Search

Bionic vision devices aiming to restore visual perception in the vision impaired rely on microelectrode arrays that can be implanted under the diseased retina. Arrays used today in first human trials are high density monopolar arrays comprising up to 1500 electrodes in a 3x3 mm a simple field calculations demonstrate that such high density arrays suffer from degradation of contrast between those 1500 stimulation sites when driven simultaneously. This effect can be described as electric crosstalk between the electrodes that strongly depends on the number of electrodes on such an array and proximity of electrodes to the target cells. The limit of spatial frequency of visual patterns that could be resolved by such arrays can be assessed to be 4.5; 1.2; and 0.7 cycles/mm, for an anticipated distance of target neurons of 20 (m, 200 (m, and 400 (m, respectively. This relates to a theoretically best achievable visual acuity of 2%, 0.6%, and 0.3% of normal vision, respectively (logMAR 1.7; 2.2; 2.5). These data suggest that novel strategies have to be pursued to either get closer to target structures, e.g. by the use of penetrating electrode arrays, or to create more confined stimulating fields within the retina, e.g. by the use of hexagonal arrays with multiple electrodes guarding one active electrode. [ABSTRACT FROM AUTHOR]

Detection and automated interpretation of attention-related or intention-related brain activity carries significant promise for many military and civilian applications. This interpretation of brain activity could provide information about a person΄s intended movements, imagined movements, or attentional focus, and thus could be valuable for optimizing or replacing traditional motor-based communication between a person and a computer or other output devices. We describe here the objective and preliminary results of our studies in this area. [ABSTRACT FROM AUTHOR]

Many people have neuromuscular conditions or disorders that impair the neural pathways that control muscles. Those most severely affected lose all voluntary muscle control and hence lose the ability to communicate. Brain-computer interfaces (BCIs) might be able to restore some communication or control functions for these people by creating a new communication channel – directly from the brain to an output device. Many studies over the past two decades have shown that such BCI communication is possible and that it can serve useful functions. This paper reviews the different sensor methodologies that have been explored in these studies. [ABSTRACT FROM AUTHOR]

This article reports on an electrical retinal stimulation system for use in long-term animal electrical stimulation experiments. The presented system consists of an implantable stimulator, which provides continuous electrical stimulation and an external component, which provides preset stimulation parameters and power to the implanted stimulator via a paired RF (radio frequency) coil. A rechargeable internal battery and a parameter memory part were introduced to the implantable stimulator to avoid use of the external component during the stimulation cycles. The same inductive coil pair was used to pass the parameter data and to recharge the battery. To separate the stimulation mode and the battery recharging mode, a switch circuit is used. The implantable stimulator was implemented with IC chips and the electronics except the stimulation electrodes were hermetically packaged in a biocompatible metal case. [ABSTRACT FROM AUTHOR]