Somatotopic studies on red nucleus: spinal projection level and respective receptive fields

Abstract

The somatotopic inputs into red nucleus (RN) neurons have been studied with special reference to their level of projection in the spinal cord. As inputs we employed either volleys in predominantly cutaneous nerves of forelimb and hindlimb or cutaneous mechanoreceptor discharges evoked by taps to footpads of forelimb and hindlimb. There has been physiological confirmation of the anatomical findings that RD neurons projecting to the lumbar cord are located in the ventrolateral zone of the pars magnocellularis, whereas in the dorsomedial zone are RN neurons with cervical but not lumbar projection. Somatotopically there was found to be a differentiation of input to RN neurons according as they projected to the lumbar or only to the cervical cord. This finding was presented in the form both of tables and of somatotopic maps. As expected, this discrimination was more restrictive for the more selective inputs from pad taps than for nerve inputs. Nevertheless, forelimb inputs often had a considerable excitatory and inhibitory action on lumbar-projecting RN neurons, and vice versa for cervical-projecting neurons. There were two notable somatotopic findings that suggest specificities of connectivities. First, despite the large convergence of IP neurons onto RN neurons (about 50-fold), the degree of somatotopic discrimination was about the same for interpositus and RN neurons with two testing procedures: between inputs from forelimb and hindlimb; and between inputs from pads on one foot. Second, although there was in the interpositus nucleus a considerable topographical admixture of neurons with dominant forelimb or hindlimb inputs, the axonal projections of these neurons were apparently unscrambled on the way to the target RN neurons, so as to deliver the somatotopic specificities observed for two classes of RN neurons; those projecting down the spinal cord beyond L2 level, and those projecting to C2 but not L2. Finally, there is a general discussion of motor control with reference to the pathway; pars intermedia of anterior lobe of cerebellum leads to interpositus nucleus leads to red nucleus leads to rubrospinal tract leads to spinal motoneurons.

Effects of Red Nucleus Microstimulation on the Locomotor Pattern and Timing in the Intact Cat: A Comparison With the Motor Cortex

“…Our results also suggest some evidence for a topographical specificity, over and above that which has been described for the hindlimb and forelimb representations of the red nucleus (Eccles et al 1975;Ghez 1975;Holstege and Tan 1988;Padel et al 1972;Pompeiano and Brodal 1957). Inspection of Fig.…”

Sensorimotor Processing in the Newborn Rat Red Nucleus during Active Sleep

“…Although the RN has been investigated predominantly with respect to its motor functions (Muir and Whishaw, 2000;HermerVazquez et al, 2004;Williams et al, 2014;Morris et al, 2015), exafferent stimulation of the limbs of adult cats and turtles evokes RN activity in a somatotopic manner (Pompeiano and Brodal, 1957;Eccles et al, 1975;Sarrafizadeh et al, 1996). Here, we demonstrate for the first time that sensory feedback arising from twitches during active sleep also triggers RN activity in a somatotopic manner (Fig.…”

Anatomical organization of the limb premotor network in the turtle (Chrysemys picta) revealed by in vitro transport of biocytin and neurobiotin

“…Somatosensory responsiveness of red nucleus neuyons. Physiological studies indicate that rubrospinal neurons of the cat (Massion and Albe-Fessard, 1963;Massion and Urbano, 1968;Nishioka and Nakahama, 1973;Eccles et al, 1975a;Ghez, 1975;Fanardjian and Manvelian, 1978) and turtle (Sarrafizadeh et al, 1989; have sensory receptive fields that are usually wide and often bilaterally distribiuted over the body surface. Massion and Albe-Fessard (1963) demonstrated that, in addition to direct inputs, magnocellular RN neurons of the cat also receive sensory input via a pathway through the cerebellum.…”