In order to be able to perform auditory psychophysical and speech perception experiments a versatile research platform has been developed at ExpORL, Dept. Neurosciences, KULeuven (Laneau et al., 2005; Francart et al., 2008). 1, allows most auditory behavioral experiments to be performed without any programming, both for acoustic stimulation, direct electric stimulation via a CI or any combination of devices.
This manual describes APEX. The idea behind is that one should be able to set up an experiment without any programming knowledge. It is a generic platform with abstract interfaces to the computer monitor, computer input devices such as keyboard, mouse, and touch screen, and output devices such as sound cards or interfaces to cochlear implants. The user should be able to use any of the interfaces without programming any device specific details.
Experiments are defined in the XML format2, allowing for a structured experiment definition in a generic format. A Matlab and R toolbox is distributed together with to ease the automatic generation of experiment files and analysis of results files.
After registration, APEX can be downloaded from http://www.kuleuven.be/exporl/apex and can be used free of charge. The hardware requirements are limited to a personal computer running the Linux or Windows operating system and the necessary stimulation devices.
For proper citation see License Agreement at http://www.kuleuven.be/exporl/apex. Any publication that deals with should cite: Francart, T., van Wieringen, A., Wouters, J. APEX3: a Multi-purpose test platform for auditory psychophysical experiments. Journal of Neuroscience Methods, vol. 172, no. 2, pp. 283–93, 2008.
When using the animated child mode, you should also refer to: Laneau, J., Boets, B., Moonen, M., van Wieringen, A. and Wouters, J., “A flexible auditory research platform using acoustic or electric stimuli for adults and young children”, Journal of Neuroscience Methods, 142, pp. 131-136, 2005.
No programming is required to set up an experiment.
Multiple platforms are supported, including MS Windows and Linux.
Multiple output devices are supported, including sound cards, an interface to cochlear implants from Cochlear and an interface to cochlear implants from Advanced Bionics. The supported implant devices can be used in any combination, a CI (or hearing aid) in both ears (bilateral electrical stimulation) or simultaneous stimulation via a CI in one ear and acoustical stimulation in the other (bimodal stimulation).
Several psychophysical procedures are readily available and custom procedures can easily be added (plug-in procedure).
As much information as possible is stored per trial in the result file. This includes the subject’s response, but also response times, calibration values and much more.
Visual feedback can be given after each trial.
There is a special animated interface for testing (young) children.
There is a Matlab toolbox for experiment file creation and advanced result file analysis.
Custom signal processing filters can be added. (plug-in filter)
Custom interfaces to external controllers can be added. (plug-in controller)
There is a GUI (Graphical User Interface) to calibrate parameters.
There are 4 forms of documentation available for APEX:
The paper gives a concise high level overview. It is advisable to read it first. Note that since it was published some implementation details have changed, so please refer to the other documentation for up to date details.
You are currently reading the manual. It does not cover every feature of APEX in detail, but endeavours to describe the most often used features in more detail than the paper.
The APEX schema defines the structure of an experiment file (see section [sec:Schema’s]). It systematically contains documentation for each element, and exhaustively determines which elements can occur. It is the most up to date and most complete source of documentation, but requires some insight in the general function of APEX, which is provided by the paper and manual. The schema documentation can be consulted in 3 different ways: (1) using the HTML format schema documentation that comes with APEX, in folder , (2) when editing an experiment file with the oXygen editor, it will show the documentation for the current element in a different pane and suggest elements when you start typing, or (3) opening the schema directly in the oXygen editor.
APEX is shipped with a large number of examples, illustrating most of the features. They are stored in folder in the main APEX folder, and are documented in chapter [chap:examples] . The best way to start a new experiment, is probably to take one of the examples and modify it until it suits your needs.
APEX is installed by either running the installer (), or by simply copying the APEX folder to your computer. After installation, there is a main directory (default: ) under which the following subdirectories exist and contain the necessary files:
Binary files: the main executable (), the Qt dll’s and some Qt plugins
The experiment file schema () and the apexconfig () schema. You can point your XML editor to the former schema when editing experiment files (section [sec:Schema’s]).
The file contains general settings that are applied to all experiments.
contains different plugins (cf. appendix [sec:plugins]).
contains the APEX 4 Matlab Toolbox, for automatic generation or analysis of experiment files (cf. appendix [app:Matlab]).
contains example experiments for nearly every feature of APEX
makes use of an experiment file. An experiment file contains all the necessary information to run an experiment, such as the layout of the screen, the workings of the procedure, references to stimulus files and pictures, the way in which the stimuli are routed to a device etc. Several tools exist to create experiment files easily and analyze results, e.g. an XML editor (next section) or the .
While any text editor, such as wordpad, notepad and many others, can be used to create or edit experiment files, the use of an editor specifically suited for editing XML files has many advantages, such as syntax highlighting, automatic completion and validation.
At ExpORL we use the OxygenXML editor and will therefore give hints on how to use the syntax in this manual. You are, of course, free to use any other editor.
A free demo version of OxygenXML is available from http://oxygenxml.com. If you would decide to buy the full version, you will get a 10% discount if you enter the following coupon code during the ordering process:
oXygen-Kuleuven
A free version is available for people working in the field of life sciences.
| Basic concepts | Discusses the basic concepts of APEX 4. |
| Creating experiment | Describes the structure of experiment files. |
| Scripting | Describes how to automate (script) tasks in APEX 4. |
| Examples | Discusses 4 example experiments in detail. |
| Examplestrategies | Shows how to implement some common features of psychophysical and perceptual experiments. |
| Results | Shows how result files can be analyzed. |
| L34 | Describes the use of the L34 device |
| Matlab | the Matlab toolbox |
| Plugins | Use of plugins |
| Customizing | Customizing the appearance |
An exhaustive list of all elements that can occur in an experiment file are given in the schema documentation.
Application for Psychophysical EXperiments ↩
The complete XML specification can be found at http://www.w3.org/TR/xml11/ ↩