Most injuries to the brain or spinal cord spare some connections between the areas of brain that initiate movement and the areas of spinal cord that produce movement. A pivotal question for recovery of movement is the degree to which spared connections can compensate for injured ones. We will study the adaptation of spared motor pathways to injury of the corticospinal tract (CST), the principal pathway for voluntary movement in humans. The CST, which connects the motor cortex to the spinal cord, controls fine hand movements and modulates spinal cord reflexes. We will cut the CST emanating from one hemisphere and test the ability of spared circuits to take over the lost function. Specifically, we will examine two circuits: 1) the uninjured half of the CST through its sparse ipsilateral projections, and 2) a bypass circuit on the injured side from cortex to red nucleus to spinal cord. We will injure rats soon after birth, a time when these connections are plastic and the opportunity for compensation is highest. We then measure the response of these spared systems using two novel techniques-retrograde transsynaptic tracing using pseudorabies virus, and stereological quantification of axonal connections. Thus, we will determine which spared system sprouts greater connections in response to injury. In adult rats with neonatal injury to one half of the CST, we will test the functional limits of pathway compensation. We will use both novel and proven tests of functions that depend critically on the CST: reaching to grasp, walking over a ladder, food manipulation, and control of a spinal cord reflex. We predict that there will be incomplete recovery of the specialized motor skills. For functions that do recover, we will temporarily inactivate each of the two spared pathways, by infusing an inhibitor of neural activity, to test their contribution to recovery. We expect that the recovered functions will be lost transiently in the pathway that shows the greatest amount of injury-induced plasticity. Finally, we will selectively activate the most adaptive circuit to try to improve upon endogenous recovery. Using chronic stimulation through an implanted electrode, we intend to harness activity-dependent plasticity to strengthen motor connections. We predict that these targeted manipulations will create a more adaptive pattern of brain- spinal cord connections, as measured by tracing and stimulation techniques, and help to restore function, based on the aforementioned motor tasks. Many human infants, especially those born prematurely, sustain injury to the CST. This often results in paralysis and spasticity on one side of the body. Activity, in the form of physical therapy and non-invasive brain stimulation can be used to alter connections in humans. These studies will help to determine where activity should be applied in order to strengthen the circuits that mediate spontaneous recovery. Thus, we use anatomically precise injury, tracing, inactivation, and stimulation to determine the circuit-level logic for repair of the motor systems. This could improve our ability to restore function in people with early brain injury.

Public Health Relevance

Perinatal brain injury affects more than two in a thousand infants and can cause lasting paralysis and spasticity. In identifying alterations in brain-spinal cord connections caused by neonatal injury, these studies will help to understand why paralysis occurs and which connections need to be repaired. New strategies to selectively and non-invasively stimulate the brain can then be used to support certain brain-spinal cord connections and possibly restore function.!

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Clinical Investigator Award (CIA) (K08)
Project #
5K08NS073796-04
Application #
8720826
Study Section
Neurological Sciences Training Initial Review Group (NST)
Program Officer
Jakeman, Lyn B
Project Start
2011-09-01
Project End
2016-08-31
Budget Start
2014-09-01
Budget End
2015-08-31
Support Year
4
Fiscal Year
2014
Total Cost
Indirect Cost
Name
Winifred Masterson Burke Med Research Institute
Department
Type
DUNS #
City
White Plains
State
NY
Country
United States
Zip Code
10605
Wen, Tong-Chun; Lall, Sophia; Pagnotta, Corey et al. (2018) Plasticity in One Hemisphere, Control From Two: Adaptation in Descending Motor Pathways After Unilateral Corticospinal Injury in Neonatal Rats. Front Neural Circuits 12:28
Sindhurakar, Anil; Mishra, Asht M; Gupta, Disha et al. (2017) Clinically Relevant Levels of 4-Aminopyridine Strengthen Physiological Responses in Intact Motor Circuits in Rats, Especially After Pyramidal Tract Injury. Neurorehabil Neural Repair 31:387-396
Sindhurakar, Anil; Butensky, Samuel D; Meyers, Eric et al. (2017) An Automated Test of Rat Forelimb Supination Quantifies Motor Function Loss and Recovery After Corticospinal Injury. Neurorehabil Neural Repair 31:122-132
Kuo, Hsing-Ching; Ferre, Claudio L; Carmel, Jason B et al. (2017) Using diffusion tensor imaging to identify corticospinal tract projection patterns in children with unilateral spastic cerebral palsy. Dev Med Child Neurol 59:65-71
Gupta, Disha; Barachant, Alexandre; Gordon, Andrew M et al. (2017) Effect of sensory and motor connectivity on hand function in pediatric hemiplegia. Ann Neurol 82:766-780
Carmel, Jason B; Willis, Dianna E (2016) Neural Circuits Catch Fire. Neurotherapeutics 13:261-3
Park, Hong Geun; Carmel, Jason B (2016) Selective Manipulation of Neural Circuits. Neurotherapeutics 13:311-24
Harel, Noam Y; Carmel, Jason B (2016) Paired Stimulation to Promote Lasting Augmentation of Corticospinal Circuits. Neural Plast 2016:7043767
Meyers, Eric; Sindhurakar, Anil; Choi, Rachel et al. (2016) The supination assessment task: An automated method for quantifying forelimb rotational function in rats. J Neurosci Methods 266:11-20
Friel, Kathleen M; Kuo, Hsing-Ching; Fuller, Jason et al. (2016) Skilled Bimanual Training Drives Motor Cortex Plasticity in Children With Unilateral Cerebral Palsy. Neurorehabil Neural Repair 30:834-44

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