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M E Goldberger

Publications and source records attributed to M E Goldberger.

At least 19 recordsLinked to original sources
PubMed1995

The development of quadrupedal locomotion in the kitten.

The development of bipedal treadmill locomotion and overground locomotion has previously been studied in the kitten; the development of quadrupedal treadmill locomotion has not. We evaluated and compared all three forms of locomotion in the normal kitten and present quantitative data comparing the development of quadrupedal treadmill and overground locomotion. Overground locomotion was studied from the day of birth to 5 months of age and quadrupedal treadmill locomotion was studied in the same animals from 9 weeks to 5 months of age. Treadmill locomotion was initiated postweaning, since it could not be reliably elicited without a food reward. Three locomotor characteristics (weight support, balance, and coordination between the forelimbs and the hindlimbs) were evaluated quantitatively. Kittens first consistently demonstrated overground steps with the ventral surface of their bodies supported above the walking surface throughout the entire step cycle during the second and third postnatal weeks. By 4 weeks of age, overground locomotion consistently showed full weight support and midline positioning of the hindquarters. Coordination between the forelimbs and the hindlimbs developed differently in the two forms of quadrupedal locomotion evaluated. During overground locomotion, the kittens initially used a single pattern in which only one limb was in swing at any time. As the kittens' weight support and trunk control improved, additional swing phase coordination patterns emerged and these patterns were correlated with the animals' ability to change speeds during locomotion. The consistency with which a dominant interlimb swing phase pattern was used at a particular speed increased with age and, by 6 weeks, the frequency of each speed-related dominant pattern approached 100% during overground locomotion. At 6 weeks, interlimb coordination also was evident in the nearly consistent interlimb phase interval present between the forelimb's initiation of the first extension subphase and the ipsilateral hindlimb's initiation of the flexion phase. The consistent patterns appeared to be fostered by maturation of weight support and balance. In contrast, the interlimb phase interval was inconsistent during quadrupedal treadmill locomotion until 20 weeks of age. Moreover, the interlimb swing phase patterns used during quadrupedal treadmill locomotion differed from those used during overground locomotion. The differences in the developmental time course and patterns of interlimb coordination between overground and quadrupedal treadmill locomotion suggest that different mechanisms regulate the control of interlimb coordination during these two different forms of quadrupedal locomotion.

Age Factors↗
PubMed1995

Development of locomotor behavior in the spinal kitten.

This study was undertaken to determine the locomotor capability of kittens whose spinal cords were transected at birth. The postnatal development of reflex and goal-directed locomotion was examined during the first 5 postnatal months in kittens that received low thoracic spinal cord transections as newborns. Some spinal kittens developed aberrant quadrupedal forms of locomotion. The onset of quadrupedal locomotion, however, was delayed by 2-3 months compared to the normal kitten (42) and deteriorated by 5 months of age. Qualitative and quantitative analyses demonstrated that the quadrupedal locomotion was abnormal. Although some step cycles were characterized by full weight support, the typical hindlimb step cycle of the best performing cat showed inadequate weight support and balance. No spinal cat was able to coordinate the hindlimbs with the forelimbs during overground locomotion on a runaway or during quadrupedal locomotion on a treadmill. Neuroanatomical tracing with WGA-HRP and immunocytochemical techniques showed no axonal regeneration or growth into or across the lesion sites. The aberrant form of quadrupedal locomotion developed without descending input to the caudal spinal cord. The variability in performance among animals suggested that compensatory strategies were important factors in the spinal kitten's achievement of quadrupedal locomotion. Hindlimb weight-supported stepping during quadrupedal locomotion in some animals underscored the capacity of the isolated caudal spinal cord to generate both rhythmical stepping movements and weight support. The maintenance of developmentally immature, but functional, hindlimb postures suggested that the development of the isolated caudal spinal cord was arrested in the absence of descending input.

Age Factors↗
PubMed1995

Transplants enhance locomotion in neonatal kittens whose spinal cords are transected: a behavioral and anatomical study.

We have studied the locomotor development of kittens that received complete low thoracic spinal cord transections and embryonic spinal cord transplants as newborns. Embryonic spinal cord (E21-E26) transplanted into the site of a transection integrated well with the host spinal cord and promoted the development of overground locomotion. Spinalized kittens with transplants were first distinguished from spinalized kittens during the 2nd and 3rd postnatal weeks when kittens with transplants positioned their hindlimbs underneath their bodies which promoted support of the hindquarters. By postnatal Week 6, kittens with transplants exhibited overground locomotion characterized by full weight support and moderate balance control. By 20 weeks of age, as many as 96% of the step cycles showed full weight support and as few as 2% of the step cycles were interrupted by a fall. Most kittens also showed coordination between the forelimbs and the hindlimbs. They differed from normal in the precocious onset of reflex stepping and in the less precise interlimb coordination and more precarious balance during overground locomotion. The overground locomotor performance of kittens with transplants greatly exceeded that of spinal kittens without transplants since few spinalized kittens showed any full-weight-supported step cycles and none showed coordination between the forelimbs and the hindlimbs. In the absence of a transplant, no fibers could grow across the lesion site. In the presence of a transplant, fibers grew across the lesion site and established anatomical connectivity with the host. Host segmental systems identified by the presence of calcitonin gene-related peptide- and substance P-immunoreactive fibers were found throughout the transplants. Descending host systems of supraspinal origin were identified by serotonin- and dopamine beta-hydroxylase-immunoreactive fibers throughout the transplants. The growth of supraspinal axons into the transplant, and in one case into the caudal host spinal cord, provided a possible anatomical basis for the development of coordinated overground locomotion.

Age Factors↗
PubMed1995

Plasticity of complex terminals in lamina II in partially deafferented spinal cord: the cat spared root preparation.

Projections to the dorsal horn change in adult mammals in response to complete or partial deafferentation. The number of synaptic terminals remains constant after complete lumbosacral deafferentation, indicating replacement of lost dorsal root terminals by newly formed terminals from spared intrinsic systems. The density of a spared central projection of a dorsal root is increased in dorsal horn after partial deafferentation, consistent with sprouting by the axons in the spared root. In this study, we have used electron microscopy to study morphological changes in a specific class of terminals in the dorsal horn induced by partial deafferentation. Complex terminals (CTs) in the dorsal horn originate exclusively from dorsal roots and are readily distinguished morphologically. The CTs and the postsynaptic densities (PSDs) associated with CTs were measured in lamina II at L5 and L6 in cats subjected to unilateral spared root (L6) dorsal rhizotomies and compared to CTs in the control side. Acutely following partial deafferentation, the number of CT profiles decreased. At more chronic survivals, the number of CT profiles were restored to normal levels, and both the number and the length of PSDs were increased. The changes in CTs and PSDs suggest sprouting and synaptogenesis by the spared dorsal root fibers that produce changes in the postsynaptic neuron. Spared root deafferentation thus elicits compensatory changes in presynaptic terminals of the spared root and also in their postsynaptic target neurons.

Animals↗
PubMed1994

Grafts of fetal central nervous system tissue rescue axotomized Clarke's nucleus neurons in adult and neonatal operates.

Many conditions are thought to contribute to neuron death after axotomy, including immaturity of the cell at the time of injury, inability to reestablish or maintain target contact, and dependence on trophic factors produced by targets. Exogenous application of neurotrophic factors and transplants of peripheral nerve and embryonic central nervous system (CNS) tissue temporarily rescue axotomized CNS neurons, but permanent rescue may require transplants that are normal targets of the injured neurons. We examined the requirements for survival of axotomized Clarke's nucleus (CN) neurons. Two months after hemisection of the spinal cord at the T8 segment, there was an ipsilateral 30% loss of neurons at the L1 segment in adult operates and a 40% loss in neonates. Transplants of embryonic spinal cord, cerebellum, and neocortex inserted into the T8 segment at the time of hemisection prevented virtually all of the cell death in both adults and neonates, but transplants of embryonic striatum were ineffective. None of the grafts prevented the somal atrophy of CN neurons caused by axotomy. Retrograde transport of fluoro-gold from the cerebellum demonstrated that 33% of all CN neurons at L1 project to the cerebellum, 50% of these died following a T8 hemisection, but all these projection neurons were rescued by a transplant of embryonic spinal cord. These results suggest that the rescue of axotomized CN neurons is relatively specific for the normal target areas of these neurons, but this specificity is not absolute and may depend on the distribution and synthesis of particular neurotrophic agents.

Aging↗
PubMed1994

NMDA receptor blockade rescues Clarke's and red nucleus neurons after spinal hemisection.

Hemisection of the adult rat spinal cord at T9 transects the ascending ipsilateral axons of Clarke's nucleus (CN) neurons and the descending contralateral axons of red nucleus (RN) neurons. Eight weeks following axotomy, 30% of CN neurons and 22% of RN neurons die. Since both nuclei receive glutamatergic input, we wished to examine the possibility that glutamatergic excitotoxicity contributes to axotomy-induced neuronal death in these nuclei. To test this we studied the effects of administration of the NMDA receptor antagonist MK-801 on cell survival after axotomy. When 1 mg/kg body weight MK-801 is administered subcutaneously every day for 1-8 weeks to hemisected rats, cell death is prevented. Treatment with 0.5 mg/kg body weight MK-801 over the same time periods results in only partial rescue of axotomized neurons. Paradoxically, when 1 mg/kg MK-801 administration is restricted to the first week of an 8 week survival period, cell death in both the RN and CN is greatly exaggerated over the cell loss found in saline-treated animals. Withdrawal of 1 mg/kg MK-801 after 1 week of administration induces the loss of 92% of CN neurons, which is 63% greater than that occurring after axotomy alone. If, however, 1 mg/kg MK-801 is withdrawn after 2 weeks post-axotomy in the RN and 3 weeks postaxotomy in CN, all axotomized neurons survive. This rescue is found at 6 months postsurgery, the longest survival period studied, and therefore appears to be permanent. These results suggest that glutamatergic afferent input contributes significantly to the death of axotomized red nucleus and Clarke's nucleus neurons via NMDA receptors located on these neurons.

Animals↗
PubMed1993

The recovery of postural reflexes and locomotion following low thoracic hemisection in adult cats involves compensation by undamaged primary afferent pathways.

Spinal hemisection in the adult cat results in motor impairments followed by substantial recovery of function (16, 20, 39, 53). The present study was undertaken to assess the contribution of undamaged ipsilateral segmental and contralateral descending systems to recovery of motor function. Quantitative behavioral methods were used to examine monopedal reflex and bipedal locomotor functions after thoracic hemisection. Different facets of motor behavior recover at different times. The recovery of monopedal postural reflexes precedes the recovery of more complex motor behavior. Since the reflexes tested are initiated by segmental afferent input and show recovery and normal motor patterns during locomotion, as defined by kinematic analysis show recovery, it is likely that dorsal root input compensates for the loss of descending input to one side of the spinal cord. Quantitative immunocytochemical methods for visualizing the central projections of dorsal root fibers (monoclonal antibody RAT-102; 49) and the descending serotoninergic pathway were used to examine the response of these pathways to hemisection. Hemisection results in a permanent decrease in the density of serotoninergic projections and a permanent increase in dorsal root projections in the spinal cord. The increased density of RAT-102 may represent an increase in the projection of dorsal root fibers and provide the increased input necessary to mediate enhanced reflex control. A transient increase in GAP-43 in the dorsal horn ipsilateral to the hemisection suggests that the increased density of RAT-102 immunoreactivity is associated with growth. Taken together, our results suggest that sprouting of primary afferents within the spinal cord is one mechanism underlying the recovery of function after hemisection.

Adaptation, Physiological↗
PubMed1993

Proliferation of SP- and 5HT-containing terminals in lamina II of rat spinal cord following dorsal rhizotomy: quantitative EM-immunocytochemical studies.

The density of substance P (SP) and serotonin (5HT) immunoreactivity in laminae I and II of rat spinal cord changes following dorsal rhizotomy in a manner consistent with sprouting by intrinsic SP and descending 5HT systems (Wang et al. J. Comp. Neurol. 304: 555, 1991). In this study we used quantitative EM-immunocytochemistry to examine whether the increase in substance P and serotonin immunoreactivity seen at the light microscopic level was related to increased numbers of SP- and 5HT-containing terminals in lamina II. Dorsal roots were sectioned and their ganglia removed from L1 to S2 unilaterally in 18 rats. After 3 (acute), 10 (subacute), or 60 (chronic) days, rats were perfused, and the L5 segments of the spinal cord were removed and prepared for electron microscopy. Lumbosacral deafferentation completely and permanently eliminated complex terminals in lamina II at L5 but the number of simple terminals increased by 46% compared to the control side. This result was similar to that shown previously in cat (Murray and Goldberger, J. Neurosci. 6: 3205, 1986) and suggested that intact intrinsic systems sprouted to form new terminals to compensate for the terminals lost by deafferentation. Quantitative electron microscopic immunocytochemistry demonstrated that the number of terminals containing SP in deafferented lamina II decreased by 58% at 3 days post-operatively and then increased by 10 days and recovered to normal levels by 60 days. The loss of SP terminals in the acute group is due to the loss of SP-containing dorsal root afferents, while the recovery in the chronic group suggests replacement of lost terminals by intrinsic SP systems. These results therefore indicate that SP-containing terminals show homotypic sprouting in response to complete dorsal root deafferentation. The number of 5HT-containing terminals in lamina II of spinal cord increased by 56% on the deafferented side in the chronic group. The increase in 5HT-containing terminals indicates that descending 5HT systems undergo heterotypic sprouting in response to dorsal rhizotomy.

Animals↗
PubMed1993

Partial deafferentation of cat spinal neurons results in permanent changes in cell surface molecular expression and metabolic activity.

Partial denervation of spinal neurons often results in reactive reinnervation by spared systems and some recovery of function. Dorsal rhizotomy in the adult cat has been used for the examination of the molecular modifications that occur postsynaptically and which may underlie anatomical and behavioral plasticity. We examined two markers of postsynaptic neurons in the spinal cord. Immunolocalization of a specific marker of superficial dorsal horn and intermediolateral neurons, the limbic system-associated membrane protein (LAMP), revealed that removal of certain afferents results in a permanent decrease in LAMP expression. Cytochrome oxidase, a metabolic marker, is normally high in the neurons of Clarke's nucleus, but showed a dramatic decrease after deafferentation. Reactive reinnervation occurs in many regions of the spinal cord following partial deafferentation, including Clarke's nucleus and the dorsal horn, and these changes in presynaptic input may be manifest by permanent modifications in molecular expression and metabolic activity of spinal neurons.

Afferent Pathways↗
PubMed1993

Removal of dorsal root afferents prevents retrograde death of axotomized Clarke's nucleus neurons in the cat.

We investigated the effect of axotomy, deafferentation, and deafferentation plus axotomy on cell survival and cell size in Clarke's nucleus of the cat spinal cord. Hemisection of the adult spinal cord at T9 leads to retrograde cell death of 40% of the neurons in Clarke's nucleus at L3, as well as to a reduction in the mean soma size of the survivors. In contrast, deafferentation of Clarke's nucleus neurons by L1-S2 dorsal rhizotomy produces no cell loss and no shrinkage of the somata. These results indicate that dorsal root afferent input is not required for Clarke's nucleus cell survival. To test whether afferents may be required by the 60% of neurons that survive axotomy, we deafferented Clarke's nucleus prior to axotomy. Surprisingly, removal of primary afferents to Clarke's nucleus neurons prior to axotomy prevented the death of all neurons that would normally have died from axotomy. These results suggest that dorsal root afferent input is not required for Clarke's nucleus neuron survival after axotomy and may in fact be toxic to these axotomized neurons. This afferent toxicity is likely to be mediated through the dorsal root afferent neurotransmitter glutamate.

Afferent Pathways↗
PubMed1991

Normal development and the effects of early rhizotomy on spinal systems in the rat.

The normal postnatal development of 4 spinal systems was examined in the dorsal horn of the rat spinal cord using histochemical and immunocytochemical techniques. We used thiamine monophosphatase (TMPase), a marker for dorsal root ganglion cells and their projections, a tachykinin, substance P (SP), which is provided by both dorsal root and intrinsic systems, and two markers for descending systems, serotonin (5-HT) and the synthesizing enzyme for noradrenalin, dopamine B-hydroxylase (DBH). The responses of each of these systems to unilateral dorsal lumbosacral rhizotomy on postnatal day 5 was then examined and quantified using image analysis methods to determine whether the extent of plasticity of spinal systems is different after a neonatal lesion than after a comparable lesion made in the adult. Each system differs in development, distribution, and in response to rhizotomy. TMPase is present in the dorsal horn on the day of birth (DPN0) and reaches adult levels of density by 5 days postnatal (DPN5). SP reaction product is present in a distribution similar to the adult in the dorsal horn on DPN0 and reaches adult levels of density by the second postnatal week. 5-HT is present in the dorsal horn on DPN0, shows a laminar distribution at DPN5, and acquires the adult distribution and density at the end of the second week. DBH is present in the dorsal horn on DPN0, acquires the adult distribution at DPN5 and adult levels of density at the end of the second postnatal week. Unilateral lumbosacral rhizotomy in 5 day old rats completely and permanently abolishes TMPase in the dorsal horn by 4 days postoperatively (4DPO). SP is decreased by 4 DPO (9 DPN) but recovers almost completely by 30 DPO. 5-HT is increased by 10 DPO and remains elevated thereafter. DBH is not changed postoperatively. There is shrinkage of lamina I and II by 10 DPO but the recovery of SP and the increase in density of 5-HT staining is proportionally greater than the extent of shrinkage. Therefore, shrinkage contributes to but does not entirely account for either the apparent recovery of SP staining or the increase in density of 5-HT staining. The responses of the TMPase, 5-HT and DBH systems to neonatal rhizotomy are very similar to the response to rhizotomy in adults and there is therefore no evidence for greater plasticity of these systems after neonatal rhizotomy than after adult rhizotomy. The SP systems show more rapid depletion and a greater and more rapid recovery than after adult deafferentation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Plasticity of spinal systems after unilateral lumbosacral dorsal rhizotomy in the adult rat.

Plasticity of spinal systems in response to lumbosacral deafferentation has previously been described for the cat, by using immunocytochemistry to demonstrate plasticity of tachykinin systems and degeneration methods to demonstrate plasticity of descending systems. In this study, we describe the response to lumbosacral deafferentation in the adult rat. Application of immunocytochemical methods to visualize tachykinins (predominantly substance P magnitude of SP), serotonin (5-HT), and dopamine B-hydroxylase (DBH), the synthesizing enzyme for norepinephrine, permits us to compare the response of SP systems in rat and cat spinal cord and to examine the response of two descending systems, serotoninergic and noradrenergic, to deafferentation. We used image analysis of light microscopic preparations to quantify the immunoreaction product in the spinal cord in order to estimate the magnitude, time course and localization of changes induced by the lesion. The distribution of SP, serotoninergic (5-HT), and noradrenergic staining in the spinal cord of rat is very similar to that of the cat. Unilateral lumbosacral rhizotomy elicits a partial depletion, followed by a partial replacement of tachykinin immunoreactivity in laminae I and II. This response was similar to that described for the cat, although characterized by a longer time course, and, as in the cat, is likely due to plasticity of tachykinin containing interneurons. The same lesion elicits no depletion but a marked and permanent increase in 5-HT immunoreactivity in laminae I and II, which develops more rapidly than the response by the SP system. These results indicate sprouting or increased production of SP and 5-HT in response to deafferentation. No change was seen in DBH immunoreactivity, indicating that the noradrenergic system does not show plasticity in response to deafferentation. Our results demonstrate that dorsal rhizotomy evokes different effects in different systems in the adult spinal cord of the rat and thus suggests that the response of undamaged pathways to partial denervation of their target is regulated rather than random.

Afferent Pathways↗
PubMed1990

Plasticity of dorsal root and descending serotoninergic projections after partial deafferentation of the adult rat spinal cord.

Plasticity of dorsal root (DR) and descending serotoninergic (5-HT) projections following dorsal rhizotomy from L2 to S1 sparing L5 was studied by means of an intra-animal comparison in the adult rat spinal cord. Projections of the chronically and acutely spared root were compared by cholera-toxin conjugated horseradish peroxidase (CT-HRP) injected into the sciatic nerves as the transganglionic tracer. Projections in unoperated controls, operated controls (acute bilateral spared root), and in experimental animals (chronic spared root on one side and acute spared root on the other) were mapped and the density was measured with an image analysis system. Labeled DRG cells and motor neurons were counted to determine if there were differences in the delivery of the label between the two sides. Measurements of the area of the dorsal horn and, separately, of the superficial laminae were made to control for shrinkage. DR projections were symmetrical in operated and unoperated controls, but a significant increase in DR projection density was found from L6 to L3 in the dorsal horn and Clarke's nucleus at L1 on the chronic spared root side in animals in which an equal number of DRG cells was labeled on the two sides. Density of 5-HT immunoreactivity was symmetrical in controls. Ipsilateral to chronic spared root rhizotomy, the area fraction occupied by 5-HT projections increased in Clarke's nucleus and in the superficial dorsal horn of all partially deafferented segments except L5, the spared root segment. Partial deafferentation of the adult rat lumbosacral spinal cord may therefore elicit sprouting from the spared dorsal root and, outside of the dorsal root projection zone, sprouting from the spared descending 5-HT system. Plasticity of dorsal root projections and of 5-HT projections occur in different regions; in regions of the increased spared root projection, no increase in seen in 5-HT projections, suggesting that sprouting in the adult rat spinal cord is regulated, perhaps by competitive or hierarchical mechanisms.

Animals↗
PubMed1990

Modification of astrocytes in the spinal cord following dorsal root or peripheral nerve lesions.

Glial fibrillary acidic protein (GFAP) immunocytochemistry was used to monitor the response of astrocytes in the rat spinal cord to either dorsal root or sciatic nerve lesions. Image analysis methods were used to provide a quantitative correlate of the reactive gliosis. Multiple dorsal root section elicited a rapid increase in GFAP immunoreactivity of astrocytes unilaterally within the spinal cord along the pathway of the degenerating dorsal root axons in the dorsal and ventral horns and this gliosis persisted in the dorsal horn beyond the time at which active phagocytosis of degenerative debris occurred. Labeling of proliferating cells using [3H]thymidine revealed that none of the dividing cells contained detectable GFAP, suggesting that the increased GFAP labeling represents primarily a hypertrophy rather than a proliferation of astrocytes. Comparison of animals that had been deafferented in the early neonatal period with those deafferented as adults indicated that the GFAP immunoreactive response persisted following neonatal lesions but that it was markedly less intense than after adult lesions. Sciatic nerve section in adults does not result in extensive frank degeneration but it does evoke a rapid and marked increase in staining of astrocytes both in the dorsal horn and in the ventral horn. Transganglionic changes in GFAP staining in the dorsal horn occur by 3 days post-operatively, which is much earlier than the time of dorsal root ganglion neuron death caused by the sciatic nerve lesion. These experiments indicate that astrocytes can respond to signals from a variety of changes in neurons, including not only Wallerian degeneration, but also retrograde and transganglionic changes.

Animals↗
PubMed1988

Spared-root deafferentation of a cat's hindlimb: hierarchical regulation of pathways mediating recovery of motor behavior.

Previous studies showed that after complete hindlimb deafferentation in cats, the ipsilateral descending pathways mediated recovery of overground, goal-directed locomotion and accurate placement of the deafferented limb. In the present study deafferentations sparing one dorsal root (L6) were performed to see if the descending systems would still be responsible for the recovery. The partially deafferented hindlimb is initially impaired in postural reflexes and accurate placement during locomotion but considerable recovery occurs. A similar pattern of severe impairment and subsequent recovery is observed in cats in which the only lesion is L1 hemisection. When a hemisection is added 6 months later to chronic spared-root deafferentation the recovery (from the latter lesion) is temporarily reversed but the animals recover again in a fashion similar to that after hemisection alone. Since there is no recovery of overground locomotion when hemisection is added to complete deafferentation but there is when deafferentation is incomplete, the descending pathways apparently are not responsible for maintaining the recovery when one dorsal root is spared as they are when all are cut. The results suggest that a competitive or hierarchical control over residual systems may regulate recovery of motor function.

Animals↗
PubMed1988

Partial and complete deafferentation of cat hindlimb: the contribution of behavioral substitution to recovery of motor function.

After partial (spared-root) or complete hindlimb deafferentation, locomotion and accurate limb placement during locomotion recover considerably. In the present study movement was studied during and after recovery to determine whether altered motor patterns could substitute for normal ones in the recovery of motor behavior. In acute L6 spared-root preparations somatosensory postural reflexes are impaired, accurate limb placement deficient and joint angle measurements show altered kinematic motor patterns during locomotion. As somatosensory postural reflexes and accurate limb placement recover, so do the motor patterns. After complete deafferentation motor patterns are more disturbed. Somatosensory postural reflexes remain absent but as descending reflexes recover, so does accurate limb placement during locomotion. In deafferented hindlimbs, in contrast to spared-root preparations motor patterns observed chronically (after recovery of accurate placement) are persistently abnormal indicating that novel motor patterns can replace normal ones in the recovery of goal-directed behavior. The results suggest that behavioral substitution can contribute to recovery of useful movement.

Animals↗