Detect & Respond to Theta or SWR Oscillation
with Our Closed Loop Application

The first app from our HPP Application Project

This is a closed loop application that runs on our HPP (Hardware Processing Platform), detecting oscillation power within the sharp wave ripple (150 to 250 Hz) or Theta band (4 to 12 Hz). When the oscillation has been confirmed, this application triggers a stimulus via a TTL output pulse. An oscillation is confirmed when the oscillation power is above a user-defined threshold for the amount of time set by the user.

The Oscillation Detection application interacts with the oscillation detection algorithm programmed onto the HPP through a serial interface. The application provides access to four independent modules, allowing you to detect oscillations from the input acquisition channels of your Digital Lynx SX /SX-M (DLSX).

• Individual parameters can be set to adjust the oscillation detection sensitivity for each module
• Each detection module triggers a TTL bit output response on the DLSX when an oscillation has been confirmed

Diagram 1: Flow Implemented for Oscillation Detection Algorithm

A/D channel in  bandpass filter  calculate oscillation power  detect oscillation  output TTL

Oscillation power is calculated using an integrated “exponential moving averaging” (EMA) method applied to the bandpass filtered signal. You can adjust the sensitivity of the oscillation detection algorithm by setting the oscillation power smoothing index and adjusting the threshold level.

In order to display waveform signals in real-time while the oscillation detection application is running, the analog outputs on your DLSX front panel are integrated into the application. You can view waveforms with either a single stereo audio-to-dual BNC cable and a 2-channel oscilloscope, or two stereo audio-to-dual BNC cables and a 4-channel oscilloscope.

The “Analog Output Mode” Port {1:4} drop-down allows you to select which of the four detection modules {1:4} to output the corresponding waveform signals. The output waveforms are grouped into logical pairs (MODES) to be output through each of the two stereo analog output ports.

Table 1: Defined Modes, Ranges and Corresponding Waveform Outputs 

• AN1 and AN2 refers to left and right stereo outputs of first output jack
• AN3 and AN4 refers to left and right stereo outputs of second output jack on DLSX front panel
• At full scale (x1), the full 131,072uV input range of the DLSX is mapped to +/-1V analog output
• In (x64) scale, the input acquisition range +/- 2048uV is mapped to the +/-1V analog output range

Image 1: Screen Shot from Oscilloscope Connected to DLSX Analog Output Ports

Oscillation Detection Testing

In order for you to test the Oscillation Detection app, we provide two sample audio wavefiles converted from CSC acquisition recordings:

• test_swr_detection.wav
• test_theta_detection.wav

You can play the wavefiles from a PC or media device with audio output. Output at 100% volume with no filters applied from the audio software results in an output signal range of +/-1000uV. The audio signal is fed through a stereo to BNC cable to a Neuralynx input Signal Mouse connected to your DLSX acquisition system.

For testing purposes, set the EMA power and threshold when using the provided wav test files.

• EMA power: 12-15
• Threshold: 45-50uv