The Neural Interface, or NI, is a hypothetical CyberneticProsthesis I/O system in which the user would connect to a computer through nerve impulses (direct neural interface) or EEG patterns. 

The idea has been widely used in fiction, especially in the 'cyberpunk' genre. Many of the stories regarding it postulate a vivid sensory immersion system in which one's perceptions are partially or entirely replaced by a simulated 'cyberspace'.

In the real world, progress towards such devices has been slow, with most of the work done in the field is aimed at allowing greater communication or mobility for the disabled. EEG-based neural output systems have been in development since the 1970s; in the early 1990s a system called Mind Switch was developed which showed great promise, but work on it seems to have slowed since. Direct neural systems did not begin to develop to any great degree until the late 1990s, with systems designed to allow control over prosthetic limbs. Another system, dramatically demonstrated in a widely publicized assault trial, stimulates nerves below a break in the central nerve stem, allowing the previously paralyzed patient to walk, albeit with difficulty. There have also been a handful of 'cyborg' researchers, such as the (in)famous Dr. Kevin Warwick, who have performed a number of heavily publicized 'experiments' (often of dubious scientific value) as a way of promoting interest in and funding for the field. 

The most recent development (Oct 2004) is a system called 'BrainGate', consisting of miniature array of electrodes which is implanted into the brain directly, and can detect up to 100 separate signals. Clinical trials of this device began in June 2004, and in current tests has permitted parapalegic subjects to send e-mail, play computer games and control a television set. among other things. Details can be seen at http://www.cyberkineticsinc.com/braingate.htm

Output devices have proven more difficult. It has been known since the 1940s that certain areas of the brain, when probed, can trigger false sensory impressions, emotional responses, or even memories; however, this requires direct manipulation of the brain tissue itself, and furthermore cannot so far be used to create a specific sensory experience. While some experiments in synesthetic impulses have been performed on nerves outside of the brain, only very simple signals - pain, light touch, and so forth - have proven possible to date.