The Conversation discusses an engineering problem with electronic brain implants intended to restore vision, like Neuralink’s hyped Blindsight. They can add more pixels to the resolution, sure… but human neurons don’t operate on pixels:
In our newly published research, we created a computational model of human vision to simulate what sort of vision an extremely high-resolution cortical implant might provide. A movie of a cat with a resolution of 45,000 pixels is sharp and clear. A movie generated using a simplified version of a model of 45,000 cortical electrodes, each of which stimulates a single neuron, still has a recognizable cat but most of the details of the scene are lost.
The reason why the movie generated by electrodes is so blurry is because neurons in the human visual cortex do not represent tiny dots or pixels. Instead, each neuron has a particular receptive field, which is the location and pattern a visual stimulus must have in order to make that neuron fire. Electrically stimulating a single neuron produces a blob whose appearance is determined by that neuron’s receptive field. The tiniest electrode – one that stimulates a single neuron – will produce a blob that is roughly the size of your pinkie’s width held at arm’s length.
Consider what happens when you look at a single star in the night sky. Each point in space is represented by many thousands of neurons with overlapping receptive fields. A tiny spot of light, such as a star, results in a complex pattern of firing across all these neurons.
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You can read more of the implant research here, in Nature: Scientific Reports.