Influences of sensory input from the limbs on feline corticospinal neurons during postural responses

Abstract

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.

Activity of motor cortex neurons during backward locomotion

“…The absence of any simple correlation between the activity of many cortical neurons on one hand and the variables characterizing the motor pattern on the other hand is a common finding in many studies on the motor cortex (see e.g., Beloozerova et al 2010;Drew 1993;Kakei et al 2003;Karayannidou et al 2008Karayannidou et al , 2009. It seems likely that these neurons do not directly participate in the production of motor output.…”

“…The present paper focuses on their activity during BW and on comparison of the activity during BW and FW. Some of the methods of data collection and analysis have been described earlier Karayannidou et al 2008;Prilutsky et al 2005;Zelenin et al 2011) and will be reported briefly here. All experiments were conducted at Barrow Neurological Institute (Phoenix, AZ) in accordance with NIH guidelines and with the approval of the Barrow Neurological Institute Animal Care and Use Committee.…”

“…Four mechanical sensors monitored the anterior-posterior (AP) position of limbs during walking (Karayannidou et al 2008); two of the sensors (attached to the left forelimb and the left hindlimb) are shown in Fig. 1A.…”

“…trained to perform different locomotor tasks (see the six forms of locomotion below) and were rewarded by a paste-like food, continuously ejected from a feeder (Karayannidou et al 2008). The feeder (a plastic tube of 18 mm outer diameter and 6 mm inner diameter) was always positioned in front of the cat at a height of 21-23 cm (Fig.…”

Modelagem e simulação do sistema neuromuscular responsável pelo controle do torque gerado na articulação do tornozelo.

“…Similarmente, os achados de Fitzpatrick e McCloskey (1994) também sugerem que apenas a propriocepção da articulação do tornozelo é efetiva para a manutenção do equilíbrio de um pêndulo invertido. No entanto, outros estudos sugerem que o córtex tem um papel importante nesta tarefa motora (Beloozerova et al, 2003;Forner-Cordero et al, 2007;Horak, 2007;Karayannidou et al, 2009;Karayannidou et al, 2008;Taube et al, 2006;Zelenin et al, 2010), porém, a atividade cortical estaria mais associada às respostas corretivas após perturbações da postura quasi-estática, que não é o foco do presente estudo.…”