assessing-forelimb-function-after-unilateral-cervical-sci-using-novel

Assessing Forelimb Function after Unilateral Cervical SCI using Novel Tasks: Limb Step-alternation, Postural Instability and Pasta Handling

Cervical spinal cord injury (cSCI) can cause devastating neurological deficits, including impairment or loss of upper limb and hand function. A majority ...

The University of Texas at Austin

Cervical spinal cord injury (cSCI) can cause devastating neurological deficits, including impairment or loss of upper limb and hand function. Recently there has been increasing interest in cervical spinal cord injury models because the majority of spinal cord injuries are at cervical levels. Here we examined spontaneous functional recovery of adult rats with either laminectomy or lateral hemisection of the cervical spinal cord at C3-C4. Behavioral tests were carried out, including the forelimb locomotor scale (FLS), a postural instability test (PIT), a pasta-handling test that has been used to assess forepaw digit function and latency to eat, forelimb use during vertical-lateral wall exploration in a cylindrical enclosure, and vibrissae-elicited forelimb placing tests. In addition, a forelimb step-alternation test was developed to assess functional recovery at 12 weeks post-injury. All tests detected cSCI-induced deficits relative to laminectomy. Interestingly, the severity of deficits in the forelimb step-alternation test was associated with more extensive spinal damage, greater impairment, and less recovery in the FLS and other tests. For the pasta-handling test we found that rats with a milder cervical injury (alternators) were more likely to use both forepaws together compared to rats with a more severe injury (non-alternators). In addition, using the PIT, we detected enhanced function of the good limb, suggesting that neural plasticity on the unaffected side of the spinal cord may have occurred to compensate for deficits in the impaired forelimb. These outcome measures should be useful for investigating neural events associated with cSCI, and for developing novel treatment strategies.

Assessing forelimb function after unilateral cervical spinal cord injury: novel forelimb tasks predict lesion severity and recovery.

Unilateral nigrostriatal dopamine depletion in animals induces contralateral sensorimotor deficits that are like symptoms associated with Parkinson's disease (PD). Unilateral nigrostriatal dopamine depletion also causes a contralateral deficit in disengagement behavior (e.g., ability to stop an ongoing activity to orient/attend to a new stimulus). This disengagement deficit has been shown to be resistant to treatments that rescued other motor and somatosensory deficits. Thus, disengagement behavior may involve unique sensorimotor information integration potentially important for attentional allocation and may rely strongly on a mechanism that includes extranigrostriatal circuitry. The central nucleus of the amygdala (CeA) and its connections with the nigral dopamine system have been reported to modulate cognitive processes dependent substantially on attentional allocation. CeA dopamine function might be also important for disengagement behavior. In Experiment 1, rats received microinfusions of 6-hydroxydopamine unilaterally to induce dopamine terminal loss in the CeA and were tested for disengagement behavior in addition to several sensorimotor functions. These rats showed deficits in contralateral disengagement behavior and an asymmetry in adhesive dot removal from the paws, but not in forelimb use in a cylinder or amphetamine rotation. In Experiment 2, rats received D1 or D2 antagonists into the CeA unilaterally prior to behavioral tests. The D1 antagonist disrupted disengagement behavior without affecting the other sensorimotor tests examined. The D2 antagonist had no effects on any of the behaviors tested. Our results suggest that CeA dopamine function is involved in modulation of disengagement behavior.

Sydney A. Geissler

Department of Biomedical Engineering

The University of Texas at Austin

Assessing Forelimb Function after Unilateral Cervical SCI using Novel Tasks: Limb Step-alternation, Postural Instability and Pasta Handling

Sydney A. Geissler

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The University of Texas at Austin

Assessing Forelimb Function after Unilateral Cervical SCI using Novel Tasks: Limb Step-alternation, Postural Instability and Pasta Handling

Department of Biomedical Engineering