Cylinder Test (Forelimb Asymmetry)

The cylinder test (also known as the spontaneous forelimb use asymmetry test) places a rodent in a transparent glass or Plexiglas cylinder and quantifies the relative use of left versus right forepaws during spontaneous vertical exploratory behavior (rearing and wall contact). In neurologically intact animals, forelimb use is approximately symmetric (50% left, 50% right), but unilateral lesions to the nigrostriatal dopaminergic pathway (6-OHDA model of Parkinson disease), motor cortex (stroke models), or corticospinal tract produce a measurable bias toward the ipsilesional (unaffected) forepaw. The neural circuits assessed include the contralateral motor cortex, basal ganglia direct and indirect pathways, and descending corticospinal projections that control voluntary forelimb movements, making this test a sensitive and ecologically valid measure of lateralized motor deficits.

The experimenter (or automated system) counts three categories of forepaw wall contacts during rearing episodes: left-only contacts, right-only contacts, and simultaneous bilateral (both paws touching the wall together). The primary outcome is the forelimb asymmetry score, calculated as (ipsilateral contacts - contralateral contacts) / total contacts, where a score of 0 indicates symmetric use and positive values indicate bias toward the unaffected limb. Alternatively, contralateral paw use can be expressed as a percentage of total contacts. A minimum of 20 rearing events is typically required for reliable scoring. The test is performed without any drug challenge, making it a pure measure of spontaneous motor lateralization uncontaminated by drug-induced rotation artifacts.

ConductMaze records overhead and lateral video simultaneously to detect rearing events and classify forepaw wall contacts using pose estimation algorithms trained on labeled paw-contact frames. The system automatically identifies rearing onset (both hindpaws on the floor, body vertical), classifies each wall contact as left, right, or bilateral based on paw position relative to the cylinder wall, and computes asymmetry indices in real time. A minimum contact threshold is enforced to ensure statistical reliability, and the system flags sessions with insufficient rearing activity for extended recording or environmental enrichment to promote exploration.