Ledged Balance Beam
Description by James E. Groer, Dragonfly R&D, Inc.
Ledged Balance Beam for Rats
with Automated Foot Fault Counters
The need for such a device was pointed out to me by Dr. Frank
Tortella and Dr. Anthony Williams from Walter Reed Army Instituteof Research in Forest
Glenn, Maryland. The original designer of the Ledged Balance Beam, Dr. Timothy Schallert,
University of Texas, has given me permission to offer this elegant automated model or his
original idea, using his recommended dimensions.
The unit features Balance Beam designed for the adult rat, constructed of solid oak, and
mounted on each end to a sturdy, wide based, adjustable height pole stand. The beam is
divided into six (6) equal sections, three on the right, and three on the left. Each
counter has a light narrow wooden rail sitting atop a switching array which allows only
one count increment for each press and release (200 ms re-trigger specification between
presses) of about 6 grams or more. The counts from each of the 6 sections are tallied and
displayed on 6 individual count processors. Each processor has an individual reset button
to return the count to zero. On the wide end of the beam (departure end) is a thin oak
starting platform. On the narrow end of the beam (destination end) is a black Plexiglas TM
enclosed "shelter" with a removable lid for easy removal of the animal. We can
also optionally supply an appropriate noise generator for the departure end of the beam if
you require. The unique design allows the beam to be assembled/disassembled easily by one
A totally computerized automated model via a data acquisition system connected to a PC,
which replaces of the stand alone counters is also available (data acquisition system).
The PC based system can record and store each of the six (6) switching events in
real-time. Each switching array produces a DC square wave which is viewed graphically
using commercially available software package for graphing DC voltage, which provides a
very accurate graphic representation of the event time (i.e. how long the switch remains
closed for each foot fault). A start and stop pulse (departure and destination) is
generated automatically by a switching array mounted at the departure platform and another
mounted at the entrance of the shelter/enclosure. The event begins when the rat leaves the
platform, and ends when it enters the shelter/enclosure.