Question

If we have a spot of light hitting the center of the ON center receptive field of a retinal ganglion cell, will the LGN neuron be activated? Will the V1 neuron be activated? I mean its receptive field looks different, see the image below. I am just so confused on what the receptive field of an LGN and V1 neuron even means. In other words, how is the receptive field of the retinal ganglion cell related to or how does it affect the receptive field of the LGN neuron? If light shines in the center of the ON center LGN neuron receptive field that is not in the receptive field of the ganglion cell, then the LGN neuron is activated and the ganglion cell is not. How does that work? How can it skip a stage? Does not the RGC first need to get activated for the LGN neuron to get activated? Since a V1 neuron to get activated for example needs a shine of light that is 45 degrees diagonal to the right, will it get activated if only a spot of light is shone to the ON of the ON center retinal ganglion cell? This RGC is connected to the V1 neuron is it not? In conclusion, I think that I am confused inwhy is the ganglion cell connected to the LGN cell, which is connected to the V1 cell, when they all have different receptive field. What does the connection bring about?

Answer 1

Receptive fields from retinal ganglion cells to LGN to V1 neurons differ and are designed to process specific visual information. An ON-center RGC can activate LGN and V1 neurons, but V1 activation depends on specific patterns or orientations, not just light presence. These connected stages allow simple visual signals to transform into complex perceptions.

Step-by-step explanation:

Understanding Receptive Fields and Visual Processing Pathways

The neural pathway from the retina to the brain encompasses multiple stages. Each stage includes cells with receptive fields that respond to specific aspects of the visual field. When light stimulates the center of the receptive field of an ON-center retinal ganglion cell (RGC), the cell increases its firing rate and can activate a neuron in the lateral geniculate nucleus (LGN). Similarly, an LGN neuron stimulated in this way can then activate a neuron in the primary visual cortex (V1). The receptive fields of LGN and V1 neurons differ from RGCs as they process more complex visual stimuli.

RGCs are the final output neurons of the retina, collecting information from rods and cones via bipolar cells and transmitting it through their axons, which form the optic nerve. At the LGN of the thalamus, information gets relayed to V1, where various neurons respond to specific types of visual information, such as orientation or movement. Therefore, a V1 neuron might not activate just by light on an RGC but would activate if the light aligns with the specific pattern or orientation the V1 neuron is responsive to, connecting it to the broader visual perception.

While each receptive field is different, the connections between cells allow for a cumulative effect where simple responses at the retinal level combine to yield increasingly complex visual processing at higher levels like the LGN and V1. This enables us to perceive detailed and dynamic visual scenes.