Rhythm Plugins

Streams data from any device running Intan’s “Rhythm” firmware. It is currently compatible with the Open Ephys acquisition board and the Intan RHD USB Interface Board by selecting the appropriate processor (Acquisition Board and Intan RHD USB). The Open Ephys FPGA version of the Acquisition Board needs the plugin OE FGPA Acquisition Board which works in the same way.

Plugin Type	Source
Platforms	Windows, Linux, macOS
Built in?	Yes
Key Developers	Josh Siegle, Aarón Cuevas López
Source Code	open-ephys-plugins/rhythm-plugins

Tip

For more in-depth documentation on the Open Ephys Acquisition Board, please refer to the Acquisition Board docs site.

Plugin configuration

Headstages

On the left-hand side of the module, there are slots for each of 8 headstages (A1, A2, B1, B2, etc.). Each row corresponds to one 12-channel Omnetics connector on the input board (from left to right, there are A, B, C, and D), and each column corresponds to one headstage on that input. Up to two headstages can be connected to each input using a dual headstage adapter. The module will automatically detect headstages that are connected. However, if you add or remove headstages after the module has been loaded, you need to press the “RESCAN” button. Clicking on the button for one of the detected headstages will toggle it between 32-channel and 16-channel mode. This is necessary because the difference between 16-channel and 32-channel headstages cannot detected in software, and has to be selected manually.

Sample rate selection

Sample rates between 1 and 30 kHz can be selected with this drop-down menu. This will determine the sample rate for all headstages, digital inputs, and ADCs. Please note that available sample rates can vary between different hardware.

Bandwidth interface

Used to determine the settings for the analog high and low cut filters on the Intan chip. Because only certain values are possible for each, the number that appears may be different from the number you typed in; the chip will automatically select the nearest value, and that will be indicated in the GUI.

DSP button

in addition to the analog filters, the Intan chips also have an on-chip DSP high-pass filter for removing the DC offset on each channel. This can be toggled on and off by clicking the “DSP” button (yellow = on), and the cutoff frequency can be changed by typing a value into the associated text box. Again, there are only certain values for the cutoff frequency; the chip will choose the one closest to what you selected and return this value to the GUI.

Audio output

The “AUDIO OUT” interface will allow you select up to 2 channels to preview in real time, directly from the acquisition board/evaluation board.There is an audio jack (see the red circle in the picture below) that’s mirrored to the first two analog output channels (CH1 and CH2 of the Digital & Analog I/O for L and R sound outputs when connected to HDMI port for analog output — it is the leftmost HDMI port; see a picture below). To select a channel for monitoring, click on one of the two “Audio Out” buttons to reveal the pop-up channel selector.

Noise slicer

Sets the threshold for the noise slicer on the hardware audio outputs (sets any values below threshold to zero, to improve the signal-to-noise ratio). In practice, this doesn’t work particularly well.

ADC selection

Pressing the “ADC 1–8” button toggles the ADC inputs on and off. If the button is off (gray), the ADC channels on the acquisition board/evaluation board will be discarded. If the button is on (yellow), they will be sent as parallel data channels, with the same sampling rate as the neural data. A Digital & Analog I/O board needs to be connected to the second HDMI port from the left.

DAC TTLs

UNTESTED FEATURE

DAC High-pass filter

UNTESTED FEATURE Sets the high-pass filter cutoff for the DAC outputs

TTL settle

UNTESTED FEATURE Ties one of the digital inputs on the acquisition board/evaluation board to the “fast-settle” functionality of the Intan chips. If the selected digital input channel goes high, it will trigger the reset of the amplifiers across all headstages.

Impedance testing

To open the impedance measurement interface, click the “window” or “tab” buttons at the top of the plugin editor. This will bring up an impedance measurement interface that looks like this: