partial or incomplete.</p> Signup and view all the answers

<p>Perimetry stimuli design should consider the receptive fields and spatial summation principles to optimize stimulus detection.</p> Signup and view all the answers

<p>Bloch's Law (temporal summation) is analogous to Ricco's Law (spatial summation), with critical duration analogous to Ricco's area.</p> Signup and view all the answers

<p>Alterations in receptive fields and the visual pathway can lead to defects in perimetry, which are characteristic of glaucoma.</p> Signup and view all the answers

<p>Spatial summation refers to the absorption of quanta over space, i.e., over the area of a receptive field. The critical factor is the total amount of light falling on a receptive field, which determines whether a stimulus will be seen or not.</p> Signup and view all the answers

<p>A small bright light and a larger dim light can have the same visibility, provided the total amount of light falling on a receptive field is equivalent.</p> Signup and view all the answers

<p>Changes in receptive fields can lead to alterations in the visual pathway, contributing to the progression of glaucoma. In perimetry, this can affect the accuracy of threshold measurements.</p> Signup and view all the answers

<p>The hill of vision represents the height of the hill of vision at a particular location in the visual field, and the threshold is the minimum difference in brightness between a stimulus and the background.</p> Signup and view all the answers

<p>Commercially-available perimeters differ in their stimulus design, with some using specific stimulus sizes and brightness levels to detect visual field defects.</p> Signup and view all the answers

<p>The size of a stimulus affects its visibility, as a larger stimulus can be seen at a lower brightness due to spatial summation.</p> Signup and view all the answers