Question

How can V1 cells detect lines when photoreceptors detect only spots of light?

Answer 1

How can V1 cells detect lines when photoreceptors detect only spots of light?

Photoreceptors are specialized cells called rods and cones that detect light in the retina as the spots. They signal their levels of electrical polarization which is connected by network of horizontal, bipolar, and amacrine cells to the retinal ganglion cells. These informations are carried to brain by optic nerve to the LGN which is the relay station. The next processing happens in the cerebral cortex and V1 which is the primary receiving area of the brain. They majorly transform the information since because they are orientation selective and direction selective. There are about 140 million V1 neurons per hemisphere that is about 40 V1 neurons per LGN neuron. The optimally oriented visual stimulated response exhibit cross-orientation suppression which is supressed by the simultaneous presence of an orthogonally oriented stimulus. They are orientational selective that is the response to lines and bars are strong when compared to the orthogonal orientation. Simple cells of V1 are orientation selective, have separate ON and OFF subregions. They do length summation and respond to elongated bars or edges. Botht he hemisphere have area V1. The left VGN processs information to V1 in the left from the left portion of the two retinas, which capture images from the right visual field. The simialr happens to left visual field which is processed to right side of V1. Thereby, the cells of V1 detect lines when phototrecpetors detects spots of light.