We recorded the activity of PTNs from the limb representation of motor cortex in the cat maintaining balance on a platformperiodically tilted in the frontal plane. Each PTN was recorded during standing on four limbs, and Cuscutin when two or three limbs were lifted from the platform and thus did not signal its displacement to motor cortex. By comparing PTN responses to tilts in different tests we found that the amplitude and the phase of the response in the majority of them were determined primarily by the sensory input from the corresponding contralateral limb. In a portion of PTNs, this input originated from afferents of the peripheral receptive field. Sensory input from the ipsilateral limb, as well as input from limbs of the other girdlemadeamuch smaller contribution to thePTNmodulation.
These results showthat, during postural activity, a key role Droxinostat of PTNs is the feedback control of the corresponding contralateral limb and, to a lesser extent, the coordination of posture within a girdle and between the two girdles. Corresponding author T. G. Deliagina: Department of Neuroscience, Karolinska Institute, SE 171 77, Stockholm, Sweden. When standing, quadrupeds maintain a specific, dorsal side up body posture due to the activity of the postural control system. This system is driven by sensory feedback signals and generates corrective motor responses when the body orientation deviates from the desired one. Lesion experiments have shown that the forebrain, and the motor cortex in particular, are not necessary for the occurrence of essential aspects of postural behaviour.
On the other hand, recent experiments with recording the activity of cortical neurons in freely behaving animals have shown that this activity strongly correlates with postural corrections, suggesting that the motor cortex is involved in some aspects of the postural control. However, the role of the motor cortex in postural control is not clear. To understand the functional role of cortical activity in the control of body posture, one has to answer two questions: What is the origin of posture related cortical activity? What are the motor effects of this activity? In the present study, we addressed the first of these questions and assessed the origin of posture related cortical activity. We used our previously developed experimental design.
A cat stood on a platform and maintained balance when the platform was periodically tilted in the frontal plane. It was previously shown that in these experimental conditions the postural system equally well compensates for predictable and unpredictable perturbations, suggesting that it can well operate on the feedback principal. We examined the tilt related activity of the main cortical output pyramidal tract neurons from the limb representation of the motor cortex. In the previous study it was found that almost all PTNs were profoundly modulated in the rhythm of tilts. What are the sources of this modulation? 248 A. Karayannidou and others J Physiol 586. 1 The postural system operates on the basis of sensory information. It was shown that corrective postural responses, underlying trunk stabilization in quadrupeds, are driven primarily by the signals from limb mechanoreceptors rather