The primary purpose of ACQ4 is to provide a system to automate experiments combining traditional electrophysiology, photostimulation, and imaging. The broader scope of ACQ4 is to provide a generic system for controlling research equipment including analog and digital input-output boards, cameras, motorized position control, and any devices that can be interfaced through analog or digital channels, serial port communication, or a manufacturer-provided application programming interface (API). ACQ4 is a modular and extensible system, making it possible to add support for new types of devices and experimental protocols. Likewise, ACQ4 makes few assumptions about the hardware configuration, allowing arbitrary combinations and arrangements of experimental hardware. The tools currently included with ACQ4 provide support for a wide range of neurophysiology techniques including patch-clamp electrophysiology, laser scanning photostimulation, calcium imaging, intrinsic imaging, and multiphoton imaging. In addition, the system provides services for data management and an extensible set of analysis tools.

ACQ4 is written in Python and is built entirely on free and open-source tools, with the exception of some commercial hardware drivers. The use of open-source software affords many benefits over closed-source software. First, experimenters with the necessary expertise may modify the program to suit their own needs and contribute the code back to the community for others to use. In this way, open-source software is developed by those who have the best understanding of their own experimental needs. Second, labs need not rely on the survival of a business or a particular product for long term support. Finally, virtually any task that can be done manually may be automated through the inclusion of custom scripts.