Neurosurgeons from the University of Utah have developed new tiny electrode arrays that do not penetrate the surface of the brain, potentially preventing many of the side effects common to modern high precision electrodes. Similar to electrocorticography ECoG arrays, the microECoG devices may be small enough for permanent placement under the skull.
From the University of Utah:
The researchers tested how well the microelectrodes could detect nerve signals from the brain that control arm movements. The two epilepsy patients sat up in their hospital beds and used one arm to move a wireless computer “mouse” over a high-quality electronic draftsman’s tablet in front of them. The patients were told to reach their arm to one of two targets: one was forward to the left and the other was forward to the right.
The patients’ arm movements were recorded on the tablet and fed into a computer, which also analyzed the signals coming from the microelectrodes placed on the area of each patient’s brain controlling arm and hand movement.
The study showed that the microECoG electrodes could be used to distinguish brain signals ordering the arm to reach to the right or left, based on differences such as the power or amplitude of the brain waves.
The microelectrodes were formed in grid-like arrays embedded in rubbery clear silicone. The arrays were over parts of the brain controlling one arm and hand.
The first patient received two identical arrays, each with 16 microelectrodes arranged in a four-by-four square. Individual electrodes were spaced 1 millimeter apart (about one-25th of an inch). Patient 1 had the ECoG and microECoG implants for a few weeks. The findings indicated the electrodes were so close that neighboring microelectrodes picked up the same signals.
So, months later, the second patient received one array containing about 30 electrodes, each 2 millimeters apart. This patient wore the electrode for several days.
Images: Top: These two images show two kinds of microelectrode arrays, known and microECoGs, that were placed on the brains of severe epilepsy patients. The patients already had parts of their skulls removed temporarily for placement of larger ECoG electrodes, which are used to locate and treat the brain area responsible for their seizures. These larger, metallic, button-like electrodes are numbered in both images. The left image also shows two microECoG arrays, each with 16 microelectrodes connected to microwires that pass through the orange and green tubes. Because the arrays are made of fine wires embedded in clear silicone, photo-editing software was used to draw in their outlines in both images. The right image shows one microECoG array with 32 individual microelectrodes, connected with microwires entering via a clear tube from the bottom of the image. The green wires are connected to the large, conventional ECoG electrodes. Side: Microwires emerging from the green and orange tubes connect to two arrays of 16 microelectrodes. Each array is embedded in a small mat of clear, rubbery silicone. (University of Utah)
Press release: Reading the Brain without Poking It…
Full article in Neurosurgical Focus: Human neocortical electrical activity recorded on nonpenetrating microwire arrays: applicability for neuroprostheses
(hat tip: Gizmag)