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This Article Full Text Full Text (PDF) All Versions of this Article: 586/1/247    most recent jphysiol.2007.144840v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Karayannidou, A. Articles by Beloozerova, I. N. Search for Related Content PubMed PubMed Citation Articles by Karayannidou, A. Articles by Beloozerova, I. N. Related Collections Neuroscience

¹ Barrow Neurological Institute, Phoenix, AZ 85013, USA
² Department of Neuroscience, Karolinska Institute, Stockholm, SE-171 77, Sweden

The dorsal-side-up body posture of standing quadrupeds is maintained by coordinated activity of all limbs. Somatosensory input from the limbs evokes postural responses when the supporting surface is perturbed. The aim of this study was to reveal the contribution of sensory inputs from individual limbs to the posture-related modulation of pyramidal tract neurons (PTNs) arising in the primary motor cortex. We recorded the activity of PTNs from the limb representation of motor cortex in the cat maintaining balance on a platform periodically tilted in the frontal plane. Each PTN was recorded during standing on four limbs, and 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 girdle made a much smaller contribution to the PTN modulation. These results show that, during postural activity, a key role 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.

(Received 11 September 2007; accepted after revision 26 October 2007; first published online 1 November 2007)
Corresponding author T. G. Deliagina: Department of Neuroscience, Karolinska Institute, SE-171 77, Stockholm, Sweden. Email: tatiana.deliagina{at}ki.se