Programming Instructions
72
RNS
®
System User Manual
Bandpass detector
The bandpass detector provides highly specific and early detection of rhythmic and spiking activity
(types of ECoG activity). It acts like a frequency filter and can therefore be used to detect activity
within specific frequency bands (e.g. theta, alpha, beta, and gamma).
The bandpass detector analyzes the ECoG to determine when a signal is present within a specified
bandwidth that meets specified amplitude and duration requirements. Four configurable parameters
define the bandpass detector operation: the minimum and maximum frequencies that define the
bandpass, the minimum signal amplitude and the minimum signal duration. Detection will occur when
a signal within the bandpass meets the minimum amplitude requirement for the minimum duration
time. As minimum duration is increased, the detector will become less sensitive and it will take longer
for a signal at a given frequency to be detected. As minimum duration is decreased, the detector will
become more sensitive and it will take less time for a signal at a given frequency to be detected.
Figure 31: Bandpass detector example.
Detection settings should be programmed for early detection of activity. Detection settings that result in
early activity detection usually also result in numerous detections; this is expected and acceptable
behavior.
•
Evaluate
D
ETECTOR
C
HANNELS
.
•
After several stereotypical ECoGs with activity have been stored, the
D
ETECTOR
C
HANNELS
may need to be changed to those that capture the earliest activity.
•
Adjust
L
INE
L
ENGTH
detector settings (Figure 32).
•
The line length
D
ETECTION
T
HRESHOLD
may be adjusted to improve specificity and sensitivity.
Decreasing the percentage will result in earlier, but more frequent detections; increasing the
threshold percentage will have the opposite effect.
•
Decreasing the
S
HORT
T
ERM
T
REND
from 4 to 2 seconds also gives earlier, more frequent
detections. This adjustment allows the device to redetect more quickly.
•
Gradual and systematic adjustments to detection will result in more predictable changes in
the detection rate.
