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

The results published by Grani et al. address crucial topics in the field of brain-computer interfaces for vision restoration. The authors demonstrate that the levels of neuronal activity that are recorded from regions of the visual cortex that are close to the site of electrical stimulation are significantly correlated with perceptual reports from blind human patients. 

Specifically: 

1. Neuronal activity levels were systematically higher when the two patients reported seeing phosphenes, meaning that it may be possible to determine current thresholds using recorded activity, instead of relying solely on behavioural reports. This would allow faster, more efficient calibration of the prosthesis system, allowing future patients to start using their device within a shorter period from the time of implantation. It would also allow the determination and delivery of lower levels of electrical current to the tissue- just enough to generate useful vision. Keeping current levels as low as possible is important as excessive levels of stimulation have been known to cause seizures.

2. In experiments conducted in one of the patients, the patient reported that phosphenes were brighter when the stimulation frequency and/or duration of stimulation trains were higher. Furthermore, the levels of recorded neuronal activity showed a significant relationship with perceived brightness. To my knowledge, this relationship (between neuronal activity and perceived brightness) has not been explored in such detail, using intracortical microelectrodes, in blind individuals before. The importance of this finding is two-fold: firstly, it provides insights into how the brightness of individual phosphenes could be controlled, which in turns gives patients an additional channel of information. To date, scientists have been able to control the locations of phosphenes to some degree, but not so much their brightness. By adding luminance information to spatial location, patients would likely be able to recognize objects more easily. For example, they would potentially not only be able to see simple shapes, but also extract information about luminance or colour. Secondly, it would allow clinicians to estimate the brightness of phosphenes more quickly by analysing levels of neuronal activity, instead of requiring future blind prosthesis users to verbally report their brightness for each individual phosphene.

3. In both patients, successively delivered stimulation trains yielded two temporally distinct phosphenes when separated by an interval of around 300 ms. Furthermore, neuronal activity levels significantly correlated with whether the patients reported seeing one single phosphene, or two consecutively occurring phosphenes. This finding provides insight into the possible temporal resolution (or 'refresh rate') of artificial vision: if you think of stimulation of the cortex to produce phosphene vision as being analogous to updating a display on a monitor, how quickly can visual input be 'updated' to provide a blind person with useful information as the move and interact with objects and people in real time?