NeuroNexus SmartBox Instruction Manual page 15

SOFTWARE
can be used in neural recording applications to record
wideband neural data but to view only spikes by filtering
out the low-frequency local field potentials (LFPs) in the
display. When this filter is enabled, an identical version
of the filter is enabled in the FPGA on the USB interface
board that high-pass filters waveforms routed to the eight
DACs and threshold comparators (see the "DAC/Audio"
tab).
The "Bandwidth" tab also contains a combo box for en-
abling an optional 50 Hz or 60 Hz software notch filter to
help remove mains interference. The notch filter is used
only for displaying data; pre-notch-filtered raw data is
saved to disk. However, each data file contains a parame-
ter in its header noting the notch filter setting. The MAT-
FIG. 21: The Bandwidth tab is used to select FIG. 22: The amplifier bandwidth selection dialog box allows
LAB function provided by Intan reads this parameter and,
frequency-related parameters users to set upper and lower cutoff frequencies.
if the notch filter was applied during recording, applies the
identical notch filter to the data extracted in MATLAB.
The last control in the "Bandwidth" tab is a check box that changes all waveform plotting from lines to individual points to reduce CPU load. If the soft-
ware is run on a particularly slow computer at a high sampling rate with many amplifier chips connected, it is possible that the software could not keep
up with the data streaming across the USB port. The "FIFO lag" indicator near the "Stop" button shows the estimated amount of data waiting in the FIFO
USB buffer on the FPGA module. If this number begins growing beyond a few milliseconds it turns red, indicating that the computer is having trouble
keeping up with the data streaming from the SmartBox ™ . If the computer has difficulty keeping up with the data flow, you can check this box to reduce
the graphics-related overhead. Alternatively, you can disable the notch filter or reduce the amplifier sampling rate to reduce CPU load.
NOTE: When streaming 256 channels, use sampling rates of 20 kS/s or lower to prevent the FIFO USB buffer from filling up.
p.15
NeuroNexus Technologies, Inc. ©2014 | 655 Fairfield Court, Suite 100, Ann Arbor, Michigan USA
Telephone: +1.734.913.8858 | Fax: +1.734.786.0069 | support@neuronexus.com