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[Effects of intracortical microstimulation on the muscle activity of the extremities in waking rabbits]
Abstract:
Intracortical microstimulation (IM) revealed separate sites of motor representation (MR) for contralateral limbs in the rabbit neocortex. The site of wrist control is in the MR center surrounded by the antebrachial and brachial sites. No isolated finger responses to the IM could be obtained. A more caudal MR for the hindlimb where the IM evoked separated responses of the crus and femoral muscles, revealed no geometric regularity of organization. The minimal thresholds of IM in the brachial and antebrachial MRs reached 3-10 microA and in the crus and femoral MRs 30-200 microA. Latencies of the EMG brachial, antebrachial, crus and femoral responses were, respectively, 25-52, 24-73, 36-71 and 32-54 msec. The organization of cortical regulation of limb movements is concluded to be primitive in rabbits, particularly for hindlimbs.
Insights
Intracortical microstimulation in rabbits shows distinct motor representations for forelimbs but a primitive, disorganized hindlimb representation in the neocortex. This suggests a basic cortical control of limb movements in these animals.
Area of Science:
- Neuroscience
- Comparative Neurology
Context:
- The neocortex plays a crucial role in motor control.
- Understanding the organization of motor representation is key to deciphering neural control of movement.
Purpose:
- To investigate the somatotopic organization of motor representation for contralateral limbs in the rabbit neocortex using intracortical microstimulation (IM).
Summary:
- Intracortical microstimulation revealed distinct motor representation sites for forelimb (wrist, antebrachial, brachial) and hindlimb (crus, femoral) muscles in the rabbit neocortex.
- Forelimb representation showed some organization, with wrist control at the center, while hindlimb representation lacked geometric regularity.
- Lower microstimulation thresholds and shorter latencies were observed for forelimb responses compared to hindlimb responses, indicating more sensitive cortical control.
Impact:
- This study reveals a primitive organization of cortical motor control in rabbits, particularly for hindlimbs.
- Findings contribute to comparative studies on the evolution and organization of motor systems in mammals.