Thanks for the quotes.

To begin with, there are significant risks of medical complications—including infections, electrode displacement, hemorrhage, and cognitive decline—when implanting electrodes in the brain. ... One study of Parkinson patients who had received deep brain implants showed reductions in verbal fluency, selective attention, color naming, and verbal memory compared with controls.

I was aware that BCI would be dangerous, but I wasn't aware that current BCI, with very limited bandwidth, was already so dangerous. As I said, one could try only interfacing with the surface of the brain - the exact opposite of deep brain stimulation - which is less invasive but does massively reduce options.

Not only can the human retina transmit data at an impressive rate of nearly 10 million bits per second, but it comes pre-packaged with a massive amount of dedicated wetware, the visual cortex, that is highly adapted to extracting meaning from this information torrent and to interfacing with other brain areas for further processing.

Outgoing bandwidth, OTOH, is only a few bits per second. Better to pick the low-hanging fruit.

Coincidentally, I ran into a paper Reconstructing Visual Experiences from Brain Activity Evoked by Natural Movies which seems to claim to extract large amounts of information from the visual cortex via fMRI:

The decoder provides remarkable reconstructions of the viewed movies.

Although I don't know the specifics because of the paywall.

Even if there were an easy way of pumping more information into our brains, the extra data inflow would do little to increase the rate at which we think and learn unless all the neural machinery necessary for making sense of the data were similarly upgraded. Since this includes almost all of the brain, what would really be needed is a “whole brain prosthesis–—which is just another way of saying artificial general intelligence.

As I said, I think taking information out of the brain would happen long before this scenario. But in the more futuristic case of an exocortex, there would still be a period where some parts of the brain can be emulated, but others can't, and so a hybrid system would still be superior.

I noticed that you don't have a green arrow pointing from BCI to WBE or AI in your diagram. It seems like if BCIs make people smarter, that should allow them to do WBE/AI research more effectively. Thoughts?

To begin with, there are significant risks of medical complications—including infections, electrode displacement, hemorrhage, and cognitive decline—when implanting electrodes in the brain.

This is all going to change over time. (I don't know how quickly, but there is already work on trans-cranial methods that is showing promise.) If we can't get the bandwidth quickly enough, we can control infections, electrodes will get smaller and more adaptive.

enhancement is likely to be far more difficult than therapy.

Admittedly, therapy will come first. That also means that therapy will drive development of techniques that will also be helpful for enhancement. The boundary between the two is blurry, and therapies that shade into enhancement will definitely be developed before pure enhancement, and be easier to sell to end users. For example, for some people, treatment of ADHD spectrum disorders will definitely be therapeutic, while for others it be seen as attractive enhancements.

Not only can the human retina transmit data at an impressive rate of nearly 10 million bits per second, but it comes pre-packaged with a massive amount of dedicated wetware, the visual cortex, that is highly adapted to extracting meaning from this information torrent and to interfacing with other brain areas for further processing.70 Even if there were an easy way of pumping more information into our brains, the extra data inflow would do little to increase the rate at which we think and learn unless all the neural machinery necessary for making sense of the data were similarly upgraded.

The visual pathway is impressive, but it's very limited in the kinds of information it transmits. It's a poor way of encoding bulk text, for instance. Even questions and answers can be sent far more densely with a much narrower channel. A tool like Google Now that tries to anticipate areas of interest and pre-fetch data before questions arise to consciousness could provide a valuable backchannel, and it wouldn't need near the bandwidth, so ought to be doable with non-invasive trans-cranial techniques.

True - in fact, this has been going on since the invention of the printing press. But I think we've exhausted all the low-hanging fruit here, in that we already have access to all the public domain knowlage of humanity at our fingertips, including crude automatic translations of other languages and tools like Siri or Wolfram alpha.

Indeed, the mechanical component is far better at recursive self improvement, which is why I wrote:

Of course, in the end it would transition to a fully or mostly machine intelligence, either through offloading increasingly more cognition to the machine components until the organic brains were only a tiny fraction of the mind, or though using the increased intelligence to develop FAI/WBE.

It also occurs that for a 'hive mind' using the enhanced intelligence to acquire the resources to connect more people to the hive mind counts as quantitative, if not qualitative, biological self improvement.

I'd guess it'd make very little difference in ‘regular’ chess but it would help somewhat in bullet chess.

I read somewhere that Kasparov was considering three moves per second while deep blue considers billions. If you consider a move and it takes a few seconds to enter it into a computer, as opposed to being read from your brain, a analysed, and a preliminary evaluation (enough to check that there are no obvious flaws) returning to your brain within milliseconds, then this seems like a several-fold speed up. True, its a quantitative not qualitative speedup, but then this is just a BCI capable of transmitting thoughts consisting of a few bytes.