Karayannidou - 2009 - Activity of pyramidal tract neurons in the cat ...

Citation

Karayannidou A, Beloozerova IN, Zelenin PV, Stout EE, Sirota MG, Orlovsky GN, Deliagina TG. Activity of pyramidal tract neurons in the cat during standing and walking on an inclined plane. J Physiol. 2009 Aug 1;587(Pt 15):3795-811. PUBMED

10 Word Summary

PTNs contribute to modification of limb configuration in postural perturbations.

Abstract

To keep balance when standing or walking on a surface inclined in the roll plane, the cat modifies its body configuration so that the functional length of its right and left limbs becomes different. The aim of the present study was to assess the motor cortex participation in the generation of this left/right asymmetry. We recorded the activity of fore- and hindlimb-related pyramidal tract neurons (PTNs) during standing and walking on a treadmill. A difference in PTN activity at two tilted positions of the treadmill (+/- 15 deg) was considered a positional response to surface inclination. During standing, 47% of PTNs exhibited a positional response, increasing their activity with either the contra-tilt (20%) or the ipsi-tilt (27%). During walking, PTNs were modulated in the rhythm of stepping, and tilts of the supporting surface evoked positional responses in the form of changes to the magnitude of modulation in 58% of PTNs. The contra-tilt increased activity in 28% of PTNs, and ipsi-tilt increased activity in 30% of PTNs. We suggest that PTNs with positional responses contribute to the modifications of limb configuration that are necessary for adaptation to the inclined surface. By comparing the responses to tilts in individual PTNs during standing and walking, four groups of PTNs were revealed: responding in both tasks (30%); responding only during standing (16%); responding only during walking (30%); responding in none of the tasks (24%). This diversity suggests that common and separate cortical mechanisms are used for postural adaptation to tilts during standing and walking.

Notes

• Aim of study is to explore the role of the motor cortex when maintaining an asymmetrical configuration of the body during standing and walking.
  • Recorded from pyramidal tract neurons
• There actually appears to be two populations of PTN for ipsilateral/contralateral tilt (Fig 6)
• Some PTNs had a higher firing rate for a particular direction of tilt of the platform