Neuroscientist here. I have personally implanted many animals of different species with similar apparatus as the ones described by neuralink, and published numerous papers in the field, including theoretical papers on neural activity coding and modeling. Here are my two cents about this. Sorry if it’s long, I m hoping that this will help provide perspective on the topic at hand.

As a scientist, the first thing that is striking is that this is another example of science by press conference. It’s probably why there is a lot of eye rolling in the field. No data has been released (including in the single author elon musk paper published a couple of years ago), and it is therefore impossible to judge the results independently, let alone have a scientific discussion about it.

First off, it should be noted that not much here is completely new. Chronic implantation of multielectrode arrays, with wireless recordings have been around for roughly 15 years. These arrays are able to record and stimulate. This is usually done in mice, in which space is even more limited than the pig. The number of contacts (i.e recording points) of 1000 is also on par with the current state of the art (see, e.g the neuropixel implants). The fact that neuralink managed to reproduce this seemingly from scratch is an impressive feat, but in no way is it novel. Dozens of labs around the world do this every day.

The issues with electrode recordings are to get close enough to each cell without damanging anything. If the contact is too far, the recording is polluted by other neurons, and one has to rely on blind signal separation to make out each cell. As a result in typical experiments, each electrode is manually positioned In the close vicinity of the neuron (think micrometers). This is a challenge with large arrays because each contact is not independant which reduces the yield. This likely happens here.

Another important problem arises with chronic implantantion. When you insert something in the brain, make it as thin as you wish the brain will not like it. There is going to be pushing and shoving of cells, and when the brain reset in position (within minutes) it will have moved. This requires fine tuning of each electrode’s position to keep it close to the neurons. More importantly, it will create a scar. Cells will die around it, the organism will try and isolate the foreign object. This takes weeks. This is the reason why, roughly speaking, no single cell has been recorded from for more than weeks (the record i believe is around 3 months): after a while the electrode is simply too isolated from the actual neurons to pick up a signal. There are endeavors around this, With other electrode materials, etc but neuralink does not do that. (Another really cool way to do chronic implant is with calcium imaging with small implanted confocal microscopes)

In addition, this is likely bad for the organism, and possibly not something you would want happen in your brain. BTW I believe that (in addition to size constraints) this is why they are doing studies on pigs now (although their neural activity is not well documented as opposed to mice/rats or primates): it is commonly used as a model for human injuries.

Finally, do be aware that some humans are already implanted chronically in the brain with electrodes:
- For parkinsons, in a specific, non cortical area. These electrodes can record and stimulate to alleviate crises
- For hearing, it’s not stricto sensu in the brain (in the cochlear cavities) but it stimulates neurons
- On the surface of the brain, with ecog electrodes mostly used during surgery but sometimes chronically for epilepsy diagnosis

In addition to these technical issues (which are serious enough, by the way), the claims made here are just sort of outlandish. Even in very well controlled laboratory conditions, there is very little evidence that it is remotely possible to “record” memories (let alone replay them). For the most part it is because we have _strictly no idea_ how _anything is encoded_ in the brain (there is even raging debate as to whether it “encodes” anything). (Sorry to my neuroscientist friends and colleagues, but we are not close to anything the layperson would qualify as “understanding what the brain does”, by a long stretch.) In addition, some of the less outlandish claims (e.g. controlling robotic limbs, etc) made by neuralink are things on which neuroscientists have been working on for decades. It’s not impossible for sure (as many of us argue in their grant proposals), but it is hard. And the plan presented by neuralink (more electrodes) is in no way innovative to an insider in the field. In fact, I doubt that it would get NIH funding.

TLDR there are many well documented issues with this endeavor that many people have been working on for decades. It’s frustrating that the general public be exposed to the uninteresting sugar coated sci fi version of an otherwise complex, nuanced and thus interesting field of science.