Supplementary Information: text description of linear filters

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.