Description of linear filters A set of linear filters were constructed from a response matrix containing the firing rate over a 1 second history for each neuron (twenty 50 msec bins), and regressing this matrix onto hand position using a psuedoinverse technique. The least-squares formulation comprises a closed-form solution: u = R•f = R(RTR)-1RTk where R is the neural response matrix, f is the linear filter, k is the kinematic value (x,y position), and u is the reconstruction Between 7 and 30 neurons were used for closed-loop investigations. Movie legend: Acquisition of targets with neural control signal. The red circle represents a target 0.6 ° visual angle (13 mm on the screen). The green circle represents the neural control cursor. Each time the subject touches the target, he receives a reward and a new target appears at a random location.