San Diego Instruments: GEMINI™

Conduct learning and memory studies with unparalleled reliability and accuracy.

The GEMINI active and passive avoidance system is uniquely designed to ensure accuracy, reliability and ease of use in your learning and memory studies.

The system will connect to your computer through a standard USB connection, requiring no special training or technical expertise. Once setup is complete, run a wide range of avoidance tests with GEMINI’s flexible hardware and software features, including setting up your entire active avoidance or passive avoidance study in advance, saving all data in a single file, and the ability to run stations independently which allows for continuous testing.

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SDI’s GEMINI active and passive avoidance system was designed specifically to test active avoidance and passive avoidance in rats and mice. Unlike many others, GEMINI’s hardware and software have been developed for the sole purpose of your avoidance study.

GEMINI’s unique design allows you to run up to 8 independently operated stations directly from your laptop using a standard USB.  In addition, by allowing you to define a complete study in advance, GEMINI eliminates run time data entry that could affect the accuracy of your results.

When defining your study, the avoidance testing protocol definitions will offer you multiple cues that can be used individually or in combination to test passive avoidance and active avoidance.  The sound cue offers a broad range of options as you can set any frequency or white noise necessary. Further, the unconditioned stimulus is delivered by SDI’s proprietary Shocker, which scrambles the shocks to prevent the subject from learning the pattern and therefore avoiding the shock stimulus.

GEMINI Avoidance System Highlights:

Setup GEMINI Stations with Limited Technical Knowledge

Eliminate the need for any specialized interface cards or extensive technical knowledge with GEMINI. Your apparatus will connect directly to your PC through a standard USB interface.  If you use multiple stations, connect them just as easily using standard USB hubs. 

The Most Flexible Active and Passive Avoidance Software Available

GEMINI’s latest software gives you more flexibility and accuracy than ever. Not only is all of your data saved in one, easily accessed file—but you can define your complete study in advance by pre-assigning animals to specific stations for each session, and then assigning a predefined protocol to every test session. 

The software will automatically record your session data and keep it all together in the study’s single file. When you are ready, display your data right on your computer monitor or choose to export it with one click to Microsoft® Excel or to a delimited file type(TAB, CSV, etc.). Other software features include:

  • Consistent Results with Protocol Definitions

    GEMINI’s Protocol Definitions control the cues, shock level, and duration of shock. Another key feature is the setting of the Inter-Trial intervals either for fixed durations or random durations, which prevents the subject from determining a pattern. When you save your Protocol Definitions and reuse them in multiple studies, you’ll save time by eliminating redundant data entry and will also ensure the consistency of your results.

  • Define Your Study in Advance

    Make sure you collect the most accurate data possible by defining each of your planned test sessions. You will be able to plan session parameters, set subject identifiers, assign subjects to specific test stations, and specify subject parameters such as dose level.  To keep from losing any critical data, it will all be stored in a single file format.

  • Automatically Run Sessions

    Defining your study in advance not only saves you time by automating sessions, but eliminates run time decisions and data entry that can cause mistakes. You’ll also ensure your results are tightly coupled to your predefined subject identifiers. Simply follow the GEMINI software instructions to execute the test session.

  • Export Directly to Microsoft® Excel (or any delimited file type)

    The Gemini software makes table formatted results available for direct export to Microsoft® Excel or to a delimited file type(TAB, CSV, etc.) and automatically identifies data by column headers.  Since the data is exported from a single file, you won’t lose critical information and you’ll save time by removing the need to aggregate multiple single files and possibly reformat them again.

Start and Stop Stations Independently

Continually test animals by running each GEMINI chamber individually.  Loading and unloading animals into individual chambers does not affect the operation of other stations.

Maximize Your Options with Multiple Cues

Using the GEMINI software, select your desired cues and the duration of each. This feature provides you with the maximum flexibility in protocol design.

Choose from two light cues: House Light and Cue Light, and/or sound cues with the ability to define the exact frequency, or white noise that you want—creating virtually unlimited options.  All cues can be used individually or in combination to test passive avoidance, learned helplessness, and active avoidance. 

No False Crossing Errors

GEMINI stations have 8 photobeams on each side which accurately locate the animal. The photobeams can also be disabled near the Auto Door to make sure the animal has fully entered a compartment.  This feature will end false crossing errors.  Systems without this feature—or fewer beams—have been known to record exploratory behavior as a crossing, affecting the accuracy of results.

Delay Your Unconditioned Stimulus

Make sure your passive avoidance test results are not tainted by delaying the onset of your unconditioned stimulus (US), either foot shock or air puff.  When your US is not delayed, the subject’s learning ability can be affected by inadvertently tying the US to the gate closing.

One System that Works for Both Rats and Mice

Change your grid floors in under five minutes and avoid the need for two distinct systems.

Scrambled Shock Provides More Accurate Responses

The SDI animal shocker – a solid state feedback-controlled, constant current shocker uses 8 unique outputs to scramble the shock across the grid floor.  Scrambling the shock prevents the animal from determining a pattern and leads to more accurate responses.

In addition, GEMINI ’s shocker is the only one of its kind to display the actual current being administered to the subject—bringing clarity and accuracy to your research. 

Ensure Subjects Respond to the Right Cues

GEMINI’s quiet Auto Door helps to keep your subject from attaching the cue to the closing of the door in passive avoidance tests. In addition, the door closes by gravity, assuring the animal will not be injured while in the box.

Monitor Learned Helplessness Behavior

GEMINI™ is an ideal choice to study learned helplessness behavior, in addition to active and passive avoidance. If your study calls for learned helplessness testing, use GEMINI™-- the system built for it.

Kinder, Gentler Unconditioned Stimulus

The Gemini System offers an alternative air puff unconditioned stimulus. This is a kinder and gentler unconditioned stimulus.

GEMINI Avoidance System Components

  • Active & Passive Avoidance Software (on CD ROM)
  • Driver Software (on CD ROM)
  • Test station with 2 chambers and grid floor for rats (or mice), 16 photobeams, 2 LED “house” and 2 “cue” lights, two sound speakers and Auto Door
  • Cables, connectors and power supply
  • USB Hub (for multiple station GEMINI configurations)

GEMINI Optional Components

  • Air puff stimulation unit (AIRSTIM)
  • Additional test stations
  • Mouse passive avoidance start box
  • Grid floors (for rats or mice)



  • Configure up to 8 independent avoidance chambers for rapid testing of subjects
  • Ensure data accuracy by setting up your study in advance
  • Run the entire system from your laptop or PC using a standard USB port
  • Deploy continuous testing with independent station starts
  • Choose an array of cues including non-heating LED house light
    s, user selectable auditory stimuli, and quiet auto door
  • Switch between rats and mice in under 5 minutes using interchangeable grid floors


Outside: 26”(W) x 13”(D) x 17.25” (H) Inside: 9.5”(W) x 8”(D) x 8”(H) (each side)
Weight: 35 lbs.
Material Composition: Acrylic and aluminum, stainless steel (Gate)
Maximum number Stations: 8
Number of Photobeams: 16 infrared per enclosure
Photobeam Spacing: 1”
Standard Cable Length: 16 feet
Stimuli Options: Cue lights, house lights, sound, shock, gate
Color Options: Black
Stainless Steel Grids: 28 for rats, 62 for mice


Q: What does the Gemini mouse start box do?

A: The mouse start box makes your test more consistent because it reduces the size of the start chamber. This more readily orients the mouse toward the shock (dark) chamber, and reduces the time to shock (dark) chamber entry.

Q: Why am I not getting the shock to work on Gemini?

A: The selector switch on the front of the Gemini unit may not be set to ‘manual mode’.