Coordination between head and hindlimb motions during the cat scratch response

Area of Science:

• Neuroscience
• Biomechanical Engineering
• Animal Locomotion Studies

Background:

• The scratch reflex in cats involves complex motor coordination between the hindlimbs and other body parts.
• Understanding the role of neck muscles during this reflex provides insights into sensorimotor integration.

Purpose of the Study:

• To investigate the coordination between head movements and hindlimb paw activity during the scratch cycle in freely moving cats.
• To characterize the electromyographic (EMG) activity of specific neck and ankle muscles during scratching.

Main Methods:

• Electromyography (EMG) was used to record activity from neck muscles (biventer cervicis, complexus, obliquus capitis inferior, splenius) and ankle muscles (medial gastrocnemius, tibialis anterior) in cats.
• Filming and in vivo force transducers were employed to analyze head motion and ankle extensor muscle tension during the scratch cycle phases (precontact, contact, postcontact).

Main Results:

• Head trajectory showed oscillation, moving away during paw contact and repositioning during noncontact phases.
• Neck muscle EMG activity was phasic or tonic, with ipsilateral muscles exhibiting more frequent phasic bursts.
• Specific neck muscles (iBC, iSP, iOC, cOC) showed distinct activity patterns related to scratch cycle phases and ankle extensor forces.

Conclusions:

• Phasic neck muscle activity is not obligatory for the cat scratch response but is modulated by factors like high extensor tendon force and head repositioning requirements.
• The study elucidates the nuanced role of neck muscles in coordinating head and hindlimb movements during a complex motor behavior.