Electromyographic Responses From the Hindlimb Muscles of the Decerebrate Cat to Horizontal Support Surface Perturbations

Abstract

The sensory and neural mechanisms underlying postural control have received much attention in recent decades but remain poorly understood. Our objectives were 1) to establish the decerebrate cat as an appropriate model for further research into the sensory mechanisms of postural control and 2) to observe what elements of the postural response can be generated by the brain stem and spinal cord. Ten animals were decerebrated using a modified premammillary technique, which consists of a premammillary decerebration that is modified with a vertical transection near the subthalamic nucleus to eliminate spontaneous locomotion. Horizontal support surface perturbations were applied to all four limbs and electromyographic recordings were collected from 14 muscles of the right hindlimb. Muscle activation was quantified with tuning curves, which compared increases and decreases in muscle activity to background and graphed the difference against perturbation direction. Parallels were drawn between these tuning curves, which were further quantified with a principal direction and breadth (range of directions of muscle activation), and data collected by other researchers from the intact animal. We found a strong similarity in the direction and breadth of the tuning curves generated in the decerebrate and intact cat. These results support our hypothesis that directionally specific tuning of muscles in response to support surface perturbations does not require the cortex, further indicating a strong role for the brain stem and spinal cord circuits in mediating directionally appropriate muscle activation patterns.

Attentional costs of walking are not affected by variations in lateral balance demands in young and older adults

“…The presence of postural responses in decerebrated cats underscores the role of subcortical structures in mediating balance reactions, at least in mammals [21]. It has been suggested that this finding may be generalized to humans in view of a similar reliance of postural reactions on brain stem structures [22].…”

“…Perhaps the primarily subcortical nature of postural responses [21,22] requires minimal use of attentional resources. The higher attentional costs observed for walking on visual lines indicated that visuolocomotor demands contributed more to the attentional costs of walking than balance demands.…”

Limb and Trunk Mechanisms for Balance Control during Locomotion in Quadrupeds

“…Together with the results of the present study, these findings show that neuronal mechanisms of the brainstem, cerebellum, and spinal cord are able to maintain lateral stability during locomotion and to compensate for a wide range of destabilizing factors. Decerebrate animals are also able to generate appropriate postural reactions to different perturbations during standing (Musienko et al, 2008;Honeycutt et al, 2009;Honeycutt and Nichols, 2010). One can thus conclude that the feedback control of posture and balance under different conditions is basically the hindbrain and spinal cord function.…”

“…It causes strong bilateral activation of back muscles (red lines in Fig. 13D3), which results in an increase of the trunk stiffness (Hu et al, 2009). This increase in stiffness leads to trunk straightening (Fig.…”

“…We suggested that coactivation of back muscles (caused by trunk bending) leads to an increase in the trunk stiffness (Hu et al, 2009), and therefore to a reduction in the externally caused trunk bending, which will result in a postural correction. This hypothesis was tested in the experiments with suspended hindquarters (Fig.…”