Last modified by Iris Spruit on 2024/05/14 16:15


Actiview is free open source software used for recording with BioSemi (mainly for EEG) equipment. 

Availability, support and advice

Actiview is available for researchers at FSW Leiden and comes preinstalled on all lab computers (see the Software List to check which version).


To analyze EEG data, markers that signal the onset of certain events need to be sent from stimulus presentation pc to the BioSemi device. These markers will be visible during recording in Actiview. See for more information on sending markers the pages Sending Markers in E-Prime and Sending Markers in OpenSesame and the Markers and Events page for more information on markers in general.

Configuration file

ActiView uses a configuration .cfg file for the channel labels and other settings.

A .cfg file can be edited by opening it in Notepad. Be careful when editing, the .cfg file needs specific components, removing any of the necessary components may lead to a corrupted file that cannot be read by ActiView. 

To setup the channel labels for standard caps, the cap layout can be found here: Headcap, Headcaps ( Make sure to use the correct cap (the 32 channel labels are different from the 64 channel labels). Alternatively, .cfg files with standard cap layouts can be found in the folder Configuring in the ActiView zip file that can be downloaded here: Download software ActiView (

It is possible to start and pause the EEG recording in ActiView from your stimulus presentation software such as E-Prime or OpenSesame. To allow pausing by external trigger, set the PauseOff (start) to a value  0-255 (recommended is to use value 253) and PauseOn (pause) to a value 0-255 (recommended is to use value 254). Thus: 

PauseOff = "253"
PauseOn = "254"

This means that when BioSemi receives a marker with value 253, the recording is started and when BioSemi receives a marker with value 254, the recording is paused. Be careful when using these values that these values are not used to signal any events, to prevent accidental pausing of the recording.


2021/10/25Timing difference E-Prime and BiosemiIt is important to know that Biosemi outputs data in number of samples, not in ms. In one case, there seemed to be a timing delay: The time between two markers in E-Prime was 2000 and in Biosemi 2048. Time in E-Prime was given in ms, but in Biosemi in samples. With a sampling rate of 1024, 2048 samples equaled 2000 ms. Always double-check the unit that is outputted.


Tags: Physiology EEG
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