Locomotor/Neuromotor Function
Gait Analysis (Treadscan)
Rationale: This test measures the pattern of movement of the limbs of animals during locomotion over a motion belt.
Instrument: ExerGait Treadmill from Columbus Instruments. Treadscan Software from Clever Sys Inc.
Measures: Animals are tested on the ExerGait treadmill inside an adjustable running space at a fixed speed of 15 cm/sec for 10 sec. A digital camera records the reflected images of the footpads. Output was fed directly to a computer. Video recordings are analyzed by TreadScan™ 1.0 software (Clever Sys Inc.).
Data Inference: Averages from strides within a 20 – 100 mm range, and average length of front, rear and total strides are collected. Over 40 parameters can be obtained from data analysis.
Controls: Treadmill speed needs to be carefully adjusted until the mouse can maintain a consistent walking speed.
Neurological Development/Neuromotor Function
Rationale: Measures of neurobehavioral development, activity and arousal, motor function (coordination, balance, and muscle strength).
Instrument: Mouse cage observations.
Measures:
Righting Reflex: Placing a mouse on its side will immediately induce a movement of turning over to rest in the normal position with all four feet on the ground (principally labyrinthine and body righting mechanisms).
Crossed Extensor Reflex: Pinching the foot of one of the hind limbs lightly causes the flexion of the stimulated limb, while the opposite hind limb is extended (reflex mediated at the spinal level).
Forelimb and Hindlimb Placing Responses: Contact of the dorsum of the foot against the edge of an object causes the foot to be raised and placed on the surface of that object when the animal is suspended and no other foot is in contact with a solid surface.
Grasp Reflex: Stroking a fore or hind foot with a blunt instrument will cause the foot to flex to grasp the instrument.
Vibrissa Placing Response: When the mouse is suspended by the tail and lowered so that the vibrissae make contact with a solid object (e.g. a bar or table top), the head is raised and the forelimbs are extended to grasp the object.
Visual Placing Response: When the mouse is suspended by the tail and lowered toward a solid object, it raises its head and extends its forelimbs in a placing response.
Negative Geotaxis: When the mouse is placed on a 45-degree slope with its head pointing down the incline, it turns around and crawls up the slope.
Auricular Startle Response: A loud sharp noise (bell or Galant’s whistle) should cause an immediate startle response, seen either as a sudden extension of the head and fore and hindlimbs followed by withdrawal into a crouching position, or as flight (escape/avoidance) behavior.
Vertical Screen Test: Placement of a mouse at one end of a wire mesh screen that is then rotated to a vertical position should result in climbing.
Data Inference: Data from neurobehavioral/neurological tests can serve as criterion for inclusion in specific behavioral studies as well as guide the choice of behavioral tools to minimize potential confounds. Outcomes also provide a first measure of age-related phenotypes.
Rotarod
Rationale: Motor coordination and balance.
Instrument: Columbus Instruments Rotamex-5 Rotarod.
Measures: Animals are placed on the rods of a Rotarod apparatus. The latency to fall is measured. In one-time ‘endpoint’ studies interindividual variability in performance is limited by using slow acceleration during the test session. In studies that factor in practice and familiarity with the task performance is measured before and after 4 consecutive days of training.
Data Inference: Impaired rotarod performance (increased latency to fall from the rotating rod with respect to a control group) is indicative of motor deficits, which are commonly associated with aging.
Controls: Care is taken to normalize data to body weight. Animals over 60 g that show consistently latencies <=5s are removed from the study.