Facilitation of ipsilateral actions of corticospinal tract neurons on feline motoneurons by transcranial direct current stimulation.
Ipsilateral actions of pyramidal tract (PT) neurons are weak but may, if strengthened, compensate for deficient crossed PT actions following brain damage. The purpose of the present study was to examine whether transcranial direct current stimulation (tDCS) can strengthen ipsilateral PT (iPT) actions; in particular, those relayed by reticulospinal neurons co-excited by axon collaterals of fibres descending in the iPT and contralateral PT (coPT) and of reticulospinal neurons descending in the medial longitudinal fascicle (MLF). The effects of tDCS were assessed in acute experiments on deeply anaesthetized cats by comparing postsynaptic potentials evoked in hindlimb motoneurons and discharges recorded from their axons in a ventral root, before, during and after tDCS. tDCS was consistently found to facilitate joint actions of the iPT and coPT, especially when they were stimulated together with the MLF. Both excitatory postsynaptic potentials and inhibitory postsynaptic potentials evoked in motoneurons and the ensuing ventral root discharges were facilitated, even though the facilitatory effects of tDCS were not sufficient for activation of motoneurons by iPT neurons alone. Facilitation outlasted single tDCS periods by at least a few minutes, and the effects evoked by repeated tDCS by up to 2 h. The results of this study thus indicate that tDCS may increase the contribution of iPT actions to the recovery of motor functions after injuries to coPT neurons, and thereby assist rehabilitation, provided that corticoreticular and reticulospinal connections are preserved.
Department of Neuroscience and Physiology, Sahlgrenska Academy, University of Gothenburg, Medicinaregatan 11, Box 432, 405 30, Gothenburg, Sweden; Department of Neurobiology, University School of Physical Education, 61-871, Poznań, Poland.
Marcin
M
Bączyk
Lars-Gunnar
LG
Pettersson
Elzbieta
E
Jankowska
D000818:Animals; D002415:Cats; D008526:Medulla Oblongata / Q000502:physiology; D009046:Motor Neurons / Q000502:physiology*; D011712:Pyramidal Tracts / Q000502:physiology*; D013126:Spinal Nerve Roots / Q000502:physiology*; D055366:Synaptic Potentials; D065908:Transcranial Direct Current Stimulation
motor cortex; plasticity; reticular formation; transcranial direct current stimulation