American scientists have managed to achieve the appearance of complex visual images through deep stimulation of the visual cortex. To do this, they dynamically change the current strength and duration of stimulation of closely spaced electrodes so that they formed letters. The methodology was tested in sighted and blind patients implanted in the occipital lobe electrodes: and those and others were able to recognize and draw letters on the touch screen. Article published in the journal Cell.
In most cases blindness is due to direct lesions of the retina or the optic nerve, and visual cortex and other departments that can process visual information remains intact. To restore vision, at least partially, so you can use direct stimulation of the visual departments — in the same way as, for example, are forced to move the limb through direct stimulation of the motor cortex.
Of course, to make it more complicated: visual cortex is much specific than the engine (however, it is arranged not easy). From the visual cortex, however, is quite important for possible stimulation feature: the neurons in it are retinotomies their activity spatial replicates the image that falls on the retina.
This feature in his study have used scientists under the leadership of Daniel Yoshor (Daniel Yoshor) from Baylor medical College. Their experiment involved three sighted patients with epilepsy and two blind patients in the occipital (the one where the visual cortex) the area which was implanted plate electrodes 24. Scientists have suggested that sequential stimulation of each of them will lead to the formation of participants ‘ sight — phosphene.
Scientists began with the stimulation of two closely spaced electrodes with a duration of 100 milliseconds, a frequency of 60 Hz and different amperage. During stimulation (at this stage, the scientists stimulated the visual cortex of one blind patient) participants were asked to portray the images on the touch screen. Calibration showed that the phosphene in the upper right corner of the visual field appears when the stimulation current is 4 milliampere through the right upper electrode, a phosphene in the upper left corner — the stimulation of the corresponding electrode current 3.6 ampere.
Interestingly, by varying the supply of current to two electrodes, scientists were able to achieve the appearance of phosphenes between the original two: for example, stimulation of the right electrode current of 2 ampere, and the left — 1.8 milliampere led to the fact that the phosphene appeared exactly in the middle. The researchers concluded that to achieve the appearance of phosphenes can be not only stimulating the physical electrodes, but also “virtual”, the intermediate electrodes varying the current strength of two nearby electrodes.