Reacción a "Electrodes capable of evoking vision and adapting in real time are implanted in the brains of two blind people"

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For decades, researchers in the field of cortical visual prostheses have accumulated evidence, in both humans and primates, of how cortical electrical stimulation can generate artificial visual perceptions (which we call phosphenes).

In previous work, we demonstrated simple visual perceptions generated with this same technology in humans, thanks to our first blind participant in the CORTIVIS study.

In this new work, Fabrizio Grani and the rest of the team, thanks to two new participants, conducted a comprehensive study of how this type of visual neural implant generates artificial perceptions (phosphenes), and how stimulation parameters modulate (change) these perceptions. For example, they examined how varying the current intensity, the frequency of the biphasic pulses, and the duration of stimulation modifies the brightness perceived by the participants.

Furthermore, and critically, the research team analyzed the responses of the neurons recorded after stimulation and were able to correlate the amount of neuronal activity with the brightness perceived by the participants in one experiment, with the ability to detect phosphenes in another experiment, and finally with the ability to distinguish two phosphenes separated in time in other tests (that is, perceiving two electrical stimuli as a single phosphene or as two separate phosphenes, which is important for understanding the temporal resolution that these neural implants will be able to achieve in the future). This is especially important and a major breakthrough. Normally, if we can automatically decode some properties of a user's perception of a future neural implant, these implants will be able to be calibrated much more easily and quickly.

[Regarding possible limitations] The first limitation is that, although the results are very clear and robust, it is usually possible to find individual variations. Therefore, it will be necessary to replicate these results in the future to establish the generalizability of the analyses and results in a larger population. Another limitation (perhaps more of a difficulty for the analysis) is the presence of stimulation artifacts. This means that when we stimulate and record neuronal responses with the same electrodes, it is necessary to process the signal to obtain a clear signal. Fabrizio and his colleagues did an exceptional job with signal processing in this case.